What are the disadvantages of polyurethane?

The disadvantages of polyurethane include health, environmental, aesthetic, and practical issues. Health wise, uncured oil-based polyurethane releases high levels of volatile organic compounds and isocyanates that cause strong odors, headaches, dizziness, nausea, eye and throat irritation, and can trigger asthma and allergic reactions, requiring respirators and excellent ventilation and forcing you to vacate the house for several days. Environmentally, polyurethane is a petroleum-based plastic that is not biodegradable and eventually breaks down into microplastics, and its production uses fossil fuels. Aesthetically, oil-based polyurethane adds an amber yellow tint that changes the color of light woods and can look plasticky, while water-based can raise grain and look less warm. Practically, polyurethane is difficult to spot repair, you often must sand the entire surface to recoat, it is slippery when wet, it can scratch and show white scuffs, and it is not suitable for outdoor use without special UV-resistant formulations because it will crack and peel in sun. It is also not food safe for cutting boards, as film can chip into food, and it can be difficult to apply without dust nibs, bubbles, and brush marks if not done in a clean environment.