The study, led by Dr. Ivo Iavicoli of Catholic University of the Sacred Heart, Rome, may help to explain previous reports suggesting increased rates of autoimmune disorders among workers exposed to TCE.
The researchers assessed the impact of TCE a solvent and degreaser that is widely used for cleaning of metal parts on the immune systems of exposed workers. The study included 35 printing plant workers who were exposed to TCE through degreasing processes. Thirty plant workers whose jobs did not involve direct exposure to TCE were studied for comparison, along with 40 office workers.
Environmental monitoring tests confirmed that the workers involved in degreasing activities were directly exposed to TCE. The directly exposed workers also had higher average levels of a TCE metabolite in urine, compared with non-exposed workers. Both the monitoring and urine test results were well under safety standards for occupational TCE exposure.
However, even within these limits, workers exposed to TCE had significant changes in certain immune system proteins called cytokines. Levels of the "type 1" cytokines interleukin-2 and interferon-gamma were significantly increased in the TCE-exposed workers, while the "type 2" cytokine interleukin-4 was significantly reduced.
Cytokines are proteins with specific immune system functions. Normally, there is a delicate balance between type 1 and type 2 cytokine responses. An elevated type 1 response may favor the development of autoimmune reactions, in which the immune system attacks the body's own tissues.
At high levels of exposure, TCE has known toxic effects in humans, mainly related to the central nervous system. However, some studies have suggested that TCE may also be linked to autoimmune diseases, such as systemic lupus erythematosus and systemic sclerosis.
The new study does not prove that on-the-job exposure to TCE causes autoimmune disease or any other type of health problem in humans. However, it does provide strong evidence that relatively low-level TCE exposure alters the immune system in specific ways. Researchers note that more research will be needed to clarify how TCE affects the human immune system, and the possible resulting health effects.