This transcript has been edited for clarity.
Indu Subramanian, MD: It’s my pleasure to have Ray Dorsey on our program today. Ray is a professor of neurology at the University of Rochester and has been doing some amazing advocacy work in largely the space of trying to end Parkinson’s disease.
E. Ray Dorsey, MD: Thanks very much for having me, Indu. I’m delighted to be with you.
Trichloroethylene and PD
Dr. Subramanian: I wanted to first 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.
Dr. 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 – 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 Dr. Carlie Tanner and Dr. 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.
Dr. Sam Goldman and Dr. 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 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.