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What Does Isocyanate Mean?

Isocyanates are a family of chemicals used in the production of polyurethane, a common plastic used in many industrial and commercial goods. They are identified by the number of -NCO (nitrogen-carbon-oxygen) groups that they contain, and most are liquid at room temperature.

Isocyanates are highly reactive, have a low molecular weight, and are commonly employed as an ingredient in the manufacture of flexible and rigid foams, paints, varnishes, glosses, building insulation, and certain types of synthetic rubbers. They are often used as part of coatings that can be applied as a spray, such as in various protective coatings used for buildings, vehicles, and other structures like machinery that could potentially be exposed to harmful or degrading chemicals or environmental conditions.

Safeopedia Explains Isocyanate

Isocyanates are toxic to humans, and they act as powerful irritants to human mucous membranes located in the eyes, as well as the gastrointestinal and respiratory tracts. Both the manufacturing of products containing isocyanates and the application of products containing isocyanates are dangerous to human health and pose an especially significant danger to human respiratory health.

The use of isocyanates is constrained by a number of regulatory standards that govern exposure limits and respiratory safety. These exposure limits vary depending on the particular isocyanate being considered. For instance, OSHA’s permissible exposure limit (PEL) for the commonly used Methylene bisphenyl isocyanate (MDI) is a maximum value of 0.02 ppm, which is considered quite low. Other recognized occupational exposure limits (OELs)—such as the American Conference of Governmental Industrial Hygienists’ limit of 0.005 ppm per eight-hour time-weighted average—are even lower.

OSHA requires the use of a respiratory program that includes a risk assessment and the provision of hazard controls such as personal protective equipment (PPE) in workplaces in which workers are at risk of isocyanate exposure. Under the general duty clause provided by OSHA and many OHS standards in other jurisdictions, employers have an obligation to provide for employee safety by reducing exposure to isocyanates to as low as reasonably practicable.

The most catastrophic incident of harmful exposure to isocyanates is a disaster that occurred in Bhopal, India, in 1985. In this incident, methyl isocyanate—one of the most toxic isocyanates—leaked out of a pesticide production facility and killed thousands of people. Acute harmful exposure to an isocyanate can result in irritation to the eyes, nose, and throat, as well as fever and fatigue. Symptoms are often delayed by six to 10 hours post-exposure, which may result in workers not realizing their symptoms are the result of exposure. Chronic skin exposure may also result in irritation.

Workers who are exposed to isocyanates may become sensitized to it, meaning that future exposures to small amounts can result in more-severe adverse health reactions. Studies have shown that roughly one percent of workers exposed to isocyanates for a year will develop asthma as a result.


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