Chlordane in birds: A study of lethal residues and loss rates

Lethal residues of heptachlor epoxide in brains of birds fed heptachlor ranged from 9 to 27 ppm wet weight; residues of oxychlordane in birds fed oxychlordane ranged from 6 to 16 ppm; both were diagnostically distinct from those in equally exposed survivors. In birds fed chlordane, brains of those that died contained less than 30% of these amounts but also contained trans-nonachlor, compound C, and compound E, suggesting additivity or synergism. In birds fed chlordane followed by untreated feed, oxychlordane was most persistent; trans-nonachlor, heptachlor epoxide, and compounds C and E followed, in that order. Loss rates were best expressed on a wet weight basis because lipid-based rates were distorted by seasonal weight gains.