 Some researchers are warning about industrial chemicals called perfluorinated compounds or PFCs. A new study found that PFCs weakened the effectiveness of vaccines designed to protect children from diseases like polio, measles, and diphtheria. The protection is supposed to last a lifetime. This was quite serious because we could also see that some of the children were so low in antibiotic concentrations that they were essentially not protected. So they had been vaccinated four times and the vaccines had not worked. Dr. Philippe Grandjean is with the Harvard School of Public Health. He led a study of 500 children who had been vaccinated against diphtheria and tetanus. The study found children who had higher levels of PFCs in their blood had very low levels of antibodies against these infections. There was quite a striking effect, one that I would not have anticipated. Dr. Peter Hotez is president of the Sabin Vaccine Institute. Dr. Hotez says that if PFCs do interfere with antibody production, children in poor areas, areas where PFC levels can be much higher, will suffer. Even a modest reduction in vaccine coverage and vaccine immune responses could lead to subsequent outbreaks of childhood diseases, that there's a risk that we could see recurrences of childhood killers such as diphtheria or pertussis or other childhood diseases not become more common in the world's poorest countries. Scientists say PFCs have been used in many places for many years. They say it is likely that everyone has measurable levels of the chemicals in their body. We have not done enough in regard to protecting the population against these old compounds. And now we're stuck because we all have them in our bodies. The children in the study ate a lot of fish. Critics of the study say that researchers should have considered that polyunsaturated fatty acids may suppress the body's ability to fight disease. Those fatty acids are found in fish. I'm Christopher Cruz.