How unhealthy is polyurethane?

Polyurethane's health impact depends on whether it is uncured during application or fully cured in final use. In its fully cured solid form, such as on hardwood floors after 30 days, in furniture, or as foam in mattresses that has off-gassed, polyurethane is considered low risk and not significantly unhealthy for most people, as it becomes an inert plastic that does not release large amounts of chemicals. However, during manufacturing and application, polyurethane is considerably unhealthy. Uncured liquid polyurethane contains isocyanates, which are potent respiratory sensitizers that can cause asthma, allergic reactions, and lung irritation, and volatile organic compounds that cause headaches, dizziness, nausea, and eye irritation. Workers who apply polyurethane without respirators have higher rates of occupational asthma. Sanding polyurethane creates fine dust that irritates lungs. For mattresses, new polyurethane foam can off-gas VOCs for a few days, causing temporary irritation for sensitive individuals, though CertiPUR-US certified foam is low emission. Long term, polyurethane as a plastic contributes to microplastic pollution. So while living with cured polyurethane is not highly unhealthy, applying it and manufacturing it without protection is unhealthy, which is why ventilation and protective gear are essential.