NIOSH Safety and Health Topic:
Isocyanates
Isocyanates
are a family of highly reactive, low molecular weight chemicals.
They are widely used in the manufacture of flexible and rigid foams,
fibers, coatings such as paints and varnishes, and elastomers, and
are increasingly used in the automobile industry, auto body repair,
and building insulation materials. Spray-on polyurethane products
containing isocyanates have been developed for a wide range of
retail, commercial, and industrial uses to protect cement, wood,
fiberglass, steel and aluminum, including protective coatings for
truck beds, trailers, boats, foundations, and decks.
Isocyanates are powerful irritants to the mucous membranes of the
eyes and gastrointestinal and respiratory tracts. Direct skin
contact can also cause marked inflammation. Isocyanates can also
sensitize workers, making them subject to severe asthma attacks if
they are exposed again. Death from severe asthma in some sensitized
subjects has been reported. Workers potentially exposed to
isocyanates who experience persistent or recurring eye irritation,
nasal congestion, dry or sore throat, cold-like symptoms, cough,
shortness of breath, wheezing, or chest tightness should see a
physician knowledgeable in work-related health problems.
Preventing exposure to isocyanates is a critical step in
eliminating the health hazard. Engineering controls such as closed
systems and ventilation should be the principal method for
minimizing isocyanate exposure in the workplace. Other controls,
such as worker isolation and personal protective clothing and
equipment may also be necessary. Early recognition of sensitization
and prompt and strict elimination of exposures is essential to
reduce the risk of long-term or permanent respiratory problems for
workers who have become sensitized.
The most widely used compounds are diisocyanates, which contain
two isocyanate groups, and polyisocyanates, which are usually
derived from diisocyanates and may contain several isocyanate
groups. The most commonly used diisocyanates include
methylenebis(phenyl isocyanate) (MDI), toluene diisocyanate (TDI),
and hexamethylene diisocyanate (HDI). Other common diisocyanates
include naphthalene diisocyanate (NDI), methylene
bis-cyclohexylisocyanate (HMDI) (hydrogenated MDI), and isophorone
diisocyanate (IPDI). Examples of widely used polyisocyanates include
HDI biuret and HDI isocyanurate
courtesy of http://www.cdc.gov/niosh/topics/isocyanates/ |