A breakthrough study published in JAMA Neurology has found a link between exposure to trichloroethylene (TCE), a solvent used as paint thinners and an agent to remove grease in industrial units, and the neuromuscular disorder of Parkinson’s.
The University of California-San Francisco (UCSF), USA researchers found that individuals exposed to TCE had a 70 per cent higher risk of developing Parkinson’s than those without exposure. Furthermore, the study revealed that the risk increased with the duration and intensity of TCE exposure.
Dr Samuel Goldman, professor of occupational, environmental, and climate medicine at UCSF and lead author of the study, tells Happiest Health, “There had been a lot of studies in animals and in in vitro [laboratory] models that looked at TCE as a potential major player for Parkinson’s caused by environmental factors.”
In the current study, the researchers examined nearly 85000 Navy and Marine Corps veterans who trained at Camp Lejeune in North Carolina, USA, between 1975 to 1985. “During this time at the training camp, the water had very high levels of TCE due to contamination, which the soldiers were exposed to,” says Dr Goldman.
When they compared the data with 72000 non exposed personnel at another camp without TCE contamination, they found the Camp Lejeune veterans had a high risk of Parkinson’s. This is the largest participant size to confirm TCE as a possible cause of Parkinson’s in human beings.
Wide use in industries
Trichloroethylene is a common solvent used in the heavy metal industry and it is also found in wood finishes and adhesives. The clear colourless liquid is a volatile organic compound that contaminates the groundwater reserves, polluting the drinking water sources. “If you are exposed to it in the environment, it is either through drinking or eating foods that have measurable TCE in them,” says Dr Goldman.
Being volatile, TCE evaporates quickly and enters buildings, contaminating indoor air (by vapour intrusion). TCE vapours can pass through the skin and nasal pathways, further increasing the risk of diseases in the person. The International Agency for Research on Cancer has identified TCE as a potent carcinogen.
Furthermore, many studies have found that sustained TCE exposure causes multiple myeloma, non-Hodgkin’s lymphoma, and renal and liver cancer.
Surpassing the brain’s barrier
TCE has a strong affinity for fats and can cross the cell membranes and the blood-brain barrier. Several studies on mice have shown that after entering the brain, TCE affects a part of the midbrain responsible for movement control. “It gets converted into another compound in the brain which is a very strong mitochondrial poison,” says Dr Goldman. This toxic compound damages the dopamine-generating neurons in the midbrain’s substantia nigra. Parkinson’s is characterized by the progressive loss of dopamine-producing cells in the brain.
Read more: Substantia nigra: its role in Parkinson’s disease
Higher risk
In the current study, Dr Goldman and his team analysed the health records of the Camp Lejeune personnel from 1991 to 2021. The personnel were exposed to TCE for at least three months during the training period.
They factored in parameters such as sex, race, ethnicity, and age and performed an extensive statistical multivariable analysis on the data. The analysis revealed that the veterans from Camp Lejeune had a 70 per cent higher rate of Parkinson’s disease. The researchers also found they had a higher rate of symptoms that precede Parkinson’s, such as tremor, anxiety, erectile dysfunction and loss of smell.
Through this study, Dr Goldman wants to bring home the need to test the levels of chemicals in the water. “It is necessary to test water supplies to make sure that people are not consuming levels of TCE that would put them at risk,” he says.
Read more: Experts red-flag arsenic exposure for its effects on brain
