Pesticides' effect on generations of field-workers

Salinas -- On a recent morning, the sun streamed through the doorway of Emelia Gonzalez's cozy store and onto rows of peaches, onions and tomatoes. Virtually every fruit and vegetable had been grown in or near the Salinas Valley, one of the most thriving agriculture regions in the world.

This region nestled in Monterey County, two hours south of the Bay Area, bears the nickname "the nation's salad bowl." Gonzalez knows its leafy greens well. As a former field-worker, she gathered them. As the co-owner of Lupita's Produce, she sells them. As a mother, she serves and eats them.

But Gonzalez, 38, also wonders if the pesticides used on them could sicken her family. "They say you should eat a lot of fruits and vegetables," she said in Spanish. "But all the chemicals that they put on them, they also harm us."

For more than a decade, UC Berkeley researchers have been trying to figure out how much truth there is to that.

In the late 1990s, the federal government announced it would fund research about environmental chemicals and children's health. Brenda Eskenazi, a professor of maternal and child health and epidemiology at UC Berkeley, hatched a plan to study Salinas Valley and the people who live there.

She and her team would attempt to understand how pesticides affect the health of families across generations. They would later expand their research to include other potential sources of environmental harm, such as the chemicals manufacturers put in their products.

Agriculture and health

Over the years, the study's dozens of findings would draw the attention of residents, doctors, scientists and activists. Hundreds of Mexican American families, many of them employed in the county's $4 billion agriculture industry, would take part. Because of them, the study is called the Center for the Health Assessment of Mothers and Children of Salinas - or Chamacos, which means "little children" in a Mexican dialect of Spanish.

At first, Eskenazi knew little about the Salinas Valley. But a colleague told her it had farming nearly year-round, meaning residents tended to stay put.

It sounded like an ideal place to dig.

Eskenazi had joined the UC Berkeley faculty in 1984 with a passion for environmental epidemiology, a nascent field at the time. Half Cuban, she also harbored a love of Hispanic culture, although she confesses to speaking Spanish poorly.

"California is a leading agricultural state in the nation," she recalled telling colleagues. "It is a no-brainer to me that we are obligated to study the health of people involved in agriculture."

Health problems prevalent

Good health is precarious for many of Monterey County's 422,000 residents. One-third of adults are uninsured; a quarter of children are in poverty. From 2002 to 2012, the percentage of special-education students with learning disabilities fell, but those with autism, intellectual disabilities and speech impairments increased, according to county data. Researchers wanted to understand the health problems that might be getting overlooked.

Then there were the pesticides. About 9 million to 10 million pounds were used annually throughout the county during the late 1990s. The amount has dropped slightly, though the county still ranks sixth in the state for pesticide use.

Eskenazi submitted a proposal to the National Institutes of Health to study low-income pregnant women and environmental effects on their children, and won the funding.

Now she just had to find moms.

Gonzalez moved to Salinas from Michoacán, Mexico, two decades ago, landing a job in the fields. She was among thousands of farmworkers in Monterey County who rise before dawn to gather an estimated three-fourths of the nation's salad greens.

In late 1999, Gonzalez became pregnant with her fourth child, a boy. During a checkup at Natividad Medical Center in Salinas, a volunteer with Eskenazi's study talked her into enrolling.

So began a series of annual or biannual visits to the researchers' trailer outside the hospital. During her pregnancy and delivery, Gonzalez gave them samples of blood, urine, cord blood and breast milk, let them inspect her house and answered dozens of questions about her lifestyle. She was among 601 pregnant women in the initial stages of the study.

Gonzalez's son, Richard Luna, was born in July 2000, one of more than 500 infants in the Chamacos project born between 2000 and 2002.

From the time they were 6 months old, and every one to two years after, researchers analyzed their urine, blood, saliva, teeth and hair. The kids had physical exams and took tests that assessed their motor skills and intelligence.

Much of what the scientists later reported was troubling. They found, for instance, that mothers in the study have higher traces of pesticides in their systems compared with the general U.S. population. Children with high prenatal exposure to pesticides show greater signs of developmental delays than those with low prenatal exposure.

There are limits to what researchers can learn. They can know Richard's blood pressure, IQ scores or pesticide levels. But they don't have enough information to link those factors to his poor eyesight or asthma, or tell his mother whether her time in the fields played a role in those issues. None of their research attributes a health problem to a single direct cause, and they stress that not every potentially harmful factor is equally dangerous in everyone.

"People aren't exposed to one thing," Eskenazi said. "They're exposed to everything around them, including air pollution and alcohol and smoking."

First focus: pesticides

Still, researchers have a lot of educated guesses.

They began their study by examining organophosphate pesticides, a commonly used type known to harm the human nervous system.

One of the researchers' first findings, in 2005, showed the chemicals' presence in the urine of the women in their study group in greater quantity than women of child-bearing age in the general U.S population.

Scientists also noticed that the higher the mother's pesticide levels prior to delivery, the higher the chance their baby would demonstrate abnormal reflexes, such as passive leg movements, after the first three days of life.

The finding preceded many others. At age 5, youths who had been exposed to high levels of pesticides in the womb were more likely than others to score high on tests that determine the likelihood of attention deficit hyperactivity disorder, or ADHD.

When the children were 7, researchers noted a 5.5-point drop in overall IQ scores for every 10-fold increase in the mothers' pesticides level during pregnancy.

There is difficulty, researchers admit, in pinning prenatal pesticide exposure directly to those issues. But Asa Bradman, the research team's associate director of exposures assessment, said there are problems after adjusting for factors such as age, smoking and other neurotoxicants.

Even so, Dr. Max Cuevas, CEO of La Clinica de Salud del Valle de Salinas, a clinic for low-income patients, said the study has illuminated potential causes of his patients' problems.

"The agricultural industry is very successful throughout California and throughout the nation because they're able to increase the means of production of food through the use of chemicals," he said. "Hopefully we can coexist with these chemicals so we're not suffering an inordinate amount of injury."

Flame retardants

In the mid-2000s, researchers decided to turn their attention on another kind of chemical, flame retardants, which are in virtually all couches sold in California and nationwide.

Curious about the compounds that at the time were drawing the attention of other scientists, Eskenazi said, "It was kind of a no-brainer to look at those." In a small study, 24 pregnant, mostly Mexican-born women revealed levels of flame retardants called polybrominated diphenyl ethers, or PBDEs, that exceeded levels found in people in Europe and Japan. They have been linked to hormonal and neurodevelopmental disruption in human and animal studies.