Читать книгу Analytical Methods for Environmental Contaminants of Emerging Concern - Группа авторов - Страница 14

The presence of these pollutants poses a potential risk for the environment and human health and, therefore, international organizations have set legal limits regarding the presence of pesticides in water and other environmental matrices, for controlling and preventing contamination of environmental ecosystems.

For instance, in Europe, the Water Framework Directive (WFD) is intended to protect transitional waters, inland surface waters, coastal waters and groundwater. Strategies against the chemical pollution of surface waters led to the Directive 2008/105/EC [9], establishing concentration limits of 33 priority substances and 8 other pollutants, including some pesticides such as simazine and trifluralin. Priority substances are considered to pose a significant risk to or via the aquatic environment, so environmental quality standards (EQSs) were set for each of them. Then, amending Directive 2013/39/EU [10] introduced 12 new compounds to the list and the need to establish an additional list of potential water pollutants (Watch List) that should be carefully monitored to support future reviews of the priority substances list. Currently, among the priority substances are 24 pesticides with Annual Average EQS (AA-EQS) values ranging from 1 × 10⁻⁸ µg l⁻¹ for heptachlor and heptachlor epoxide to 1 µg l⁻¹ for simazine. In 2020, the European Union (EU) established a new Watch List of substances, including azole compounds and providing maximum acceptable method detection limits for them from 29 to 199 ng l⁻¹ [11]. Additionally, the Drinking Water Directive 98/83/EC, amended by EU 2015/1787 [12], set special quality requirements for water for human consumption. It set concentration limits for a range of hazardous substances, including pesticides, establishing a general maximum individual concentration of 0.1 µg l⁻¹ for individual pesticides (0.030 µg l⁻¹ in the case of aldrin, dieldrin, heptachlor and heptachlor epoxide) and 0.5 µg l⁻¹ for the sum of all individual pesticides and relevant metabolites/TPs detected. The same values, 0.1 and 0.5 µg l⁻¹, for individual and total pesticides respectively, are established as groundwater quality standards in Directive 2006/118/EC [13] on the protection of groundwater against pollution and deterioration.

In the same way, the Clean Water Act (CWA) in the United States (US) establishes the basic structure for regulating quality standards for surface waters discharges of pollutants into the waters. In addition, the Safe Drinking Water Act (SDWA) was aimed at protecting drinking water and its sources (rivers, lakes, reservoirs, springs and groundwater wells). SDWA authorizes the US Environmental Protection Agency (US EPA) to set national health-based standards for drinking water to protect against contaminants, such as pesticides, that may be found in drinking water [14–16]. In this case, the proposed substance priority list is based on a combination of their frequency, toxicity and potential for human exposure at National Priorities List (NPL) sites, setting criterion maximum concentration (CMC) values for each of the pollutants listed. Aldrin, dieldrin, heptachlor and heptachlor epoxide show the lowest CMC values, between 7.7 × 10⁻⁷ and 3.2 × 10⁻⁵ µg l⁻¹.

Whereas different countries have set pesticide regulation in water matrices, regulation in soils is scarce. For instance, Spain set generic reference levels for a limited number of substances (< 60), some of them considered as persistent organic contaminants, such as dichloro-diphenyl-trichloroethane (DDT) or dichloro-diphenyl-dichloroethane (DDE), whose reference levels were 0.2 mg kg⁻¹ and 0.6 mg kg⁻¹ respectively [17]. These reference levels, in terms of human protection, are the maximum concentration of a substance in the soil that guarantee that contamination does not pose an unacceptable risk to humans. In addition to complying with generic reference levels, it is necessary to determine through toxicological tests that these substances do not present a serious risk to the ecosystem.