Developmental Immunotoxicity Testing and Protection of Children's Health

P renatal and postnatal exposure to persistent organochlorine pollutants, such as polychlorinated biphenyls (PCBs), has been implicated as a possible cause of impaired immune function in children. For example, studies have shown that children who have been exposed to PCBs and related compounds from their mothers' contaminated diets have reduced concentrations of immunoglobulins and increased frequency of childhood infections [1– 3]. And a new study by Heilmann et al. published in PLoS Medicine shows that children exposed to PCBs have reduced antibody responses to childhood vaccinations, adding to the growing evidence that PCBs are associated with developmental immunotoxicity (DIT) [4]. The study provides a stark example of the heightened immune vulnerabilities that exist during early life and that must be adequately protected from environmental insult if we are to minimize health risks to children. In their prospective epidemiological study, Heilmann and colleagues studied two birth cohorts from the Faroe Islands. These islands are a unique setting for studies of PCB immunotoxicity because average PCB exposures are up to 10-fold higher than average levels in Northern Europe, due to the traditional habit of eating pilot whale blubber. Heilmann et al. assessed PCB exposure perinatally by using quantitation of major PCB congeners (components) in pregnancy serum, transition milk (produced immediately following colostrum secretion), and children's serum. Following routine childhood vaccinations with two T cell–dependent vaccines (tetanus and diphtheria), children were examined at 18 months and at seven years, and serum was analyzed for tetanus and diphtheria toxoid antibodies and for PCBs. The researchers found that prenatal and perinatal PCB levels were excellent predictors of antibody responses to the vaccines (for example, antibody response to diphtheria toxoid decreased at age 18 months by 24.4 percent [95 percent confi dence interval, 1.63–41.9] for each doubling of the cumulated PCB exposure at the time of examination). It is interesting that early-exposure PCB levels were better predictors of antibody response to vaccines at seven years of age than were contemporary PCB levels, despite the capacity of PCBs to be retained in fatty tissues. This suggests that even transitory early-life exposures to an immunotoxicant have the potential to produce immune problems in later life. Furthermore, one should not assume that toxicant body burdens determined at the time of immune assessment represent effective correlates for DIT. In Heilmann and colleagues' study, PCB exposure was negatively associated with antibody responses to the immunizations. For example, even after receiving a …