It could for instance be that for some reason, parents with higher autistic traits tend to be less bothered by/concerned about the noise, smell etc from roads. Which could explain differences in parents’ exposure, since autism has such a strong hereditary factor. I’m not saying this is the case, just pointing out one of many possible alternative explanations... But building weak arguments based on it only makes it easier for corps to defang this type of research.
The irony is very thick.