Evaluation of the pollution pressures posed by groups of chemicals on <scp>B</scp> ritish riverine invertebrate populations

Globally, rivers receive a diverse range of chemicals, including metals, pesticides, persistent organic pollutants, petrochemicals, human and veterinary pharmaceuticals and personal care products. However, the extent to which these different chemical groups affect riverine invertebrate communities is not well defined. Here we set out to evaluate the available evidence for associations between British riverine invertebrate communities and different chemical groups (and individual members of these chemical groups). Our assessment comprised three elements, (i) an evaluation of whether environmental concentrations of these chemicals exceed the lowest effect concentrations (ECs) based on laboratory tests, (ii) an assessment of associations between chemical groups and changes in British riverine invertebrate communities using the existing published literature, and (iii) calculated potential risk of toxicity of the chemical groups to invertebrates based on measured exposures (Environmental Agency monitoring data) and laboratory-based measurements of the lethal concentration required to kill half of the tested population (LC₅₀). Our conclusions indicate that metal and pesticide pollutants (including the veterinary medicine fipronil) are of greatest concern for British riverine invertebrate communities. Petrochemicals were also of potential concern, however, risk calculations indicate this risk is lower than that for metals and pesticides. All other chemical groups assessed appeared to be of relatively low risk to British riverine invertebrates based on the available information. However, the concentrations of some pharmaceuticals and personal care products in British rivers exceeded the lowest ECs for some invertebrate species and require further investigation. Given the widespread concern regarding declines in freshwater invertebrates, studies on chemical impacts on invertebrate populations in British rivers are surprisingly limited and further targeted studies are warranted.