Children exposed to PCBs in their first years of life are less likely to develop immunity to disease after they are vaccinated, according to a new study. Overall, the study shows that cumulative exposure to environmental PCBs – particularly leading up to 18 months of age – may decrease immune system development, leaving vaccinated children still at risk for developing disease.
What did they do?
Researchers measured PCB concentrations and antibodies in the blood of pregnant women and their children from the Faroe Islands. The Faroe Islands are a Nordic fishing community in the North Atlantic Ocean, near Iceland. PCB exposure among the Faroese can be quite high, due to PCB contamination of pilot whale blubber, which is eaten by many, but not all Faroese.
The researchers determined cumulative PCB exposures and then compared the PCB levels to antibody concentrations produced against diphtheria and tetanus in children vaccinated for these diseases to determine if the chemicals would reduce antibody production and affect the children's ability to fight disease. The “ability to fight disease” was based on post-vaccination blood antibody levels.
Blood samples were taken from the mothers in the 32nd week of pregnancy and from their children at 3, 5, 12 and 18 months and at 5 and 7 years of age. Breastmilk was collected from the mothers on the fourth or fifth day after birth. The number of children participating in the study varied from a few hundred to several hundred at each age point.
Blood and milk samples were analyzed for total PCB contamination. Antibody concentrations against tetanus and diphtheria were measured in all blood samples. Children received vaccinations against tetanus and diphtheria, following a standard vaccination schedule, at 3, 5, and 12 months, and then again at 5 years.