Standards for lead, in air

The impHcation of this wide range of blood leads within a population is important for standard setting based on PbB. For instance, the US Environmental Protection Agency (US EPA) has promulgated a standard for lead in air based on achieving a target of a population median PbB for children of <15 jug (100 ml)" [19]. They are thus implicitly accepting that 1 in every 10000 children may have a blood lead >40 jug (100 ml)". This standard is, nevertheless, effectively the same as one based on an individual PbB limit of 35-50 jug (100 ml)" as applied in some countries. 

Amidst all this uncertainty the US EPA has set a standard for lead in air of 1.5 jug m based on achieving a target of a population median blood lead for young children (1-5 years) of <15 jug (100 ml) This median has been chosen in order to prevent most children in the US from exceeding a blood lead of 30 jug (100 ml) (see Fig. 7.8). This value has been adopted as a maximum safe blood lead for individual children and is based principally upon the elevation of FEP in the blood as an index of adverse biochemical effect [19]. By adopting this approach they have avoided basing a standard on the uncertain neurobehavioural blood lead relationships. 

For example, the lead industry s technical criticisms during the pending mlemaking phase correlated closely with the quantitative significance of EPA s strategy for air lead levels. Industry s statisticians particularly challenged EPA s choice of the ratio relating PbB to air lead. The EPA value of 2 reduced the permissible air lead level to 1.5 units, while a value of 1 or 0.75 would increase the allowed air lead concentration to 3 and 4 pg/m, respectively. EPA s selection of the ratio value of 2 for children was based on the detailed analysis of this topic in Chapter 12 of the final draft of the air lead criteria document. Industry analyses of this ratio were relatively numerous both at the time of document preparation and when the proposed standard for lead in air was offered. 

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