A new study finds lower IQ (intelligence quotient) in children born to mothers who during their pregnancy were living in close proximity to chemical-intensive agricultural lands where organophosphate pesticides were used. This study adds to the body of scientific literature that links prenatal exposure to organophosphate pesticides with lower IQ’s in children.

Organophosphate pesticides, a relatively older generation of highly neurotoxic pesticides still widely used on farms in California, have been associated with a broad range of diseases in both children and adults. This latest study supports health and environmental advocates’ call to eliminate these toxic pesticides in agriculture and move toward safer, sustainable, and organic management practices.

The study, titled Prenatal Residential Proximity to Agricultural Pesticide Use and IQ in 7-Year-Old Children, looks at 283 women and children from the agricultural Salinas Valley who are enrolled in the long-term Center for the Health of Mothers and Children in Salinas (CHAMACOS) study. Specifically, researchers looked at pregnant women living within one kilometer of agricultural fields where organophosphate pesticides were used. They found that at age 7, the children of those women had declines of approximately two IQ points and three verbal reasoning points per 522 pounds of pesticides applied nearby. The researchers made sure to point out that it has been estimated that each one point decrease in IQ decreases worker productivity by approximately 2%, and reduces lifetime earnings of $18,000 (in 2005 market standards).

Organophosphates are pesticides that were used in World War II as nerve agents. As potent neurotoxicants, organophosphates are extremely harmful to the nervous system, give that they are cholinesterase inhibitors and bind irreversibly to the active site of an enzyme essential for normal nerve impulse transmission. A 2015 study, which also used participants from CHAMACOS, found that a decrease in lung function in children was linked to exposure to organophosphates early in life. Another 2015 study found that prenatal exposure to chlorpyrifos, a potent organophosphate, is linked to tremors in children.

Although organophosphate use is on the decline in the U.S., the U.S. Environmental Protection Agency (EPA) has allowed the continued registration of many of these products. As a result of a lawsuit filed by environmental groups, the agency proposed a rule that would remove chlorpyrifos’ agricultural uses. However, EPA is not expected to finalize the rule until December 2016. In 2000, EPA announced the phase-out of residential uses of chlorpyrifos, with the exception of public health mosquito uses and golf courses.

This new study also found similar cognitive declines for three other classes of pesticides: neonicotinoids, pyrethroids, and manganese fungicides. Unfortunately, because the pesticides were almost always used in combination, it is impossible to determine whether the cognitive deficits were caused by organophosphate use alone, or by the interactive effect with other classes of pesticides.

This adds to the growing body of research on the interactive effects of pesticides on human health and the environment. A 2002 study by Warren Porter, PhD., professor of zoology and environmental toxicology at the University of Wisconsin, Madison, examined the effect of fetal exposures to a mixture of 2,4-D, mecoprop, and dicamba exposure —frequently used together in lawn products like Weed B Gone Max and Trillion— on the mother’s ability to successfully bring young to birth and weaning.

Researchers looked at pesticide concentrations diluted to levels that are considered “safe” by EPA and found that it is capable of inducing abortions and resorptions of fetuses at very low parts per billion. The greatest effect was at the lowest dose. For more information on pesticide synergy, see our 2004 article, “Synergy: The Big Unknowns of Pesticide Exposure.” For information on individual pesticide health effects, see our Pesticide Gateway.

Beyond Pesticides has long been critical of EPA’s risk assessment process, which fails to look at chemical mixtures and synergistic effects (or inert ingredients) in common pesticide products, as well as certain health endpoints (such as endocrine disruption), disproportionate effects to vulnerable population groups, and regular noncompliance with product label directions. These deficiencies contribute to its severe limitations in defining real world poisoning, as captured by epidemiologic studies in Beyond Pesticides’ Pesticide-Induced Diseases Database.

Ultimately, the widespread adoption of organic management is necessary to protect consumers and the environment in the long-term. Beyond Pesticides has long sought a broad-scale marketplace transition to organic practices that disallows the use of toxic synthetic pesticides by law and encourages a systems-based approach that is protective of health and the environment. This approach never allows the use of highly toxic synthetic pesticides, let alone toxic organophosphates, and advances a viable, scalable path forward for growing food. Find out more about why organic is the right path forward for the future of farming by going to Beyond Pesticides’ organic agriculture webpage.