Effects of acute toxicity of the pesticide Chlorpyrifos and the metal Cadmium, both individually and in mixtures, on two species of native neotropical cladocerans.

The excessive use of pesticides in agriculture and the widespread use of metals in industrial activities and or technological applications has significantly increased the concentrations of these pollutants in both aquatic and terrestrial ecosystems worldwide, making aquatic biota increasingly vulnerable and putting many species at risk of extinction. Most aquatic habitats receive pollutants from various anthropogenic actions, leading to interactions between compounds that make them even more toxic. The aim of this study was to assess the effects of the compounds Chlorpyrifos (insecticide) and Cadmium (metal), both individually and in mixtures, on the cladocerans Ceriodaphnia rigaudi and Ceriodaphnia silvestrii. Acute toxicity tests were conducted for the compounds individually and in mixture, and an ecological risk assessment (ERA) was performed for both compounds. Acute toxicity tests with Cadmium resulted in EC50-48 h of 0.020 mg L-1 for C. rigaudi and 0.026 mg L-1 for C. silvestrii, while tests with Chlorpyrifos resulted in EC50-48 h of 0.047 µg L-1 and 0.062 µg L-1, respectively. The mixture test for C. rigaudi showed the occurrence of additive effects, while for C. silvestrii, antagonistic effects occurred depending on the dose level. The species sensitivity distribution curve for crustaceans, rotifers, amphibians, and fishes resulted in an HC5 of 3.13 and an HC50 of 124.7 mg L-1 for Cadmium; an HC5 of 9.96 and an HC50 of 5.71 µg L-1 for Chlorpyrifos. Regarding the ERA values, Cadmium represented a high risk, while Chlorpyrifos represented an insignificant to a high risk.

Ecological risk assessment for metals in sediment and waters from the Brazilian Amazon region.

Pollution by metals is a matter of concern around the world. In recent decades, the high population growth in urban centers has significantly magnified the entry of these pollutants into aquatic ecosystems. The Amazon region, intense migratory flow, gold mining, and industrialization have been considered the main driving forces for increasing metal pollution. Thus, the main aim of this study is to conduct, for the first time, an Ecological Risk Assessment (ERA) based on metal concentrations measured in the sediment and water of several aquatic environments from the Amazon basin, based on the risk quotient values (RQ = measured environmental concentration - MEC/predicted no effect concentration - PNEC). In addition, the metal contamination factor (CF) was estimated. Although metal concentrations in water were generally low, these values were far above the limits established by current national legislation in many areas, showing higher concentrations for the metals Co, Pb, Cr, Cu, and Ni. Concentrations of Mn, Cu, Ba, Pb, Co, Ni, Cr, Zn, Cd, and As were especially high in the sediment for several evaluated environments. The ERA for the water compartment revealed that 56% of the studied areas presented high risk (RQ > 1) for aquatic biota. In the sediment, 66% of the sites presented a high risk and 40% medium risk (RQ = 0.1-1). The CF indicated that 49% of the sampling points had high contamination and only 24%, had low contamination. These results reveal that monitoring studies in the Amazon region, provides important information so that public policies for the preservation of water resources can be strengthened in the Amazon.

Sensitivity of tropical cladocerans to chlorpyrifos and other insecticides as compared to their temperate counterparts.

The use of temperate toxicity data in tropical risk assessments has often been disputed. Previous sensitivity comparisons between temperate and tropical species, however, have not shown a consistent sensitivity difference between climatically-distinct species. Such comparisons were often limited by a small tropical toxicity dataset. In addition, differences in the taxonomic compositions of the temperate and tropical species assemblages used to construct species sensitivity distributions curves also hampered direct comparisons (e.g. type and ration of crustaceans and insects). The aim of the present study was to compare the sensitivity of temperate and tropical cladocerans to insecticides. Acute laboratory toxicity tests were conducted with five Neotropical cladocerans exposed to a concentration series of the insecticide chlorpyrifos. Subsequently, their EC50 values were compared with those reported in the literature for non-tropical cladocerans. An additional literature toxicity data search for insecticides other than chlorpyrifos was also conducted for both temperate and tropical cladocerans to enable a comparison for a wider range of insecticides and taxa. The order of sensitivity of the native cladocerans to chlorpyrifos was Ceriodaphnia silvestrii (0.039 µg L-1) > Diaphanosoma birgei (0.211 µg L-1) = Daphnia laevis (0.216 µg L-1) > Moina micrura (0.463 µg L-1) = Macrothrix flabelligera (0.619 µg L-1). A regulatory acceptable concentration based on temperate cladoceran toxicity data of both chlorpyrifos and other insecticides also appeared to be sufficiently protective for tropical cladoceran species. Implications for the use of temperate toxicity data in tropical risk assessments and indications for tropical cladoceran test species selection are discussed.