Risk for elevated blood lead levels in 3- and 4-year-old children.

OBJECTIVE: We conducted a study to evaluate the relation between environmental, demographic, and medical risk factors and late-onset childhood lead poisoning, defined as children who were poisoned at age 3 or older.
METHODS: We performed a retrospective case-control study of 262 children whose test results showed non-elevated (<10 microg/dl) blood lead levels (BLLs) before age 2 but levels > or =10 microg/dl after age 3 and of 300 control children who had non-elevated BLL test results before age 2 and also after age 3. The target population was children receiving care at MetroHealth Medical Center in Cleveland, OH. We modeled the association between demographic and clinical risk factors and BLLs > or =10 microg/dl after age 3. Covariates considered were race, gender, body mass index, immunization status, mean corpuscular volume, hematocrit, red cell volume distribution width (RDW), red blood count, hemoglobin, baseline BLL result, and time between the baseline and second BLL test.
RESULTS: Case children were more likely to be male (P < 0.0001), black (P = 0.0189) and to have a high RDW defined as > or =14.5 % (P = 0.0083). On the basis of the final model, children with BLLs 7-9 microg/dl before age 2 and again after a follow-up BLL test (<21 months) were more likely to become lead poisoned than were control children. The risk of black children developing lead poisoning increased over time, regardless of the child's first BLL test result.
CONCLUSIONS: Although national recommendations are to test children's blood lead levels at ages 1 and 2, children living in high-risk areas with such risk factors should have a blood lead test at these older ages.