Factors associated with the seasonality of blood lead levels among preschool Wisconsin children.

CONTEXT Aggregate blood lead testing data for Wisconsin children younger than age 6 exhibit seasonal trends in both average blood lead levels and in the percent of those tested and found to have blood lead levels in excess of the 10 mcg/dL threshold for poisoning. Blood lead levels and poisoning rates typically peak during the late summer and early fall months, and are at their minimum during the late winter. METHOD Blood test data was analyzed to determine variations by month and age. RESULTS Seasonal variations are evident even among the very young: infants younger than 10 months who likely have limited opportunity to encounter lead hazards within their home or in the outdoor soil. Seasonal periodicity is most evident among infants who reside in very urban and very rural communities. The observed seasonal periodicity might be associated with the seasonal availability of lead within the children's environment. Particulate matter data measured at several ambient air quality monitoring stations exhibit a similar periodic seasonality, suggesting a possible relationship between blood lead levels and the availability of dust and airborne particulates during the summer months. CONCLUSION Clinicians should consider the seasonality of blood lead levels when scheduling tests and interpreting test results.