Towards a scientific basis for regulating lead contamination

Dangers from exposure to substances released to the environment, subsequently discovered to be hazardous, have been limited as a rule by actions taken piecemeal. Recently, more analytical techniques have been devised under the title 'Risk Analysis' or some similar name in order to produce a more scientific basis for establishing environmental regulations, but the results are often too complex to use. Their application to one substance, lead, is made practicable, although still leaving a difficult task, by making two assumptions: first, that blood lead concentration in humans may be taken to be an indicator both of total exposure and of its hazards to human health, and second, that 'threshold' values of blood lead concentration above which some action is necessary can be set and adopted. Programmes to control lead usages and pathways in order to reduce exposure in value-effective, acceptable and enforceable ways can then be devised and implemented, together with monitoring programmes to check the results and effectiveness of controls. Adopting these two assumptions offers the advantage that should later research show that threshold values have been set too low or too high, the rate of applications of all or any of the individual control programmes can be modified accordingly. The method is illustrated by using the distribution curve of blood lead concentrations now available for the general population of Great Britain. This is first used to estimate the numbers above each of the agreed threshold values: this procedure establishes the size or the importance of the problem. The effects on numbers and the sizes and speeds of the responses, of each of the different ways of controlling the different sources and pathways, are then assessed qualitatively, and their feasibility, enforceability and costs reviewed. The monitoring programme to check the effectiveness of the controls so far imposed is described. By using this procedure, lead contamination can be regulated to protect the health of the general population and the results of any or all of the regulations reviewed. One immediate consequence from its general application is to demonstrate that separate and specific measures are necessary to protect those at highest risk. One immediate advantage is that the procedure identifies those decisions that require value judgements.