Isocyanates
Isocyanates are chemicals in spray polyurethane foam, polyurethane coatings, floor finishes and many auto-body paints. They are a leading cause of work-related asthma, and once you’re sensitized, even tiny exposures can trigger severe attacks for the rest of your life.
- Construction
- General Industry
Photo: spray foam applicator in a supplied-air hood with full skin protection
Where you find them
- Spray polyurethane foam insulation and roofing (SPF); the “A side” contains the isocyanate (often MDI)
- Two-part polyurethane paints, coatings and floor finishes (often HDI)
- Auto-body and truck paints and clear coats
- Some adhesives, sealants, bed liners and foam manufacturing
Spraying creates the highest exposures, but heating or cutting cured foam and brushing or rolling two-part coatings can also expose you. Product labels may list them as MDI, TDI, HDI or “polymeric isocyanate.” Check the SDS.
Health effects
- Asthma: wheezing, chest tightness, cough and shortness of breath, sometimes hours after work or at night
- Sensitization: after one large exposure or many small ones, your immune system overreacts to any later exposure
- Eye, nose and throat irritation
- Skin rashes; skin contact can also contribute to sensitization
- Hypersensitivity pneumonitis (lung inflammation with fever) in some workers
Symptoms that improve on weekends or vacations and come back at work are a classic sign of occupational asthma. Report them and see a doctor early. Workers who become sensitized usually must stop working with isocyanates.
Protection
- Follow the product’s SDS and the manufacturer’s respirator requirements. Supplied-air respirators are often required for spraying, and air-purifying respirators need a cartridge change schedule.
- Cover skin with chemical-resistant gloves (such as nitrile), coveralls with a hood, and eye protection.
- Use spray booths with working ventilation for auto-body and shop painting.
- Ventilate jobsites and keep other workers and occupants out of the spray area until the manufacturer’s re-entry time has passed.
- Turn off building HVAC or seal it off during spray foam work, as the manufacturer directs.
- Get medical evaluations before respirator use and periodically after.
- Don’t eat, drink or smoke in the work area.
- Don’t clean skin with solvents.
- Don’t heat, grind or torch-cut polyurethane foam without controls; it can release isocyanates and other toxic gases.
Before spraying
- SDS read and product hazards understood
- Respirator fit-tested and right for the job
- Gloves, coveralls and eye protection on
- Work area isolated, signs posted, occupants out
- Ventilation set up; re-entry time known
Standards & references
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