Hylea
Isocyanates (MDI, TDI) High Risk
A family of highly reactive chemicals used to make polyurethane foams, coatings, and adhesives. MDI (methylene diphenyl diisocyanate) and TDI (toluene diisocyanate) are the most common. They react on-site in spray foam insulation and two-part coatings.
Health Concerns
- Leading cause of occupational asthma worldwide
- Potent respiratory sensitizers - once sensitized, even tiny exposures trigger reactions
- Skin sensitization and dermatitis
- Eye and mucous membrane irritation
- Manufactured using numerous hazardous chemicals including carcinogens
- Can continue off-gassing for extended periods after application
Environmental Impact
- Manufacturing involves hazardous chemical processes
- Releases during application affect installers and nearby occupants
- Difficult to recycle polyurethane products at end of life
- Can contaminate air and water during production
Regulatory Status
OSHA has strict workplace exposure limits. EPA regulates as hazardous air pollutants. EU REACH requires authorization for some uses.
What to Avoid
Spray polyurethane foam (SPF) insulation, two-part polyurethane sealants and coatings, products requiring on-site mixing of polyurethane components
Safer Alternatives
Cellulose or mineral wool insulation, pre-formed foam sealant tape, acrylic or silicone sealants, mechanical fasteners instead of adhesives