Threats posed by xenoestrogenic chemicals to the aquatic ecosystem, fish reproduction and humans: a review

Abstract

Xenoestrogens mimic and interfere with natural functions of oestrogens and adversely affect fish reproduction. Pesticides, plastics, wastewaters and pharmaceuticals are sources of xenoestrogens, and are carried through surface runoffs to water bodies at concentration levels that are harmful to aquatic organisms. Fish absorb xenoestrogens through ingestion of contaminated food items, respiratory gills and dermal contact.  Xenoestrogens bioaccumulate in fish tissues, eliciting various reproductive abnormalities, e.g. males may abnormally produce vitellogenins and present with reduced sperm counts, whereas females experience reduced fecundity and hatchability of eggs. Through the food web, xenoestrogens biomagnify in fish predators, e.g. seals and humans, which in turn risk suffering from reproductive malfunctions. Studies of adverse impact of xenoestrogens on fish have mainly been limited to developed countries, yet fish are a major food and trade commodity for developing sub-Saharan African countries. This review serves as a basis for research on adverse impacts of xenoestrogens on fish reproduction, and other consumers of aquatic organisms in Lake Victoria. The lake receives high levels of pollutants from untreated or poorly-treated domestic and industrial wastes and agro-chemicals. Control of xenoestrogens requires concerted effort from multistakeholders to undertake activities such as surveillance, advocacy, legislation and biodegradation to minimise their adverse impacts.

Keywords: aquatic environment, endocrine disrupting chemicals, Lake Victoria, oestrogens, vitellogenin