EAST ST. LOUIS - Lawyers who blame weed killer paraquat for causing Parkinson’s disease tried to use the power of the U.S. district court to investigate neurotoxicologist Douglas Weed of Salt Lake City for writing an article against their theory.
They withdrew their subpoena on Weed a week after he moved to quash it, rather than respond to the motion as Chief U.S. District Judge Nancy Rosenstengel directed.
Weed’s counsel, Daniel Mohan of Chicago, stated in the motion that plaintiffs essentially asked for everything Weed has done.
Rosenstengel presides over about 5,000 paraquat suits against Syngenta and Chevron by appointment of the U.S. Judicial Panel on Multi District Litigation.
She plans to hold trials that could shape a settlement; but in August, after four days of argument over experts, she vacated an October date for the first trial.
On Aug. 27, lead plaintiff counsel, Sarah Doles of Florida, served a subpoena on Weed requesting production of ten categories of documents.
She asked for all documents relating to the article, all communications with Syngenta and Chevron, and all documents of discussions with Syngenta’s experts.
She also asked for documents relating to financial arrangements involving him or any organization or foundation in which he was involved relating to paraquat.
Mohan moved to quash on Oct. 27, claiming Doles asked Weed to find, review, and produce thousands of pages in an action that doesn’t involve him.
“It would take an extremely long time to compile all the documents and information sought and no measures have been suggested by plaintiff regarding loss of professional time,” he wrote.
He claimed Doles could readily find articles Weed cited.
Mohan wrote that many documents involved ongoing research that is not public and ethical considerations exist regarding the release of unfinished research.
He added that Weed has no connection to the case, hasn’t been sued, and isn’t a retained expert.
Rosenstengel gave Doles seven days to respond.
On the sixth day, Doles advised Rosenstengel that she and Mohan agreed to extend the deadline to Dec. 4 so they could resolve the motion without court intervention.
It took a day for the subpoena to collapse.
Weed's findings
Weed’s article not only rejected the plaintiffs' theory but also did it in the context of litigation.
“Recently, there has been an increasing number of civil lawsuits brought to the courts in the United States regarding paraquat and Parkinson’s disease,” he wrote.
“At the center of scientific and legal interests is a basic scientific question: Does exposure to paraquat cause Parkinson’s disease?” he asked.
Weed wrote that a hypothesis of relationship was introduced in the 1980s.
He quoted a researcher who wrote that the disease “presents substantial physical, emotional, and economic burdens to patients and family members as well as to society at large.”
“It follows that identification of a modifiable risk factor could represent progress in the fight against this disease,” he wrote.
Weed wrote that he searched two databases for pesticides, paraquat, and Parkinson’s disease.
He wrote that he identified 269 potentially relevant articles, selected 24 for full review, and selected 12 for his article.
He noted that five authors focused solely on paraquat and seven examined pesticides including paraquat as well as possible environmental and lifestyle factors.
“No authors of the 12 reviews conclude that paraquat causes Parkinson’s disease,” he wrote.
He wrote that authors of two publications concluded that an association existed.
“Association, however, is not the same as causation,” he wrote.
Weed wrote that conclusions of the reviews were consistent with a statement on the website of the National Institute of Environmental Health Sciences.
The institute found evidence suggesting exposure to certain pesticides could increase a risk and the exact cause of the disease was unknown.
“The Mayo Clinic states that exposure to certain toxins or environmental factors may increase the risk of later Parkinson’s disease but the risk is relatively small,” he wrote.
Weed wrote that an author examined the roles of farming, smoking cigarettes, living in rural regions, drinking well water, and using pesticides and noted that epidemiological studies on paraquat and Parkinson’s disease were inconsistent.
He wrote that an author noted that epidemiological studies lacked objective measurements of exposure and a mechanism of action lacked sufficient evidence.
He added that the author pointed out that animal studies were of short duration using high doses and young animals without creditable controls.
Weed wrote that another author concluded epidemiological studies were too few and of low quality.
“Assessment of causation is a complex process involving study design, statistical methods, and methods to synthesize evidence,” he wrote.
Weed wrote that the biomedical community is increasingly committed to making causal assessments as objectively as possible using systematic reviews.
He added that systematic reviews are preferred over narrative reviews, which tend to reflect an author’s subjective interpretation of evidence and are prone to selection bias.
He wrote that assessments of a possible link should employ rigorous systematic review rather than narrative reviews that rely more heavily on an author’s judgment.
“By no means am I suggesting that judgment is not involved in causal assessments but as a mental facility judgment is difficult to define and should not trump the results of methods applied appropriately to the available evidence,” he wrote.
Weed wrote that industry funding had no apparent impact on results of studies.
A conclusion that evidence didn’t warrant a causal conclusion emerged independent of funding source, he wrote..
Weed stated that this fact represented a refutation of a perception in epidemiology that research funded by industry is necessarily biased.
“It is important to remember that research funding comes from many sources including corporations, non governmental organizations, and government agencies each of which has interests that could potentially affect the scientific process,” he wrote.
Weed wrote that experts hired by plaintiffs can only prevail if they claim science to date represents a causal relationship, “in direct contrast to the consensus presented here.”
“That will not be easy if systematic methods are employed,” he wrote.