High levels of DDT found in eggs 

The Veterinary Medicines Directorate (VMD) in the UK has found samples of the persistent organochlorine DDT above the maximum residue limit (MRL) in eggs produced on a free-range farm. DDT was banned in the UK in 1984.

During 1999 the VMD carried out residue analysis on a range of meat, fish and poultry produce to test for pesticide and other contamination. Routine analysis of eggs has identified high levels of DDT.
    One egg sample out of nine tested contained 1,900 µg/kg (parts per billion) of DDT, which is well above the MRL of 100 µg/kg. The VMD has assessed the health significance of these results, and cites a World Health Organisation Provisional Tolerable Daily Intake (PTDI) of 1.2 mg per day for a 60 kg person. The VMD calculate that the DDT contaminated sample would contain 0.19 mg of DDT per 100g of egg. The Directorate concludes that it would be unlikely that there would be any adverse health effects from the one-off consumption of this high level of DDT, because the PTDI was not exceeded, and high levels would have to be consumed for a lifetime for ill health to occur. 
    Others are not so easily convinced. Jeanette Longfield of SUSTAIN, the alliance for better food and farming said: ‘The health calculations are based on adults and do not take into account the greater vulnerability of children and other chemically sensitive members of the population. The PTDI is based on dosing laboratory animals with relatively high levels of the pesticide, and then extrapolations are made for lower-level human exposure.’
    This incident was serious enough to merit follow-up investigation by the State Veterinary Service and the Health and Safety Executive (HSE). A veterinary officer took further egg and soil samples, which showed the wide extent of DDT contamination at the farm (see table 1).

    The free-range flock consisted of 230 birds aged 75 weeks. The birds were purchased as ‘point of lay’ pullets in August 1998. They were housed in a poultry shed, which was used by the previous owner of the farm to store chemicals. A concrete floor was laid and the walls were dry lined with plywood by the present owners of the farm, prior to occupation by the flock.
    The birds were fed and watered in the shed and had continuous access to the stretch of land in front of the hen house. There was evidence that the hens had scratched and turned over soil and straw and also dust bathed under nearby trees. The owner was very concerned about the presence of DDT in the flock and withdrew the eggs from sale.
    In 1989 the HSE served an order under the Food and Environmental Protection Act 1985 on the previous owner of the farm for the safe disposal of all existing chemicals, including DDT. The veterinary office concluded that it was unlikely that the birds picked up DDT contamination from inside the poultry shed. The most likely source of contamination was from soil on the farm.
    Was this a case of careless disposal of DDT? It is unlikely we will ever know for sure. The safety margins for DDT residues in these eggs were seriously eroded, and this incident serves to remind us that a pesticide banned 16 years ago can still today pose a persistent threat to human health and the environment. (By David Buffin)

The Veterinary Medicines Directorate Annual Report 1999, VMD, UK, 2000, pp36-37. 

[This article first appeared in Pesticides News No.49, September 2000, p22]