Some years ago the false belief developed that vaccines caused autism. That claim was rather quickly refuted when the original shoddy research by a British physician was challenged, and then numerous well-designed studies found no link between vaccines and autism. However, a fanatic anti-vaccine movement was born that has not died out. When beliefs become immune to contrary evidence, they become dangerous. For example, as too few people are vaccinated, common childhood illnesses that had become rare are re-emerging.
Now researchers and scientists at the California Department of Public Health, the Kaiser Permanente Division of Research and Drexel University have found that Polychlorinated Biphenyl (PCB) levels in the blood of pregnant women are strongly linked to the risk of autism and intellectual disabilities. The research report says, “although production of organochlorine chemicals was banned in the United States in 1977, these compounds can remain in the environment and become absorbed in the fat of animals that humans eat, leading to exposure.” PCBs were used in lubricants, coolants, insulators, and pesticides. The study looked at 1,144 children born between 2000 and 2003. Further research will give us more information about the risk of exposure to these chemicals. (http://www.eurekalert.org/pub_releases/2016-08/du-cbd082216.php)
These findings confirm several things. Autism is not caused by vaccinations. But more broadly, science is self-correcting. People who refuse to change their convictions when new evidence is presented are being doctrinaire and dogmatic, not scientific. We should not accept the safety claims of chemical companies without independent verification when introducing new chemicals. We must never stop refuting false beliefs.