Tuesday, December 21st, 2010
SALINAS VALLEY, Calif. – Locals call this region the world’s salad bowl. Dole, Naturipe and Fresh Express have farms here, where much of the global fruit and vegetable trade emerges in neat green fields just over the hills from the Pacific coast.
The difficulties facing migrant workers who plant and pick the crops is an old story. But in Salinas, a new story is emerging — one with serious implications for the rest of the country — and an ending that has yet to be written.
It is here that University of California, Berkeley public health professor Brenda Eskenazi and her colleagues have spent the past 12 years studying mothers and children who are exposed to pesticides used in the fields.
The CHAMACOS Center — Center for Health Assessment of Mothers and Children of Salinas — is a joint project of UC Berkeley, the Natividad Medical Center, Clinica de Salud Del Valle de Salinas and other community organizations. Its goal is to assess exposure to pesticides and other pollutants in pregnant women and young children, to determine what effect the exposures have on their health, and to try to prevent exposure.
After forming partnerships with local health-care providers more than 10 years ago, the researchers were able to recruit 600 women, who submitted to a series of tests to measure pesticide levels in their bodies. Investigators tracked the women throughout their pregnancies, waiting at hospitals as babies were born to collect the umbilical cord blood. As the children grew, Eskenazi and her team also charted their growth, mental development and general health.
CHAMACOS study photo
Farmworkers plant strawberries in Salinas, Calif., where a longterm study examines the effect of pesticides on children.
Eskenazi’s work has set off alarms among public health officials.
She and her colleagues have found that at age 2 the children of mothers who had the highest levels of organophosphate pesticide metabolites in their blood had the worst mental development in the group. They also had the most cases of pervasive developmental disorder based on their mother’s report.
At age 5, the children whose mothers were most exposed during pregnancy had poorer attention spans compared to those born to mothers who had lower levels of pesticide metabolites in their urine. Metabolites, as referred to here, are compounds that are formed as a chemical breaks down in the body. They are evidence that someone was exposed to a chemical.
“We have very, very high reports by the mother of behaviors consistent with pervasive developmental disorder,” Eskenazi said at a recent neurotoxicology conference. “These include signs like the child is afraid to try new things, can’t stand anything out of place, and avoids looking others in the eye. This is considered to be autism spectrum behavior.”
She and her colleagues currently are studying whether children whose mothers were exposed to pesticides during the pregnancy are more likely to develop learning disabilities, behavior problems, asthma, diabetes and obesity than the other children.
Eskenazi, who is director of the university’s Center for Environmental Research and Children’s Health, showed a slide with her study results, and quipped, “This is my anti-public health message slide. Kids who eat more fruits and vegetables have higher pesticide metabolites in their urines.”
The levels of pesticide metabolites found in the pregnant women studied by CHAMACOS are higher than women who don’t live in agricultural settings. But the Centers for Disease Control and Prevention has found evidence that the pesticides contaminating kids around the country, regardless of proximity to agriculture, is high enough to raise questions about the impact those pesticides may have on their growing brains. These days, children are exposed to pesticides used in their homes, residues in their food and spray that drifts from fields onto playgrounds and other sites.
Eskenazi’s work is being considered by the EPA as the agency decides what to do with dozens of pesticides and other chemicals suspected of being developmental neurotoxicants, that is, chemicals that can rewire the brain and nervous system while a fetus is growing and continuing to affect the brain in early life.
On a sunny day last summer, Eskenazi and Associate Director Kim Harley visited their headquarters in an old trailer squeezed between a hospital and a county jail.
The trailer is cozy, with low couches for the kids, teddy bears and dolls, videos of movies and cartoons. On the wall is a map of Salinas, with pins showing the neighborhoods where the participants live. The group has visited many of the participants at home, collecting samples of pesticides and using a GPS to determine how far they are from the fields.
Off the main room are small offices where technicians take blood and urine samples from the children and their mothers, and examiners administer a battery of tests designed to assess their memory, attention span, IQ and other cognitive and emotional indicators.
On this day, child examiner Helen Aguirre is working with a 9-year-old boy. He is shy, but they coax him into allowing them to check his height. Then he follows them into the room for the other tests. They tell him a story about a fishing trip, and then ask him to repeat the salient facts. They talk about something else for a while, then ask him how much he remembers about the fishing tale. They allow breaks for snacks and a bit of television. The whole thing takes between 2½ and 3½ hours.
This is considered an observational study, but the researchers refer the parents to a doctor if they find any health problems, such as asthma, which is increasingly prevalent in Salinas, or high blood pressure. Next door is the hospital where most of the kids were born, and just across the street, rows of lettuce, celery and broccoli.
“We have a high amount of pesticides used near this building,” Eskenazi said. “There are fields close by. When the wind is right, the pesticides blow in.”
The project has been so successful that the federal government has funded the researchers to add a few more chemicals to the testing. Eskenazi is now going back into her bank of blood, urine and other samples and checking for BPA and other pollutants. Recently, Harley published a paper showing that women who had the highest levels of flame retardants in their blood took longer to get pregnant than women with lower levels.
Their work also served as a model for the recently launched National Children’s Study, run by the National Institutes of Health, which seeks to examine the effects of the environment on 100,000 children, tracking them from before birth until age 21.