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Isocyanates have been determined to be the leading attributable cause of work-related asthma (NIOSH, 2004).  Repeated exposures to isocyanates have been shown to exacerbate existing asthmatic conditions (Mapp, 2005).  Isocyanates are the key materials used to produce polyurethane polymers. These polymers are found in common materials such as polyurethane foams, thermoplastic elastomers, spandex fibers, and polyurethane paints. Isocyanates are the raw materials that make up all polyurethane products. Jobs that may involve exposure to isocyanates include painting, foam-blowing, and the manufacture of many Polyurethane products, such as chemicals, polyurethane foam, insulation materials, surface coatings, car seats, furniture, foam mattresses, under-carpet padding, packaging materials, shoes, laminated fabrics, polyurethane rubber, and adhesives. Exposures may also occur during the thermal degradation of polyurethane products (e.g., burning or heating at high temperatures).

OSHA has Permissible Exposure Limits (PELs) for Methylene bisphenyl diisocyanate (MDI) and 2,4 toluene diisocyanate TDI of 0.02 ppm.  This corresponds to 0.20 mg/m3 for MDI and 0.14 mg/m3 for TDI.  Health effects of isocyanate exposure include irritation of skin and mucous membranes, chest tightness, and difficult breathing. Isocyanates include compounds classified as potential human carcinogens and known to cause cancer in animals. The main effects of hazardous exposures are sensitization which can lead to work-related asthma (sometimes called occupational asthma) and other lung problems, as well as irritation of the eyes, nose, throat, and skin.

Below is a list of jobs with potential isocyanate exposures and materials that may contain isocyanates.  It is important to understand additional sources of isocyanate exposures, especially for those already sensitized or with asthma, in order to avoid exacerbating an existing asthmatic condition. Because isocyanate exposures can occur across multiple jobs, it is important to understand where prior exposures have occurred. In addition to SPF applications, OSHA has identified the following industries where Isocyanate worker exposures can occur – some of which use a similar material to SPF (highlighted):

Potential Jobs-Related Isocyanate Exposures
  • Automotive - paints, glues, insulation, sealants and fiber bonding, truck bed lining

  • Casting - foundry cores

  • Building and construction - in sealants, glues, insulation material, fillers

  • Electricity and electronics - in cable insulation, PUR coated circuit boards

  • Mechanical engineering - insulation material

  • Paints – lacquers

  • Plastics - soft and hard plastics, plastic foam and cellular plastic

  • Printing – inks and lacquers

  • Timber and furniture - adhesive, lacquers, upholstery stuffing and fabric

  • Textile – synthetic textile fibers

  • Medical care – PUR casts

  • Mining – sealants and insulating materials

  • Food industry – packaging materials and lacquers
Reference

National Institute for Occupational Safety and Health.  Worker Health Chartbook 2004. NIOSH Publication Number 2004-146

Mapp CE, Boschetto P, Maestrelli P, Fabbri LM.  (2005) Occupatioanl Asthma.  Am J Respir Crit Care Med 172; 28/0-305.