Beyond spray and fog

Posted on2022-07-08 by

How to reduce exposure to isocyanates

In recent years, more attention has been paid to the risks posed by isocyanates, even in sectors where many believed that adequate control measures were already in place. You may already know the risks of isocyanates, but do you know what the first signs of exposure are and how to make sure you've properly protected yourself?

We can help you protect your workers and keep you aware of these risks. Whether you are painting in an auto repair shop, in construction applying spray foam insulation, or using polyurethane adhesives, sealants, and specialized coatings, isocyanates can pose a serious threat to your lungs and overall health. This document outlines what you need to know about isocyanates to stay safe.

What are isocyanates?

Isocyanates are a wide range of highly reactive chemicals that are typically used to react with compounds containing alcohol (hydroxyl) functional groups to create polyurethane polymers. Chemicals containing two of these isocyanate groups are called diisocyanates, and several of them are commonly used in paints and polyurethane foams.

How could they affect me?


Some of the main health effects of exposure to isocyanate vapours, spray mists and dustOther are:

  • Irritation of the eyes, nose and throat.
  • Wheezing, chest tightness, dyspnea and cough.

All workers exposed to isocyanates are at risk of becoming sensitized to them, not just those with a history of asthma, allergies, or other respiratory conditions. Sensitization can occur after a single exposure to high levels of isocyanates, or after several exposures to low levels. Once a person becomes sensitized to these substances, even very low isocyanate exposures or other triggers (such as cigarette smoke or cold air) can cause immediate or even later asthma attack symptoms.


Isocyanates are also skin irritants (causing inflammation and dermatitis) and there is evidence to show that exposure through touch can also cause respiratory sensitivity.


Isocyanates are an eye irritant. Splashes can cause severe chemical conjunctivitis.

Other health effects

Other known health effects include liver and kidney dysfunction. Isocyanates include compounds classified by the International Cancer Research Center as possibly carcinogenic to humans.(3)

What are the risk situations?

The main source of exposure of workers is inhalation of isocyanates, particularly when applying polyurethane paints, coatings, foams, tacks and floor compounds. Another important source of exposure is maintenance and cleaning of polyurethane spraying equipment.(4)

The fine mists and vapors generated by spraying can be easily inhaled and the isocyanates and other components they contain can be absorbed by the lungs, which can also get on the skin and eyes. Application of products containing isocyanates by dipping, brushing or rolling in well-ventilated areas usually reduces the risk to workers.(5)

Manual spraying of bicomponent paints is the leading cause of occupational asthma in the UK (see Figure 1).(7) Statistically, spray paint workers in vehicle repair shops are at greatest risk, with many forced to leave the industry after becoming sensitized to isocyanates and developing occupational asthma. However, it is not the only risk sector. Workers in other sectors, such as construction and metal processing, are also often exposed.

When cured, polyurethane products cease to contain free isocyanates and to be dangerous with normal use. However, welding or burning polyurethane-coated surfaces can release a wide range of contaminants, including isocyanates.(8)

What can I do to protect myself?

Use appropriate controls

There are many ways to minimise personal exposure, but one of the most important is to apply spray paints only in specially designed paint booths or rooms, following appropriate working procedures and with adequate ventilation. Applying paint by spraying causes visible and invisible fogs, which can remain in the air for many minutes or even hours after the work is finished. It is therefore important to ensure that the paint booth operates at a slight negative pressure and that workers entering the booth are aware of the spacing period (the time required for spray fogs to settle).(9)

Acquire the necessary equipment

When spraying isocyanate paints, respiratory, eye and skin protection must be worn. Recommendations and regulations vary by country. Therefore, we recommend always consulting national legislation.

• Respiratory protection with air purification

In many countries, respiratory protection with purifying filters can be used as part of an effective respiratory program. They can be half masks with protective glasses or a full mask with particle and organic vapor filters.

• Breathing devices

In some countries, there is some concern that the odor threshold for isocyanates exceeds occupational exposure limits and therefore the use of supplied-air or self-contained respirators is mandatory. Supplied-air visors are also commonly used, which continuously provide clean, breathable air as well as protecting the face and eyes.

• Skin and eye protection

Depending on the respiratory protection being used, appropriate glasses may be needed to protect the eyes from splashing and exposure to spray fog. In addition, appropriate clothing and gloves should be worn to avoid exposing the skin.

Once you know the risks and hazards present in your workplace, check out the full range of respiratory protection products and protective eyewear and clothing 3M to find the most appropriate product for your activities. Whether it's a half mask,* full mask with filters*, or heavy-duty powered or supplied-air breathing apparatus (supplied-air visors), all of our products are designed to make it easy to get the job done while you breathe comfortably and comfortably. safe.

At any time, you can contact one of our respiratory protection experts for personalized assistance with the selection and use of respiratory protection products 3M. Your job is to help you select the right products based on your risk assessment, to help you protect your lungs so you can focus on what matters: doing your job correctly and maintaining good health to enjoy with your loved ones and family. .

Most reported causative agents between 2012 and 2016 in the United Kingdom

Image 1: Statistics on the causative agents of occupational asthma in the United Kingdom between 2012 and 2016(7).
*Refer to national guidance on PPE suitability – supplied air breathing apparatus may be required.

Did you know that...?

• Spraying of two-component paints containing isocyanates is the leading cause of occupational asthma in the UK.(6)

• Spray paint workers in car repair shops are 90 times more likely to develop asthma than the rest of the UK working population.(6)

• Each year in the UK, approx. 50 painters who work with spraying.(6)


  1. Julia Smedley, Finlay Dick, Steven Sadhra. 'Oxford Handbook of Occupational Health', 2nd edition. s.l. : OUP Oxford, 2013.
  2. 'Safety and Health Topics: Isocyanates'. US Occupational Safety and Health Administration (OSHA). [En línea][consultado el 22 de febrero de 2018]. .
  3. Monographs of the International Centre for Research on Cancer on the assessment of the carcinogenic risk of chemicals for humans: some chemicals used in plastics and elastomers. the commission has not yet adopted a decision.
  4. 'Reducing ill health from isocyanate exposure in engine [4] vehicle repair (MVR)' (Reducing health problems caused by exposure to isocyanates in motor vehicle repair). UK Health and Safety Executive (HSE). [En línea] [consultado el 20 de marzo de 2018]. .
  5. 'Construction hazardous substances: Isocyanates'. UK Health and Safety Executive (HSE).[En línea] [consultado el 20 de marzo de 2018]. .
  6. Guidance on working with 2-pack isocyanate paints. UK Health and Safety Executive (HSE). [En línea] [consultado el 20 de marzo de 2018]. .
  7. Work-related asthma in Great Britain 2017. UK Health and Safety Executive (HSE). [En línea] [consultado el 20 de marzo de 2018]. .
  8. 'Determination of isocyanates, aminoisocyanates and amines in air formed during the thermal degradation of polyurethane'. Daniel Karlsson, Jakob Dahln, Gunnar Skarping * and Marianne Dalene. 2002, J. Environ. Monit, vol. 4, pp. 216-222.
  9. 'Safety in isocyanate paint spraying'. UK Health and Safety Executive (HSE). [En línea] [consultado el 20 de marzo de 2018]. .
  10. RR1064, 'Investigation into exposure when the visor of air fed RPE is raised during spraying'. s.l. : UK Health and Safety Executive (HSE), 2015.
  11. Summary Sheet - Isocyanates