Intelligent ecotoxicology of chemicals in UK rivers - development of a risk-ranking methodology

Abstract

Given the presence of 1000s’ of chemicals discharged by the human population to water, regulators and environmental scientists have to decide where best to focus their efforts. As a test case, this study used an identical protocol to rank 12 metals, 21 pesticides, 15 persistent organic pollutants (POPs), 13 pharmaceuticals, 10 surfactants/others and 2 nanoparticles (total of 73) of concern against one another by comparing their reported UK river water and published ecotoxicological effect concentrations. The chemicals were compared initially on the basis of the proximity of the median effect and median environmental concentrations. The closer the two median values are to each other, the greater the perceived risk. Further refinements to the risk-ranking were then introduced, including incorporating bioconcentration factor, using only recent water measurements and excluding either lethal or sub-lethal effects. The management of these data led to each chemical being ranked in terms of risk against every other. The top 10 chemicals which emerged as having the highest risk for UK surface waters using all the ecotoxicity data were copper, linear alkylbenzene sulfonate (LAS), zinc, aluminium, ethinylestradiol (EE2), triclosan, manganese, iron, methomyl and chlorpyrifos. In the majority of cases it is unknown if any of these chemicals are actually harming wildlife in rivers, but the implication is that reductions in water concentrations of these chemicals would be the most beneficial for UK aquatic wildlife. This approach revealed big differences in relative risk; for example, zinc presented a million times greater risk then metoprolol and LAS 10,000 times greater risk than nanosilver. With the exception of EE2, most pharmaceuticals were ranked as having a relatively low risk. The relatively high risk of EE2 suggests we should be most concerned about pharmaceuticals that could act as hormones. Some of the chemicals identified as of high risk to aquatic wildlife, such as LAS, are not regulated whilst many of the lower risk-ranked chemicals examined are.