Dieldrin pollution of a human food chain.

1 An incident is described in which excessive mortality amongst a poultry flock alerted veterinarians. Investigation revealed dieldrin in the carcasses and in the wood litter used in the nesting boxes. 2 Because high levels of dieldrin were found also in eggs the Department of Community Medicine was alerted. 3 Those most at risk were the workers who could have absorbed dieldrin by inhalation and percutaneously, and by eating contaminated eggs. A number of other people were at risk having eaten contaminated eggs. 4 Twenty-one workers or members of their families were investigated by case histories and blood levels. They were all clinically well. The highest estimated daily intake of dieldrin in the diet was 3.8 mgm. The highest blood dieldrin level found was 0.016 microgram/ml. This intake was of the same order as the upper limit of no-toxic-effect of long-term daily dosage, but the blood level is well below the level at which symptoms may be expected. The fall in mean blood level over a year is consistent with a long half-life of dieldrin in the human. 5 The conflict of interest in conducting a comprehensive investigation and preventing undue public alarm is discussed, and how this was resolved in this episode is described.