Brenda Eskenazi: An environmental epidemiologist’s journey from Woodstock to America’s salad bowl

Back in August 1969, Brenda Eskenazi hiked 15 miles in the pouring rain to reach the Woodstock Festival—but she never heard the music.

Eskenazi was so far back from the stage that she missed Janis Joplin, Jimi Hendrix, and the rest of the performers at that famous (and infamous) gathering in upstate New York. She did, however, see a young man on a very bad acid trip.

Watching him dive off the top of a car onto the cement, hallucinating water, the future scientist wondered: What on earth had happened to his brain to make him do that?

“That got me really, really interested in how chemicals affect the human brain,” she said in a recent interview.

The incident at the ‘60s most famous rock concert led Eskenazi to become a neuropsychologist and environmental epidemiologist, specializing on the impact of environmental exposures on children’s health. She joined the faculty of UC Berkeley School of Public Health in 1984 as an assistant professor in maternal and child health and epidemiology and became a professor in 1995. She was named Distinguished Jennifer and Brian Maxwell Professor of Maternal and Child Health in 2008.

A globe-hopping career

Eskenazi’s research has taken her all over the world, producing groundbreaking studies on the health hazards of exposure to pesticides, dioxins, metals, tobacco smoke, air pollution, and other toxic substances.

She has analyzed the aftermath of a chemical plant explosion near Seveso, Italy; studied what happened to workers exposed to benzene in China; and looked at in-utero DDT exposure in South Africa.

Eskenazi has also conducted research on the effects of social adversity and nutritional factors on male and female reproduction and on child development from the fetal stage to adolescence.

She is best known for building the Center for Environmental Research and Community Health (CERCH), a world-renowned science hub whose affiliated researchers have published hundreds of papers on environmental exposures and their impacts on pregnant women and children. Eskenazi became an emerita professor in 2019, but remains director of CERCH, which oversees the longest-running longitudinal birth cohort study of pesticides and other environmental exposures among children in any farmworker community in the world.

CERCH’s Center for the Health Assessment of Mothers and Children of Salinas, known as CHAMACOS, first enrolled pregnant women in 1999. Twenty-five years later, CHAMACOS is still a source of trailblazing research. Beyond their own investigations, the specimens and data that Eskenazi and her team have collected—initially from hundreds of pregnant women, and then from their children—serve as a lending library for researchers from around the globe.

When Eskenazi started her work, the fact that lead was a potent neurotoxin was beyond dispute. But the notion that pesticides and some other chemicals could also damage the developing brain was not as widely accepted.

Eskenazi’s investigators have produced some of the first evidence that the children who were exposed to pesticides in the womb had lower IQs than other children and other neuro-developmental problems. Their work showed that other chemical exposures were associated with lower birth weights, poor cognitive functioning, and additional health issues.

A massive impact

It’s hard to overstate Eskenazi’s contributions to environmental science. She has had an important impact on the regulation of chemicals at the state and federal level; on warnings about the risk of cancer, reproductive harm and birth defects now required under California’s Proposition 65; and on documents informing the Stockholm Convention, the historic international treaty to protect the public from persistent organic pollutants (toxic chemicals that resist degradation and can accumulate in living organisms).

“Brenda’s work has led the field of environmental epidemiology in designing and conducting longitudinal studies of key populations, from the Seveso Women’s Health Study to the CHAMACOS cohort, among many others,” said Linda Birnbaum, the former director of the National Institute for Environmental Science. “In addition, she’s a pleasure to collaborate with.”

Dr. Gwen Collman, director of the NIEHS office of scientific coordination, planning and evaluation, said, “Brenda is a brilliant researcher who has been very, very dedicated to expanding our knowledge base when it comes to the health effects of exposures to environmental chemicals. Her work has been very novel, very challenging. She’s not afraid to take on the tough stuff. She brings a very deliberate and rigorous approach.”

Eskenazi’s research has earned her many awards, most recently the 2023 Child Health Advocate Award from the Children’s Environmental Health Network. In 2014, she was inducted into the Collegium Ramazzini, a prestigious academy of the top 150 people in the world in occupational and environmental health. Her other honors include the John R. Goldsmith Award for Lifetime Achievement, from the International Society for Environmental Epidemiology.

Kim Harley, the faculty director of UC Berkeley’s Wallace Center for Maternal, Child and Adolescent Health, who first worked with Eskenazi on CHAMACOS in 2004 as a graduate student, praised her mentor’s innovation.

“If you look now, there are so many cohort studies and research looking at prenatal exposures and how they affect brain development,” Harley said. “But when she wrote that first grant back in 1998, there was hardly anybody doing it.

“The National Institutes of Health now has a toolbox of neurodevelopmental tests for this purpose, but none of this existed when Brenda started. She was one of the first to do this, and her PhD in neuropsychology put her in the perfect place to do it.”

From Queens to Yale

Eskenazi didn’t plan it that way.

Growing up in Queens, a borough of New York City, Eskenazi wanted to become either a surgeon or a medical illustrator. But while attending Queens College in the 1960s, her biology professor told Eskenazi that women didn’t belong in medicine. Lacking role models of female doctors, Eskenazi, at first, believed it.

Luckily, Queens College, a branch of the City University of New York, was the site of the entire university’s neuropsychology department, and Ezkenasi was welcome there.

“That was fascinating to me,” she said. “I happened to be in a good place for me, and it turned out by chance.”

Eskenazi was accepted to the CUNY doctoral program in neuropsychology, and then spent a pivotal year studying at the University of Leeds in England.

Her plan was to conduct electrical and chemical stimulation of animal brains, and study the effects. She worked on a range of animals, learning neurochemistry, neurophysiology and neuroanatomy. But soon, the head of her laboratory told her she had to stop operating because she didn’t have a license.

“You needed a license to operate on animals in England,” Eskenazi said. “And I didn’t have one. And it took a year to get a license. So I said, ‘What am I supposed to do?’ And he said, ‘Well, I guess you’re going to have to do human research.”’

She designed a study of cognitive issues in women using high-estrogen birth control pills.

“I wrote a questionnaire like an epidemiologist would, and that’s where the pieces came together. I entered into the field of epidemiology but without real training at that time.”

Eskenazi returned to the U.S., and received her PhD from CUNY Graduate Center in 1979, while also working at the Columbia University Psychiatric Institute. That led to an epidemiology and environmental health sciences postdoc at Yale University. By 1983, she was an assistant professor in Environmental Health Sciences at Yale School of Medicine, studying the neurotoxic as well as reproductive effects of many chemicals ranging from alcohol, nicotine and caffeine, to environmental chemicals. She moved to UC Berkeley School of Public Health in 1984.

The first class she taught at Berkeley was on reproductive hazards of industrial chemicals. And one of her first landmark studies was an investigation into the 1976 chemical factory explosion near Seveso, Italy, which exposed residents to high levels of 2,3,7,8-tetracholorodibenzo-p-dioxin (TCDD or dioxin), a human carcinogen and potent endocrine disruptor. She has followed the women exposed to dioxin from that disaster for more than two decades.

Tracking toxins in California’s salad bowl

An ongoing theme of her research has been the negative consequences of environmental agents on child health.

Much of Eskenazi’s most important research has come from CHAMACOS, the joint project she founded with Clinica de Salud del Valle de Salinas, Natividad Medical Center and other community groups in the Salinas Valley. This rich agricultural land is often called “the world’s salad bowl.” Dole is there, as is Naturipe Farms, Fresh Express, and since 1999, Brenda Eskenazi.

In 1996, the Food Quality and Protection Act was passed by Congress and this Act called for the protection of the health of fetuses and children from the effects of pesticides–that children were not “little adults.” In 1998, the Environmental Protection Agency and NIEHS put out a request to establish Centers for Children’s Environmental Health.

“We didn’t know very much information about children’s exposures and their effects, especially to pesticides, and how that affected child development,”’ Eskenazi said.

Eskenazi and her research team applied to establish one of these Children’s Centers to study the effect of short-acting pesticides on children.

“I said, ‘Look, we live in the largest agricultural state in the nation. We work at a land grant university. Our work needs to be on agriculture and it needs to be on pesticides,” Eskenazi said.

After forming partnerships with local health care providers, and community leaders—Eskenazi launched a birth cohort study, tracking mothers and children from primarily Mexican farmworker families who may have been exposed to pesticides used in the fields.

Her team recruited 600 women in the first half of their pregnancy. Half of these women had lived in the US less than five years, but at the time if you were pregnant you could receive MediCal, whether you were documented or not. They interviewed the women, collected maternal blood cord blood, and urine samples from them. They followed and examined their children soon after birth and at 6 months and every one to two years after. They did home walkthroughs and neighborhood assessments. They later added 305 additional children, who were followed from age 9.

As the children grew, researchers collected data on their neurodevelopment, including autism spectrum behavior; obesity, respiratory symptoms, onset of puberty and other health outcomes.

“Since I was a psychologist, I also made sure I got a lot of stuff on their social well-being and psychological well being as well as their full medical history,” Eskenazi said. Right after the 2016 Presidential election, we even collected information on their concerns about immigration policy. Another frequent subject has been gene-environment interaction, and more recently, the effects of exposure to environmental chemicals and social stressors on the epigenome of the developing child. Colleagues at UCSF and UC Berkeley have been following the health of the mothers, too.

They have been following many of the families for 25 years, ending up with more than 400,000 biological samples, fueling more than 200 studies on the impacts of pesticides and other chemicals on health as well as a myriad of other exposures; while at the same time, educating farmworker families and finding ways to reduce exposures.

In addition, the CHAMACOS has provided valuable information on the ubiquitous chemicals found in furniture, plastics, and cosmetics, and their effects on many aspects of health.

“When we started CHAMACOS, people were saying ‘Wow, this is a big undertaking, and it was really going to depend on the cooperation of the community,” said Kim Harley, who started as a student and later became study coordinator in 2004.

“From the very beginning, Brenda was really committed that the core of the study would be community-based participatory research. The staff was all bicultural, and bilingual, from the Salinas community.”

Gwen Collman, of NIEHS, praised Eskenazi for becoming part of the farmworker community, and spending the time necessary to develop and keep trust.

“The passion and connection that she has to the people in the Salinas Valley is so unique, impressive and inspiring,” Collman said. “She’s created an enormous treasure trove of information that we can mine, to look at many, many hypotheses. To this day, the CHAMACOS team is just knocking it out of the park.”

And to Collman, there was another tremendous benefit to CHAMACOS: It was a training ground for scores of Eskenazi’s former students, many of whom, like Kim Harley, and Asa Bradman, now at UC Merced, went on to become prominent environmental health researchers.

“She is so careful, not just teaching them how to do the research, but making sure every single paper is perfect,” Collman said. “I’ve gotten to know many of her trainees, and they are a wonderful group of scientists. Having Brenda as a mentor for even one year has been transformative for so many of them. She’s been an amazing leader.”

Harley said, “Working with Brenda totally defined my career. She was my mentor and continues to be my mentor. She’s been amazing. She helped me and encouraged me and enabled me to develop my own research portfolio and move into a faculty position at Berkeley, where I was able to start my own research program.”

Eskenazi believes that the mentorship role is one of the most, if not the most, important contribution a professor can make to science.

“I see my students and mentees as branches of a tree,” she said. “I train them and they train others—that is my biggest legacy.”

COVID-19 and a collaboration with Jennifer Doudna

At least it seemed that way, until the COVID-19 pandemic. As the disease emerged, Eskenazi recognized that the situations that farmworkers lived in—crowded conditions, difficulty getting medical care—made them especially vulnerable to the disease.

Quickly, she teamed up with her longtime CHAMACOS partners—Salinas Valley health clinics, agricultural companies and farmworker advocates—along with UC Berkeley Professor Jennifer Doudna, a Nobel Laureate in Chemistry.

Eskenazi and Doudna, the Li Ka Shing Chancellor’s Chair in Biomedical and Health Sciences, produced a study laying out the need for fast action to protect the agricultural workers. Their report, published in JAMA Open Network, motivated the state government to prioritize farmworkers for COVID vaccinations.

The result was an innovative van service that circulated around the Valley, inoculating farm workers against COVID and testing them and their families for the disease.

“Our coalition became a model for other counties in California and around the country,” she said. “Because of our work, farmworkers were prioritized for vaccination in many states.”