Isocyanates

Isocyanates are a family of highly reactive, low molecular weight chemicals. Isocyanates are compounds which make up most products that are made of polyurethane. 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, autobody 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. There is evidence that both respiratory and dermal exposures can lead to sensitization. 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.

How to recognize isocyanates:

You can find isocyanates in a number of construction products including polyurethane paints, coatings, foams, glues and flooring. Certain tasks, such as spraying, can produce very high exposure to isocyanates.

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.

Health effects: 

Exposure to hazardous material may be acute or chronic. Acute exposures generally refer to single dose, high concentration exposures over short periods, while chronic exposures involve repeated or continuous exposures over long periods. These exposures may have acute, immediate effects or chronic, long term effects. 

Inhalation: In relatively high concentrations, isocyanates have a strong irritant effect on the respiratory tract in most people. Some people may develop bronchial sensitivity to isocyanates. These people, when later exposed to even very low concentrations of isocyanates, which may be below the exposure standard, may react by developing asthma-like symptoms, such as chest tightness, cough, wheeze and shortness of breath. Such attacks may occur up to several hours after cessation of exposure but, if a person is particularly sensitive, the attack may occur earlier. Asthmatic people are more prone to sensitisation and other adverse reactions. People with a history of asthma should not be exposed to isocyanates. 

Skin: Isocyanates are irritants. Skin sensitization occurs rarely with TDI, but may be more common in the case of other isocyanates. 

Eyes: Isocyanates are irritant to the eyes. Splashes can cause severe chemical conjunctivitis. 

Other health effects: Other health effects which have been reported include liver and kidney dysfunction, persistent cough, difficulty breathing, wheezing, congestion, eye irritation, tightness in chest, sore or dry throat, cold symptoms

Action plan if Isocyanates are believed to be present:

Prevent: 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 use of personal protective equipment such as respirators and personal protective clothing to prevent dermal exposures 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.

Where possible think about eliminating or reducing isocyanate risks. Consider:

• using products that do not contain isocyanates or less volatile forms

• avoiding unnecessary spraying. This causes more isocyanate to get into the air compared to using a brush or roller

• being aware of anyone who is already sensitized to isocyanates. Keep them away from the work

Control: Even if you minimize some of the risk this way, you may still need to control isocyanate risks. Control this by using the appropriate measures below:

• Ventilation – make sure there is enough fresh air in the work area. Open doors and windows; use air movers such as fans, etc. wherever possible. The higher the risk the better the ventilation will need to be;  

• Eye protection – wear eye protection (eg goggles or a face shield) when doing work where splashes / aerosol may get into the eyes.

• Gloves – gloves should be right for the products you are using – single use disposable gloves made of suitable materials (eg nitrile) are preferable. Make sure the breakthrough time and permeation rate are right for the type and length of the work. Check with the manufacturer / supplier. You may need gauntlet style gloves to prevent skin exposure.

• Overalls – disposable overalls are preferred. Launder significantly contaminated reusable overalls before wearing them again.

• Washing – good washing facilities are essential. Wash off any product on the skin as soon as possible. Do not use solvents to do this. Workers should be encouraged to wash exposed skin at breaks and after finishing work. Skin care products can also help replace the natural oils that help keep the skin’s protective barrier working properly.

• Respiratory Protective Equipment (RPE) – you may need RPE where ventilation does not provide enough control – particularly in enclosed spaces if you are creating an aerosol (eg by some rollering work) or using products with significant amounts of TDI. Wearers should be fit tested where needed. It is particularly important to select the correct filter. For example, P3 particulate filters provide protection against spray mist but do not protect you from vapours. You will need the right gas / vapour filter for these. Change them at suitable intervals. Check with your supplier if you’re not sure.

• First aid – give adequate and appropriate first aid treatment to anyone affected by isocyanates. You may also need to seek further medical attention.

More information can be found at:

https://www.cdc.gov/niosh/topics/isocyanates/default.html

https://www.osha.gov/SLTC/isocyanates/

http://www.hse.gov.uk/construction/healthrisks/hazardous-substances/isocyanates.htm

https://www.safeworkaustralia.gov.au/system/files/documents/1702/isocyanates.pdf