Ecotoxicity

Résumé

Ecotoxicity, the subject of study in the field of ecotoxicology (a portmanteau of ecology and toxicology), refers to the biological, chemical or physical stressors that affect ecosystems. Such stressors could occur in the natural environment at densities, concentrations, or levels high enough to disrupt natural biochemical and physiological behavior and interactions. This ultimately affects all living organisms that comprise an ecosystem. Ecotoxicology has been defined as a branch of toxicology that focuses on the study of toxic effects, caused by natural or synthetic pollutants. These pollutants affect animals (including humans), vegetation, and microbes, in an intrinsic way. Acute vs. chronic ecotoxicity According to Barrie Peake in their paper “Impact of Pharmaceuticals on the Environment.”, The ecotoxicity of chemicals can be described based on the amount of exposure to any hazardous materials. There are two categories of ecotoxicity founded off of this descriptio

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https://en.wikipedia.org/wiki/Ecotoxicity

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Toxicity assessment of the main pesticides used in Costa Rica

Raphael Charles

The impacts of the 30 active substances, most used in Costa Rica (reference year 1998), are evaluated using two models originally developed to support comparative assertions in the context of the life cycle assessment: the multimedia fate, exposure and effect model Impact Assessment of Chemical Toxics 2002 (IMPACT 2002), and the Dynamic Model for Pesticides Residues in Plants. Results show that only five active substances - namely diazinon, mancozeb, chlorothalonil, terbutylazine and ethoprophos - contribute to more than 75% of the aquatic ecotoxicity and yet represent less than 40% of the amount used. More than 90% of the human toxicity is generated by only two active substances - namely terbufos and chlorothalonil - whereas they represent less than 10% of the total amount used. Overall, it would be possible to achieve a 90% reduction of human toxicity and a 75% reduction of aquatic ecotoxicity due to pesticide used in Costa Rica, focusing on only a few active substances. For instance, propiconazole or tridemorph could potentially be replaced by chlorothalonil; ametryn, diuron or paraquat by glyphosate; terbufos by cypermethrin; methyl bromide by metam sodium. (c) 2006 Elsevier B.V. All rights reserved.

2007

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Life cycle impact assessment aims to translate the amounts of substance emitted during the life cycle of a product into a potential impact on the environment, which includes terrestrial ecosystems. This work suggests some possible improvements in assessing the toxicity of metals on soil ecosystems in life cycle assessment (LCA). The current available data on soil ecotoxicity allow one to calculate the chronic terrestrial HC50(EC50) (hazardous concentration affecting 50% of the species at their EC50 level, i.e. the level where 50% of the individuals of the species are affected) of nine metals and metalloids (As(III) or (V), Be(II), Cr(III) or (VI), Sb(III) or (V), Pb(II), Cu(II), Zn(II) and Ni(II)). Contrarily to what is generally advised in LCIA, the terrestrial HC50 of metals shall not be extrapolated from the aquatic HC50, using the Equilibrium Partitioning method since the partition coefficient (Kd) of metals is highly variable. The experimental ecotoxicology generally uses metallic salts to contaminate artificial soils but the comparison of the EC50 or NOEC obtained for the same metal with different salts reveals that the kind of salt used insignificantly influences these values. In contrast, depending on the metallic fraction of concern, the EC50 may vary, as for cadmium: the EC50 of Folsotnia candida, expressed as free Cd in pore water is almost 2.5 orders of magnitude lower than that expressed as total metal. A similar result is obtained with Eisenia fetida, confirming the importance of metals speciation in assessing their impact on soils. By ranking the metals according to the difference between their terrestrial and aquatic HC50 values, two groups are distinguished, which match the hard soft acids and bases (HSAB) concept. This allows to estimate their affinity for soil components and potential toxicity according to their chemical characteristics. (C) 2007 Elsevier Ltd. All rights reserved.

2007

Chargement

Terrestrial ecotoxicity and effect factors of metals in life cycle assessment (LCA)

Sébastien Haye

Life cycle impact assessment aims to translate the amounts of substance emitted during the life cycle of a product into a potential impact on the environment, which includes terrestrial ecosystems. This work suggests some possible improvements in assessing the toxicity of metals on soil ecosystems in life cycle assessment (LCA). The current available data on soil ecotoxicity allow one to calculate the chronic terrestrial HC50EC50 (hazardous concentration affecting 50% of the species at their EC50 level, i.e. the level where 50% of the individuals of the species are affected) of nine metals and metalloids (As(III) or (V), Be(II), Cr(III) or (VI), Sb(III) or (V), Pb(II), Cu(II), Zn(II) and Ni(II)). Contrarily to what is generally advised in LCIA, the terrestrial HC50 of metals shall not be extrapolated from the aquatic HC50, using the Equilibrium Partitioning method since the partition coefficient (Kd) of metals is highly variable. The experimental ecotoxicology generally uses metallic salts to contaminate artificial soils but the comparison of the EC50 or NOEC obtained for the same metal with different salts reveals that the kind of salt used insignificantly influences these values. In contrast, depending on the metallic fraction of concern, the EC50 may vary, as for cadmium: the EC50 of Folsomia candida, expressed as free Cd in pore water is almost 2.5 orders of magnitude lower than that expressed as total metal. A similar result is obtained with Eisenia fetida, confirming the importance of metals speciation in assessing their impact on soils. By ranking the metals according to the difference between their terrestrial and aquatic HC50 values, two groups are distinguished, which match the hard soft acids and bases (HSAB) concept. This allows to estimate their affinity for soil components and potential toxicity according to their chemical characteristics.

2007

Chargement