In December 2020, EPA released its Proposed Interim Decision for the Registration Review of Chlorpyrifos (PID). The PID states that chlorpyrifos degrades into chlorpyrifos oxon, a toxic and potent acetylcholinesterase inhibitor that potentially causes neurodevelopmental effects.  Importantly, the PID indicates that the state of the science is still unclear after years of studies despite some studies that have found neurodevelopmental effects to pre-natal, infants, and children from chlorpyrifos exposures. This statement echoes the EPA’s statements in the draft Ecological Risk assessment and Revised Human Health Risk Assessment for chlorpyrifos released in September 2020 that seemingly walked back many of the findings that were in EPA’s 2016 risk assessment.  Only time will tell how the data and findings in the recently released PID stand up to review by the scientific community. However, the findings in the PID should not move the needle too much in favor of plaintiffs or defendants in chlorpyrifos litigation.

Pros for Plaintiffs in PID

• Identification of specific occupational uses and areas of concerning exposure risks.
• Dissipation can potentially take up to 10 days (buffer zones currently set for 24 hours).
• Concerning risk of chlorpyrifos contaminated drinking water found in some areas.
• Tolerance levels set for multiple occupational settings (possible exposure limits).

Pros for Defendants in PID

• No affirmation that chlorpyrifos causes neurodevelopmental diseases.
• Limited to no risks from residential exposures and spray-drift.
• Identifies PPE (i.e., gloves, coveralls, and respirator) users must wear to mitigate risks.
• Identifies warning labels for products that users must follow to mitigate risks.

Based on the data and findings in the PID, expert testimony will continue to play a critical role in chlorpyrifos litigation.  Notwithstanding the state bans on chlorpyrifos uses in California, Hawaii, New York, Maryland, and Oregon, anticipate that the PID to be a persuasive piece of evidence.  Therefore, an extra onus is on plaintiff experts to rely upon studies that show exposures similar in nature to the plaintiff’s exposure cause neurodevelopmental diseases.  However, a good plaintiff expert may be able to shift the onus onto the defense expert who would likely need to opine on the EPA’s findings as primer before contrasting the plaintiff’s exposure and the exposures evaluated in the studies relied upon by the plaintiff expert.

Lawyers on both sides of the aisle are aware that proving causation in chlorpyrifos litigation is not a “slam dunk” like it is proving asbestos exposure can cause mesothelioma.  Unless the state of the science changes in the eyes of EPA, chlorpyrifos litigation will likely not carry the baton after asbestos litigation.  Expect future chlorpyrifos cases to be strategically filed in states where there are chlorpyrifos bans and in specific courts that are notoriously plaintiff friendly.  Future cases will likely involve claims that the defendant failed to adequately label its product and/or provide safety equipment to mitigate risks surrounding occupational exposures related to certain types of uses (e.g., spay applications) involving certain crops where the PID indicates there are concerning risks.  Accordingly, there should be more new cases filed involving occupational exposures than residential exposures given the PID found limited risks from residential exposures and spray-drift.  However, future cases involving residential exposures carry a likelihood of involving facts that would make them high value (e.g., exposures to children, birth defects).  Overall, there is still a lot of fluidity for the future of chlorpyrifos litigation notwithstanding the recently released PID.