Figure 1

White blood cells (WBC) and prenatal exposure to PCB congeners CB-28, CB-52 and CB-101. Unadjusted and adjusted means (± SE) of WBC numbers and percentages in three months old infants prenatally exposed to the sum of CB-28, CB-52 and CB-101. Lipid adjusted serum concentrations of the PCB compounds in the blood of the mothers in late pregnancy (week 32–34) were used as a measure of prenatal exposure. Infants having an infection within a 7 day period before sampling were excluded from the statistical analyses. Adjusted means were calculated in cases when statistically significant results were found in the unadjusted analysis. Results were adjusted for age of the mother, smoking and alcohol during pregnancy, mother's education, vaccination of the infant, nursing of the infant, age of the infant, and infant's history of respiratory infections. The exposure variable was categorized since over 40% of the mothers had serum lipid levels of the PCBs below the limit of quantification (reference category 1). An effort was made to have equal numbers of participants in the two other exposure categories. *Significantly different from the group with the lowest exposure (reference category 1) (N = 75–79, p ≤ 0.01).