Isocyanates in the workplace: Exposure, effects and control

Responding is Amy Hamilton, safety product support, Grainger, Lake Forest, IL.

In an effort to control and protect workers from occupational exposure to isocyanates, OSHA has established a National Emphasis Program for industries and workplaces exposed to isocyanate hazards. This applies to all workplaces (general, construction and maritime) under OSHA’s jurisdiction. The purpose of the NEP is to increase protection for workers exposed to isocyanates by first identifying, then reducing or eliminating, incidences related to the adverse health effects associated with occupational exposure to isocyanates.

Isocyanates have been used across various industries in the United States since the 1950s. They are compounds produced by reacting a primary aliphatic or aromatic amine dissolved in a solvent such as xylene or monochlorobenzene with phosgene dissolved in the same solution to produce polyurethane polymers. Isocyanates are known to be present in rigid or flexible foams, surface coatings, paints, electrical wire insulation, adhesives, rubbers and fibers. The most commonly used isocyanate compounds are diisocyanates, which contain two isocyanate groups. The more common diisocyanates are toluene diisocyanate, methylene diphenyl diisocyanate and hexamethylene diisocyanate.

The health effects of isocyanate exposure include occupational asthma; skin irritation (dermatitis); irritation to the mucous membranes, eyes, nose and throat; gastrointestinal irritation; chemical bronchitis; and pneumonitis. Although symptoms may improve after the irritant is removed, acute asthma attacks may occur after renewed exposure to isocyanates, even if the exposure is very small or very brief. Dermal sensitivity as a result of overexposure to isocyanates may result in rash, itching, hives and swelling of extremities. Because isocyanates are typically insoluble in water, they are not easily washed off of an affected worker’s skin or clothing. Continued overexposure to isocyanates may lead to pulmonary sensitization or “isocyanate asthma,” which may include coughing, tightness of the chest and shortness of breath.

Preventing a worker’s exposure to isocyanates is a critical step in eliminating the health hazards associated with isocyanates. Applying engineering controls, such as closed systems or mechanical ventilation, and requiring personal protective equipment can help limit worker exposure to isocyanates. The use of chemical-resistant clothing and gloves is essential to protecting workers’ skin from coming in contact with isocyanates, and specific types of PPE should be selected according to the hazard assessment results of each workplace.

A complete respiratory program per OSHA 29 CFR 1910.134 is necessary to help ensure proper respirator selection, use and training. OSHA permissible exposure limits for isocyanates are very low. Because isocyanates are not easily detected by smell or taste, air monitoring should be used to determine the air concentration levels of isocyanates before selecting the appropriate level of respiratory protection for workers. Protective eyewear and/or faceshields should be included in the PPE selection, as isocyanates are known to irritate the eyes.

Under the Occupational Safety and Health Act of 1970, employers are responsible for providing a safe and healthy workplace for their employees. OSHA’s NEP targeted at identifying and controlling the hazards associated with isocyanates is one step toward creating a healthier environment for workers exposed to isocyanate hazards. For additional information about the hazards of isocyanates, including OSHA PELs on isocyanates, visit www.osha.gov/SLTC/isocyanates/index.html.

Editor's note: This article represents the independent views of the author and should not be construed as a National Safety Council endorsement.