**4. Microcystin Detection and Monitoring in Freshwater**

According to the World Health Organization (WHO) guideline, the permitted limit of MC-LR for drinking water is 1.0 <sup>μ</sup>g·L<sup>−</sup>1, and the tolerable daily intake is 0.04 <sup>μ</sup>gKg−<sup>1</sup> [91]. There are several MC detection methods, the most reported are listed in Table 2. Immunoassays (IA) are suitable methods of MC detection in Mozambique because they do not require sophisticated laboratory equipment and have a limit of detection below the maximum limit (1 <sup>μ</sup>g·L−1). Additionally, IA can be used in both laboratory and field studies.

**Table 2.** MC detection methods in drinking water. IA—immunoassays, HPLC—high-performance liquid chromatographic, PAD—photodiode-array detector, LC—liquid chromatography, MS—mass spectroscopy, MALDI-TOF MS—matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, UV—ultraviolet detector.


#### **5. The Occurrence of Microcystin in Mozambican Drinking Water**

#### *5.1. The Drinking Water Scenario in Mozambique*

The drinking water supply scenario in Mozambique still faces major challenges because a majority of the population still consumes untreated drinking water and consequently is exposed to many water-borne diseases. Only 50% of the population has access to "safe drinking water". Urban areas are the most favored, with 80%, while rural and most of the population have only 35% coverage and consume untreated water daily from rivers, lakes, and small puddles that form after or during the raining season [5,7]. The low water supply cover in Mozambique is inconceivable due to several reasons, among them, the existence of natural water cover (rivers) in the whole country and the presence of excessive fragmentation of governmental organisms for water management (Figure 1). The water management is led by the Ministry of Public Works, Habitation and Hydric Resources (MOPHRH), which operates, among others, with the National Direction of Water Supply and Sanitation, National Direction of Hydric Resource Management, Water Regional Administrations, Sanitation, and Water Supply Infra-structure Administration, Water Regulation Council, Fund for Investment

and Patrimony of Water Supply, and other private institutions, which provide goods and services. In order to improve the water management and expand the coverage, different projects funded by the Mozambican government and non-governmental organizations such as Plataforma Moçambicana de Água [6], Greater Maputo Water Supply Expansion Project [110], Integrated Water Supply and Sanitation Project for the provinces of Niassa and Nampula [111], National Rural Water Supply and Sanitation Program (PRONASAR) in Nampula and Zambezia Provinces [112], Inhambane Rural Water Supply and Sanitation Program [113], and others were implemented involving all the MOPHRH, civil society, and private organisms. However, still to date, the national water supply does not cover enough, with the population still consuming untreated water.

The water policy in Mozambique was approved in 1995, revised in 2007 and 2016, which, in the scope of water supply and sanitation, has the following relevant goals [114]:


The Ministry of Health (MH) is the legal organism responsible for water quality control and follows the regulation of the WHO, which sets the parameters of the quality of water intended for human consumption and the methods of carrying out their checks in order to protect human health. The water quality control recommended by WHO include MC among other biological parameter and the provisional guideline value is 1 <sup>μ</sup>g·L−<sup>1</sup> for drinking water [115]. The challenge is enormous in Mozambique for control or monitoring of this hepatotoxin due to the lack of adequate laboratories for the detection of MC in drinking water, even for 50% of the population that consumes treated water. This scenario shows clearly that all the Mozambican population is very vulnerable to MC exposure.

#### *5.2. Microcystin in Mozambican Drinking Water*

The drinking water is supplied by private (autonomous systems) and governmental operators. In Table 3, are listed the main sources of drinking water in Mozambique and includes underground and water river. The drinking water treatment is performed mainly by disinfection with chlorine, but is some regions such as Pemba and Niassa, the water treatment system includes the removal of iron by aeration. Not only is there no drinking water treatment for MC removal, but also MC incidence data in Mozambique are very limited. However, according to the WHO, more than 500,000 cases of diarrhea were reported, which 100 and 7 cases correspond to dysentery and cholera, respectively, and others are unknown [116].

TreatmentanddrinkingwatersupplyinMozambique.Gov—Governmentsystem.HTH—Hightesthypochlorite



These data indicate that many people of Mozambique consume food and water unsafely. Few studies (Figure 1) were done by Pedro et al. [117–119] and Bojcevska and Jergil [120] in Pequenos Libombos dam, Nhambavale lake, Chòkwé irrigation channels and Chidenguele sites in the South of Mozambique during 2003, 2008, and 2009 and their studies indicated the occurrence of MC-LR, -YR, and -RR produced by *Microcystis* sp. (*M. novacekii, botrys* and other) and *Cylindrospermopsis raciborskii* [117–120] (Table 4). MC concentration varies from less than 0.01 (below quantification levels) to 0.02 in Pequenos Libombos dam, less to 0.01 to 0.68 in Chòkwé irrigation channels, 0.86 to 7.82 in Nhambavale lake and 0.57 to 6.83 <sup>μ</sup>g·L−<sup>1</sup> in Chidenguele. Higher MC concentration values than the maximum limit ranging from 6.83 to 7.78 <sup>μ</sup>g·L−<sup>1</sup> (around 7 times above) were found in the Nhambavale lake and Chidenguele sites. These data highlight (suggest) the need to implement an operational monitoring program of MCs since the tests recommended by MH do not include the MC test [121]. Neighboring countries published other data, which support the need for MC monitoring in Mozambique (Figure 1), namely:



**4.**TheIncidenceofMicrocystinanditsproducersintheaquaticenvironmentsofMozambique.PL—PequenosLibombosdam,NL—Nhambavale


**Table 4.** *Cont.*

For example, the drinking water in the Xai Xai district (Gaza province) (Figure 1) is supplied from the Limpopo river. This river contains different MC producers such as *Synechocystis* sp. *Microcystis aeruginosa*, *Microcystis panniformis*, *Nostoc* sp., *Planktothrix* sp., *Phormidium* sp., which were detected in South Africa areas [122–126]. The presence of a potentially toxic algae is not an indication of MC production but is an indication of the need for MC screening in order to confirm the MC presence.

### *5.3. Removal of Microscystin from Drinking Water in Mozambique*

MCs can be removed from drinking water using several rapid and low-cost. The most are reported in laboratory studies, and they are not adaptable to economic conditions in Mozambique [144–150]. However, the following techniques seem to be useful in Mozambique and can be implemented in both rural and urban zones: Photolysis at 254 and 185 nm [147], use of wood-based and coconut-based activated carbons [148], use of bamboo-based charcoal adsorbent modified with chitosan [149], hydrophyte filter bed [150], biological activated carbon process [151], aquatic vegetable bed [152], and activated carbon from the seed husks of the pan-tropical tree, *Moringa oleifera* [153], among others.

#### **6. Final Considerations and Recommendations**

The drinking water supply scenario in Mozambique still faces major challenges because the majority of the population still consumes untreated drink water (from rivers, lakes, and small puddles that form after or during the raining season) and consequently exposed to many water diseases [5,7] including, for example, gastroenteritis, which is caused by hepatotoxins MCs. To date, no data of water poisoning episodes recorded were associated with MCs presence in the water. However, this might be underestimated due to a lack of monitoring facilities and/or a lack of public health staff trained for recognizing symptoms of MCs intoxication since the presence of high MCs concentration was reported in Maputo and Gaza provinces. Few studies done in Maputo and Gaza provinces indicated the occurrence of MC-LR, -YR, and -RR at a concentration ranging from 6.83 to 7.78 <sup>μ</sup>g·L−<sup>1</sup> [117–120], which are very high, around 7 times above the maximum limit (1 <sup>μ</sup>g·L<sup>−</sup>1) recommended by WHO [59]. The potential MC-producing in the studied sites is mostly *Microcystis* sp. [117–120]. However, MC distribution in Mozambique is unknown, and a monitoring program would help to understand the dimension of the problem. To date, no water MC poisoning episodes data recorded in Mozambique. The absence of MC intoxication episodes might be underestimated due to the absence of MC monitoring plan and/or a lack of public health staff trained in recognizing symptoms of MC intoxication. MC monitoring may be implemented according to recommendations of WHO [59] (1 <sup>μ</sup>g·L<sup>−</sup>1), and the respective MC analysis can be done in the existing water treatment centers in each province (Table 3). Rapid tests for MC detection, such as ELISA, can be used in each center. In the case of higher MCs content, some suitable techniques for MC removal may be used. The recommended techniques include photolysis at 254 and 185 [147], the use of wood-based and coconut-based activated carbons [148], use of bamboo-based charcoal adsorbent modified with chitosan [149], hydrophyte Filter Bed [150], Biological Activated Carbon Process [151], and aquatic vegetable bed [152], among others. These techniques can be used in both rural and urban areas due to their low-cost implementation and local access.

**Author Contributions:** Conceptualization, I.J.T.; introduction, I.J.T.; microcystin-producing species and toxicology, I.J.T.; effects of microcystin in humans, symptoms, and treatment, I.J.T.; microcystin detection and monitoring in freshwater, I.J.T.; the occurrence of Microcystin in Mozambican drinking water, I.J.T.; orientation, supervision and corrections, V.V. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Fundação para a Ciência e a Tecnologia (FCT) projects UIDB/04423/2020 and UIDP/04423/2020.

**Acknowledgments:** The authors acknowledge the Fundação Calouste Gulbenkian for the partial scholarship of Isidro José Tamele and the project EMERTOX [grant 734748], funded by H2020-MSCA-RISE 2016.

**Conflicts of Interest:** The authors declare no conflict of interest
