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Isocyanates. They sound nasty, but what are they? Isocyanates are chemical compounds derived from cyanide and hydrocarbons, such as toluene or methylene. Common compounds are TDI (Toluene Di-Isocyanate) and Methylene Bisphenyl Isocyanate (MDI). These types of hydrocarbons have a sweet, pleasant smell, and so are commonly called "aromatics." But don't let their sweet smell fool you-isocyanates require your attention and respect.

Chemical compounds containing isocyanates are frequently associated with polyurethanes. Polyurethane can be found in a number of common industry materials such as: paints, coatings, insulation, and plastics. Isocyanate compounds provide industry with a two-sided sword, since these chemicals have useful characteristics, but also introduce safety & health concerns. Materials such as polyurethane produce beautiful, long lasting gloss finishes; are resistant to wear; resistant to many chemicals; and work well indoors, outdoors and in harsh industrial environments.

The OSHA Threshold Limit Value (TLV) for these types of compounds is as low as .02 parts per million (PPM). TLVs represent the limit of exposure that an average worker can safely be subject to over the course of an 8-hour day, without the aid of engineering controls or personal protective equipment. Controls must be in place for any exposure above this level. This is an extremely low TLV level and affirms the hazards represented by this compound. Clip-on, direct-read dosimeters are available in the marketplace to monitor worker exposure levels to isocyanates.

Conditions associated with isocyanate overexposure can be both immediate and long-lasting. Immediate, acute effects can include: eye and throat irritation; choking; shortness of breath; tightness of chest; dizziness; abdominal pain; nausea; vomiting; headache and dermatitis. After continued exposure to these compounds some workers may become sensitized to isocyanates, creating a chronic health hazard. Once this happens, extremely low exposures to isocyanates can trigger an asthma like response, or a severe allergic reaction.

Exposure usually occurs during an application process when droplets of the material are airborne. Not only is the application operator exposed, but potentially, so is anyone working in the area of the spray operation. Unlike many common paints and coatings, organic cartridge respirators or other air-purifying respirators are not adequate protection against isocyanates. In situations where a worker's exposure is above the 8-hour TLV, an approved air-supplied respirator must be used.

With isocyanate compounds it is critical to review the specific chemical MSDS prior to using the product. Check the TLV, the recommended or required personal protective equipment (PPE), and all other manufacturer's information. If you don't thoroughly understand the information, have someone explain it to you.

Beware of the risks associated with all the chemicals in your workplace. If isocyanates are part of your firm's operations, respect the benefits and hazards of this chemical and take every precaution to stay safe and accident free.


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