As pediatrician Kari Nadeau and I leave California’s Pacheco Pass and head east, the Bay Area foothills give way to acres of orchards and level farmland. After three hours in the car, the jagged contours of the Fresno metropolis appear stark against a clear sky — but only because the cold air had pushed the hazy, gray smog below the horizon, Nadeau explains. She stops midsentence as the truck ahead of us coughs a cloud of black smoke. “Did you see that?” she says, eyes widening, her voice rising with a blend of awe and disgust.
Nadeau, who specializes in asthma, is heading to Fresno to meet with other researchers working on the San Joaquin Children’s Health and Air Pollution Study. It’s a trip she makes about every three months. In Palo Alto, where she lives in an airy, two-story home with her husband and five kids, she sees asthma patients a few times a week at Stanford’s Lucile Packard Children’s Hospital. Most of the children live in Palo Alto, but a few journey from Fresno for care they can’t get back home.
As we near the outskirts of the city early that afternoon, caravans of big rigs with soot-streaked trailers groan past. Not far away, dusty-faced migrant workers and their families, as well as homeless people, live in vast shantytowns — rows of tents, and shopping carts, sofas and bicycles strewn about. Although it is the most profitable agricultural area in the nation, Fresno County had the highest poverty rate in California in 2010, with 26.8 percent of its nearly 1 million residents living in poverty. Fresno-Madera ranks as the metropolitan area with the highest exposure levels to particle pollution, or soot, in the country.
Palo Alto and Fresno might as well be different worlds. And Nadeau has discovered a difference of extremes in the lungs and genes of her patients as well. She found that kids in Fresno were more likely to develop asthma not due to lung damage, but because changes on the surfaces of just two genes — and likely more — altered the way their lungs worked.
These two genes are crucial for tightening the reins on the immune system to prevent it from reacting to benign agents and triggering asthma symptoms. Unlike mutations, these changes to the surfaces of genes — part of what’s called epigenetics — alter how those genes behave without rewriting the information they encode. It’s like tagging them with Post-It notes that tell a cell to switch a gene on or off. Nadeau has discovered that in the Fresno children, long-term exposure to air pollution and secondhand smoke switched off two specific genes. Similar changes happened in the Palo Alto children, but at significantly lower rates.
