A CONTROL STRATEGY FOR LEAD IN PAINT In-House Technical Report First Draft by K. Bridbord c. Shy D. Hammer H. Goldberg V. Newill W. Nelson Division Health Effects Research Environmental Protection Agency Research Triangle Park North Carolina 27711 January 18, 1972 Backbround: Available evidence indicates that lead in hunan tissues serves no useful biological function. Even at low blood concentrations, lead adversely affects metabolism by inhibiting critical enzyme systems(1).' At higher concentrations, lead can produce severe disease and even death. Accordingly, any increase in lead body burden is undesirable. All known sources of human lead exposure must be carefully controlled. Clinical lead poisoning is caused primarily by childhood ingestion of lead-based paint (2). Every year hundreds of children die from lead poisoning and many thousands more receive permanent, irreversible central nervous system damage from lead ingestion. Recent proposals have advocated limiting lead content in paint as a means to prevent lead poisoning among future generations (3). However, agreement concerning how severe this restriction should be has not been reached. Among the general adult population, food is the primary contributor to lead body burden. Air and water are additional exposure routes. For children predisposed to pica (eating nonfood objects), the primarysource of lead body burden is lead-based paint. Lead in street dust and soil are additional potentially significant exposure mechanisms in this group (4). Comprehensive programs to decrease lead exposure have advocated eliminating lead in gasoline and rehabilitating deteriorating housing containing lead-based peeling paint. However, even low lead paint used in the rehabilitation process or in new construction could become a source of lead exposure in the future. Thus, careful thought must be given to what constitutes a safe concentration of lead in paint. Our paper will re-examine this problem to arrive at an independent estimate of a "safe" lead level in paint. The Control Strategy The physiology of lead absorption and excretion in adults in well documented. Corresponding studies in children are limited. An "average" 70 Kg adult takes in approximately 300-ug of lead via food and water. (5). Of this, up to 10% is absorbed from the gastrointestinal tract. Lead intake via the respiratory route is much more complete. Approximately one third of all inhaled lead is retained and almost all of this is absorbed (6). A figure of 30% reasonably estimates the quantity of lead absorbed from inhaled air. Studies indicate that children aged 1-3 years (10-18 Kg) ingest, on the average, 130 ug of lead each day from food and water (7). Based upon data from adults, up to 10% of this, or 13 ug per day will be Children this age inhale approximately 6 cubic meters of absorbed. air daily. Ambient air lead levels close to heavy traffic combusting gasoline containing lead are expected to average at least 5 ug lead per cubic meter. Assuming 30% absorption, a 1-3 year old child would absorb approximately 5x6x0.3 = 9 ug lead per day from the air. -2 Since significant increases in lead exposure and body burden are undesirable (especially in children prone to pica) strategies to limit lead exposure must prevent body burden increments. A maximum daily permissible intake (not absorption) of elemental lead in children of 300 ug is already established (8). Even if lead emissions from automobiles are eliminated in the future (98% of airborne lead is from gasoline combustion (9)), possible lead ingestion from peeling paint must still not be allowed to significantly exceed background lead intake from food and water. This is because lead intake of 130 ug per day in a 1-3 year old child is already nearly half his daily permissible intake. Acceptable Levels When considering Peeling paint is significantly denser than water. potential lead ingestion from specific volumes of peeling paint, assumptions that the density of paint equals that of water yield conservative estimates. On this basis the following tables can be constructed. -3 |