Continuing Persistence and Biomagnification of DDT and Metabolites in Northern Temperate Fruit Orchard Avian Food Chains.

DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) is an organochlorine insecticide that was widely used from the late 1940s to the 1970s in fruit orchards in the Okanagan valley, British Columbia, Canada, and in the process, contaminated American robin (Turdus migratorius) food chains with the parent compound and metabolite p,p'-DDE (1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene). Here, we examined the biological fate of these DDT-related (DDT-r) compounds at the same sites/region 26 years after a previous study by: 1) collecting soil, earthworms, and American robin eggs from apple, cherry, and pear orchards; 2) characterizing the diet and trophic positions of our biota using stable isotope analyses of δ13 C and δ15 N; and 3) estimating fugacity, biota-soil-accumulation factors (BSAFs), and biomagnification factors (BMFs). Mean p,p'-DDE concentrations (soil: 16.1 µg/g organic carbon-lipid equivalent; earthworms: 96.5 µg/g lipid equivalent; eggs: 568 µg/g lipid equivalent) revealed that contamination is present at elevated levels similar to the 1990s and our average soil DDE:DDT ratio of 1.42 confirmed that DDT is slowly degrading. American robins appeared to feed at similar trophic levels, but on different earthworms as indicated by egg stable isotope values (mean δ15 N = 8.51‰ ± 0.25; δ13 C = -26.32‰ ± 0.12). Lumbricidae and Aporrectodea worms shared a roughly similar δ15 N value; however, Lumbricus terrestris showed a markedly enriched δ13 C isotope, suggesting differences in organic matter consumption and physiological bioavailability. BSAFs and BMFs ranged over several orders of magnitude and were generally > 1 and our fugacity analyses suggested that p,p'-DDE is still thermodynamically biomagnifying in American robin food chains. Our results demonstrate that DDT-r in fruit orchards remains bioavailable to free-living terrestrial passerines and may pose a potential toxicological risk. This article is protected by copyright. All rights reserved.