Monterey County, in Northern California, is one of those places that appear to tell a tale of two Americas. The part that runs along the Pacific coastline, from Pebble Beach and Carmel in the north down to Big Sur, is breathtaking and breathtakingly affluent. Travel 20 miles inland, over a narrow ridge of mountains, and you end up in the Salinas Valley, informally known as the Salad Bowl of the World, which is greened by endless rows of lettuce, cauliflower, and broccoli erupting out of rich brown soil and tended by a predominantly immigrant and poor community of farmworkers. Some of those fields run practically up to the main entrance of Natividad Medical Center in the town of Salinas, where, more than two decades ago, an environmental epidemiologist named Brenda Eskenazi came to study the effects of pesticides on children’s brain development. If there is a comforting illusion that barriers — be they a ridge of mountains or sheer wealth or a “wall” — can somehow seal off the dangers of modern life, the data that Eskenazi and her colleagues at the University of California, Berkeley, have produced tell a different story.
Sitting in an office on the grounds of the Natividad center recently, Eskenazi, by turns caustic and conscientiously precise, jokes that she could not have picked a more inconvenient group of experimental subjects. More than half of the primarily Latina mothers she and her team began studying in 1999 lived at or below the poverty level, 85 percent of them came from Mexico (some of uncertain immigration status), almost none of them spoke English, and they were scattered across 100 miles of rich agricultural real estate — “in a place,” says Eskenazi, a native New Yorker, “where there’s no public transportation.” Despite the inconvenience, these women and their children helped the Berkeley group make a series of alarming discoveries: Elevated levels of pesticide exposure in the womb were linked to neurological delays and autismlike symptoms in 2-year-olds; by age 7, the children with the highest exposures showed behavioral problems and a loss of IQ; by age 14, the link to autism-spectrum traits persisted; and researchers continue to assess these problems in older teens who return for assessments at 18 years old. Other research has found traces of the same pesticides to be ubiquitous in the U.S. population, and no one yet knows what a safe level of exposure might be.
It’s a cliché to say children are the most vulnerable members of society, but over the past three decades, scientists have established this as a physiological fact. Children eat more food and drink more water per unit of body weight than adults. They breathe more rapidly (and tend to breathe that air close to the ground). Those facts alone make children particularly susceptible when they are exposed to chemicals and pollutants. But that is especially true in the prenatal period and during early childhood, when the brain undergoes tremendous development.
Eskenazi’s project — the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study — was part of a wave of epidemiological studies launched in the late 1990s to explore the possible effects of environmental chemicals and toxins on fetuses and children. Eskenazi and her fellow scientists across the field have amassed an increasingly consistent, grim picture of possible neurological harms from a variety of environmental poisons, including chemicals found in agricultural pesticides (that also turn up in food), microscopic particles of carbon and other pollutants in the air, barely detectable levels of lead in the water — all are toxins that travel across state lines and abide by no barriers, socioeconomic or otherwise. In 2012, David Bellinger of Harvard’s school of public health published an eye-popping analysis of the impact of just three toxins — lead, methylmercury, and organophosphate pesticides — on neurological development, concluding that American children between the ages of 0 and 5 had suffered a collective loss of more than 41 million IQ points because of their environmental exposure. That may not sound like a lot when spread across 24 million children, but Bellinger analyzed only three types of toxicants out of an estimated 40,000 chemicals currently in use, many of which have not been studied in children to the same extent.
It’s hard to underestimate the impact of this research. Until the mid-1990s, regulatory agencies had calculated health risks based on studies of adult males; children didn’t become part of the calculus until 1996, when Congress mandated they be considered. And not until 2016, after years of “hotly debating” the issue, according to a former EPA official, did the agency finally embrace epidemiological studies, for the first time, in its decision to ban virtually all uses of chlorpyrifos, an organophosphate pesticide among the chemicals in use during Eskenazi’s Berkeley study. It was a huge moment for the scientists who study children’s environmental health.
The celebration was short-lived. Almost immediately after taking office, Trump’s first EPA administrator, Scott Pruitt, overturned the proposed ban on chlorpyrifos — a decision that Columbia University scientist Virginia Rauh, in a commentary for The New England Journal of Medicine, said “may be putting an entire generation of young brains in harm’s way.” Since then, the EPA has relaxed air-pollution standards, proposed rolling back regulations on mercury emissions, and introduced a plan for lead poisoning that critics say turns back the clock 20 years — all acts concerning toxins that epidemiologists have flagged as harmful to children. At the same time, the agency overhauled the regulatory process to diminish scientific input. Beginning last summer, the EPA requested raw data from Eskenazi and other scientists whose research has shown adverse neurological effects in children; public health experts view the move as a hostile act meant to either discredit or exclude the findings from consideration in setting federal health standards. And in September, the EPA abruptly placed Ruth Etzel, its highest-ranking (and most tenacious) advocate for children’s health, on administrative leave. It was, writ large, an attempt to purge the science that has established compelling evidence of environmental harms to the neurological development of children throughout the country.