Relationship between the levels of biological indicators of lead exposure in children and their mothers environmentally exposed to lead.

From a follow-up study (1976-1985) on lead exposure in population groups living in the vicinity of a lead smeltery, and those from a control area, data were selected on 222 simultaneous measurements of biological indicators of effective lead exposure (absorption) in the blood of children and their mothers. The range of lead exposure levels in both the children and the mothers was very wide (from "normal" to largely excessive lead exposure) as indicated by blood lead (PbB), activity of delta-aminolaevulinic acid dehydratase (ALAD) and erythrocyte zinc-protoporphyrin (ZnPP). A highly significant (P less than 0.001) exponential decrease in ALAD with respect to PbB, as well as an exponential increase in ZnPP with respect to PbB, was found in children and their mothers. Highly significant (P less than 0.001) relationships were found between the levels of PbB, ALAD, and ZnPP in the children with respect to those found in their mothers, indicating the relevant influence of a similar microenvironment (e.g. lead in indoor air and in household dust) and life-style (e.g. household hygiene habits and food preferences) on the level of effective individual lead exposure. Although these relationships have indicated generally higher levels of lead in children with respect to their mothers, the hypothesis of a relatively higher absorption and retention of lead in children of a lower age than that in children of a higher age could not be confirmed, which is in agreement with our previous observations. However, when the three subgroups according to the age of the children were compared (i.e. 0.3-4.5 years, 5-10 years, and 10.5-15 years), it appeared that children aged 0.3-4.5 years had the lowest lead absorption and those aged 5-10 years the highest in relation to their mothers. Within each of these subgroups, a tendency towards relatively higher effective lead exposure in children (i.e. the child/mother ratio of PbB, ALAD and ZnPP levels) with respect to an increase in environmental lead exposure level has been observed.