Higher Risk of Stillbirth Found Among Women Exposed to Pesticides
Pesticide exposure is linked to negative birth outcomes in a recent study in the American Journal of Epidemiology.
This study adds to that body of science, but is novel research since, “Epidemiological studies of pesticide exposures and stillbirth in the United States have not been published in the past two decades, a time period that has seen dramatic changes in pesticide use compared to the 20th century,” the authors state.
The study analyzes Arizona pesticide use records and birth certificates from 2006-2020. Researchers correlate mothers living within 500 meters of any pyrethroid, organophosphate (OP), or carbamate insecticide applications during specific windows before and during pregnancy with stillbirth.
The authors focus on exposure during the prenatal period, as it is a susceptible time frame in which any contact with pesticides can negatively impact health. Numerous studies report several adverse birth and childhood outcomes with prenatal exposure.
To link pesticide exposure and negative birth outcomes, Arizona records that encompass 1,237,750 births, 2,290 stillbirths and 27 pesticides were analyzed.
The authors “evaluate associations of pyrethroids, OPs, and carbamate insecticides with stillbirth by using data from the Arizona Pregnant Women’s Environment and Reproductive Outcomes Study (Az-PEARS), a project that links Arizona’s Pesticide Use Registry with birth certificates in the state of Arizona.”
The geocoded birth certificates were provided by Arizona’s Department of Health Services, which mandates the recording of all birth certificates for stillbirths/fetal deaths for fetuses greater than 20 weeks gestation.
Arizona also requires that all commercial agricultural pesticide applications, including aerial applications be reported, allowing the authors to determine maternal exposure.
“Mothers were defined as exposed,” the researchers comment, “if their residential address on the birth certificate was within 500 meters of a given pesticide application, during a specified trimester (preconception/Trimester 0; Trimester 1).”
During the first preconception window (the window from 180 days to 90 days prior to conception), correlation to stillbirth for only the OP insecticide tribufos is noted, while the second preconception window (the 90 days immediately preceding conception) shows associations for the specific pyrethroids cyfluthrin, zeta-cypermethrin and pyrethroids as a class.
OP associations are observed as a class, specifically malathion, during the second preconception window, as well as the carbamates, carbaryl and propamocarb hydrochloride.
During the first trimester, the pyrethroids fenpropathrin and permethrin, OPs as a class, the specific OPs acephate and dimethoate and the carbamate formetanate hydrochloride are associated with stillbirth.
“Stillbirth, fetal death, and miscarriage present major physical and psychological health burdens for pregnant women,” the authors state.
They continue, “Stillbirth occurs in approximately 4-5 per 1,000 births in developed countries, and up to 3% of births in low and middle income countries.”
In finding a correlation between the incidence of stillbirth and pesticide exposure, the study highlights additional risks during pregnancy and for those who wish to become pregnant. Those who live near agricultural areas and specifically female farmworkers are at a disproportionate risk for these adverse effects.
Previous toxicology studies document the pyrethroid cyfluthrin as altering placental development, which has been hypothesized as a cause of stillbirths and miscarriages.
As pesticide exposure causes biological effects on female reproductive organs and hormonal activity, this provides a possible explanation for the correlation of exposure to negative birth outcomes.
“Metabolites of permethrin and cypermethrin (which are shared with zeta-cypermethrin) act as endocrine disruptors and interact with cellular estrogen receptors.
Such hormonal influences can affect women’s reproductive cycles and cycle lengths, and the overall quality of the uterine environment during pre-implantation,” the authors say.
Any effects on uterine and reproductive cells and placental health from pesticide exposure can influence the outcomes of pregnancy.
Impacts on male reproduction from pesticide exposure are also documented. Beyond Pesticides has a long history of highlighting the relationship between reproductive anomalies and toxic pesticides, particularly with endocrine-disrupting compounds.
Studies show decreased male fertility including reduced sperm count and quality, as well as abnormal sperm development.
The U.S. Environmental Protection Agency (EPA) fails to regulate endocrine disruptors, which prompts advocates to call for proper data analyses prior to product registration, as they say the agency’s evaluation process is too narrow.
More extensive examination is needed prior to products being approved for use since many widely used pesticides lack comprehensive testing.
On Aug. 6, the EPA issued an emergency suspension of all registrations of the pesticide dimethyl tetrachloroterephthalate, or Dacthal, under the Federal Insecticide, Fungicide and Rodenticide Act due to pregnant mothers, who were exposed to this compound, experiencing negative birth outcomes.
The press release says exposure to Dacthal leads to “changes to fetal thyroid hormone levels, and these changes are generally linked to low birth weight, impaired brain development, decreased IQ and impaired motor skills later in life, some of which may be irreversible.”
EPA has not issued an emergency action such as this in almost 40 years, which raises flags and highlights how this would have been avoidable if initial testing had been more thorough.
Active ingredients in pesticide products are proven harmful years after being approved for use and after deleterious and often irreparable, damage to human health and the environment has occurred.
By transitioning to organic agriculture and land management, these impacts can be avoided.
The principles of organic offer a holistic solution that alleviates climate change improves soil health, restores biodiversity, enhances ecosystems and contributes to human health for future generations.
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