Pesticides' effect on generations of field-workers
More than a decade of research in the Salinas Valley of California - one of the most thriving agriculture regions in the world - has shed light on environmental hazards and their potential health risks.
Stephanie M. Lee reported this story for the San Francisco Chronicle as a 2013 California Endowment Health Journalism Fellow. Other fellowship stories by Lee include:
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."
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.
"We said, 'Whoa, we better do a bigger study,' " Eskenazi said.
More than 260 children in their study, all born in California, turned out to have some of the world's highest documented levels. Their PBDE serum concentrations were seven times higher than those in children living in Mexico.
Studies found that the higher a pregnant woman's PBDE levels, the slightly lower were her odds of becoming pregnant each month, although it wasn't clear why. Her baby also tended to weigh less at birth.
And when they reached elementary school, children whose mothers had high PBDE levels at pregnancy tended to score lower on some IQ tests, have decreased motor skills and struggle to pay attention.
Advocates and politicians have cited the Chamacos findings, among others, to criticize flame retardants, and a state agency is in the process of reversing the law that led to the chemicals' inclusion in furniture.
But the North American Flame Retardant Alliance, an industry group, takes issue with the findings. "In a study that looks at such a broad array of environmental and socioeconomic factors, it is nearly impossible for scientists to actually determine cause-and-effect relationships," it said. "Correlations between PBDE exposure and adverse health effects are not conclusive."
Eskenazi's team has also scrutinized a controversial compound in plastics. In newborn boys and pregnant mothers, bisphenol A seems to alter thyroid hormones, which are key for healthy growth, the researchers said last year when many states had banned or were considering banning BPA from products.
Eskenazi and her team aren't done with their research, but she says it's up to policymakers to make changes. Turning findings into policies, however, can be tricky.
Advocates may seize on the Chamacos studies to argue for the elimination of pesticides. But Eric Lauritzen, the county's Agricultural Commissioner, says the chemicals are not universally toxic and are essential to keeping the industry productive.
Policies should instead be crafted to reduce harm in the specific ways pesticides reach people, he said - ways that, in his view, have not been positively identified. "It's way more complex than just saying, 'We think this has a health effect and therefore this is the action we should take,' " he said.
The state's Department of Pesticide Regulations has protocols for field-worker health and safety, and Chamacos studies show that glove-wearing and hand-washing in the fields reduce pesticide exposure.
But some workers still are forced to walk unprotected into areas sprayed with pesticides, said Jesus Lopez, a community worker for California Rural Legal Assistance in Monterey County. Despite the Chamacos study, he said, "I don't see a difference in the fields."
As a scientist, Eskenazi toes a careful line. She's quick to dismiss the label "advocate," but she also acknowledges that "it's not enough to just be a scientist in the ivory tower. We needed to translate, and we needed to empower the community with knowledge."
Researchers have had some success educating residents, although earning their trust took time. At first, undocumented families thought they were a front for immigration enforcement.
So the researchers had health, agriculture and immigration leaders vouch for them in the community. They've trained a team of bilingual locals to collect data. Today, in lectures and puppet shows, the staff imparts tips in plain language: Produce is great - just wash it first.
When they spot problems like ADHD, they refer participants to social services. They also invite families to annual forums to learn more about the research. Last year's drew 500 people.
Sandy Carranza, 34, said she has learned a lot since she enrolled while pregnant with her son, now 12. "We always wash everything, even the vegetables."
The findings may resonate beyond the valley and across the nation, other researchers say.
"They're helping us understand the links between early exposures and health outcomes that are significant not only in terms of children's functioning and well-being in their early years, but also ... over the entire life course," said Frederica Perera, director of the Columbia Center for Children's Environmental Health in New York, which has collaborated with UC Berkeley.
Other scientists have reached similar conclusions about the same exposures. In a 2011 study of New York City children, for example, Mount Sinai School of Medicine found that those with prenatal exposure to pesticides were likely to lag in mental development in their early years.
More than just a study
More studies will follow. Right now, the UC Berkeley team is examining baby teeth for traces of banned fungicides that contain manganese, a chemical element toxic in high doses.
Eskenazi's intent is not to scare residents, but to give them meaningful knowledge. "In my heart, this is more than just a study for me," she said. "This is a population I deeply care about."
The professor plans to keep up the studies as long as there is funding - and Gonzalez and her son plan to keep showing up. Maybe, the mother says, they can help their neighbors understand what is all around them.
"We are all breathing it in," she said.
The story originally ran in the San Francisco Chronicle on September 23, 2013.