Organochlorine pesticide residues in domestic fowl (Gallus domesticus) eggs from central Kenya

In 367 domestic fowl (Gallus domesticus) eggs collected from 61 farms, residues of 10 pesticides were detected in various combinations and in the following order of frequency: p,p'-DDE (in 100% of the eggs), p,p'-DDT (98%), dieldrin (95%), lindane (66%), p,p'-DDD (46%), o,p'-DDT (17%), beta-HCH (9%), gamma-HCH (5%), endrin (4%) and aldrin (0.5%). No residues of heptachlor, heptachlor expoxide, HCB or PCBs were found. The mean concentration (0.70 mg kg-1 eggs; range less than 0.01-10.25) of total DDT exceeded the extraneous residue limit (ERL) of 0.50 mg kg-1. The mean dieldrin residue level (0.35 mg kg-1; range 0.01-14.90) was 3.5 times higher than the ERL (0.10 mg kg-1). Only 3% of the eggs exceeded the ERL for lindane. The 156 eggs from free-range hens had significantly (P less than 0.05) higher residue concentrations of total DDT, dieldrin and lindane than eggs collected from hens kept in enclosures. The mean ratio [p,p'DDT]/[p,p'-DDE] in eggs from enclosed hens (0.97) was significantly higher (P less than 0.01) than in eggs from free-range hens (0.53), indicating that the former had a more direct exposure to p,p'-DDT, whereas the latter obtained more of it after environmental conversion to p,p'-DDE. Eggs from a rice-growing area had the highest concentrations of all pesticide residues detected. Accumulation ratios indicated that the levels of DDT and lindane in the feed of enclosed hens could account for the levels in the corresponding eggs. The much higher accumulation ratios calculated for the free-range hens demonstrated that the feed ingested by these chickens obviously contained ingredients additional to those sampled, and revealed probable extensive environmental contamination by these persistent pesticides. The present results indicate that there is a need to identify sources of dieldrin in the eggs of domestic fowls and, where necessary, to investigate local wildlife samples. The amounts of total DDT and dieldrin in eggs in this study seem to be higher than reported from any other country. Toxicological evaluation of the results indicates that, at least in parts of Kenya, there is a local need for improved practices in the use of some organochlorine pesticides.