After two years of sustained exposure to TCE, a liquid chemical that lingers in the air, water, and soil, the risk of Parkinson’s disease may increase by 70%. TCE, or trichloroethylene, has previously been linked to various malignancies, but new research that will be published in JAMA Neurology on May 15, 2023, is expected to be the first important study to indicate a link between TCE and Parkinson’s.
TCE has been used for about 100 years in industrial and commercial applications, and it was used as a surgical anaesthetic until it was prohibited in 1977. It was most recently employed as a degreasing solvent. It is now mostly used to degrease industrial metal components.
This involves heating TCE in degreasing tanks to produce a vapour that dissolves the grease while also releasing the chemical into the atmosphere. TCE can stay in the soil or groundwater for decades after it enters it.
Researchers from UC San Francisco and the San Francisco VA Medical Centre led the study, which compared Parkinson’s diagnoses in about 160,000 Navy and Marine veterans. A little more than half of the samples came from Camp Lejeune in North Carolina, where TCE was used to degrease military equipment and the water was contaminated; the rest came from Camp Pendleton in California, where the water was not affected.
Between 1975 and 1985, servicemen spent at least three months in the camps, during which time TCE levels in the water at Camp Lejeune surpassed maximum safety norms by a factor of 70. The researchers had access to follow-up health data on military members from 1997 to 2021, when Parkinson’s disease may be predicted to occur. Researchers discovered that 430 soldiers had been diagnosed with Parkinson’s disease and that the risk for Lejeune veterans was 70% greater than for Pendleton veterans. From 1975 through 1985, military men from both camps were stationed there for an average of two years.
Parkinson’s disease was diagnosed at an average age of 54 at Lejeune and 53 at Pendleton, indicating that the condition takes decades to develop following TCE exposure. The civilian population is also in danger of TCE exposure, according to first author Samuel M. Goldman, MD, MPH, of the UCSF Division of Occupational, Environmental, and Climate Medicine and the SFVA, who noted that the chemical is present in between 9% and 34% of U.S. water sources.
“TCE is still a widely used chemical in the United States and around the world.” Its manufacturing has increased in recent years, and it is freely available online,” he stated. “Unfortunately, unless you’ve worked directly with it, there’s no easy way to know if you’ve been exposed.” Many of us have measurable TCE levels in our systems, but it is quickly metabolised and eliminated, so blood and urine testing only indicate recent exposure.”
Furthermore, the researchers discovered that the Lejeune veterans had a greater frequency of prodromal Parkinson’s disease, which is defined as symptoms that are indicative of Parkinson’s but do not yet meet diagnostic criteria for the condition.
“Loss of sense of smell, a sleep disorder known as RBD, anxiety, depression, and constipation can be early signs of Parkinson’s, but only a very small fraction of people with them will develop it,” said senior author Caroline M. Tanner, MD, PhD, of the UCSF Department of Neurology, the Weill Institute for Neurosciences, and the SFVA.
“A risk score based on these symptoms can be used to estimate the risk of developing Parkinson’s disease in the future.” The Lejeune veterans received higher risk ratings than the Pendleton veterans, indicating a greater likelihood of developing Parkinson’s disease in the future.”