The UC Berkeley School of Public Health’s CHAMACOS study—the longest running longitudinal birth cohort study of pesticides and other environmental exposures among children in a farm worker community—has found maternal exposure to pesticides during pregnancy is associated with earlier labour, poorer neonatal reflexes, developmental disorders and increased risk of attention problems in children. The research also shows a link between organophosphate pesticide exposure and lower IQ at school age.

◊ By Dr Jessica Shade, PhD

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For farm workers and those living in agricultural areas, pesticides can have a direct impact on human health. These pesticides not only affect those who handle them on farms, but can also be found in the homes of nearby families and children due to drift, or by being carried home on the clothing and boots of farm workers. Over the last decade, dozens of studies have shown associations between exposures to agricultural pesticides and serious health concerns. For example, recent research has shown that pesticide exposure can harm reproductive health, is linked with respiratory illness in children, rheumatoid arthritis, coronary heart disease, renal disease, and Parkinson’s disease, and can contribute to cancers such as thyroid cancer, prostate cancer, colorectal cancer, lung cancer and breast cancer.

Children in agricultural communities are at particular risk for pesticide exposure at a time in their lives when they are most vulnerable to harmful chemicals. Children have higher exposures to environmental chemicals than adults because they eat, drink and breathe more than adults on a per-bodyweight basis. They also spend time near the floor where house dust may be contaminated with pesticides. Children explore their environments with their hands and mouths, increasing exposure even more. They also have undeveloped metabolic pathways and, thus, often have a reduced ability to metabolise chemicals such as pesticides into non-toxic water soluble forms that can be excreted as urine.

Unfortunately, even before birth, exposure to pesticides can have long term impact on children’s lives. Prenatal exposure to chemicals may alter the development of networks that build our individual neural architecture. Being exposed to a neurotoxic chemical during this process can permanently alter the structure of that architecture, causing long term impacts such as learning difficulties or behavioural issues.

Children have higher exposures to environmental chemicals than adults because they eat, drink and breathe more than adults on a per-bodyweight basis. They also spend time near the floor where house dust may be contaminated with pesticides. Children explore their environments with their hands and mouths, increasing exposure even more. They also have undeveloped metabolic pathways and, thus, often have a reduced ability to metabolise chemicals such as pesticides into non-toxic water soluble forms that can be excreted as urine

Recent studies examining prenatal exposure to pesticides are concerning, with studies showing that exposure before birth may be linked to several conditions, including the development of obesity and metabolic disorders, developmental problems, poorer neurodevelopment, and decreased IQ, among other health challenges.

One of the most important studies looking at the impacts of exposure to pollutants on children’s health is a long term study being conducted by the Center for Environmental Research and Children’s Health (CERCH). CERCH is a world renowned research centre at UC Berkeley School of Public Health that leads the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study, which is the longest running longitudinal birth cohort study of pesticides and other environmental exposures among children in a farm worker community. CHAMACOS also means ‘little children’ in Mexican Spanish, which reflects the population engaged in the study.

This community-university partnership commenced in 1999, when pregnant women in California’s Salinas Valley enrolled in the study. Over the last 17 years, the families have been tested for exposures to pesticides and other chemicals while assessing the children’s growth, health and development. The study was expanded around 2010 to include 300 additional 9-year-olds, and currently has over 600 children participating in the study.

The CHAMACOS study has resulted in almost 150 publications, with some truly groundbreaking results. For example, their research has found that maternal exposure to organophosphate pesticides during pregnancy is associated with earlier labour, poorer neonatal reflexes, developmental disorders and increased risk of attention problems in children. The research also showed a link between organophosphate pesticide exposure and lower IQ at school age.

Unfortunately, children growing up in stressful environments are even more likely to experience the negative impacts on mental function from prenatal organophosphate pesticide exposure.

There are several ways to reduce exposure to pesticides for this especially vulnerable demographic group. Organic farms, for example, can protect farm workers and farming communities from exposure to many harmful chemicals, because organic certified farming operations are prohibited from using most synthetic pesticides. The benefits of organic farming associated with farmer and farm worker health have been characterised as “one of the most important advantages of organic management for farm workers” by a recent review of the impacts of organic food and farming on environmental and human health published in the journal, Science Advances.

If transitioning to organic farming is not an option, there are also many ways that exposure can be reduced through proper safety practices. For example, studies have shown that wearing gloves can reduce pesticide exposure to farm workers. Additionally, pesticides can accumulate on clothing, so wearing coveralls and changing clothes and shoes before returning home, as well as, washing work clothes separately from other clothing, can reduce exposure for farm worker families. Other practices, such as increased hand-washing, may also help. To make things easier for farm workers, growers can decrease the distance farm workers must walk to reach hand washing facilities, increase break times, and change worker payment policies from piece-rate to hourly compensation so workers can take the time to wash their hands. Education is critical for ensuring safe use of pesticides in the field, and studies examining training programmes and worksite interventions have shown that these sessions can reduce pesticide exposure for children of farm workers.

It is essential to provide farmers and farm workers with educational sessions that both provide information about practices for pesticide exposure reduction and the vulnerability of exposure to children and other family members. The newly revised Worker Protection Standards in the United States provide a good model for rules and education about pesticides for farm worker protection. This education is important to reduce pesticide exposure to farm workers and their families and also to protect public health.

The author is Director of Science Programmes, The Organic Center, Washington DC