Environmental lead and its paediatric significance.

Although paediatricians are familiar with the problem of childhood lead poisoning in association with the ingestion of lead paint, little attention has been given to the problem of other environmental sources of lead. Since both nature and industry continuously transfer lead from the lithosphere to the biosphere, it is appropriate to consider the magnitude of these contributions and their significance for the human foetus and child. The total body burden for lead of man in his natural state is calculable, and would be about 2 mg compared with 200 mg in many civilized communities. The magnitude of present day environmental lead contamination is emphasized by the recent calculation that 20 tons of lead are consumed annually by the population of the United States (Patterson, 1965). Comparison of the daily ingested and inhaled burdens of lead with the total daily intake which will precipitate poisoning, provides some measure of the importance of environmental lead for children. Until recently few estimates of this were available; however, on the basis of faecal lead determinations it can be shown that the ingestion of as little as 1 mg/ day by a 2-year-old child during a 6-month period might cause lead poisoning (Barltrop & Killala, 1967). Since 200-300 pg of lead might be ingested from 'normal' sources it will be apparent that this may form a substantial proportion of the lead burden responsible for poisoning. Restriction of the environmental lead burden might at least postpone the onset of poisoning in a child with pica for leadcontaining materials and perhaps diminish the severity of a poisoning episode. Whether the continued exposure of sections of the population to increased environmental lead levels has any other significance, apart from increasing the likelihood of childhood lead poisoning, has yet to be determined. The lead industry tends to minimize the attendant dangers and points to the relatively high levels of exposure that are apparently safely tolerated by lead workers. The appropriate health standards that have been devised for industry are based on the requirements of healthy adult males exposed to lead during a 40-hr working week. It has been cogently argued that the standards for lead workers might not be applicable to other population groups which are continuously exposed to lower levels; the foetus and the child would seem to deserve particular attention with regard to this environmental problem (Hardy, 1966). Some natural environmental lead is radioactive 210Pb and this provides an additional reason for minimizing the total body lead burden. The study of the origins and distribution of stable and radioactive lead has been pursued in a variety of disciplines with which the paediatrician has little contact. It is hoped that this review of some aspects of the problem might stimulate a reconsideration of the relevance of this element for human growth and development.