Reproductive Impact of Natural, Synthetic and Emerging Chemicals on Wildlife and Domestic Animals

Wildlife and domesticated animals are exposed to a wide range of natural and synthetic chemicals throughout their life span. Many of these chemicals possess endocrine-disrupting properties which have the potential to disrupt reproductive and developmental process in certain animals. Organochlorine compounds, used as pesticides or in industrial and consumer products in the 1950s, were one of the earliest examples of synthetic endocrine-disrupting chemicals to be linked with adverse reproductive effects in animals. These legacy chemicals have since been restricted for use but continue to persist in the environment and threaten reproductive health of top predators, including porpoises, dolphins and whales. Newer chemicals, including some that were made to replace legacy chemicals and in use today, have been reported to also have endocrine-disrupting properties. These chemicals are manufactured for a wide range of uses, covering a broad range of chemically diverse substances, which include brominated flame retardants, plasticizers and pharmaceutically active ingredients among many other classes of chemicals. When present in the environment, they have been collectively termed emerging contaminants and have been linked with many adverse effects in animals, including impairments in reproduction and development. Whilst exposure to individual chemicals receives regular regulatory interest, there remains a particular concern about wildlife exposures to cocktails of endocrine-disrupting chemicals, which, combined with other stressors, may play a significant role in reproductive disorders that cannot be reproduced in laboratory experiments with single- or multi-chemical exposures. Regulation of chemicals, including restriction on the use of some chemicals, affords some protection to animals of the adverse effects of exposure to some EDCs, but there are presently no specific regulations on a holistic cross-government discharge limit for EDCs into the environment that would significantly reduce or eliminate animal exposure to EDCs.