Putting pharmaceuticals into the wider context of challenges to fish populations in rivers

Abstract

The natural range of fish species in our rivers is related to flow, elevation, temperature, local habitat and connectivity. For over 2000 years, humans have altered to varying degrees the river habitat. In the past 200 years, we added to the environmental disruption by discharging poorly treated sewage, nutrients and industrial waste into our rivers. For many rivers, the low point arrived during the period of 1950s–1970s, when rapid economic development overrode environmental concerns and dissolved oxygen concentrations dropped to zero. In these more enlightened times, gross river pollution is a thing of the past in the Developed World. However, persistent legacy chemical contaminants can be found in fish long after their discharge ceased. Changes in habitat quality and morphology caused and continue to cause the disappearance of fish species. The range of fish stressors has now increased as temperatures rise, and non-native fish introductions bring new diseases. The threat from pharmaceuticals to fish populations remains hypothetical, and no studies have yet linked change in fish populations to exposure.

Medicines, shaken and stirred: a critical review on the ecotoxicology of pharmaceutical mixtures

“…Furthermore, physical and biological factors might impose additional environmental stress upon chemically exposed organisms and populations [67].…”

Medicating the environment: assessing risks of pharmaceuticals to wildlife and ecosystems

“…Hopefully, ecologically relevant endpoints will be increasingly accepted, but this requires validating them as reliable indices of survival and reproduction that can be interpreted as part of ecological risk assessments. Linked to this is the need to establish the relative importance of pharmaceuticals in causing changes to fitness-related traits, including behaviour, that in turn impact upon wildlife populations [16,21]. This is important not least because risk assessors require evidence of population-level outcomes [38].…”

“…As with other environmental stressors, pharmaceuticals in the environment should be investigated in a holistic fashion. Pharmaceutical impacts, where they occur, need to be teased apart from variation in fitness-related traits due to natural and also anthropogenically-mediated fluctuations in food and habitat availability, competition and parasitism or disease, as discussed by Johnson & Sumpter [21]. All these ecological factors, as well as prescribing patterns for pharmaceuticals, may also be influenced by climate change.…”

“…Cuthbert et al [12] present data on the effectiveness of mitigation measures mediated by conservation organizations and the Indian government designed to reverse the dramatic declines in populations of scavenging raptors. Fundamental to this has been to understand why the LD 50 of diclofenac to vultures is 0.1 mg kg 21 [74] compared with 9.8 mg kg 21 for the domestic chicken [75] and up to 1500 mg kg 21 for some mammals [76] (which also highlights the taxonomic diversity in responses to pharmaceuticals). In this issue, Hutchinson et al [49] investigate how some taxa, such as Gyps vultures, possess low metabolic competency, which can lead to zero-order metabolic ( pharmacokinetic) profiles and thus high pharmaceutical toxicity.…”

“…Moreover, pharmaceutical effects can act indirectly on populations through the food chain, for example, if a key prey species is negatively affected [13]. Finally, we examine the prospective interactions of pharmaceuticals in environmental mixtures [20] and begin to explore their relative impacts on wildlife compared with the other environmental stressors, both natural and anthropogenic [21].…”