Movers and Shakers: Can you sue over Parkinson's?

This week’s episode of the Movers and Shakers podcast explores whether it is open to we PWPs (people with Parkinson’s) to sue over our condition. But in reality we are looking at a much deeper question, our old friend “what causes Parkinson’s?”

Sometimes, we have found, it is useful to have a retired judge on your team and this week was a case in point. Nick Mostyn still keeps an eagle eye on the courts and he presented us with the fascinating case of Holmes v Poeton, of huge relevance to those Parkies who subscribe to the idea that their condition can be attributed to environmental factors such as exposure to noxious chemicals.

The Movers and Shakers

Michael Holmes claimed that while working for a company in South Wales called Poeton he was exposed over a period of 25 years to dangerous levels of an organic solvent trichloroethylene (TCE). In particular, he remembers having to clean out a tank containing TCE on regular occasions. The thrust of the argument that his lawyers put in a Cardiff court was that Poeton’s negligence had allowed TCE to damage Mr Holmes’s dopaminergic neurones, thereby causing his Parkinson’s.

The judge in Cardiff agreed with this claim but this was then overturned by the Court of Appeal which said that while it was possible that TCE caused Mr Holmes’ Parkinson’s, the scientific and epidemiological evidence was not sufficient to say that it was probable.

Before we get down to examining the nitty gritty of the law, we remind ourselves of the case made by a number of notable scientists that there is a clear causal link between various environmental factors and the development of Parkinson’s. At last summer’s World Parkinson’s Congress we spoke to perhaps the leading proponent of this argument, the neurologist Ray Dorsey, who maintained that chemicals such as the weedkiller Paraquat were clearly linked to Parkinson’s.

Nick Mostyn goes back to Professor Dorsey for his views on TCE - he paints a terrifying picture:

“It’s estimated that in England, one in 12 workers worked with trichloroethylene. That's 8% of your population working with trichloroethylene, and most of them don't even know, and many of them have gotten cancer. Many of them have likely gotten Parkinson's disease. Many of them have probably had miscarriages. Many of them have had children with congenital heart disease. Many of them have had autoimmune disorders.”

He cites some evidence of the link between TCE and Parkinson’s from a study of Camp Lejeune, a US Marines base which was polluted with trichloroethylene over a long period:

“They looked at Marines who served at this base that was heavily contaminated compared to a Marine base that was less contaminated, and they followed these individuals. They looked at them 35 years later, and they had a 70% higher risk of Parkinson's disease among the Marines who served at Camp Lejeune than those who didn't.”

The question we the Movers and Shakers in the pub had to address was whether this evidence was strong enough to prove that chemical exposure was behind Mr Holmes condition. Fortunately, the judge has summoned an expert witness in the form of Professor Yoav Ben-Shlomo, a distinguished epidemiologist.

He takes us on a journey through the various studies showing a potential link between TCE and Parkinson’s and points out a number of challenges to proving that correlation - people exposed to the chemical tend to be more likely to develop Parkinson’s later in life - equals causation. One issue is the relatively small sample size in some of the studies, another is what statisticians call confounding:

“People who are exposed to TCE have very different lifestyles to people who work in an office or do other jobs where they're not exposed.

So how do you know whether it's the TCE or something else about people who do those sort of jobs? “

He says the Camp Lejeune study is interesting and is only going to get better as it continues to track the marines later in life when they are more likely to get Parkinson’s. But the Camp Lejeune study was not put before the Court of Appeal.

Judge Nick Mostyn (retired) reads out what the appeal court judge Lord Underhill had to say in overturning the original judgement:

“I do not believe it was open to the judge on the evidence before him to conclude that such exposure as the claimant had experienced to TCE made a material contribution to his developing Parkinson's disease. The evidence about a possible causative link between the exposure and Parkinson's amounts to no more than the identification of a plausible mechanism, and that by itself is not enough.”

Nick asks Professor Ben-Shlomo whether he thinks the Court of Appeal judges would have reached a different conclusion if they had seen the Camp Lejeune study:

“I think they would have had a lot more doubt. On the base of what was presented, I totally agree with the Judge of Appeal that I would have rejected the claim. I think if they had had the Camp Lejeune study, they would have scratched their heads a lot more.”

We end by admitting that we Movers and Shakers do not really have the scientific brain power to assess whether the case against chemicals like TCE really stands up, but for most of us the old Scottish verdict of “not proven” seems to fit the bill. Have a listen and let us know what you think.

You can read a lot more about Holmes v Poeton and the evidence about links between TCE and Parkinson’s on our website.