Moisture Cure Urethanes (MCUs) are a type of polyurethane that is used to coat wood floors in homes. They make a very durable and scratch resistant finish and are often used on gymnasium and bowling alley floors.
MCUs contain solvents and reactive chemicals that evaporate into the air and cause strong odors. Brief exposures to elevated levels of MCU vapors can cause temporary irritation of the eyes, nose, and throat, worsen asthma, and cause health effects such as headaches, nausea, and dizziness.
Very high and/or long-term (e.g. lifetime) exposures can lead to more serious health effects such as organ damage, birth defects or pregnancy complications, chemical allergies, and, possibly, cancer.
First, you should always consider using a safer and less volatile product. If MCU is being applied in your home, it is recommended that you leave your home until the product fully cures (more than 48 hours) or until the odors subside. When you return to your home, open windows and doors to air out lingering odors. If your neighbor uses MCU and you live in a multi-family building, ventilate common hallways and stairwells during application and curing to remove odors and vapors.
The specific chemicals in MCUs vary from brand to brand but they typically contain:
In response to community concerns, the New York City Department of Health and Mental Hygiene (DOHMH) performed limited sampling in a multi-family building while MCU was being used. Air samples were collected in common hallways and in an apartment where MCU was not used. DOHMH found that the levels of MCU chemicals in the air in the common hallways of the building were much higher than in the untreated apartment. The hallway levels detected could cause headaches, irritation of the eyes, nose, throat and lungs, and worsen asthma in some individuals. More severe health effects would not be expected.
It is important to note that these sampling results do not provide us with information about how long or at what levels these chemicals would continue to be present. Also, air levels at different buildings where MCUs are used will vary based on the amount of product used, surface area treated, and ventilation. For a complete copy of this report, see Environmental Investigation of Chemical Ingredients of Moisture Cure Urethanes Used as Wood Floor Coatings .
After the MCU is applied, the curing process begins and the liquid coating is transformed into a hardened surface. The hardened surface is generally considered to be inert and non-hazardous. In addition to being used in coating surfaces, polyurethane products are commonly used in clothing, such as "spandex", foam products, packing materials, and cushions.
Common alternatives to MCUs include water-based polyurethanes and oil-based polyurethanes. These products also use chemical solvents that evaporate into the air.
If you have additional questions regarding MCUs, you can call 311 for more information. If you think that an MCU product is being used in violation of New York State Law, call DEC at (718) 482-4944.