Cross-placental transfer of organochlorine pesticides in Mexican free-tailed bats from Oklahoma and New Mexico.

A total of 41 pregnant Mexican free-tailed bats (Tadarida brasiliensis) were collected from Carlsbad Caverns, New Mexico, and Vickery Cave, Oklahoma, in May and June 1990 and May 1991 for organochlorine pesticide analyses. Residues of p,p'-DDE were detected by gas chromatography in 40 embryos at levels highly correlated with brain concentrations (r = 0.496) but were not correlated mother's body tissues (r = 0.060). Embryonic levels also did not correlate with either embryonic fat content (r = 0.018) or maternal fat content (r = 0.300), suggesting that placental membranes offer only marginal protection for developing embryos against exposure to lipophilic organochlorine pesticides.