In our daily life, we use various chemicals including personal care products and detergents. Biocides are defined as a class of active substances used for destroying or inhibiting any harmful organisms, but are harmless to human beings. According to their usage pattern, they are classed into five categories: disinfectants, preservatives, pest control (e.g. insect repellents), and other biocidal products (e.g. antifouling agents). In recent years, biocides have received increasing attention as emerging contaminants due to their wide uses, frequent detection and designed biocidal properties. These chemicals are prevailingly used in various household and personal care products, as active ingredients, to inhibit or destroy harmful organisms, and their usages are very large in these products. For instance, up to 0.3% and 5% (w/w) of triclosan and triclocarban, respectively, can be added to a variety of consumer products, while climbazole is usually used in antidandruff shampoos, with the maximum content of up to 2.0%, equivalent to approximately 15 g/L. After use of these products, biocides contained in them are released directly or indirectly into the receiving environments through wastewater treatment plants (WWTPs). Furthermore, those biocides present in the aquatic environment can cause some adverse effects on aquatic organisms. For example, climbazole showed ecotoxicity to many aquatic organisms such asalgae, duck weed and fish. Algae were also found to be sensitive to triclosan and triclocarban, and both chemicals showed bioaccumulation in aquatic organisms such as algae, snails and fish with a log bioaccumulation factor (BAF) of 2.9-3.4. Parabens and azole fungicides have been regarded as potential endocrine disruptors to various aquatic organisms such as fish. Therefore, it is essential to understand their occurrence and potential ecological risks in the receiving environments.
The research group led by Professor Ying carried out screening research on the levels of various personal care products including biocides, musks and UV filters as well as nonylphenols in influents and effluents of STPs in south China, and found low removal efficiencies for some chemicals such as triclosan, triclocarban, benzotriazoles, azole fungicides and musks in the STPs. National river survey also found wide detection of various contaminants from personal care products in the large Chinese rivers including the Pearl River, Yellow River, Hai River and Liao River. Both river basin monitoring and modeling suggest that the mass fluxes of these personal care products in these rivers are mainly related to urban domestic wastewater discharges.
We also investigated the distribution and ecological risks of 16 household biocides in aquatic environments of a highly urbanized region in South China, evaluated triclosan as a chemical indicator for this group of household chemicals, and proposed a novel approach to predict the environmental occurrence and fate of these household biocides by using triclosan usage data and a level-III fugacity model. Eleven biocides were quantitatively detected at concentrations up to 264 ± 15.3 ng/L for climbazole in surface water, and up to 5649 ± 748 ng/g for triclocarban in sediment of four rivers in the region. The distribution of biocides in the aquatic environments was significantly correlated with environmental variables such as total nitrogen, total phosphorus and population. Domestic sewage in the region was the dominant pollution source for most biocides such as azole fungicides (fluconazole, climbazole, clotrimazole, ketoconazole, miconazole, and carbendazim) and disinfectants (triclosan and triclocarban). Preliminary risk assessment showed high ecological risks posed by three biocides climbazole, carbendazim and triclosan in river waters. Mostly important, triclosan was found to be a reliable chemical indicator to surrogate household biocides both in water and sediment based on the correlation analysis. In addition, the fugacity modeling could provide simulated concentrations comparable to the monitoring results. Therefore, with the usage data of the chemical indicator triclosan and correlation formula with other biocides, this model can be applied for predicting the occurrence and fate of various household biocides in a catchment.
Emission and multimedia fate as well as potential risks of typical biocides (triclosan and climbazole) in all of 58 basins in China were investigated. The total usage of tirclosan and climbazole in whole China were 100 and 345 t/yr, and the discharge to the receiving environment was estimated to be 66.1 and 254 t/yr, respectively. The biocides emission levels in east China were found generally higher than in west China. The predicted triclosan and climbazole concentrations by the level III fugacity model were within an order of magnitude of the reported measured concentrations. The sensivitity and uncertainty analysis (Monte Carlo simulation) further verified the reliability of the model. The transfer fluxes analysis showed that both triclosan and climbazole were prone to the sediment. The mass inventory of triclosan in whole China was estimated to be 75.3 t, with 2.4% in water, 96.7% in sediment, 0.9% in soil, and remaining in air. In contrast, the mass inventory of climbazole in whole China was estimated to be 294 t, with 6.79% in water, 83.7% in sediment, 9.49% in soil, and 0.002% in air. A level IV fugacity modelling for triclosan showed that seasonal and regional variations existed and those variations make great impact on the degradation and advection fluxes. The input flux for triclosan to seawater was largely attributed to the seasonal variations in advection flows. Preliminary risk assessment showed that medium to high ecological risks for TCS would be expected in the eastern part of China due to the high population density. Higher risks were located in the Bohai Bay Rim and Pearl River delta region when compared with other basins. Although the predicted risks for the biocides were relative low, higher aquatic risks are expected from this group of chemicals as co-occurrence of other biocides with climbazole and triclosan in surface water, which were with similar ecotoxicological effects to the aquatic organisms.
Figure 11. Predicted concentrations of triclosan in river basins of China.
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