Public Comment Period on Paraquat Open Through February 13.
By Natalie Willis, Reporter, Valley Ag Voice
On Dec. 30, the Department of Pesticide Regulation provided an end-of-year update on pesticides undergoing reevaluation as well as its estimated timeline for the completion of each reevaluation.
According to California’s Food and Agricultural Code, section 12824 requires DPR to continuously evaluate registered pesticides in the state — reevaluation serves as one of the primary methods DPR employs to fulfill this requirement. The department utilizes this information to assess potential risks from pesticide use and to inform any potential mitigation measures.
Active reevaluations include paraquat dichloride, chloropicrin, cyfluthrin, diphacinone, non-agricultural outdoor neonicotinoids, and second-generation anticoagulant rodenticides.
PARAQUAT REEVALUATION
Initially introduced as a proposal to completely ban the use and sale of paraquat dichloride in California, Assembly Bill 1963 has since evolved into a reevaluation of the pesticide following multiple legislative sessions and revisions.
AB 1963 was signed by Governor Gavin Newsom on Sept. 27, 2024, requiring DPR to complete a reevaluation of paraquat dichloride before Jan. 1, 2029, and make the determination to retain, cancel, suspend its registration, or place appropriate restrictions on the use of pesticide products containing the active ingredient.
On Dec. 30, DPR published preliminary scientific reports and opened a 45-day public comment period. DPR’s preliminary findings include an ecological report and a human health report.
The Center for Biological Diversity stated that paraquat is linked to Parkinson’s disease. According to DRP’s preliminary human health report — which utilized five observational studies evaluating the relationship between paraquat and Parkinson’s disease — the findings do not establish a clear link between paraquat use and the development of Parkinson’s disease.
“Tomenson et al. (2021) did not find evidence of an increased risk of Parkinson’s disease-related mortality among the UK workforce who manufactures paraquat when compared to the expected national mortality,” the report stated. “And, while Cheng et al., 2017 found a significant association between ambient exposure to paraquat and the development of Parkinson’s disease, issues with the way investigators ascribed paraquat for the Taiwanese population call into question the veracity and applicability of the findings.”
The strongest evidence linking paraquat exposure to Parkinson’s disease comes from studies by Shrestha et al. (2020) and Paul et al. (2024) — cited in DPR’s report. The 2020 study showed no clear dose-response relationship between the amount of paraquat exposure and the risk of developing Parkinson’s disease, and while the study found a slight increase in risk for pesticide applicators, it was not statistically significant.
The study identified a higher risk for individuals exposed to paraquat who also had a history of head injuries.
The 2024 study, part of the Parkinson’s Environment and Genes study, examined paraquat exposure using a combination of geographic analysis and detailed residential and work histories from 1974–2015.
Geographic data from the Pesticide Use Report database identified participants living or working within 500 meters of paraquat application sites, and interviews provided personal exposure histories. The study found links between paraquat exposure and Parkinson’s disease, ranging from a 19% increased risk to more than double the risk across various exposure types and locations.
However, DPR noted that the reliance on pesticide application records does not confirm direct individual exposure, and evolving safety regulations and protective equipment over the years likely reduced exposure risks compared to the study timeline.
“The majority of these studies capture paraquat use in the US prior to the implementation of current mitigation and safety measures or were conducted outside of the US in countries which may have different pesticide regulations. Overall, HHA identified data gaps relative to impacts to the thyroid and birth defects that may be linked to adverse impacts from the use of paraquat,” the preliminary report stated. “With respect to paraquat exposure and Parkinson’s disease, HHA has found that there is currently insufficient evidence to demonstrate a direct causal association with paraquat exposure and the increased risk of developing Parkinson’s disease.”
PUBLIC COMMENT PERIOD
The preliminary DPR reports are not a determination of whether additional restrictions on paraquat will be necessary. According to DPR’s website, the department is anticipating announcing any next steps, including potential regulatory changes or other mitigation measures, by fall 2025.
Public comment on the preliminary paraquat human health and ecological reports must be submitted by Feb. 13, 2025, through DPR’s online portal or emailed to paraquat@cdpr.ca.gov.