Methylene Diphenyl Isocyanate (MDI) Fact Sheet

Methylene Diphenyl Isocyanate (MDI) is a poison when inhaled. At room temperature MDI is a solid, but it is sold and used in molten form. Workplaces are the primary source of exposure to MDI, which is an intermediary chemical in the manufacture of polyurethanes. In Massachusetts MDI use is on the rise due to a single facility, which used over 10 million pounds in 1997 to manufacture roofing insulation.