Grading Lead in Schools.

New Test Shows Safety

In this month's issue, investigators Charles V. Shorten and Marijane K. Hooven of West Chester University in Pennsylvania report on a method that may give a more realistic measure of the exposure of preschool children to lead-contaminated dust [EHP 108:663-666].

Shorten and Hooven set out to assess the relationship between 168 preschool children attending Philadelphia Head Start programs and various methods used to determine their exposure to lead in their classrooms. The scientists chose these young children because they are most susceptible to the deleterious effects of lead poisoning; in addition, their hand-to-mouth activities can lead to ingestion of lead-contaminated dust, and they spend up to eight hours per day in the classrooms. Ten classrooms in five buildings, each with a confirmed presence of lead-based paint, were included in the assessment. The scientists sought to determine whether the children were at significant risk of lead exposure by their presence in rooms likely to contain lead-contaminated dust.

To do so, they went a step farther in their wipe sampling protocols than previous studies had--they analyzed wipe samples from the children's palms and from both accessible and inaccessible surfaces within the rooms. Previous studies had not made this crucial differentiation between accessible surfaces such as desktops, windowsills, and doorknobs, and inaccessible surfaces such as the tops of filing cabinets and light fixtures. While high concentrations of lead were found in the dust on the inaccessible surfaces, the concentrations on the children's palms and the accessible surfaces, which are cleaned daily, were uniformly low. Determinations of the children's blood lead concentrations taken before enrollment in Head Start and after six months of exposure to the study settings confirmed the sampling data--156 children experienced no change in blood lead concentration, while 12 experienced only a minimal increase.

The authors conclude that current cleaning methods are effective at preventing lead-contaminated dust exposure within these classrooms, and the higher concentrations of lead in the dust on the inaccessible areas does not automatically constitute a health hazard because there may not be a completed exposure pathway. Prior studies, which the researchers say assessed only the presence of lead-contaminated dust, assumed that children were necessarily exposed simply because lead was present in the rooms. Shorten and Hooven limit their conclusion to the assertion that "there is no completed exposure pathway for lead from the most contaminated surfaces to the children in these schools."