Agricultural pesticide use is a significant source of occupational and environmental endocrine disruptor exposure in the United States. Farmworkers and their families are at higher risk of exposure than the general population. Pregnant women in farmworker families may be exposed to high levels of endocrine disrupting pesticides as the result of their work in the fields, contamination of their homes, or both. Over 600,000 pounds of endocrine disrupting (ED) pesticides are used annually in the Salinas Valley. Additionally, women born in Mexico have been found to have elevated levels of DDT and DDE and other persistent ED organochlorine pesticides compared to levels found in U.S.-born participants. Approximately 90% of our study' population was born in Mexico. Although animal studies suggest that ED pesticides potentially affect neurodevelopment, no studies to date have examined these effects in humans. We examined this relationship in approximately 550 children from predominantly low-income Latino farmworker families living in the Salinas Valley of Monterey County, California. These children, whose mothers were enrolled during pregnancy, are participants of Center for Health Assessment of Mothers and Children of Salinas or CHAMACOS, birth cohort study which alms to investigate the effects of pesticides and other environmental exposures on the health of pregnant women and their children living in the Salinas Valley, CA, an agricultural area. We measured biomarkers of exposure to 14 persistent organochlorine pesticides in archived CHAMACOS serum samples. Tests for non-persistent pesticides in urine of pregnant women included fungicides organophosphate insecticides, pyrethroid, carbamate, and organochlorine insecticides, triazine and choroacetanilide herbicides, naphthalene; and pentachlorphenol, and included development of a new test for ETU, a toxic metabolite of bis-dithiocarbamate fungicides. Prenatal and delivery medical records were abstracted by a registered nurse. Mothers were interviewed prenatally and postnatally about their sociodemographlc characteristics, habits, housing, exposure, work and medical history. We assessed neurodevelopment of neonates < / = 2 months old using the Brazelton Neonatal Behavioral Assessment Scale. The Bayley Scales of infant Development, a well-known method for developmental assessments of young children, were used to test the mental and physical skills of the women's babies at six, 12 and 24 months. The Bayley Scales were administered in Spanish or English by study staff who were blind to exposure status. All women had organochlorine pesticides in their blood, and median levels of DDT and DDE were several times higher than the general U.S. population. For each tenfold increase in DDT levels measured in the mother, we found a corresponding two- to three-point decrease in the children's mental development scores at 12 and 24 months. The highest in-utero DDT exposures in children were associated with a seven- to 10-point decrease in Bayley mental scores, compared to the lowest exposures. In 'the physical skills evaluations - known as psychomotor testing - there were two-point decreases in children's scores at six and 12 months for each tenfold increase in DDT levels in the mothers. No decrease was found at 24 months. When we evaluated the effects of DDE on development, we found associations that were similar to those for DDT, but not as strong. We observed no adverse associations between organochlorine pesticide levels and birth weight or crown-heel length. Higher HCB levels were associated with reduced gestational duration. Most pesticides in urine had low detection frequencies. For example, ETU was detected in approximately 20% of the maternal urine samples. Nine compounds were detected greater than 50%, with two potentially related to current use pesticides in the Salinas Valley (TCPy, derived from chlorpyrifos, and 1-napthol, derived in part from carbaryl). Malathion and chlorpyrifos urinary metabolites levels were not associated with birth weight, birth length, head circumference, ponderal index and duration of gestation; however, higher levels of total dimethyl organophosphate metabolites in maternal urine were associated with shorter gestational duration. Median levels for five pesticides (2,4-dichlorophenol, 2,5,dichlorophenol, 2-naphthol, para-nitrophenol and 3,4,6-trichloro-2-pyridinol (TCPy)) were higher in our population compared to levels reported for pregnant women in NHANES (n=224). This finding suggests that exposures to the parent compounds of these metabolites were higher in our population of pregnant women compared to the general population of United States pregnant women. Overall, we did not observe associations between agricultural exposure risk factors and levels of nonpersistent metabolites in maternal urine, nor did we observe associations between exposure to non-persistent pesticides and child development. This study provided the first data on in utero exposure and health effects of ED pesticides in a highly exposed population. Our key finding was that prenatal exposure to DDT, and to a lesser extent DDE, was associated with neurodevelopmental delays during early childhood, although breastfeeding was found beneficial, even among women with relatively high exposure. Although use of DDT in agriculture is now banned worldwide, the World Health Organization and the United States Agency for International Development are implementing programs to increase use of DDT internationally for control of mosquitoes carrying malaria. Our results indicate that programs to protect worker health are needed to ensure that workers applying DDT for malaria control are not excessively exposed. Additional research is also needed to assess the specific contribution of Indoor Residual Spraying (IRS) of DDT to general population exposures.
Brenda Eskenazi, PhD, School of Public Health, University of California at Berkeley, 2150 Shattuck Avenue, Suite 600, Berkeley, CA 94704-7380