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The Case For Some Toxic Chemicals Causing Parkinson’s Disease

For years research has linked some pesticides and toxic chemicals with the development of Parkinson's disease. Recent research from the military base Camp Lejeune strongly suggests that one possible cause of PD is the toxic chemical trichloroethylene (TCE). The drinking water at Camp Lejeune was contaminated with high levels of TCE and perchloroethylene (PCE) for 35 years at 280 times safety standards.

In the past century, TCE (and the similar chemical PCE) has had numerous industrial, consumer, military, and medical applications. For example, it is used in dry cleaning clothes, removing paint, as a degreaser, carpet cleaner, and engine cleaner. It even was used to produce  decaffeinated coffee in the past! It's still used today - much less in the US, but increasing in China.

The problem is that TCE is environmentally persistent, and contaminates soil, air, and water. Vapors from underground water and soil contamination seep out into homes, schools, and workplaces. It is known to be carcinogenic (cancer causing) and associated with numerous cancers and other health harms, including birth defects.

The neurologist Ray Dorsey (at Univ. of Rochester), who was part of a team looking at TCE and Parkinson's disease (see post), was recently interviewed about the research linking TCE and PD. One finding: there has been a major increase in Parkinson's disease in the past decades, making it the "world's fastest-growing brain disease".

What you can do: Dr. Ray Dorsey (and fellow researchers) feel that PD is preventable. (their book). He recommends that everyone, but especially all persons with Parkinson's disease, try to avoid pesticides as much as possible. For example, use a carbon filter for drinking water, eat organic foods, don't put pesticides on the lawn, etc.

Excerpts from Dr. Subramanian (Professor at UCLA) interview with Dr. Ray Dorsey, from the medical site Medscape: Is Most Parkinson's Disease Man-Made and Therefore Preventable?

Subramanian: I wanted to first highlight some of the work that has come out and gotten a large amount of media attention around Camp Lejeune and specifically trichloroethylene (TCE) as a cause of Parkinson's, and one of the environmental toxins that we talk about as something that is in pretty much everywhere. This paper came out, and you wrote a commentary in JAMA Neurology as well. Perhaps we can summarize the paper and its findings.

Dorsey: Like most people, I didn't know what TCE was until about 5 or 6 years ago. TCE is a very simple molecule. It's got six atoms, including two carbon atoms, one hydrogen atom, and three chlorine atoms — hence, its name "trichloroethylene." There's a very similar chemical called perchloroethylene, which is widely used in dry cleaning. It's got one additional chlorine atom, and the prefix "per-" means "four." I'll talk about TCE predominantly, but both of these chemicals probably have similar toxicity with respect to Parkinson's disease.

Research done by Drs Carlie Tanner and Sam Goldman about a decade ago showed that in twins who were exposed to this through their work (it's widely used as a degreasing agent) or hobbies (it's used in printing and painting, by varnish workers, or by anyone that needs it as a solvent) had a 500% increased risk of developing Parkinson's disease. Importantly, in that study, they showed that there was a lag time of 10-40 years between exposure to that chemical and the diagnosis of the disease. Because TCE was so widely used, they said that public health implications could be substantial.

What's Camp Lejeune? Camp Lejeune is a Marine base in North Carolina where many Marines are trained. Between 1953 and 1987 at that Marine base, the drinking water was contaminated with TCE, perchloroethylene, and other toxic chemicals. The reason Camp Lejeune is so infamous is because the Marines knew about the contamination for many years and covered it up.

Indeed, this story only came to the forefront because Jennie Ensminger, the daughter of a Marine drill instructor, developed leukemia at age 6 and died at age 9. Her father, Jerry Ensminger, a retired master sergeant, found out after the fact that these cancer-causing chemicals, including TCE, a known carcinogen, were found at the Marine base and could be an explanation for why his daughter developed and died of leukemia.

Drs Sam Goldman and Carlie Tanner and colleagues from UCSF looked at the rates of Parkinson's among Marines who served at Camp Lejeune during the 1970s and compared that with rates in Marines who served Camp Pendleton on the West Coast. It turned out that the Marines who served at Camp Lejeune had a 70% higher risk of developing Parkinson's disease than the Marines who served at Camp Pendleton.

Importantly, these Marines, by definition, were healthy. They were young. They were only 20 years old, on average, when they were at Camp Lejeune. They only stayed at a Marine base for a short period of time, so on average, they were only there for 2 years. Yet 30 years later, they had a 70% increased risk of developing Parkinson's disease.

Subramanian: Wow, that's pretty profound. You've done a large amount of work, and in fact you, along with some of our colleagues wrote a book about ending Parkinson's disease. I read that book when it came out a couple of years ago, and I was really struck by a few things. Parkinson's has doubled in the past 40 years and is going to double again in the next 20 years. Can you tell me a little bit about that statistic and why that is? It's not just because people are aging. What is the sense of that? How do we interpret that?

Dorsey: According to the Global Burden of Disease study, which I was fortunate to be part of, the number of people with Parkinson's disease has more than doubled in the past 25 years. A conservative projection based on aging alone suggests that it's going to double again unless we change something about it. It's now the world's fastest-growing brain disease, and it is growing faster than can be explained by aging alone.

If you look at the map of Parkinson's disease, if you thought it was purely genetic, you would have a relatively uniform map of rates of Parkinson's disease. In fact, we don't see that. Rates of Parkinson's are five times higher in industrialized parts of the world, like the United States and Canada, than they are in sub-Saharan Africa. Rates of Parkinson's disease are increasing most rapidly in areas of world that are undergoing the most rapid industrialization, such as India and China, where adjusted for age, the rates of Parkinson's have more than doubled in the past 25 years.

The thesis of our book is that much of Parkinson's disease is man-made. Work done by your colleagues at UCLA, including Jeff Bronstein and Beate Ritz, have demonstrated that air pollution and certain pesticides are likely fueling the rise of Parkinson's disease.

Given that in the United States, rates of Parkinson's disease are actually higher in urban and suburban areas than they are in rural areas, I think that this dry-cleaning chemical — which was widely used in the 1970s in everything from typewriter correction fluid to decaffeinated coffee and [over] 2 pounds per American [was produced] — could be one of the most important causes or contributing factors to Parkinson's disease.

It's pretty easy to identify whether people grew up in a rural area and drank well water, which is prone to be contaminated with pesticides. We know that people who drink [contaminated] well water have about a 75% increased risk of developing Parkinson's disease. I think you can find for people, especially when they grew up, when they were young, that the most relevant exposure might be that when people were young children.

Some people who know that they work with chemicals or with solvents might know about this. In New York City, these chemicals are widely used in dry cleaning. They're readily volatile. These chemicals can evaporate from dry-cleaning buildings and go into the indoor air of apartments above dry cleaners, for example, in New York City. That can be in toxic levels. These readily dissolve in fat, hence their use in degreasing.

There have been studies, for example, in Germany, that found that supermarkets that are simply near a dry cleaner will have TCE or perchloroethylene in the butter and the cheese that they're selling.

I tell people to be concerned about those, and then I tell people to avoid pesticides if they have Parkinson's disease in all its forms, not only in the drinking water but in the produce you buy, the food you eat, what you put on your lawn, what's on the golf course where you play, and the like.

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