Persistent Organic Pollutants (POPs): A Review Focused on Occurrence and Incidence in Animal Feed and Cow Milk

Round 1

Reviewer 1 Report

This reviewer recognizes the importance of this review on POPs and their occurrence in animal feed and milk and appreciates the effort the authors put forward in compiling this information together.  However, the manuscript was difficult to read due to a translation issue. This manuscript requires extensive editing into English language. It would be great if the authors could spend more time on editing the manuscript in order to improve the translation into English.

Author Response

Response to referee # 1

 First of all, we want to thank to referee #1 for his/her kind suggestions and for supporting us in improving our work.

Please find below our response accordingly.

1. This reviewer recognizes the importance of this review on POPs and their occurrence in animal feed and milk and appreciates the effort the authors put forward in compiling this information together.  However, the manuscript was difficult to read due to a translation issue. This manuscript requires extensive editing into English language. It would be great if the authors could spend more time on editing the manuscript in order to improve the translation into English.

Response: We apologize for the translation issues. We made an new editing into English language. Please see our edited work.

Author Response File: Author Response.docx

Reviewer 2 Report

The main detraction from this paper is the poor English translation.  That and the way the paper was organized made it very difficult for me to understand.  

The tables are useful for showing the important information, and for the most part they stand alone.  The explanations in the sections associated with the different tables are over-reaching and, combined with the translation issues, don't add very much.  I would use the sections associated with the tables to just make major points, which to me are that milk contamination is caused by contamination of the feed the cattle were given, which in turn depends on where it was grown.  If the milk was shipped from a rural area to an urban area, the contamination in the milk does not represent the place where the milk was sold.  If the feed was grown far from the location of the dairy and shipped, then the contamination in the feed does not represent the location of the dairy, and nor does the contamination in the milk.  The figures don't make much sense to me because they are based on time-points, rather than locations, and I think the locations are more important to the source than the time that the study was published.

 

Here are more specific comments.

 

Introduction:

P2, L76-778:  There have been many studies of POPs in food systems (PCBs, organochlorine insectides) dating back to the 1990s at least.

P2, L81-82:  What global anti-pollution measures specifically?  Maybe omit this sentence, since it is addressed in the next section.

Characterization:

P3, L100:  “it is well recognized that various papers” I’d omit “it is well recognized that” and just say “various studies have demonstrated . . . “

P3, L103: “The characteristics and the toxic potential” this sentence isn’t referenced and doesn’t add much.  I’d omit this sentence and combined the following sentence (“Organic pollutants considered dangerous . . . “) with the paragraph below.

P3, L113: Replace “Nowadays” with “currently”  Maybe combined with the paragraph above it?

P3, L118: either put a colon after OCPs or put the actives in parenthesis. 

P3, L122: Most, if not all, of these chemicals (PCBs, HCBs, PBBs, PFCs, et) had industrial applications and were produced intentionally for those applications.

P4, L141-142:  What are the three categories?  This single-sentence paragraph needs to be expanded to be more explanatory.

P4, L146-151:  “identified residual amounts of pesticides in areas of historical but not current OCP production.”  Can you explain what the time period between the industries closing and the environmental analyses?

P5, L152-155: Omit the first sentence, which restates the previous paragraph, and add the last sentence to the paragraph at the bottom of paged 4.

P5, L157-158:  “have been reported as the main sources of pollution specific to some of the most toxic OCPs.”  Can this be shortened and clarified to say “are the main sources of some of the most toxic OCPs”?

P5, L166: “omit “after these years” (redundant after “almost two decades”)

P5, L168: OCP should not be plural before “metabolites”

P5, L187-188:  I’m having difficulty with this sentence “To all this is added the negative impact created by unintended sources . . . no control evidence to date.”  I don’t think it adds more information than the sentence about unintentional release in the previous paragraph.  Is the source of unintentional release mostly due to combustion?

P5, L200-208” studied by S-S et al, who mention low biodegradability and high bioaccumulation potential in living organisms.”

P5, L203: “Different amounts of HCB residues have been detected in various substrates, including . . . “

P5, L180, P6, L205-207: Maybe just list the “dirty dozen” chemicals under the Stockolm Convention section on page 3.  The paragraph at the top of P6 is redundant with a lot of the material above it.  I would move the regulatory paragraph below (European Scientific Committee, Canadian Council info) to immediately after the Stockholm Convention section on page 3 as well.

Table 1: 

I’d put dieldrin after aldrin, since they are so closely related.

PCBs:  I believe there are still PCB-containing transformers in the US that have not been replaced, but I don’t know about the rest of the world.  https://www.epa.gov/pcbs/registering-transformers-containing-polychlorinated-biphenyls-pcbs

Occurrence and Incidence:

P7, L237:  “applicable to” do you mean applicable to the matrix?

P7, L248:  “Nevertheless, in despite” remove “in.” 

P7, L248-251:  Do you think that the pollutants in the study from India are continuing to be used, or that the elevated concentrations are due to old contamination of the growing area?  I guess I’m having trouble understanding the “ABC” code for Table 2.

P7-P9:  This section is really disorganized and uses a lot of technical jargon, but I’m having difficulty understanding what they’re trying to say.  This could be an issue with translation to English.  The table is much more clear than the text, and I think the authors are trying to put describe the table in the text, but they might be better off with just a few sentences describing the major points that the table makes:  that some feeds are used locally and others are sourced from outside the area (Poland studies, possibly Indian study).  That the profiles of the fodder grown locally are more likely to reflect the pollution sources (combustion of fossil fuels or combustion of municipal waste in these examples.)

P7, L251-254:  I am not understanding what you are trying to tell me in this sentence.  The topic is nonuniform interaction between release compounds and environmental receptors and different degrees of exposure of elements (the environmental receptors?) to pollutant actions?  Please clarify here.  I’m not sure what environmental receptors are.

P7, L256-260:  Are you saying that you determine pollution point-source by testing the environment (what part of the environment) for pollutants?  What are preliminary pollutant identification actions?  What kind of methodology model are you talking about?  Is it a mathematical model?

P7, L261-267:  This appears to be more about identifying point sources, and this is specifically on dairy farms.  Then it says that the amount of POPs in feed is likely to be proportional to the fat content (I think) but that sentence does not seem to relate to the rest of the paragraph.

P8, L268-276:  This paragraph is about determining point sources based on industrial pollution vs combustion, but it’s really difficult to follow.  There are grammatical and punctuation errors.

P8, L277-280:  Differentiating proportions of organic pollutants in an area where sources of pollution are unclear?

P8, L281-285:  Again, grammatical English errors, I think the authors are saying that the contaminants in the animal feed were from industrial and combustion point-sources?

P8, L289-291: explains that previous study looked at areas where fossil fuel combustion were expected to be the primary sources of contamination.

P8, L301-309:  Compares two studies that looked at combustion sources vs industrial sources, though they found the same contaminants?  Concluding that the same contaminants come from combustion and industry?  Or not?  Based on the table, it seems like the studies are mostly looking at combustion pollutants.

P8, L315-321:  Looks at a specific method (GC-HRMS) used in three studies that found similar pollutant profiles based on industry and combustion, I think?  Based on the table, I think they were looking for combustion products, but found industrial PCBs as well (which would make sense if there had been old electrical transformers in the area that came down).

P9, L322-331:  This paragraph is a little more clear, and I think the major point was that the source of the contamination was the feed, which was not produced locally.  This is a pretty important consideration. 

P9, L332-337:  More explanation of why it is important to consider the source of the feed.

P9, L338-342:  Goes back to the India study, which was mentioned P7, L248-251.  The feed was fodder, therefore most likely produced locally, but the source of contamination was not mentioned in the study.

P9, L343-347:  I think they’re saying that there needs to be more studies on fodder in livestock grazing/feeding areas.

Table 2:  You need to define the “Annex Stock. Conv.” The abbreviation confused me a for a little while, and the table should stand alone from the text.

Milk:

Table 3:  I think I would organize the table based on the source of the milk (farm vs market) first, just to make them easier to compare.  Again, I think the source of the feed (local vs shipped-in) will make a lot of difference.  I might move the milk section to above the feed section.  I would avoid trying to describe each paper in the section following the table and just make the big-picture points: the contaminants in the milk came from the feed that the cattle ate, and finding the source of the contaminants becomes less possible when the milk was collected from a shop vs a local dairy, and when the dairy used feed from an outside source vs grown locally.

P12, L390-402:  These paragraphs try to compare milk purchased in urban and industrialized areas vs rural areas, and I think this comparison is very tenuous, because most of the milk is likely to be produced in more rural areas and shipped to urban centers.  There may be some smaller countries where supply lines are more localized, but you would have to specify this in the discussion. 

P12: 403-407:  Unless the dairies are producing their own feeds locally, and only selling locally, I don’t think it would be possible to localize the source of contamination for the milk samples.  Certainly, if the milk was purchased from a market in an urban area, especially in heavily industrialized nations where milk companies pool milk from many dairies, it would be impossible to locate a point source.

P12, L408-417:  Here you compare two studies, one where milk was purchased from urban supermarkets that might be farther removed from the diary farms vs milk purchased in an urban area where the diary farms were close by the point of sale.  I think this comparison is important.

P12, L419-427:  It would be more meaningful to compare the milk taken from stores in these urban areas in these different countries if we had more information about food systems and supply chains.  If the milk is shipped from a location very far from the city, it really doesn’t tell us much about urban pollution.

P12-13, L428-435:  This is a key point that should be made earlier in this section: the pollutants came from the fodder that the animals ingested.

P13, L436-439:  This paragraph says its comparing the Romanian paper to the Indian paper, but they are dealing with different pollutants, and I’m really not sure what point the authors are trying to make.

List of POPs found:

Figures 1 and 2:  These are attractive figure, but I don’t think the year is as important as the location in this case?  Most of the OC pesticides were in India, based on the tables, so therefore all of the OCs were detected in 2018 because that is the year that that study was done, not because there was a sudden release of OCs that year.  I also don’t understand the list of dates on the Y axis of fig 2.

P14, L493-495:  There are some grammatical errors in this sentence that make it difficult to understand.  Also, since these are PERSISTANT organic pollutants, eliminating production and use will not immediately impact the amount of contamination in fodder and milk.

P15, L537:  What is the “specificity of pollutants”?

P15, L540: “not only environmental contamination can be blamed, but some elements can also be accidentally contaminated.”  What is “accidental contamination” and how is it different from “environmental contamination” here? 

 

References: 

2:  Stockholm Convention should be capitalized

12, 13, 26, 29, 30, 52, 62, 65, 71,75, 92, 93, 95, :  Except for the first word in the title of the journal article, the rest should not be capitalized.

25: Why is Korean in all caps?

97: “Gas” should be “gas”

Author Response

Response to referee # 2

First of all, we want to thank to referee #2 for his/her kind suggestions and for the valuable comments which indeed were useful in elaborating this review. Your observations helped us to improving our work.

Please find below our response accordingly.

Introduction

Point 1. P2, L76-778:  There have been many studies of POPs in food systems (PCBs, organochlorine insectides) dating back to the 1990s at least.

Response: We thank you for your suggestion, that was really useful. Indeed, as we wrote, initially it would be understood that the first studies regarding POPs in the food system would have appeared recently but we wanted to highlight how much researches areas on this topic has evolved, not saying that these were the first studies on this topic.

According your suggestion, minor sentences modifications were done in the paragraph. We also moved the sentences with the paragraph above.

 

Point 2. P2, L81-82:  What global anti-pollution measures specifically?  Maybe omit this sentence, since it is addressed in the next section.

Response: Regarding the global measures to reduce pollution referred in this paragraph, we specified about the great efforts that have been made to reduce pollution worldwide through various actions, such as the measures to reduce pollution from industrial facilities, reducing municipal waste, replacing harmful chemical substances with safer alternatives and others (measures mentioned by the European Commission in the European Union Action Plan "Zero pollution for air, water and soil", May 2021* - not mentioned as a distinct source in the text, we just wanted to highlight that actions to reduce pollution were taken constantly).

Since this topic is covered in the following section, we really appreciate your suggestion, we omitted this sentence and reworded the paragraph; the modifications can be tracked.

 *European Environment Agency (EEA), 2021 – Persistent organic pollutant emissions, available on–line https://www.eea.europa.eu/data-and-maps/indicators/eea32-persistent-organic-pollutant-pop-emissions-1/assessment-10, Mai 2021 .

Characterization:

Point 3. P3, L100:  “it is well recognized that various papers” I’d omit “it is well recognized that” and just say “various studies have demonstrated . . . “

 Response: Thank you for this suggestion. The modification was done and can be tracked. 

Point 4. P3, L103: “The characteristics and the toxic potential” this sentence isn’t referenced and doesn’t add much.  I’d omit this sentence and combined the following sentence (“Organic pollutants considered dangerous . . . “) with the paragraph below.

Response: Because this sentence isn’t referenced and doesn’t add much, according your suggestion, we omitted the sentence and combined with the paragraph below; please see the modified paragraph.  

 

Point 5. P3, L113: Replace “Nowadays” with “currently”  Maybe combined with the paragraph above it?

 Response: Thank you for this kind observation. The modification was done; we replaced the word and we combined this paragraph with the paragraph above it, according to the references listed.

 Point 6. P3, L118: either put a colon after OCPs or put the actives in parenthesis. 

Response: Because the enumeration of OCPs was unclear, after the abbreviation of organochlorine pesticides (OCPs) we inserted a colon, according to your suggestion.

  Point 7. P3, L122: Most, if not all, of these chemicals (PCBs, HCBs, PBBs, PFCs, et) had industrial

Response: According to your suggestion, we reworded this paragraph to highlight that these chemical compounds (PCBs, HCBs, PBBs, PFCs) are commercial chemicals with various industrial applications "thanks to their excellent physical and chemical properties"; indeed, they are produced intentionally for those applications (eg. combustion and chlorinated chemical industry processes). Also, we specified about their release from various chemical industries where they are used.

Point 8. P4, L141-142:  What are the three categories?  This single-sentence paragraph needs to be expanded to be more explanatory.

 Response: According to your suggestion, we expanded the single-sentence paragraph in order to clarify which are the three categories of persistent organic pollutants that were discussed in the mentioned references. Thus, the classification included the same three categories of POPs (OCPs, Industrial chemical pollutants, Combustion chemicals) as those mentioned in the Stockholm Convention. Since they were already discussed, we considered their enumeration and particular definition was no longer necessary, but information regarding their use and sources of release was presented, and some studies talking about their characteristics were mentioned. Please see the modifications in the paragraph.  

 Point 9. P4, L146-151:  “identified residual amounts of pesticides in areas of historical but not current OCP production.”  Can you explain what the time period between the industries closing and the environmental analyses?

 Response: Thank you for the opportunity to explain and to improve our work.  According to reference listed, the time period between the industries closing and the environmental analyses was approximately 24 years, the industries having intense activity until the 1990s, and the environmental analyses in the presented study was carried out in 2014. However, the authors considered that the amounts of organic pollutants identified in those matrices may come from the pollution generated from OCPs ex-factories from that area, especially because of low decomposition rates and the long half-life of the types of OCPs identified.

To clarify this point, we added in the paragraph the time period since the production of OCPs was closed in those factories. 

Point 10. P5, L152-155: Omit the first sentence, which restates the previous paragraph, and add the last sentence to the paragraph at the bottom of paged 4.

Response: Thank your for your kind suggestion, the modifications can be tracked. We omitted the first sentence which restates the previous paragraph and we added the last sentence into the paragraph above.

  Point 11. P5, L157-158:  “have been reported as the main sources of pollution specific to some of the most toxic OCPs.”  Can this be shortened and clarified to say “are the main sources of some of the most toxic OCPs”?

 Response: Thank you for this useful observation. We replaced the words, according your suggestion. Please see the paragraph.

  Point 12. P5, L166: “omit “after these years” (redundant after “almost two decades”)

 Response: Thank you for this observation. Indeed, because we tried to clarify the subject as well as possible, we used too many explanations in this context. Therefore, according to your suggestion, we omitted the redundant words.  

 Point 13. P5, L168: OCP should not be plural before “metabolites”

 Response:  According your suggestion, we replaced OCP to singular; the modification can be tracked.

  Point 14. P5, L187-188:  I’m having difficulty with this sentence “To all this is added the negative impact created by unintended sources . . . no control evidence to date.”  I don’t think it adds more information than the sentence about unintentional release in the previous paragraph.  Is the source of unintentional release mostly due to combustion?

Response: We thank you for the opportunity to explain. As you previously suggested, we understand that "unintentionally" is not an appropriate word to describe the emission of PCBs as a residue of various chemical industrial processes. Indeed, we associated "intentionally" production with chemical compounds commercially produced for various industrial applications and "unintentionally" release with residues from combustion.

Also, regarding the meaning of the sentence and related to the above mentioned, we wanted to highlight that the measures to reduce the release of PCBs were applied only with regard to the production of such substances with different industrial applications, but we did not find clear measures to limit the release of these pollutants as a residue following the industrial processes in which they are used (e.g. replace them with products with similar applications).

Considering that the informations are unclear and understanding that the meaning of the word "unintentionally" is inappropriate, we reformulated the paragraph for explaining the informations about PCBs; the modifications can be tracked.

Point 15. P5, L200-208” studied by S-S et al, who mention low biodegradability and high bioaccumulation potential in living organisms.”

 Response: Thank you for the observation. The modifications were made, according your suggestion.

Point 16. P5, L203: “Different amounts of HCB residues have been detected in various substrates, including . . . “

Response: We replaced ”Environmental elements” with ”substrates”, according to your suggestion.

Point 17. P5, L180, P6, L205-207: Maybe just list the “dirty dozen” chemicals under the Stockolm Convention section on page 3.  The paragraph at the top of P6 is redundant with a lot of the material above it.  I would move the regulatory paragraph below (European Scientific Committee, Canadian Council info) to immediately after the Stockholm Convention section on page 3 as well.

Response: According to your useful suggestions, we considered it appropriate to move the list of "dirty dozen" chemicals under Stockholm Convention on the section above; the 12 substances was presented in Table 1.

We checked carefully and we rewrite the paragraph to present a brief description of the combustion chemicals, as we did for the other two groups of pollutants, presented above. We also move the regulatory paragraph after the Stockholm Convention, according to your suggestion.

Table   1

Point 18. I’d put dieldrin after aldrin, since they are so closely related.

Response: Because there are closely related, we put dieldrin after aldrin. Thank you for your suggestion.

Point 19. PCBs:  I believe there are still PCB-containing transformers in the US that have not been replaced, but I don’t know about the rest of the world.  https://www.epa.gov/pcbs/registering-transformers-containing-polychlorinated-biphenyls-pcbs

Response: We checked carefully, according your suggestion. Thank you for this useful observation. Indeed, in the US are still PCB-containing transformers that have not been replaced. There are also other countries, for example England and Wales were, if some conditions are met (the fluids in transformers do not contain more than 0.005 % by weight of PCBs, or more than 0.05 dm³ of PCB), is no necesarry to remove the transformers and can continue to hold them until the end of their useful life, at which point they must then be decontaminated or disposed of.

*https://www.gov.uk/government/publications/transformers-containing-pcbs-new-rules-rps-246/transformers-containing-pcbs-new-rules-rps-246

Occurrence and Incidence:

Point 20. P7, L237:  “applicable to” do you mean applicable to the matrix?

Response: Yes, we talked about the analytical methods and techniques applicable to the matrix. We added the word, according your suggestion.

Point 21. P7, L248:  “Nevertheless, in despite” remove “in.” 

Response: We remove the word suggested. Thank you for your observation.

Point 22. P7, L248-251:  Do you think that the pollutants in the study from India are continuing to be used, or that the elevated concentrations are due to old contamination of the growing area?  I guess I’m having trouble understanding the “ABC” code for Table 2.

Response: About the presence of some OCPs in the different matrices analyzed, although they were included in Annex A of the Stockholm Convention (so they are no longer produced and used as such), we wanted to say that the measures applied to reduce their emission in the environment are particularly useful, but with these measures, we cannot talk about a total reduction of pollution because important residues persist in the soil; so, to consider a substantial reduction of pollution with these compounds it takes a long time for them to decompose. Therefore, the results of these measures will continue to appear, so this means that these pollutants still continue to be a concern for us.

As for the ABC code used in Table 2, it is taken according to the Stockholm Convention (http://chm.pops.int/TheConvention/ThePOPs/ListingofPOPs/tabid/2509/Default.aspx) and each letter represents the code of an annex from the convention with specific action measures, depending on the degree of risk of the chemicals it contains in the list.

  A – includes high-risk pollutants, the production and use of which is no longer allowed;

"Parties must take measures to eliminate the production and use of the chemicals listed under Annex A"

B – limiting their use as rarely as possible;

"Parties must take measures to restrict the production and use of the chemicals listed under Annex B in light of any applicable acceptable purposes and/or specific exemptions listed in the Annex.

C – their intended use is accepted only under specific conditions;

"Parties must take measures to reduce the unintentional releases of chemicals listed under Annex C with the goal of continuing minimization and, where feasible, ultimate elimination."

We want to thank from this suggestion; because the paragraph is not clear enough, we added additional explanations, according your suggestion.

Point 23. P7-P9:  This section is really disorganized and uses a lot of technical jargon, but I’m having difficulty understanding what they’re trying to say.  This could be an issue with translation to English.  The table is much more clear than the text, and I think the authors are trying to put describe the table in the text, but they might be better off with just a few sentences describing the major points that the table makes:  that some feeds are used locally and others are sourced from outside the area (Poland studies, possibly Indian study).  That the profiles of the fodder grown locally are more likely to reflect the pollution sources (combustion of fossil fuels or combustion of municipal waste in these examples.)

Response: We want to thank for the suggestion and for the opportunity to clarify our ideas. Your suggestions help us to improve our work and using your observations, some modifications were made on this section; modifications can be tracked. 

Point 24. P7, L251-254:  I am not understanding what you are trying to tell me in this sentence.  The topic is nonuniform interaction between release compounds and environmental receptors and different degrees of exposure of elements (the environmental receptors?) to pollutant actions?  Please clarify here.  I’m not sure what environmental receptors are.

Response: We want to thank for the suggestion and for the opportunity to clarify our ideas. In this paragraph we said that the subject related to pollution cannot be generalized. Therefore, it is a complex subject, since the interaction between the chemical compounds released into the environment and the environmental substrates is different from one component to another (soil, water, air, plants ), which thus implies challenges in understanding how each pollutant behaves in the contaminated substrate.

  e.g. Pollutants in the air are circulated along the food chain without bioaccumulate, which shows that air is not a substrate whose particularity allows it to store pollutants for long periods of time, unlike plants, where pollutants can arrive once by transfer from the soil, but also by deposition from the air, and some plant properties (e.g. fat content) can favor their bioaccumulation.

To clarify the ideas, according to your suggestion, we rewrote the paragraph; the modifications can be tracked.

Point 25. P7, L256-260:  Are you saying that you determine pollution point-source by testing the environment (what part of the environment) for pollutants?  What are preliminary pollutant identification actions?  What kind of methodology model are you talking about?  Is it a mathematical model?

Response: Hope that we thinked correctly, we said that if several analyzes are made regarding the level of contamination of the various substrates (water, plants, soil) in a certain areas, there is a possibility that at some point to identify a typical contamination profile, so, that if there are proven or potential sources of contamination, it would be possible to rank the risks; thus biomonitoring is more effective (quick measures can be taken in case of high risks). It is important to note that we cannot discuss about a point- source of pollution for each type of pollutant, it is only a method by which the presence of some pollutants can be anticipated for the efficiency of control actions, but it is a measure that requires great initial efforts and a long duration of time to achieve (carrying out numerous pollutant analyzes to be able to establish a point-source of pollution is a complex process), but it can be a method with good results.

Preliminary pollutant identification actions refer to the initial monitoring of possible pollutants that could be found and may refer for example to the identification or prediction of environmental factors that could favor the risk of contamination (as mentioned by Battisti et al., 2020).

The methodological model mentioned, as you rightly said, is a mathematical model of risk ranking for some farms (in the example provided by Battisti et al., 2020) using a scale of standardized scores for each identified risk factor in order to finally a risk-based classification is obtained. Thus, the score for seven risk factors was entered into a mathematical formula to estimate the probability that a farm has a higher level of contamination compared to other farms located in the same area.

Considering your suggestions very useful, we rewrote the paragraph.

Point 26. P7, L261-267:  This appears to be more about identifying point sources, and this is specifically on dairy farms.  Then it says that the amount of POPs in feed is likely to be proportional to the fat content (I think) but that sentence does not seem to relate to the rest of the paragraph.

Response: We thank you for this observation. The paragraph was rewrote and the modifications can be tracked.

Indeed, the assessment of the possibility of contamination is more than the identification of environmental factors that favor pollution and the identification of point-sources of pollution. Such an example is shown for the dairy cow farms, where it is highlighted that the particularities of the feed are also important and can provide clues about the presence of some pollutants (e.g. the fat content of the fodder is proportional to the amount of POP that could be found in the fodder).

Point 27. P8, L268-276:  This paragraph is about determining point sources based on industrial pollution vs combustion, but it’s really difficult to follow.  There are grammatical and punctuation errors.

Response: We want to apologize for the grammatical and punctuation errors, some English terminology modifications were done. According to your suggestion, we also rewrote the point sources of pollution based on industrial pollution and combustion.

Point 28. P8, L277-280:  Differentiating proportions of organic pollutants in an area where sources of pollution are unclear?

Response: We want to thank you the possibility to explain our ideas for improving our work. Indeed, the expression used was a bit exaggerated, in the paragraph reworded we specified that, in the mentioned works, no particular reference was made to the sources of pollution from industry and combustion, which thus suggests that in some works the pollutants found were not always associated with point-sources of pollution, but only their presence at a quantitative level was confirmed.

According to your suggestion, we rewrote the point sources of pollution based on industrial pollution and combustion. Indeed, the referee is right, there was some grammatical and punctuation errors and they were replaced; the modifications can be tracked. 

Point 29. P8, L281-285:  Again, grammatical English errors, I think the authors are saying that the contaminants in the animal feed were from industrial and combustion point-sources?

Response: As you mentioned in your suggestion, the contaminants in the animal feed were from industrial and combustion point-sources. Indeed, the referee is right, we replaced some terminology; please see the modifications.

Point 30. P8, L289-291: explains that previous study looked at areas where fossil fuel combustion were expected to be the primary sources of contamination.

Response: The referee is right, we confirm this paragraph explains that previous study looked at areas where fossil fuel combustion were expected to be the primary sources of contamination. We wanted to present an example to demonstrate that, by monitoring the primary sources of contamination, the presence of some pollutants could be anticipated. Thus, in the mentioned study it was expected that fossil fuel combustion would be the primary source of contamination, so the study wanted to confirm that different point sources of pollution can be quickly associated with certain pollutants (eg. Transport emissions - we can expect to the PAHs to be present).

Point 31. P8, L301-309:  Compares two studies that looked at combustion sources vs industrial sources, though they found the same contaminants?  Concluding that the same contaminants come from combustion and industry?  Or not?  Based on the table, it seems like the studies are mostly looking at combustion pollutants.

Response: The two studies compare the different sources of pollution from which two groups of pollutants belonging to the same category can come: Combustion chemicals (PCDD/F and HAP). It was reporting that PCDD/F represent residues from incomplete combustion in industry, waste incinerators (stationary sources of pollution), and PAHs, although they are also Combustion chemicals, come from emissions, especially combustion from transport (mobile sources).

 PCDD/F and HAP = Combustion chemicals, but PCDD/F = come mainly from stationary sources; PAH = mainly come from mobile sources.

So we do not generalize that all Combustion chemicals come from mobile sources or from stationary sources, but can be both.

We apologize that the paragraph was not so clear. In order to not confuse incomplete combustion in industry with chemical emissions from industry, some modifications were done: we added some additional information and we deleted the redundant sentences.

Point 32. P8, L315-321:  Looks at a specific method (GC-HRMS) used in three studies that found similar pollutant profiles based on industry and combustion, I think?  Based on the table, I think they were looking for combustion products, but found industrial PCBs as well (which would make sense if there had been old electrical transformers in the area that came down).

Response: We want to thank you for the opinion on this topic and for the additional explanations.

Indeed, as you well understood, the GC-HRMS method was used in three studies where similar pollutant profiles were found based on industry and combustion. Their goal was to find both combustion chemicals (PCDD/Fs) and also industrial PCBs, but, based on the table, it is clear that industrial PCBs were found only in one study.

Some sentences modification were done: we added some additional information and we deleted the redundant sentences.

Point 33. P9, L322-331:  This paragraph is a little more clear, and I think the major point was that the source of the contamination was the feed, which was not produced locally.  This is a pretty important consideration. 

Response: We thank you for the positive reviews, which we will be certainly very useful for improving our work. Indeed, in this case, the contamination was the feed, which was not produced locally.

Point 34. P9, L332-337:  More explanation of why it is important to consider the source of the feed.

Response: According your very useful suggestion, we added more explanation of why it is important to consider the source of the feed starting from the example mentioned in another previously used reference. Ensuring traceability and also the economic negative consequences on the animals and productions obtained were among the most important mentions added; please see the paragraph. 

Point 35. P9, L338-342:  Goes back to the India study, which was mentioned P7, L248-251.  The feed was fodder, therefore most likely produced locally, but the source of contamination was not mentioned in the study.

Response: Thank you for your observation. Because the sources of pollution in the studied areas were not mentioned in the study, as you understand, we considered that the source of the feed is most likely local.

Point 36. P9, L343-347:  I think they’re saying that there needs to be more studies on fodder in livestock grazing/feeding areas.

Response: Thank for this very useful suggestion. Indeed, we`re saying that there needs to be more studies on fodder in livestock grazing or feeding areas. Thus, some modifications were done; please see the paragraph.  

Point 37. Table 2:  You need to define the “Annex Stock. Conv.” The abbreviation confused me a for a little while, and the table should stand alone from the text.

Response: We want to thank you for this kind observation. We added “Annex Stock. Conv.” definition. 

Milk

Point 38. Table 3:  I think I would organize the table based on the source of the milk (farm vs market) first, just to make them easier to compare.  Again, I think the source of the feed (local vs shipped-in) will make a lot of difference.  I might move the milk section to above the feed section.  I would avoid trying to describe each paper in the section following the table and just make the big-picture points: the contaminants in the milk came from the feed that the cattle ate, and finding the source of the contaminants becomes less possible when the milk was collected from a shop vs a local dairy, and when the dairy used feed from an outside source vs grown locally.

Response: Thank you for these extremely helpful suggestions. We reorganized the table according to the source of the milk to make them easier to compare and we mentioned the source of the food in the first paragraph (only in one case the food was shipped-in [28]).

Paragraph modifications were done: we use your suggestion for rewrote the milk section and we eliminated redundant data; please see the milk section. We move also the milk section to above the feed section. For each of the suggestions below, we will mention how it was used.

Also, because of moving the milk section additional modifications were necessary: e.g. tables number, the references number; the modifications can be tracked.

Point 40. P12, L390-402:  These paragraphs try to compare milk purchased in urban and industrialized areas vs rural areas, and I think this comparison is very tenuous, because most of the milk is likely to be produced in more rural areas and shipped to urban centers.  There may be some smaller countries where supply lines are more localized, but you would have to specify this in the discussion. 

Response: Thank you for this observation. We used your suggestion to reword these paragraphs. We have thus mentioned the difficulty of identifying the sources of pollution in most of the works due to the fact that in the presented works no information is known about the source of milk and the source of animal feed. Also, the paragraph was moved below the paragraphs that presented two examples of studies that allowed the identification of pollution sources.

Please find the paragraph modified according to  your suggestions.

Point 41. P12: 403-407:  Unless the dairies are producing their own feeds locally, and only selling locally, I don’t think it would be possible to localize the source of contamination for the milk samples.  Certainly, if the milk was purchased from a market in an urban area, especially in heavily industrialized nations where milk companies pool milk from many dairies, it would be impossible to locate a point source.

Response: According to your suggestion, we eliminated the redundant information (those that were not relevant in the context of the study) and we included the main idea mentioned in your suggestion in a single paragraph (the same paragraph as above) by which to render the impossibility of identification to all sources of pollution, presenting the arguments suggested by you (impossible to locate a point source because of the milk purchased from a market in an urban area, especially in heavily industrialized nations where companies pool milk from many dairies). Thank you again for this suggestion.

Point 42. P12, L408-417:  Here you compare two studies, one where milk was purchased from urban supermarkets that might be farther removed from the diary farms vs milk purchased in an urban area where the diary farms were close by the point of sale.  I think this comparison is important.

Response: Thank you for the positive reviews. We used the suggestion and we added this comparison to show the importance of knowing the source of the milk. We moved this comparison to the paragraphs below, where we discussed urban pollution sources.

Point 43. P12, L419-427:  It would be more meaningful to compare the milk taken from stores in these urban areas in these different countries if we had more information about food systems and supply chains.  If the milk is shipped from a location very far from the city, it really doesn’t tell us much about urban pollution.

Response: According to your suggestion, we considered it appropriate to remove the redundant information that did not say much about urban pollution, especially because above we tried to show the importance of the sources of urban pollution through the two studies used in the comparison.

Point 44. P12-13, L428-435:  This is a key point that should be made earlier in this section: the pollutants came from the fodder that the animals ingested.

Response: Thank you for this suggestion. We used this key point, we moved it earlier in the section and we tried in the paragraphs below to argue this information through several studies.

Point 45. P13, L436-439:  This paragraph says its comparing the Romanian paper to the Indian paper, but they are dealing with different pollutants, and I’m really not sure what point the authors are trying to make.

Response: Through this paragraph we tried to make the connection between two works that we considered similar because both studied OCPs. Indeed, because they did not study exactly the same types of OCPs, we consider this paragraph irrelevant and we give up the redundant information.

List of POPs found:

Point 46. Figures 1 and 2:  These are attractive figure, but I don’t think the year is as important as the location in this case?  Most of the OC pesticides were in India, based on the tables, so therefore all of the OCs were detected in 2018 because that is the year that that study was done, not because there was a sudden release of OCs that year.  I also don’t understand the list of dates on the Y axis of fig 2.

Response: We thank you for this observation. We put the location in the figures, instead of the year. Indeed, we understand that the year is not relevant in this case because it only shows the year of the study, not the year of release of pollutants. The list of dates on the Y axis of figure 1 and 2 indicates the year when the chemical compound was included in one of the annexes of the Stockholm Convention. We added additional explanations below figures.

Point 47. P14, L493-495:  There are some grammatical errors in this sentence that make it difficult to understand.  Also, since these are PERSISTANT organic pollutants, eliminating production and use will not immediately impact the amount of contamination in fodder and milk. 

Response: Thank you for your observation. We apologize for this grammatical errors, they were replaced with English terminology; please see the paragraph.

In this paragraph we said that it is important to understand that the measures applied for eliminating production and use, will see their results in the future time period. So, because these pollutants still persist in the environment, it is important to understand that they still represent an important concern for us and we must continue to act to reduce pollution.

We carefully checked the paragraph to be according your suggestion.

Point 48. P15, L537:  What is the “specificity of pollutants”?

Response: Thank you for the opportunity to improve our work. When we mentioned ”specificity of pollutants” we talked about their characteristics, including: persistence in the environment/ resistance to degradation/ decomposition time in the environment, lipophilic character, bioaccumulation capacity or transfer capacity in the food chain. 

We replaced ”specificity of pollutants” with ”characteristics of pollutants”.

Point 49. P15, L540: “not only environmental contamination can be blamed, but some elements can also be accidentally contaminated.”  What is “accidental contamination” and how is it different from “environmental contamination” here? 

Response: Thank you for giving us the opportunity to explain our ideas. We said ”accidental contamination” for the contamination produced as a result of an accident or as a result of an action carried out without permission, therefore an unpredictable event. We considered ”Environmental pollution” the result of willful, intentional anthropogenic actions.

If normally, accidental contamination can be included in environmental contamination, in this case the idea was that environmental contamination referred to any kind of intentional contamination, adding the risk of accidents that determine an unpredictable contamination in the environment that we called in this case ”accidental contamination”. 

            References: 

Point 50.    2:  Stockholm Convention should be capitalized

Response: The modifications were done, we capitalized the words. Thank you for the observation.

Point 51.  12, 13, 26, 29, 30, 52, 62, 65, 71,75, 92, 93, 95, :  Except for the first word in the title of the journal article, the rest should not be capitalized.

Response: The modifications were done, according your suggestion. Thank you for this observations.

Point 52.       25: Why is Korean in all caps?

Response: We used ”Korean” in all caps because of the title of article ( https://doi.org/10.3390/ijerph13030270 ”Korean” is with all caps in the title). Thank you for this observations. The modifications were done, according your suggestion.

Point 53.     97: “Gas” should be “gas”

Response: The modifications were done, according your suggestion. Thank you for the observation.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

This reviewer thanks the authors for making the time to edit the manuscript.  However, there are several edits/suggestions this reviewer has regarding this manuscript revision (see below).

Overall:

1.     There are several places in the manuscript where the authors describe, individually, how the POPs play a role in environmental contamination, how they bioaccumulate, how they are persistent in the environment, etc.  The authors should consider combining all of this information in the introduction section to eliminate the redundancy throughout the manuscript.  This reviewer finds themselves reading this information over and over again and would appreciate just having this summarized in the introduction.

2.     The tables have abbreviations in them that need to be spelled out completely or changed. For example, in Tables 2 and 3, spell out or change the headings labeled “In. Chem. Comb.” and “Annex Stock. Rev. Conv.”  Creating column borders might make these tables easier to read as well.

3.     How do the levels of the different type of POPs compare to:

a.      The enforceable action levels?

b.     The minimum tolerance level in feed or other source contaminant?

                                                  i.     For example, the FDA has a tolerance level for PCBs in food/feedstuffs between 0.2 to 3 ppm (200 ppb to 3,000 ppb). These levels are much higher than what is reported in the manuscript. Do the authors have any information on this that they can provide in the discussion to help the reader understand, appreciate, and put into context the data that is being presented?

4.     See comment # 41 (Lines 232-234 and also Table 2):

a.      This reviewer finds it hard to believe that HPLC with fluorescence detection can detect ppb levels of the compounds listed in table 2. Without reviewing the original references and methodology, this reviewer cannot assess the credibility of the studies mentioned. Since there are only 2 of these studies referenced in the manuscript, this reviewer recommends deleting associated data from references 86 and 92 and suggests the reviewers include this information as a point of discussion in the discussion section if the authors feel compelled to include it.

 

 

Manuscript:

 

5.     Lines 31-35 – Suggest deleting paragraph and adding this sentence to 2^nd paragraph:

a.      “Environmental pollution represents a threat to human health, quality of life, and the natural function of ecosystems.”

6.     Line 36: Do the authors mean environmental pollution instead of environmental degradation?

7.     Lines 36-37:  Suggest changing to “Whether intentional or accidental, humans can…”

8.     Lines 40-43:  Suggest changing to “Environmental pollution has been widely studied...”

a.      Do the authors mean “the most prevalent pollutants” instead of the “most important properties?” If “properties,” to what properties of each of the pollutants are they referring?

9.     Lines 44-45: Suggest changing to “Recent increases in industrial and technological activities have led to high emissions of pollutants.”

10.  Line 47: delete comma after “society”

11.  Line 49: delete “and less from natural sources.” This is implied by anthropogenic sources. Please define “POPs” first here – spell out acronym for readers since this is the first place authors use the acronym.

12.  Live 50: delete “resistant” and consider changing sentence to “compounds which are resistant to chemical…”

13.  Line 53: delete entire first sentence

14.  Line 54: Consider changing to “character of POPs facilitates…”

15.  Lines 58-60: The way this paragraph reads, it seems like a reference should be included at the end of sentence. Sentence needs reworded and can be combined with paragraph below it.

16.  Lines 61-63: Sentence structure needs editing.

17.  Lines 63-65: Consider changing to “Food samples that have been tested were shown to be contaminated with several types of POPs.”

18.  Line 66:  Consider changing to “Feed is particularly implicated in the transfer and…”

19.  Line 69:  Consider changing to “In recent years, most research has included studying transfer of ….. and their accumulation and excretion in milk.”  The last part of the sentence in the manuscript as written by the authors is confusing.

20.  Lines 72-74: The sentence structure makes it difficult to understand the message the authors intend on communication. Please consider revising.

21.  Line 75: Consider changing to “This review aims to describe different classes of POPs as well as to discriminate between specific sources of pollution as it relates to the concentrations of POPs in feed and milk.

22.  Lines 77-78: The sentence “there were analysed…” is confusing. Please revise.

23.  Lines 81-82: Consider deleting this sentence.

24.  Lines 83-85: Consider changing sentence to “POPs consist of a group of halogenated, lipophilic, organic compounds that persist in the environment.

25.  Lines 87-88: This sentence is redundant as the authors have explained this other times previously in the manuscript.

26.  Lines 89-90: Consider revising to “Regulations addressing these organic pollutants have aimed at reducing the consequences of pollution, eliminating existing pollutants, or preventing potential contamination.” Combine this sentence with the paragraph below it.

27.  Lines 92-95: Consider revising to “…the so called “dirty dozen,” were included in 2001….”

28.  Line 103: Consider revising to “agricultural usage, which include organochlorine pesticides (OCPs) such as:…”

29.  Line 110: Consider revising to “compounds that are formed from incomplete…”

30.  Line 114: 33 PAHs were described by the European…”

31.  Table 1:

a.      Delete “(found in small amounts as such) from Aldrin

b.     Consider revising to “Contamination in dairy products and meat.”

c.      Lines denoting rows missing between Endrin and Mires and Toxaphene

d.     Consider revising to “Includes 209 different types of PCBs”

e.      Consider revising to “Residues of the pesticide production” for HCB

f.      Consider revising to “Highly toxic chemical compounds originating from …” for PCDDs

g.     Consider revising to “…human tissue through contaminated food.” And “Low concentrations in the environment, but are persistent, bioaccumulate, and are easily transferred.”

32.  Lines 133-136: It is difficult to understand what the message is that the authors are trying to explain in this long sentence. The authors need to revise this to improve readability and understanding.

33.  Lines 137-139:  First sentence – consider deleting this sentence or major revision.

34.  Line 142: Consider revising to “OCP residues in samples”

a.      Delete the “s” after OCP in line 151 as well

35.  Line 166: What is meant by “intentionally produced?”  Do the authors mean “inadvertently?”

36.  Lines 172-174: The sentence “PCBs released…” – the language used in this sentence makes it hard to read. For example, “processes have also a negative contribution to…”  Consider rephrasing sentence structure.

37.  Line 179: Consider revising to “foodstuffs seem to be the main route for human exposure.”

38.  Line 188: Consider revising to “Regarding combustion chemicals…”

39.  Line 197: Consider revising to “by various authors.”  The authors use the phrase “around the world” a lot throughout this manuscript.

40.  Line 198: Consider revising to “The literature describes pollutant…”

41.  Lines 232 and 234: Delete “the techniques of the”

42.  Line 238: What is considered an “important” amount of OCPs? Do the authors have actionable levels of OCPs to show that detecting 0.01 ppb to 41.4 ppb are “important” or significant levels?

43.  Line 244: Change sentence to “In most situations, the feed was implicated as the source of POPs in dairy animals, which ultimately resulted detectable levels of POPs in milk.”

44.  Line 247: Change to “former, greatest OCP producers in Romania.”

45.  Lines 256-262: Sentence starting with “Costera et al.” – this sentence is a run-on sentence (it is too long). Please condense and rewrite this.

Author Response

Response to referee # 1

First of all, we want to thank to referee #1 for his/her kind suggestions and for the valuable comments which indeed were useful in elaborating this review. Also, we want to thank you for appreciating our efforts to improve this paper; your observations helped us to improving our work.

Please find below our responses accordingly (in the manuscript, the comment are noted with (R1)).

Point 1. There are several places in the manuscript where the authors describe, individually, how the POPs play a role in environmental contamination, how they bioaccumulate, how they are persistent in the environment, etc.  The authors should consider combining all of this information in the introduction section to eliminate the redundancy throughout the manuscript.  This reviewer finds themselves reading this information over and over again and would appreciate just having this summarized in the introduction.

Response: We thank you for this useful suggestion and we really appreciate it. Since this topic about the role of POPs in environmental contamination is all covered in Introduction, we combined and summarized all of this information in this section and we reworded some paragraphs. The redundant informations was founded especially in section 2 (Characterization of POPs), so, in some cases we omitted that information, and if there was other new information on the same topic, it were added to the Introduction paragraphs.

Point 2. The tables have abbreviations in them that need to be spelled out completely or changed. For example, in Tables 2 and 3, spell out or change the headings labeled “In. Chem. Comb.” and “Annex Stock. Rev. Conv.”  Creating column borders might make these tables easier to read as well.

Response: We thank you for all this kind suggestions. In Table 1 and in Table 2, we changed completely the headings labeled and we replaced with the symbols for the chemicals targeted by the Stockholm Convention; their description can be found at the bottom of the table.

We also modified the abbreviations:

-  ”Annex Stock. Conv” = Annex* and using (*) we explain in the bottom of the table what we taking about

- ”Ref” = we spelled out completely

Regarding the column bordes, we appreciate your suggestions that tables to be easier to read but we think that if we put column borders then we do not respect the template of the paper (if we misunderstood, we kindly ask you to excuse us).

Point 3. How do the levels of the different type of POPs compare to:

1. The enforceable action levels?
2. The minimum tolerance level in feed or other source contaminant?
3. For example, the FDA has a tolerance level for PCBs in food/feedstuffs between 0.2 to 3 ppm (200 ppb to 3,000 ppb). These levels are much higher than what is reported in the manuscript. Do the authors have any information on this that they can provide in the discussion to help the reader understand, appreciate, and put into context the data that is being presented?

Response: The levels of different type of POPs presented in the studies listed are not comparable with enforceable actions levels or with minimum tolerance levels in different products. As you rightly mentioned, the levels mentioned in the manuscript are much lower than these and, after us, this is a good think because we wanted to emphasize that our efforts to reduce environmental pollution must be kept constant and must be continuous. Highlighting also especially the sources of contamination of the environment with POPs is important for reader to understand why everyone must care about the relation with the environment.

In order for a reader to understand and put into context the data that is being presented, we consider it useful, according to your suggestion, to adding any paragraph to mention the relevance of the data presented so that the reader can make a comparison with some enforceable levels and thus, they will understand our message.

Point 4. See comment # 41 (Lines 232-234 and also Table 2):

2. This reviewer finds it hard to believe that HPLC with fluorescence detection can detect ppb levels of the compounds listed in table 2. Without reviewing the original references and methodology, this reviewer cannot assess the credibility of the studies mentioned. Since there are only 2 of these studies referenced in the manuscript, this reviewer recommends deleting associated data from references 86 and 92 and suggests the reviewers include this information as a point of discussion in the discussion section if the authors feel compelled to include it.

Response: We thank you for your suggestion, that was really useful. We understand the issues about the use of HPLC to detect the compounds listed in table 2. According your suggestion, modifications were done in the Table 2:  we deleted associated data from references mentioned.  We only kept this information as a point of discussion in the discussion section, as it was initially.

Manuscript:

Point 5. Lines 31-35 – Suggest deleting paragraph and adding this sentence to 2^nd paragraph:

1. “Environmental pollution represents a threat to human health, quality of life, and the natural function of ecosystems.”

Response: Thank you for this kind observation. The modification was done; we deleted the paragraph and we added the sentence with the paragraph below it, according to your suggestion.

 Point 6. Line 36: Do the authors mean environmental pollution instead of environmental degradation?

Response: Thank you for the opportunity to explain and to improve our work. Indeed, we mean environmental pollution, so, to clarify this point, we replaced ”degradation” to ”pollution” in the sentence.  

 Point 7. Lines 36-37:  Suggest changing to “Whether intentional or accidental, humans can…”

Response: Thank you for this useful suggestion. We changed the words, according your suggestion. Please see the paragraph.

 Point 8.   Lines 40-43:  Suggest changing to “Environmental pollution has been widely studied...”

1. Do the authors mean “the most prevalent pollutants” instead of the “most important properties?” If “properties,” to what properties of each of the pollutants are they referring?

      Response: Thank you for the suggestions because it help us to improve our work. Using your observations, some modifications were made on this sentence: we considered it appropriate to mention also that we indeed talking about the most prevalent pollutants. In the same time, initially, we talked about the most important properties of the most prevalent pollutants, listed in the next sentence: long lasting persistence, non-degradability, eco-toxicological risks. Thus, we combined your suggestions hoping that the sentence will be more clear.

Point 9. Lines 44-45: Suggest changing to “Recent increases in industrial and technological activities have led to high emissions of pollutants.”

Response: Thank you for this suggestion. The modification was done and can be tracked. 

Point 10. Line 47: delete comma after “society”

Response: According your suggestion, we deleted the comma. 

 Point 11. Line 49: delete “and less from natural sources.” This is implied by anthropogenic sources. Please define “POPs” first here – spell out acronym for readers since this is the first place authors use the acronym.

      Response: According your suggestion, we deleted the listed words. With respect to your observation, we want to mention, respectful, that this is not the first place where we used the acronym for POPs. We use first this acronym in the paragraph above it: ” Generated from various developing productive sectors, persistent organic pollutants (POPs) …. ” and we spelled out the acronym there.

Point 12. Live 50: delete “resistant” and consider changing sentence to “compounds which are resistant to chemical…”

      Response: Thank you for this suggestion. We deleted the listed word and we replaced some words in the sentence, according your suggestion. This change meet the changes made at Point 1 from the references listed, when we combined and summarized all the information about the role of POPs for environmental pollution.  We tried to adapt your suggestion to the modifications made at Point 1 and we hope that now is better.

 Point 13. Line 53: delete entire first sentence

Response: First sentence deleted, according your suggestion.

 Point 14. Line 54: Consider changing to “character of POPs facilitates…”

Response: Thank you for your suggestion. After we deleted the first sentence, we changed the second sentence using your suggestion; the modification can be tracked.

 Point 15. Lines 58-60: The way this paragraph reads, it seems like a reference should be included at the end of sentence. Sentence needs reworded and can be combined with paragraph below it.

Response: Thank you for the opportunity to improve our work. Indeed, at the end of the sentence was missing a reference and we added it (it is a new reference, please see it on the references section). According your useful suggestion, we reworded the mentioned sentence and we combined it with the paragraph below it. Please see the modified paragraph.

 

 Point 16. Lines 61-63: Sentence structure needs editing.

Response: Thank you for this suggestion. Respectful to your opinion, we only change the order of some words in the sentence structure considering, that modification match better now the previous sentence reworded.

 Point 17. Lines 63-65: Consider changing to “Food samples that have been tested were shown to be contaminated with several types of POPs.”

Response: We used your kind suggestion to improve this sentence; the modification can be tracked.

 Point 18. Line 66:  Consider changing to “Feed is particularly implicated in the transfer and…”

Response: The modification was done, according your suggestion; please see it in the paragraph.

 Point 19.  Line 69:  Consider changing to “In recent years, most research has included studying transfer of ….. and their accumulation and excretion in milk.”  The last part of the sentence in the manuscript as written by the authors is confusing.

Response: We thank you for your kind suggestion, it is was very helpful for us to explain clearly our ideas. Using your suggestion, we considered appropriate to changed the sentence to improve it.

 Point 20. Lines 72-74: The sentence structure makes it difficult to understand the message the authors intend on communication. Please consider revising.

Response: Thank you for this observation. Indeed, because we tried to clarify the subject as well as possible, we used too many explanations in this context. Therefore, according to your suggestion, we revised the sentences; please see the modified paragraph. 

 Point 21.  Line 75: Consider changing to “This review aims to describe different classes of POPs as well as to discriminate between specific sources of pollution as it relates to the concentrations of POPs in feed and milk.

Response: Thank you for your kind suggestion. According to the reference listed, we considered it appropriate to change this sentence; the modification can be tracked.

 Point 22. Lines 77-78: The sentence “there were analysed…” is confusing. Please revise.

      Response: Thank you for this observation. Because the sentence can be confusing for the reader, according your suggestion, we revised it; please see the modification in the paragraph.

 Point 23. Lines 81-82: Consider deleting this sentence.

Response: According to your suggestion, we deleted the mentioned sentence; the modification can be tracked. The reference on this sentence was also deleted from the references section.

 Point 24. Lines 83-85: Consider changing sentence to “POPs consist of a group of halogenated, lipophilic, organic compounds that persist in the environment.

Reponse: Thank you for this suggestion; we modified this sentence. However, according the modification suggested at the Point 1 from the references listed, we moved the this paragraph at the Introduction section where we combined and summarized the information about the role of POPs in environmental pollution, including also the definition of POPs; please see the modified paragraph in the Introduction section where you can find this sentence modified.  

 Point 25. Lines 87-88: This sentence is redundant as the authors have explained this other times previously in the manuscript.

Response: According to your suggestion, we deleted the redundant sentence. Some sentences from this paragraph were moved to the Introduction section (according to the reference on Point 1) because it were explained more times previously in the manuscript; please see how we included this information in the Introduction section, keeping also the reference listed.

Comment:

Point 26. Lines 89-90: Consider revising to “Regulations addressing these organic pollutants have aimed at reducing the consequences of pollution, eliminating existing pollutants, or preventing potential contamination.” Combine this sentence with the paragraph below it.

Response: Thank you for these useful suggestions. We revised the sentence and we combined it with the paragraph below it; the modifications can be tracked.

 Point 27. Lines 92-95: Consider revising to “…the so called “dirty dozen,” were included in 2001….”

Response: According your suggestion, we checked carefully and we revised the sentence, removing the redundant information.

 Point 28. Line 103: Consider revising to “agricultural usage, which include organochlorine pesticides (OCPs) such as:…”

Response: The modification was done, according your suggestion. Thank you for helping us to improve our ideas.

 Point 29. Line 110: Consider revising to “compounds that are formed from incomplete…”

Response: Thank you for this suggestion. We replaced the suggested words; please see the modified paragraph.

 Point 30. Line 114: 33 PAHs were described by the European…”

Response: Thank you for your kind suggestion. Using your observation, we removed the redundant information. We apologize that the sentence was not so clear; in order to present better our ideas, we used unfortunately too much redundant explanations.

 Point 31. Table 1:

 Delete “(found in small amounts as such) from Aldrin

Response: We deleted the suggested words; the modifications can be tracked.

 Consider revising to “Contamination in dairy products and meat.”

Response: We replaced the word, according your suggestion.

 Lines denoting rows missing between Endrin and Mires and Toxaphene

Response: Thank you for this observation. We apologize for this missing, we checked carefully and we added the lines denoting rows which were missing.

 Consider revising to “Includes 209 different types of PCBs”

Response: We want to thank your for this suggestion; the suggested words were replaced and the modifications can be tracked.

 Consider revising to “Residues of the pesticide production” for HCB

Response: We revised the description for HCB, according your suggestion.

 Consider revising to “Highly toxic chemical compounds originating from …” for PCDDs

Response: We use your kind suggestion and we replaced some words in the sentence; modification can be tracked.

 Consider revising to “…human tissue through contaminated food.” And “Low concentrations in the environment, but are persistent, bioaccumulate, and are easily transferred.”

Response: Thank you for your useful suggestion; the modifications were done. About the ”persistent and easily transferred”, we considered that are important information in relation to the low concentrations. Thus, even if they are repeated, respecful to your opinion, we kept the information only this time.

 Point 32. Lines 133-136: It is difficult to understand what the message is that the authors are trying to explain in this long sentence. The authors need to revise this to improve readability and understanding..

Response: Thank you for the opportunity to improving our ideas, your observation was very helpful. Because our ideas was not so clearly, we reworded the entire paragraph and we hope to be more easily understable; the modification can be tracked.  

 Point 33. Lines 137-139:  First sentence – consider deleting this sentence or major revision.

Response: Thank you for your suggestion. Because the sentence presents in brief some important characteristics of OCPs, respectful to your opinion, we considered better to reword the sentence; please see the modified paragraph. 

 Point 34. Line 142: Consider revising to “OCP residues in samples”

a.Delete the “s” after OCP in line 151 as well

Response: The modifications were done, according your suggestion we deleted the ”s”.  

Point 35. Line 166: What is meant by “intentionally produced?”  Do the authors mean “inadvertently?”

Response: Thank you for giving us the opportunity to explain better our ideas. We associated ”intentionally” production with chemical compounds commercially produced for various industrial applications; they are produced intentionally (knowingly) for those applications (eg. used in electrical equipment like capacitors and transformers).

In this context, we wanted to say that when we use PCBs as components of different electrical equipment or construction material, we know that in the future they will be a pollutant for environment; so, the release of pollutants is knowingly.

We do not consider ”intentionally produced” the same with ”inadvertently”. We consider that ”inadvertently” contamination can meant, by example, the contamination produced as a result of an accident or as a result of an action carried out without permission, therefore an unpredictable event.

Because this sentence can be confusing for the reader, we wanted to improve the readability and understanding, so we removed the words ”intentionally” and ”unintentionally”. We reworded the sentence, please see it modified in the paragraph.

 Point 36. Lines 172-174: The sentence “PCBs released…” – the language used in this sentence makes it hard to read. For example, “processes have also a negative contribution to…”  Consider rephrasing sentence structure.

Response: Thank you for your suggestion, that was really helpful for us for improving our ideas.

Indeed, the language used in this sentence can make it hard to read. According your suggestion, we reworded the sentence; the modification can be tracked.

 Point 37. Line 179: Consider revising to “foodstuffs seem to be the main route for human exposure.”

Response: We want to thank you for your kind suggestion, we used it to modify the paragraph; the modification can be tracked.

  Point 38.   Line 188: Consider revising to “Regarding combustion chemicals…”

Response: The modification was done, according your suggestion.

 Point 39. Line 197: Consider revising to “by various authors.”  The authors use the phrase “around the world” a lot throughout this manuscript.

Response: We modified the sentence, according your suggestion. We want to thank you for your kind observations, we understand that our ideas was not always presented as well, so your opinion was very helpful for us for improving this work and also the future works.

 Point 40. Line 198: Consider revising to “The literature describes pollutant…”

Response: We replaced the word suggested, according to the reference listed. Thank you for this suggestion.

 Point 41. Lines 232 and 234: Delete “the techniques of the”

Response: We deleted the suggested words; please see the modified paragraph.

 Point 42. Line 238: What is considered an “important” amount of OCPs? Do the authors have actionable levels of OCPs to show that detecting 0.01 ppb to 41.4 ppb are “important” or significant levels?

Response: Thank you for helping us to improve our work. We want to apologize for this passing this ideas.  Indeed, this explanations about the amounts of OCPs is a little overdone without the actionable levels for showing this. Respectful to your opinion, we removed ”important” and only presented the levels of OCPs found.

 Point 43. Line 244: Change sentence to “In most situations, the feed was implicated as the source of POPs in dairy animals, which ultimately resulted detectable levels of POPs in milk.”

Response: According your suggestion, we changed the sentence; the modification can be tracked.

 Point 44. Line 247: Change to “former, greatest OCP producers in Romania.”

Response: The modification was done, according your suggestion: we added a comma and we deleted ”s” from OCP.

Point 45. Lines 256-262: Sentence starting with “Costera et al.” – this sentence is a run-on sentence (it is too long). Please condense and rewrite this.

Response: Thank you for this useful suggestion. Indeed, the sentence is too long and we apologize for this. We condensed and reworded the entire paragraph to present the main idea of those studies. Also, we reorganized the paragraphs and we done some modifications for a better understanding (we mentioned exactly what analyzed each team of authors).

Author Response File: Author Response.docx

Reviewer 2 Report

This revised edition of the paper is much improved over the previous.  The writing is more clear and it is more organized.  I would strongly suggest listing some of the limitations of the way this was done: not all of the studies used the same analytical techniques and instrumentation, and not all looked for the same list of POPs, so it makes comparing the results challenging.

I had a (relatively) few specific comments:

 

Abstract:

P1, L15 & L42:  POPs aren’t so much non-degradable as very slow to degrade, hence their persistence.

P1, L22:  I’m not clear on what “timing and lasting” mean in this sentence.  Time of exposure?  Duration of persistence?

Introduction:

P1, L41: Long lasting persistence is kind of redundant. 

P2, L54-55:  What “fatty components” of the environment?  Are you speaking of lipids in biological organisms?

P2, L71:  “physiological secretion bounded to milk yielding” do you mean milk secretion?  Please simplify.

P2. L73-74: “effects of pollutants in feedstuffs on animal yields” can have several meanings: effects on growth or milk production?  I think you mean contamination of animal products (milk specifically) but this needs clarification.

Characterization

P2, L84: “that induces persistence”

P2, L87: “environmental chains” do you mean food chains?  I’m not sure what “environmental chains” means.

P3, L105: “used in dyes or plastics”

P3, L124: “identified in analytical studies”

Table 1:  Characteristics of POPs listed in the Stockholm Convention

OCPs: It is my understanding that much of the DDT use was for public health purposes: killing mosquitoes to prevent malaria and other pathogen spread.

Throughout the table, you say “1/2.”  Does this refer to the t_1/2 (half-life)?

“include over 670 chemical compounds” I’m not sure what this is referencing, it is after toxaphene, but I can’t imagine 670 variations on toxaphene.

P5, L149-150:  This sentence needs clarification.  Are you saying that agriculture causes ecological degradation even in the absence of POPs?  Which is certainly true, but doesn’t really add much to the paper.

P5, L151:  “after 2 decades” many of these compounds have been regulated variably by different countries for more than 50 years.  If you are specifically considering the Stockholm Convention (22 years ago) please specify.

P5, L155: “historical POPs and their breakdown products” this includes parent compounds, metabolites, and environmental degradation products.

P5, L167:  I would omit the term “waste” since some of the pollution came from normal uses of these products rather than just toxic wastes.

Occurrence

P5,L199:  “sources in some areas” remove analysed.

P5, L200:  “the quantitative profile” remove “identification of the”

Table 2:  much improved!

P8, L232-235:  Include abbreviation for GC/MS and explain HRMS.  Compare with list of analytical instruments on P10, L312-314 to make sure everything is spelled out with the abbreviation the first time it is used, and then abbreviated thereafter.

P9, L292:  Instead of the second use of “reporting” in this sentence, maybe just say “and.”

P11, L319-320:  Please clarify this sentence.  Despite prevention measures, these (these what?) will provide effective results?

P11, L330:  “control actions.” Sentence needs to be referenced.

P11, L328-334:  This paragraph is overall vague and I don’t know how it fits into the context of this paper.  I’m not sure if it refers to information in the subsequent paragraphs or not.

P11, L350-365:  This paragraph is about the POPs that occur due to burning of fossil fuels associated with the transportation industry.  I have a little difficulty with the terminology around “mobile pollution source” because we are considering the airports and roads rather than the individual vehicles.  I think I would consider airports and roads to be point sources of contamination, since they themselves aren’t mobile despite the source of burning fossil fuel is the vehicles that concentrate in these areas.

P12, L345:  Define concentrate feeds: grain? Soy? Mixed?

List:

P12, L402:  Replace “polluting” with “pollution”

P12, L410:  omit “types” after 6.

P12, 411:  “due to their toxic potential and persistence for years”

P13, end:  I would add a brief section on the limitations of this review: not all studies used the same technology.  Not all studies looked for the same analytes. 

Conclusions:

P14, L452-453:  I’m not sure what this sentence about accidental contamination means or adds to the conclusions. 

Author Response

Response to referee # 2

 

First of all, we want to thank to referee #2 for his/her kind suggestions and for the valuable comments which indeed were useful in elaborating this review, we really appreciate it. We also want to thank you for appreciating our efforts for improving this paper and for giving us the opportunity to explain our ideas.

Please find below our response accordingly (in the manuscript, comment are noted with (R2)).

 

Point 1. This revised edition of the paper is much improved over the previous.  The writing is more clear and it is more organized.  I would strongly suggest listing some of the limitations of the way this was done: not all of the studies used the same analytical techniques and instrumentation, and not all looked for the same list of POPs, so it makes comparing the results challenging.

Response: We really appreciate your suggestions and, according those, we considered appropriate to add one paragraph to mention the limitations of this review; please see the added paragraph at the final of the paper.

Abstract:

Point 2. P1, L15 & L42:  POPs aren’t so much non-degradable as very slow to degrade, hence their persistence.

Response: We really appreciate your observation, it help us to improve our ideas. Indeed, ”non-degradable” seems not to be the appropriate word for be used in this context. According your suggestion, we replaced ”non-degradable” to ”persistent” (Abstract section) and ”slow degradability” (Introduction section).

 

Point 3. P1, L22:  I’m not clear on what “timing and lasting” mean in this sentence.  Time of exposure?  Duration of persistence?

Response: Thank you for the opportunity to clarify our ideas. As you said, in this sentence ”lasting” referred to duration of persistence. With respect to ”timing”, this is reffered to ”time of exposure” as a measure of the duration of the contaminantion event, thus a description regarding the time trend of the contamination.

 

Introduction:

Point 4. P1, L41: Long lasting persistence is kind of redundant. 

Response: Thank you for your suggestion. To improving our work, we reworded this sentence; please find the modification in the paragraph.

 

Point 5. P2, L54-55:  What “fatty components” of the environment?  Are you speaking of lipids in biological organisms?

Response: Yes, we spoked about the lipids in biological organism or lipids from fatty tissues. We apologize for our improper expression that we used. According your suggestion, we modified the sentence; the modification can be tracked. Thank you for the opportunity to explain our ideas.

 

Point 6. P2, L71:  “physiological secretion bounded to milk yielding” do you mean milk secretion?  Please simplify.

Response: With respect to your suggestion, indeed, we reffered to milk secretion or to excretion of POPs in milk. According your suggestion, we modified the sentence; please find the sentence simplified in the paragraph. 

 

 Point 7. P2. L73-74: “effects of pollutants in feedstuffs on animal yields” can have several meanings: effects on growth or milk production?  I think you mean contamination of animal products (milk specifically) but this needs clarification.

Response: Thank you for your suggestion. As you said, we referred at the negative effect of pollutants in feedstuffs on animal yields, so, the contamination of animal products. We used your suggestion and we reworded the sentence. Hope that our ideas are more clearly after modification; please see the paragraph modified.

Characterization

Point 8. P2, L84: “that induces persistence”

Response:  We thank you for your suggestion, we really appreciate it. Since this topic about the role of POPs in environmental contamination is all covered in Introduction, some sentences from this paragraph were reworded and moved to Introduction section.

 Because we reworded the sentences before move it in the Introduction section, respectful to your opinion, no modification was needed in this case; please see the modified paragraph in the Introduction section, we hope that our ideas are more clear. 

Point 9. P2, L87: “environmental chains” do you mean food chains?  I’m not sure what “environmental chains” means.

Response: Thank you for the opportunity to explain our ideas. Indeed, ”environmental chains” mean ”food chains”.

Response: Because we reworded this sentences and we moved it in the Introduction section, respectful to your opinion, we replaced ”environmental chains” to ”food chains” in the paragraph in Introduction section; the modification can be tracked. 

 

Point 10. P3, L105: “used in dyes or plastics”:

Response According to your suggestion, the modification was done.

 

Point 11. P3, L124: “identified in analytical studies”

Response: The modification was done, we modified the word. Thank you for the observation.

 

Point 12. Table 1:  Characteristics of POPs listed in the Stockholm Convention

Response: According your suggestion, we modified the name of the table; the modification can be tracked.

 

Point 13. OCPs: It is my understanding that much of the DDT use was for public health purposes: killing mosquitoes to prevent malaria and other pathogen spread.

Response: Thank you for your opinion, we appreciate it and it is really helpful to improving our work. Indeed, we consider too that much of the DDT use was for public health purposes. However, even if the using of DDT was for public health, is important to understand that different amounts of DDT can pollute the environment. For this reason, we continue to consider important the use of this pollutant.

 

Point 14. Throughout the table, you say “1/2.”  Does this refer to the t_1/2 (half-life)?

Response: Thank you for the opportunity to explain our ideas. Throughout the table, “1/2” refer to the t1/2 (half-life). We apologize for using this incomplete abbreviation. We used your suggestion and we added the right abbreviation in the table. We modified also the meaning of abbreviation below the table. 

 

Point 15. “include over 670 chemical compounds” I’m not sure what this is referencing, it is after toxaphene, but I can’t imagine 670 variations on toxaphene.

Response: Thank you for your suggestion. Because we tried to describe better all the OCPs we used some improper explanations and we apologize for this.  According to your suggestion, we considered it appropriate to remove the redundant information and we only kept the mentions about the half-life.

 

Point 16. P5, L149-150:  This sentence needs clarification.  Are you saying that agriculture causes ecological degradation even in the absence of POPs?  Which is certainly true, but doesn’t really add much to the paper.

Response: Thank you for suggesting us to improve this sentence. Indeed, we said that agriculture causes ecological degradation even in the absence of POPs. We added this in our paper only for highlight how important is to not forget about the historical OCPs and their breakdown products who still remain a threat to the environment (therefore the agricultural activities are still included in the category of polluting factors). Repectful to your suggestion, we considered appropriate to improve this sentence for a better understand.

 

Point 17. P5, L151:  “after 2 decades” many of these compounds have been regulated variably by different countries for more than 50 years.  If you are specifically considering the Stockholm Convention (22 years ago) please specify.

Response: Thank you for this suggestion. Indeed, when we said ”2 decades” we referred at that time when, through the Stockholm Convention,  the OCP usage in agriculture has been prohibited or limitated. According your suggestion, we added this explanation in the paragraph; the modification can be tracked.

 

Point 18. P5, L155: “historical POPs and their breakdown products” this includes parent compounds, metabolites, and environmental degradation products.

Response: Thank you for your kind suggestion. We considered appropriate to modified the words in the paragraph and seems to be easier to understand than the first time. Like always, your suggestion was really helpful.

 

Point 19. P5, L167:  I would omit the term “waste” since some of the pollution came from normal uses of these products rather than just toxic wastes.

Response: Thank you for your suggestion, we deleted the term ”waste”; please see the modified paragraph. 

Occurrence

Point 20. P5,L199:  “sources in some areas” remove analysed.

Response:  According your suggestion, we removed the word from the paragraph.

 

Point 21. P5, L200:  “the quantitative profile” remove “identification of the”

Response: The modification was done, according your suggestion.

 

Point 22. Table 2:  much improved!

Response: Thank you very much for appreciating our efforts to improve this paper.

Point 23. P8, L232-235:  Include abbreviation for GC/MS and explain HRMS.  Compare with list of analytical instruments on P10, L312-314 to make sure everything is spelled out with the abbreviation the first time it is used, and then abbreviated thereafter.

Response: Thank you for this observation. According to your suggestion, we included the abbreviation for GC-MS and we explained HRMS. With respect to the list of analytical instruments from section 3.2 Animal feed, we checked carefully to be everything spelled out with the abbreviation the first time it is used (here we spelled out with the abbreviation only one analytical instruments: HRGC-HRMS).

 

Point 24. P9, L292:  Instead of the second use of “reporting” in this sentence, maybe just say “and.”

Response: Thank you for this suggestion. The modification was done; we replaced the word.

 

Point 25. P11, L319-320:  Please clarify this sentence.  Despite prevention measures, these (these what?) will provide effective results?

Response: Thank you for the opportunity to improving our ideas. In this sentence, ”these” were the actions taken for preventin pollution. We apologize for our improper explanation. We added this clarification in the sentence; please see the modified paragraph.

 

Point 26. P11, L330:  “control actions.” Sentence needs to be referenced.

Response: Thank you for this observation. We added the references for this sentence.

Point 27. P11, L328-334:  This paragraph is overall vague and I don’t know how it fits into the context of this paper.  I’m not sure if it refers to information in the subsequent paragraphs or not.

Response: Thank you for this suggestion. In our opinion, this paragraph can be important in the context of the paper because it is refer to predicting some environmental risks associated with pollution and this can be useful estimate the probability of contamination from a certain area. However, to improve the understand of the ideas, we remove the redundant information from the final of the paragraph.

Point 28. P11, L350-365:  This paragraph is about the POPs that occur due to burning of fossil fuels associated with the transportation industry.  I have a little difficulty with the terminology around “mobile pollution source” because we are considering the airports and roads rather than the individual vehicles.  I think I would consider airports and roads to be point sources of contamination, since they themselves aren’t mobile despite the source of burning fossil fuel is the vehicles that concentrate in these areas.

Response: Thank you for this useful suggestion. We understand that airports and roads can be considered to be point sources of contamination, rather than the individual vehicles, so, the terminology ”mobile pollution sources” can be confused. In order to remove the confusing terminology such as ”mobile pollution source”, according your suggestion, some modifications were made in this paragraph; the modification can be tracked.

 

Point 29. P12, L345:  Define concentrate feeds: grain? Soy? Mixed?

Response: In order to define concentrate feeds mentioned in the reference listed, we checked carefully the reference, but, unfortunately, the composition of the ”concentrate feeds” was not presented.

However, the study mention at the Material and methods section that ” concentrate feed, fodder/silage, water and milk samples” were analyzed. Based on this, we can consider that ”concentrate feed” refers to grains.

List:

Point 30. P12, L402:  Replace “polluting” with “pollution”

Response: The word was replaced, according your suggestion.

 

Point 31. P12, L410:  omit “types” after 6.

Response: The modification was done, according your suggestions.

 

Point 32. P12, 411:  “due to their toxic potential and persistence for years”

Response: Some modifications were made, according your suggestion.

 

Point 33. P13, end:  I would add a brief section on the limitations of this review: not all studies used the same technology.  Not all studies looked for the same analytes. 

Response: We really appreciate your suggestions and, according those, we considered appropriate to add one paragraph to mention the limitations of this review; please see the added paragraph.

Conclusions:

Point 34. P14, L452-453:  I’m not sure what this sentence about accidental contamination means or adds to the conclusions. 

Response: Thank you for your opinion. We checked carefully the conclusions and, indeed, the sentence about accidental contaminantion seems improper in that context. According your suggestion, we removed this sentence.

 

 

Author Response File: Author Response.docx