Mercury Contamination in Reptiles: An Emerging Problem with Consequences for Wild Life and Human Health

Methyl mercury is a persistent environmental contaminant that threatens the health of organisms in ecosystems throughout the world. Since methylmercury bioaccumulates over time and biomagnifies at each trophic level, long-lived, carnivorous species such as reptiles are at greatest risk. Reptiles have often been used as bioindicators of local mercury contamination, and many species have been shown to accumulate large concentrations of mercury in affected habitats. Annually worldwide, millions of reptiles, both wild and farm-raised, are sold for human consumption. Consuming wildlife contaminated with mercury poses a serious threat to human health, particularly for pregnant women and children. In this chapter, we review data of mercury concentrations in reptile species harvested for food. Mercury concentrations in reptile species are compared considering their trophic status and origin (wild-caught or farm-raised) to assess how different groups of organisms respond to mercury contamination. Also, the different origins of Hg are considered in order to understand the effects of different bioaccumulation routes. The issue of legal and illegal trade of reptiles for food in both developed and developing countries is described here to demonstrate the potential health risks to humans. In order to assess the contamination risk per species, we compared Hg concentrations in reptiles with consumption limits developed by the U.S. Environmental Protection Agency and Food and Drug Administration to evaluate mercury consumption through ingestion of fish. Few studies have examined health risks associated with reptile consumption. Although reptiles are not consumed in high numbers in most developed countries, they are a major source of protein in many developing countries where consumers may be at high risk from mercury-related health problems. To conserve endangered species, non-invasive techniques to measure mercury concentrations, by use of skin, shell and blood of reptiles, are described. Shell samples from turtles are especially important because they are composed of layers of keratin deposited throughout an individual's life span, thus providing a history of mercury contamination in turtles.