Nadeau was able to infer that the genes of her patients—who lived in Fresno, in California’s Central Valley, the most polluted city in the state, due to a deadly combination of diesel exhaust and agricultural pesticides—were fundamentally altered so that they would be more likely to develop asthma and allergies. And those genetic changes could be passed down to their children, and their children’s children, even if those later generations had moved away and were no longer exposed to the pollution.
