June 1, 2022 – The Emmett Environmental Law & Policy Clinic submitted an amicus brief today on behalf of three leading experts supporting a challenge to an action by the U.S. Environmental Protection Agency (EPA) involving the toxic herbicide paraquat dichloride (often simply called “paraquat”).  Specifically, EPA approved paraquat’s use for the next fifteen years under certain conditions, despite the risks paraquat poses to public health.

The Clinic filed the brief on behalf of J. Timothy Greenamyre, Michael Okun, and Beate Ritz.  They are medical doctors and scientists with expertise in neurology or epidemiology, and they have studied and written extensively about the link between toxic substances like paraquat and neurodegenerative disorders—in particular, Parkinson’s disease.  The brief argues that EPA failed to adequately recognize the paraquat-Parkinson’s link when approving paraquat’s continued use.

Paraquat is one of the most widely and increasingly used herbicides in the United States, and it is acutely toxic.  A single exposure to paraquat can cause skin and eye irritation and respiratory harm, including lung inflammation, scarring, and compromised lung function.  Swallowing even a teaspoonful can be fatal.  In addition, as the Clinic’s brief details, a growing body of research has linked paraquat exposure to Parkinson’s for more than twenty years.

Based on these health effects, at least thirty-three countries have banned the use of paraquat.  In fact, it is one of only two pesticides that are approved for use in the United States despite being banned or phased out in the European Union, Brazil, and China.

Parkinson’s is a progressive, neurodegenerative disorder with no known cure. Approximately one million Americans currently live with Parkinson’s, making it the second-most-common neurological disorder in the country, behind Alzheimer’s.  Genetic factors can play a role in causing Parkinson’s, particularly for those diagnosed when they are less than 50 years old.  But for those diagnosed later in life—who constitute a majority of Parkinson’s patients—the disease is most commonly caused by environmental factors. Those risk factors include exposure to a number of pesticides, including paraquat.

Despite paraquat’s acute dangers and its association with Parkinson’s, last year EPA issued an “Interim Registration Review Decision” for paraquat under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA).  Having previously approved paraquat’s use, EPA approved it again, while this time requiring certain exposure mitigation measures, such as the use by pesticide handlers of gloves and other protective equipment.  Nonetheless, several groups representing farmworkers, environmentalists, and others concerned about pesticides challenged EPA’s decision, arguing that the mitigation measures would not sufficiently reduce the health risks of paraquat exposure.

The Clinic’s brief explains the robust lines of evidence developed over many years linking paraquat exposure and Parkinson’s, including in human epidemiology studies, animal model studies, and analyses of paraquat’s effects on the cellular and subcellular level.  As just one example, a recent systematic review and meta-analysis synthesizing 13 epidemiology studies found a statistically significant association between paraquat exposure and Parkinson’s, with an overall 64% increase in Parkinson’s risk for those exposed to paraquat.

The brief then explains several errors EPA made in evaluating these multiple lines of evidence and finding an insufficient showing of causation.  Generally for the epidemiology studies, for instance, EPA over-valued the mere potential for certain errors in those studies’ methodologies, without either attempting to assess the actual level of any error or conducting standard analyses that can help correct for them.  These and other flaws prevented EPA from appreciating the compelling convergence of the multiple lines of evidence demonstrating that paraquat exposure is causally linked to the onset of Parkinson’s.

Clinical student Rose Whitlock (JD ’22) worked on the brief under the supervision of Acting Director Shaun Goho and Clinical Fellow Tommy Landers.

The brief is available here: California Rural Legal Assistance Foundation v. U.S. Environmental Protection Agency (9th Cir. No. 21-71287)