Persistent organochlorine pesticides and their metabolites in alligator livers from Lakes Apopka and Woodruff, Florida, USA

Abstract

Reproductive disorders in American alligators (Alligator mississippiensis) inhabiting Lake Apopka, Florida, have been observed for several years. Such disorders are hypothesised to be caused by endocrine disrupting contaminants occurring in the lake due to pesticide spills and runoff from bordering agricultural lands. Various studies have resulted in identification of several persistent chlorinated organic pollutants, some of them known endocrine disrupters, in various alligator tissues and fluids. In this report, livers from 12 juvenile alligators inhabiting Lake Apopka and 10 from Lake Woodruff, a control lake, were extracted and analysed using gas chromatography–mass spectrometry with chiral GC columns for identification of both chiral and non-chiral organochlorine pesticides (OCPs, including their metabolites); in so doing, the enantiomer fractions of any chiral OCPs identified were also measured. In Lake Apopka, p,p′-DDE was the most prominent OCP identified, being found in all samples at concentrations ranging from 4 to 779 ng g−1, based on wet weight of the liver samples. Trans- and cis-nonachlor were also detected in all samples at a concentration range of 0.3 to 64 ng g−1; p,p′-DDD was also detected in all samples, but at an even lower concentration of 0.2 to 11 ng g−1. Only 5 chiral OCPs were identified; their enantiomer fractions were mostly non-racemic, indicating pre-ingestion enantioselective biotransformation or enantioselective metabolism by the alligators. p,p′-Dichlorobenzophenone (p,p′-DCBP), a known metabolite of p,p′-dicofol, was detected in all but one sample; most concentrations were <1 ng g−1. Dicofol is known to have been used and spilled near Lake Apopka, and is highly toxic to fish and aquatic invertebrates. Experiments showed that the p,p′-DCBP identified in these samples occurred via thermal degradation during GC analysis of p,p′-dicofol that was present in the liver sample extracts. Only 5 OCPs, at levels much below those in Lake Apopka, were found in control Lake Woodruff.