Chronic exposure to environmental DDT/DDE in two species of small rodents: measures of contaminant load, immune dysfunction and oxidative stress.

Persistent contaminants are ubiquitous in our water and soil; thus, chronic exposure to environmentally relevant levels of these contaminants may pose a risk to humans and wildlife. Two species of small mammals (deer mouse, Peromyscus maniculatus and cotton rat, Sigmodon hispidus) were collected from historically DDT contaminated and reference areas at the Redstone Arsenal, an EPA designated Superfund site. Soil samples taken concurrently with mammal collection from the DDT abatement site exhibited DDT and DDE levels above 1 ppm [EPA Total Threshold Limit Concentration for DDT and DDE (<1ppm)], while those from the reference area had undetectable levels. Liver samples from individuals of both species collected in the contaminated areas also had significantly elevated DDT/DDE levels; P. maniculatus averaging a ~20x greater load than that documented for S. hispidus. Both rodent species collected from the contaminated site had significantly lower total leukocyte counts and total differential blood cell counts (p=0.01; p=0.04) than those collected from the nearby (~7000 m) reference site. Cellular stress indices also trended higher in both species suggesting a potential for chronic exposure to DDT to act as a mediator of oxidative damage. The present study provides support that environmental exposure to low levels of contaminants can cause physiological consequences that may influence immune responsiveness and initiate cellular stress in resident mammals. This article is protected by copyright. All rights reserved.