What is Chloroprene and What are the Effects of Exposure?

Chloroprene is a chemical that has been used in the production of the synthetic rubber neoprene since 1931. Neoprene is a valuable material because it is resistant to weathering, oil, abrasion, heat, flame, oxygen, ozone, and solvents. It is used in wire and cable sheaths, hoses, fabrics, adhesives, automotive and industrial parts, belts, caulks, flame-resistant cushioning, and other applications where chemical or weather resistance is needed. Developed in the United States by Carothers, it was originally introduced by the Du Pont company under the brand name Duprene. Today, neoprene has become the generic name for synthetic rubber. However, research suggests that chloroprene exposure has toxic effects on workers. It’s estimated that 2,500 workers are exposed to chloroprene in the United States. Exposure to chloroprene is primarily occupational, and workers may be exposed via inhalation or dermal exposure. Chloroprene may also be released into the environment during its manufacture, transport, and storage. The current threshold limit of permissible chloroprene exposure in the workplace is 25 ppm. This is the Occupational Safety and Health Administration’s standard.

Chloroprene exposure is not without its dangers. Exposure can cause central nervous system depression, along with injury to the lungs, liver, spleen, gastrointestinal tract, and kidneys. It can also cause dermatitis, conjunctivitis, corneal necrosis, cardiac palpitations, nausea, anemia, and temporary hair loss. Acute exposure can affect the circulatory and immune systems, as well as irritate the mucous membranes. Psychological symptoms include giddiness, headache, nervousness, irritability, insomnia, and fatigue. Chloroprene’s chronic effects include rapid heartbeat, chest pain, and changes in blood cell count.

Two Russian studies suggest that exposure to chloroprene is associated with increased incidence of lung and skin cancer. These results were taken from a large-scale investigation of industrial workers in Russia’s Yerevan region. Throughout 1956-1970, 137 cases of skin cancer out of 24,989 people were examined. The patients were divided into several different groups, with two groups in particular being people who worked with chloroprene and chloroprene derivatives. These groups had higher incidences of skin cancer than the groups who did not work with chloroprene. The researchers also concluded that development of chloroprene-induced skin cancer is preceded by chronic dystrophic and inflammatory skin ailments which are caused by the binding of chloroprene to the free SH groups in the cells, with the formation of RS-CH compound types.

A similar study was also performed, this one on the incidence of lung cancer among 19,979 workers in the same region. Throughout 1956-1970, there were 87 cases of lung cancer identified from the local oncology department’s records. The workers were divided into four subgroups based on their type of employment. Just like the other study, the people working around chloroprene had a significantly higher incidence of cancer. Similar studies suggest that chloroprene exposure may cause a two-to-five-fold risk increase for liver cancer. The EPA has classified chloroprene as likely to be carcinogenic to humans. The Du Pont company, which is a major producer of both chloroprene and neoprene, has informed its employees of the Russian studies, as well as alerted its customers to the possibility of escaping chloroprene during neoprene processing. The company is conducting human and animal studies to ascertain the carcinogenic potential of chloroprene.

The ill effects of chloroprene are not limited only to humans. Animal experiments have demonstrated that a concentration of at least 75 ppm of chloroprene can be toxic with continued exposure. Chloroprene is lethal because it can cause respiratory depression and asphyxiation. It can cause severe degenerative changes in the vital organs, along with drops in blood pressure. During tests with rats, it was demonstrated that chloroprene can cause a decrease in lymphocyte count, as well as changes in adrenal gland function. It can also interfere with the reproductive system, particularly in males. Functional spermatogenesis may be impaired, along with degeneration of the testes.