| 1. |
- Carvalho, Raquel N., et al.
(author)
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Mixtures of chemical pollutants at European legislation safety concentrations : how safe are they?
- 2014
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In: Toxicological Sciences. - : Oxford University Press (OUP). - 1096-6080 .- 1096-0929. ; 141:1, s. 218-233
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Journal article (peer-reviewed)abstract
- The risk posed by complex chemical mixtures in the environment to wildlife and humans is increasingly debated, but has been rarely tested under environmentally relevant scenarios. To address this issue, two mixtures of 14 or 19 substances of concern (pesticides, pharmaceuticals, heavy metals, polyaromatic hydrocarbons, a surfactant, and a plasticizer), each present at its safety limit concentration imposed by the European legislation, were prepared and tested for their toxic effects. The effects of the mixtures were assessed in 35 bioassays, based on 11 organisms representing different trophic levels. A consortium of 16 laboratories was involved in performing the bioassays. The mixtures elicited quantifiable toxic effects on some of the test systems employed, including i) changes in marine microbial composition, ii) microalgae toxicity, iii) immobilization in the crustacean Daphnia magna, iv) fish embryo toxicity, v) impaired frog embryo development, and vi) increased expression on oxidative stress-linked reporter genes. Estrogenic activity close to regulatory safety limit concentrations was uncovered by receptor-binding assays. The results highlight the need of precautionary actions on the assessment of chemical mixtures even in cases where individual toxicants are present at seemingly harmless concentrations.
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| 2. |
- Tlili, Ahmed, et al.
(author)
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Addendum to Tolerance Patterns in Stream Biofilms Link Complex Chemical Pollution to Ecological Impacts
- 2021
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In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 55:1
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Journal article (peer-reviewed)abstract
- Following publication of our paper, we were made aware that we might not have sufficiently pointed out the potential role that microorganisms released with wastewater effluents could play in the increased tolerance of downstream biofilms toward micropollutants. Indeed, a large survey in 23 wastewaterimpacted streams, including the three sampling sites investigated in our study, showed that downstream bacterialcommunity profiles in the water column were a mixture between the upstream and the effluent.1 Whether these microorganisms go from a planktonic into a benthic biofilm state and play a role in the tolerance to micropollutants remains unclear. Nevertheless, it is plausible that suchmicroorganisms might have developed a tolerance to micropollutants in the wastewater treatment plants (WWTP) before their release into the streams. Mußmann et al.2 have shown that, among all identified nitrifying bacteria in the WWTP effluent, only one taxa preferentially added to the downstream biofilm community whereas the others did not. Similarly, Chonova3 showed that less than 5% and not the most abundant bacterial taxa were found in the biofilms downstream of urban and hospital WWTP. Even if actively colonizing downstream biofilms, monitoring the diversity profile of these microorganisms alone does not answer the question whether they contribute to the community tolerance to micropollutants. Therefore, controlled experiments focusing on both benthic bacterial and algal communities are needed to address this issue.
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