What does polyurethane do to humans?

Polyurethane in its cured solid form, such as in furniture, floors, and clothing, is generally considered safe for humans and does not cause harm under normal use. However, uncured liquid polyurethane and its fumes can be harmful. When polyurethane is being applied, it releases volatile organic compounds and isocyanates which can irritate eyes, nose, throat, and lungs, cause headaches, dizziness, nausea, and trigger asthma attacks or allergic reactions in sensitive individuals. Prolonged inhalation without ventilation or a respirator can cause respiratory sensitization. Skin contact with liquid polyurethane can cause irritation, dermatitis, or allergic reactions. If ingested, liquid polyurethane is toxic and can cause chemical burns. Sanding cured polyurethane can create dust that irritates lungs if inhaled, so a mask is needed. Once polyurethane is fully cured, which takes about 30 days for oil-based and 7 to 14 days for water-based, it forms an inert plastic that does not off-gas significantly and is safe to touch, walk on, and live with. This is why furniture and floors are safe after curing, but application requires ventilation, gloves, and respirators. Polyurethane foam in mattresses is also safe after off-gassing period.