PETITION TO REVOKE ALL TOLERANCES AND CANCEL ALL REGISTRATIONS FOR THE PESTICIDE CHLORPYRIFOS

The petition argues that the EPA's risk assessments for chlorpyrifos are flawed because they ignore robust peer-reviewed data on developmental neurotoxicity, endocrine disruption, and inhalation exposure. The petitioners claim that prenatal and early-life exposure causes permanent cognitive impairment and that the EPA's reliance on a 10% cholinesterase inhibition benchmark is insufficient to protect vulnerable populations. They further highlight that inhalation exposure in rural areas far exceeds dietary exposure and that the U.S. continues to export high volumes of the pesticide to developing countries.

• Chlorpyrifos is an organophosphate insecticide used extensively in the U.S., with approximately 10 million pounds applied annually, primarily on corn (5.5 million pounds ai).
• Genetic variability in the Paraoxonase (PON1) enzyme, which detoxifies chlorpyrifos, creates significant differences in susceptibility; one study reported a 164-fold variation in sensitivity between the most sensitive newborn and the least sensitive mother.
• Prenatal exposure to chlorpyrifos is linked to poor birth outcomes and long-term developmental delays. In a New York City cohort, children with plasma levels > 6.17 pg/g were significantly more likely to experience delays in cognitive and psychomotor development, as well as ADHD and pervasive developmental disorder problems.
• Chlorpyrifos may act as an endocrine disruptor, interfering with thyroid hormone function and reproductive hormones. Evidence suggests it can reduce thyroid stimulating hormone (TSH) and thyroxine in men and inhibit pituitary cell growth in rats.
• Data from the 2004 National Institutes of Health Agriculture Health Study indicates a statistically significant association between chlorpyrifos lifetime exposure and lung cancer; those in the highest quartile of exposure had a relative risk of 2.18.
• Chlorpyrifos causes neurotoxic effects through non-cholinergic mechanisms that occur at doses below the 10% cholinesterase inhibition (ChEI) threshold used by the EPA, including the inhibition of Cyclic Adenosine Monophosphate (cAMP) production in the rat brain.
• The EPA's Cumulative Risk Assessment (CRA) is accused of misrepresenting data from a study by Zheng et al. to eliminate the FQPA safety factor, despite the study showing that neonates are more sensitive to acute toxicity than adults.
• Inhalation exposure in rural areas is a primary source of chlorpyrifos exposure that the EPA failed to quantify. Monitoring in Tulare County, California, showed air concentrations exceeding the acute 24-hour Reference Exposure Level (REL) for one-year-old children by factors of 31 to 48.
• Inhalation exposures for infants living near application sites can be over 75 times higher than the acute Population Adjusted Dose (PAD) estimated by the EPA for dietary exposure.
• The U.S. exports high volumes of chlorpyrifos—between 7 to 9 million pounds annually since 1997—creating hazards in developing countries where required safety equipment is likely unavailable.

APA

Earthjustice (2007). PETITION TO REVOKE ALL TOLERANCES AND CANCEL ALL REGISTRATIONS FOR THE PESTICIDE CHLORPYRIFOS. https://earthjustice.org/wp-content/uploads/cpr.petitiontorevokealltolerances2007.pdf

Chicago

Earthjustice. PETITION TO REVOKE ALL TOLERANCES AND CANCEL ALL REGISTRATIONS FOR THE PESTICIDE CHLORPYRIFOS. 2007. https://earthjustice.org/wp-content/uploads/cpr.petitiontorevokealltolerances2007.pdf.

Wikipedia

{{cite press release |author=Earthjustice |title=PETITION TO REVOKE ALL TOLERANCES AND CANCEL ALL REGISTRATIONS FOR THE PESTICIDE CHLORPYRIFOS |date=12 September 2007 |url=https://earthjustice.org/wp-content/uploads/cpr.petitiontorevokealltolerances2007.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@misc{earthjustice2007petition, author = {{Earthjustice}}, title = {{PETITION TO REVOKE ALL TOLERANCES AND CANCEL ALL REGISTRATIONS FOR THE PESTICIDE CHLORPYRIFOS}}, publisher = {Earthjustice}, year = {2007}, month = sep, url = {https://earthjustice.org/wp-content/uploads/cpr.petitiontorevokealltolerances2007.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }