Exposure to multiple pesticides increases the chances of pregnancy complications compared to exposure to just one pesticide, new peer-reviewed research suggests. The findings raise new questions about the safety of exposure to widely used pesticides and herbicides in food and agricultural communities.
The study, which bio-monitored pregnant women in a heavily agricultural state in Argentina, adds to recent-but-limited evidence pointing to heightened dangers in mixtures of pesticides.
The authors say research into how pesticide mixtures impact human health is important because the vast majority of studies look at exposure to a single pesticide, and regulations on the substances’ use are developed based on toxicity to just one.
However, people are frequently exposed to multiple pesticides in non-organic meals, or when living in agricultural regions around the world. Studying exposure to those mixtures and other environmental factors is “essential” to protecting people’s health, said the authors, with the National University of the Littoral in Argentina.
“The concept of the exposome, which encompasses all lifetime environmental exposures, underscores the importance of studying pesticides as mixtures rather than in isolation,” the authors wrote.
The study comes on the heels of University of Nebraska research that found state cancer records and bio-monitoring data showed that exposure to multiple pesticides could increase the chances of children developing brain cancer by about 36%.
The new study checked for pesticides in the urine of nearly 90 pregnant women in Santa Fe, Argentina, a heavily agricultural region, and monitored their pregnancy outcomes. About 40 different pesticides were detected.
At least one pesticide was found in the urine of 81% of women, and 64% showed multiple pesticides. Of those, 34% had pregnancy complications.
The number of women living in urban areas who had at least one pesticide in their body was only slightly lower than those in rural districts, suggesting that food is also a meaningful exposure route. But about 70% of women in rural settings showed multiple pesticides, compared to 55% of women in urban settings, highlighting a greater risk among the former.
Rural participants were over twice as likely to have pregnancy-related complications compared to urban, in part because they are more frequently exposed to mixtures.
The Santa Fe region grows dozens of crops, including lettuce, cabbage, chicory, tomato, parsley, spinach, carrot, bell pepper, potato and strawberry, and the wide range of crops leads to the use of more pesticides, the authors wrote.
“The increased prevalence of pregnancy-related complications among rural participants highlights the need for a comprehensive review of pesticide use protocols, exposure limits and health risk assessments in agriculture and horticulture programs,” the authors said.
Gestational hypertension was among the most common pregnancy-related complications, and the most common outcome was intrauterine growth restriction, a condition in which the fetus does not grow to a normal weight during pregnancy.
The findings may also point to dangers in the type of pesticide to which women are exposed, the authors wrote. Those who had complications showed higher levels of triazole fungicides, a pesticide class that is widely used on crops like corn, soybeans and wheat. Some previous evidence suggests it’s a reproductive toxicant, and the authors say their findings show the need for more research on the class’s potential effects.
Though not all the same pesticides are used in the US or other countries as in Argentina, the use of triazole fungicides increased four-fold in the US between 2006 and 2016, especially in the southeast and midwest. Still, it has drawn little regulatory scrutiny.
Exposure to mixtures of pesticides in general “is the rule, not the exception”, said Nathan Donley, a pesticides researcher with the Center for Biological Diversity, who was not involved with the study.
“For the most part we have absolutely no clue how different mixtures interact in utero, in a child or in an adult,” Donley said. “Some mixtures probably aren’t doing much of anything, others are probably causing significant harm that we have not identified yet.”
There is little regulatory oversight of pesticide mixtures in the US, in part because determining health impacts of mixtures is complicated, Donley added.
“The US tends to just default that it’s all safe until proven otherwise, and since there is very little research on pesticide mixtures, it’s rarely proven otherwise,” Donley said, adding that the unknown risks calls for the use of greater precaution.
The authors note that the paper’s sample size is small, and the findings point to the need for a larger bio-monitoring study.
“Greater efforts are required to deepen and expand the evaluation of human exposure to pesticides in vulnerable populations,” the authors wrote.