Autism and Pesticides

Increased autism spectrum disorders found in children of mothers exposed to pesticides during early pregnancy

Short Summary:

This study showed that fetuses exposed to specific pesticides during early gestation are born with massively increased chances of having autism spectrum disorders.

Study Design

  1. This research project was performed by Public Health Institute of Oakland, CA; California Department of Health Services, Richmond, CA; and School of Public Health, University of California, Berkeley, CA.
  2. The researchers identified 465 children with Autism Spectrum Disorders (ASD) born during 1996-1998 using the California Department of Developmental Services electronic files and matched them by maternal date of last menstrual period to 6,975 live born, normal birth weight, term infants as controls.
  3. The mother's proximity and exposure to pesticide application was determined using California Department of Pesticide Regulation records and refined using Department of Water Resources land use records.
  4. Exposure levels for mothers of normal babies and mothers of ASD babies were compared.

ASD Background Information

  1. "Austism" is a term that refers to a set of neurodevelopmental disorders that are characterized by impaired social interaction, restricted communication, and repetitive, stereotypic behaviors. The number of children reported as having Autism Spectrum Disorders (ASD) has risen dramatically since the early 1990s.
  2. The current theories for development of ASD suggest that functional impairment happens during brain development either through genetic or environmental causation, or both.

Pesticide Backgroung Information

  1. Many of the pesticides in use today have known neurological toxicities that could damage the fetus during early gestation, when neurological development is extremely rapid. Current knowledge suggests that ASD damage is very likely to happen in early fetal brain development.
  2. Pesticides are prone to drift, and dose calculations are possible for some distance from sprayed fields.
  3. Pesticides are easily transferred across the placental barrier, and the child's blood-brain barrier is known to be permeable to these toxins well into the first year of life. Researched links of maternal residency in pesticide usage proximity have been shown for cancer and neurodevelopmental delay in children.
  4. Despite the above knowledge and theories, little is known about early gestational exposure to pesticides and ASD.

Results

  1. Two pesticides were selected for intense study due to extensive use in the study area, and because they are not used in any consumer obtainable products. The pesticides were dicofol and endosulfan, both of which are organochlorines and both were used on cotton, fruits, vegetables, beans, and nuts. Residues of each of these chemicals are routinely detected in a wide variety of food sources in the US. In this study area, these two pesticides accounted for 98% of the total pounds of pesticides used.
  2. Risk for ASD was consistently associated with residential proximity to organochlorine pesticide applications occurring around the period of CNS embryogenesis; this association appeared to increase with dose and was attenuated with increasing distance of residence from the field site.
  3. In this study, the results indicate that the chances of ASD development for any exposure was 6.1 times the rate in unexposed fetuses. More specifically, fetuses exposed to the highest level of pesticides during the critical period of neural tube closure were 7.6 times more likely to subsequently be diagnosed with ASD. This is 760% higher ASD rate than expected!
  4. The authors are cautious and conclude that this information needs to be duplicated to be strengthened.

Complete Study is available online at (http://dx.doi.org/), with DOI number of 10.1289/ehp.10168