Non-dietary routes of contaminant exposure in reptiles: Laboratory studies with the Western fence lizard (Sceloporus occidentalis) to improve the ecological risk assessment process for reptiles
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Reptiles are a globally declining taxon and remain the least studied of all vertebrate taxon with regard to ecotoxicology. Performing studies with reptiles is not required by any regulatory statutes in the United States, or abroad. Because reptiles are not required under federal regulations such as the Federal Insecticide, Fungicide, and Rodenticide Act or the Toxic Substances Control Act, there is very little toxicity data available for reptiles, except what has been generated by academia and government. With very little data available for reptiles, performing ecological risk assessments on reptiles is exceptionally difficult. Often, a surrogate species (such as a bird) is used in place of reptiles and is assumed to be protective. The purpose of this research is to improve the risk assessment process for reptiles by better understanding reptile toxicity and exposure. My experiments have revealed (1) birds are not necessarily good surrogates for reptiles as reptiles have a dissimilar exposure profile compared to birds, and in many cases very dissimilar toxicant sensitivity; (2) given similar doses, oral and dermal contaminant exposures result in similar body residues in reptiles; (3) reptile oral and dermal toxicity is context dependent and may be very different for some pesticides; (4) there is no strong relationship between bird and reptile toxicity; and (5) applying my methods to a real-world application has found that neither H2S gas nor herbicide spraying represents a significant acute toxicity threat to lizards in the shin-oak sand dune system of west Texas. I propose a mechanism to explain the difference between oral and dermal contaminant exposure routes which may guide future research on these topics.