Gas Particle Partitioning of PAHs Emissions from Typical Solid Fuel Combustions as Well as Their Health Risk Assessment in Rural Guanzhong Plain, China
Xiansheng Liu
Round 1
Reviewer 1 Report
This manuscript is overall clearly written and technically sound. I would recommend a minor revision before it being accepted for publication. My specific comments are as follows:
1. The authors should elaborate more on gas-particle partition measurement. Quartz fiber filters can absorb some gaseous PAHs. Was any measure taken to correct for associated sampling artifacts?
2. Although the given cancer risk equation is still being used, many recent human health risk assessment efforts in the U.S. consider multiple age groups and accordingly age-specific BW and CR/IR values. Are similar data available in China?
3. Why is gas-particle partition necessary in this study? Obviously, regardless of gaseous and particulate PAHs, their cancer risk calculations are the same.
4. Line 33, affecting should be affects.
5. Line 99, mg should be ug (microgram).
6. References should be reformatted as per mdpi journal requirements.
Author Response
We greatly appreciate the editor and referees for their careful and constructive comments, which have greatly helped improving the paper.
Reviewer #1:
This manuscript is overall clearly written and technically sound. I would recommend a minor revision before it being accepted for publication. My specific comments are as follows:
Thank you for the valuable comments and suggestions. We have made a point-to-point response to each comment, in which the corrections have been highlighted in blue color for your reference.
- The authors should elaborate more on gas-particle partition measurement. Quartz fiber filters can absorb some gaseous PAHs. Was any measure taken to correct for associated sampling artifacts?
Response: It is widely reported that particulate phase PAHs were only based on quartz filter sampling while gas phase ones were from PUF filters (Dos Santos et al., 2020; Ishtiaq et al., 2021). Therefore, in this study, the effects of quartz fiber filters on gaseous phase PAHs were negligible, and no measures were taken to correct for associated sampling artifacts.
Reference:
Dos Santos, R.R., Cardeal, Z.d.L., Menezes, H.C., 2020. Phase distribution of polycyclic aromatic hydrocarbons and their oxygenated and nitrated derivatives in the ambient air of a Brazilian urban area. Chemosphere 250, 126223.
Ishtiaq, J., Syed, J.H., Jadoon, W.A., Hamid, N., Iqbal Chaudhry, M.J., Shahnawaz, M., Nasir, J., Haider Rizvi, S.H., Chakraborty, P., Li, J., Zhang, G., 2021. Atmospheric polycyclic aromatic hydrocarbons (PAHs) at urban settings in Pakistan: Spatial variations, sources and health risks. Chemosphere 274, 129811.
- Although the given cancer risk equation is still being used, many recent human health risk assessment efforts in the U.S. consider multiple age groups and accordingly age-specific BW and CR/IR values. Are similar data available in China?
Response: As stated by the reviewer, it was found that significant differences in cancer risk among multiple age groups have been demonstrated in recent health risk assessment efforts in the U.S. However, the manuscript focused on investigating cancer risk variation among seven fuel-stove combinations instead of people with different ages. Due to the incomplete statistics of some relevant data in China, age-specific BW and CR/IR values were not available till now. Therefore, the relationship between age groups and cancer risk was not considered much in this study. We highly agree with the suggestions raised by the reviewer, and the suggestion would be fully considered in our future study.
- Why is gas-particle partition necessary in this study? Obviously, regardless of gaseous and particulate PAHs, their cancer risk calculations are the same.
Response: Although the gaseous and particulate phases cancer risk calculations are the same, the PAHs species in the gaseous and particulate phases are different, resulting in differences in gaseous and particulate phases cancer risks. For example, gaseous phase PAHs exceeded 2/3 of the total PAHs emissions due to naphthalene (NAP) mostly existed in the gas phase. Therefore, it is necessary to distinguish between the gaseous and the particulate phases PAHs in this study.
- Line 33, affecting should be affects.
Response: Corrected as suggested in the revised manuscript.
- Line 99, mg should be ug (microgram).
Response: Corrected as suggested in the revised manuscript.
- References should be reformatted as per mdpi journal requirements.
Response: References have been reformatted as MDPI journal requirements in the revised manuscript.
Author Response File: 
Author Response.docx
Reviewer 2 Report
In this study, the authors characterized the gas and particulate phases PAHs emission, and analyze their BaPeq and cancer risks. They showed that particulate phase PAHs dominated the total BaPeq which has less proportion in total PAHs emissions. In addition, the cancer risk exposure to PAHs from all combustion combinations were over the threshold (10-4), emphasizing the nagative impact against residents caused by solid fuel combustion. Overall, this study provided information about human health-oriented policy making and support the clean energy heat-ing strategy in China. The paper is generally well-written and informative. However, there are some concerns that authors should be addressed before acceptance.
1. More documents published during the recent years should be reviewed, compared and discussed.
2. I would encourage to briefly mention the aim of the study in the abstract section.
3. Is it possible to calculate Mutagenic values of PAHs, since some special PAHs are mutagenic associated with some health effects, i.e., pulmonary diseases (https://doi.org/10.4209/aaqr.2019.06.0301).
Author Response
We greatly appreciate the editor and referees for their careful and constructive comments, which have greatly helped improving the paper.
Reviewer #2:
In this study, the authors characterized the gas and particulate phases PAHs emission, and analyze their BaPeq and cancer risks. They showed that particulate phase PAHs dominated the total BaPeq which has less proportion in total PAHs emissions. In addition, the cancer risk exposure to PAHs from all combustion combinations were over the threshold (10-4), emphasizing the nagative impact against residents caused by solid fuel combustion. Overall, this study provided information about human health-oriented policy making and support the clean energy heat-ing strategy in China. The paper is generally well-written and informative. However, there are some concerns that authors should be addressed before acceptance.
Thank you for your constructive advices. We have addressed all the comments in the revised version and highlighted in blue color for your convenience.
- More documents published during the recent years should be reviewed, compared and discussed.
Response: More recent studies have been cited and compared in the revised manuscript as suggested.
Line 54-60:
In this study by Ma et al (2020), a national scale cancer risk assessment with atmospheric PAHs showed that BaPeq was 8.45 ± 14.1 ng/m3, which was higher than the new ambient air quality standards of China (GB 3095–2012, 1 ng/m3) [17]. Zhang et al (2022) reported that the emissions and their associated health risks of 16 priority-controlled PAHs in Jiangsu Province, and the results showed that the estimated cancer risks for different population groups were between 10−6 and 10−5, indicating high potential carcinogenic risks [41].
Line 195-198:
BaPeq for the seven solid fuels combustion scenarios ranged from 0.95 to 55.5 mg·kg-1, which were comparable with observed by Ngo et al (2022) (34.4 ± 23.9 mg·kg-1) and Zhang et al (2021) (2.79-41.9 mg·kg-1) [22,48].
Line 269-274:
For example, the mean cancer risk value was reported to be 3.85 × 10−5 to 4.36 × 10−5 for population in the study by Mosallaei et al (2022), indicating potential cancer risk as a result of exposure to PAHs [19]. Liu et al (2021) reported that the average values of sum of cancer risks were 2.22 × 10–7 for adults and 2.51 × 10–7 for children, suggesting that there is a low health risk posed by PAHs [13].
Reference:
Liu, B., Huang, F., Yu, Y., Dong, W., 2021. Polycyclic Aromatic Hydrocarbons (PAHs) in Indoor Dust Across China: Occurrence, Sources and Cancer Risk Assessment. Arch. Environ. Contam. Toxicol. 81, 482-491.
Ma, W.-L., Zhu, F.-J., Liu, L.-Y., Jia, H.-L., Yang, M., Li, Y.-F., 2020. PAHs in Chinese atmosphere Part II: Health risk assessment. Ecotoxicology and Environmental Safety 200, 110774.
Mosallaei, S., Hashemi, H., Hoseini, M., Dehghani, M., Naz, A., 2023. Polycyclic Aromatic Hydrocarbons (PAHs) in household dust: The association between PAHs, Cancer Risk and Sick Building Syndrome. Building and Environment 229, 109966.
Ngo, T.H., Yang, H.Y., Pan, S.Y., Chang, M.B., Chi, K.H., 2022. Condensable and filterable particulate matter emission of coal fired boilers and characteristics of PM2.5-bound polycyclic aromatic hydrocarbons in the vicinity. Fuel 308, 121833.
Zhang, P., Zhou, Y., Chen, Y., Yu, M., Xia, Z., 2022. Construction of an atmospheric PAH emission inventory and health risk assessment in Jiangsu, China. Air Quality, Atmosphere & Health.
Zhang, Y., Shen, Z., Sun, J., Zhang, L., Zhang, B., Zou, H., Zhang, T., Hang Ho, S.S., Chang, X., Xu, H., Wang, T., Cao, J., 2021. Parent, alkylated, oxygenated and nitrated polycyclic aromatic hydrocarbons in PM2.5 emitted from residential biomass burning and coal combustion: A novel database of 14 heating scenarios. Environmental Pollution 268, 115881.
- I would encourage to briefly mention the aim of the study in the abstract section.
Response: The aim of this study has been provided in the abstract section in the revised manuscript.
Line 3-7:
To quantify the health effects of different fuel-stove combinations, gas and particle partitioning of twenty-nine species of polycyclic aromatic hydrocarbons (PAHs) emitted from seven fuel-stove combinations were examined in this study, and the benzo (a) pyrene toxicity equivalent (BaPeq) and cancer risks were estimated accordingly.
- Is it possible to calculate Mutagenic values of PAHs, since some special PAHs are mutagenic associated with some health effects, i.e., pulmonary diseases (https://doi.org/10.4209/aaqr.2019.06.0301).
Response: The mutagenic values of PAHs from different combustion scenarios have been calculated in the revised manuscript.
Line 139-145:
The total BaPeq (TEQ) and MEQ (Mutagenic equivalent) of gas and particulate phases PAHs were calculated based on equation (3) and (4):
(3)
(4)
Where Ci is the concentration of PAH congener i; is the toxicity equivalency factor (TEF) of PAH congener i; is the mutagenic equivalency factor (TEF) of PAH congener I; All TEF and MEF are summed in Table S3.
Line 196-199:
To assess the potential risks of PAHs under different combustion scenarios, the total gas and particulate phases BaPeq and MEQ of seven combinations were calculated and results are shown in Figure 1 and Table S5. The results presented that bituminous coal combustion had higher mutagenic values than other combustion scenarios.
Author Response File: Author Response.docx
