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Isocyanate Exposure in the Workplace 

26 April 2024

Automotive spray paint

Here we answer any common questions around isocyanate exposure in the workplace – do you know your exposure limits, and how to monitor and control isocyanate exposure?  

Isocyanate Testing and Biological Monitoring are two simple, cost-effective ways of checking that workplace control measures are effective so that exposure is being adequately controlled. 

What are Isocyanates?

Isocyanates are a type of compound found in a range of products, including “two pack” spray paints (spray paints with two parts that you mix before application), lacquers, adhesives, certain coatings, and insulation foam.  

Isocyanates are common in motor vehicle repair (MVR), printing, boat maintenance and furniture manufacture. According to the HSE there is widespread potential for work-related ill health in MVR bodyshops. Many of the substances used require careful storage, handling and control. 

What can Isocyanates do to me and why test for exposure? 

The main routes of entry are inhalation and skin contact. However, ingestion is possible where poor personal hygiene is observed (e.g., not washing hands at break times). Isocyanate exposure can cause irritation of the eyes, nose, and throat, and it has also been linked to dermatitis and occupational asthma. 

In fact, spraying isocyanate products is a significant cause of occupational asthma as exposure can occur in paint-spraying 

Symptoms can develop immediately following exposure but can also appear several hours later outside working hours in the evening or early morning.  

Early signs of respiratory sensitisation to isocyanates include one or more of the following: 

  • chest tightness (also outside of working hours) 
  • persistent cough 
  • wheezing 
  • breathlessness 
  • flu-like shivers 
  • Recurring blocked or runny nose 
  • Recurring sore or watering eyes 

If exposure continues, an individual may suffer from permanent and severe asthma, for which there is no cure. Where poor isocyanate management occurs, workers can experience irreversible poor health impacts, and this may result in early retirement of employees, applications for compensation, and reduced quality of life.  

Once a person has been sensitised to isocyanates, it only takes a very small amount to trigger an asthma attack. This would mean that the individual affected would have to give up work where they risk exposure.  

Nearly every bodyshop uses isocyanate-containing paints. According to the HSE, the introduction of the Paints Directive restricted the availability of certain paints used by Motor Vehicle Repair bodyshops but rumours that isocyanate-containing paints will be banned persist. Isocyanates will continue to be used in some primers and base coats as well as UV-cured coatings and some water-based paints. 

The industry (as a whole) is also in the top 10 industries for cases of disabling dermatitis.   

Do I legally need to monitor Isocyanates levels?

You must adequately control exposure to isocyanates to protect your employees from life-limiting and irreversible health impacts. 

Under the COSHH Regulations 2002 you must protect your workers from isocyanate exposure. Failure to comply would result in fines or prosecution. 

The HSE recommends that vehicle spray painters undertake biological monitoring annually to check that exposure is being adequately controlled. Some individuals may believe that their water-based /UV-cured paints are isocyanate-free.  The HSE points out that ‘water-based’ does not mean ‘isocyanate-free’ and almost all top-coats contain isocyanates. ‘Water-based’ does not, just means that it is emulsion based and has reduced levels of solvents.   

It is recommended that sites where isocyanates are used undergo regular air monitoring, to compare levels in the workplace with the relevant Workplace Exposure Limits (currently 0.02 mg/m3 over 8 hours). 

Both air monitoring and health surveillance results should be retained and used to update COSHH (Control of Substances Hazardous to Health) Assessments

How Should I Control Isocyanate Exposure?

For control methods, the hierarchy of control should be used to determine the most effective, but most reasonably practicable route, to minimise exposure. 

Elimination or Substitution 

First, is it possible to eliminate isocyanate use entirely, or alternatively substitute current isocyanate-based materials for less hazardous materials or substitute an alternative process? Where this is not possible, then engineering controls need to be investigated. 

Engineering Controls 

‘Conventional’ spraying uses compressed air to atomise the paint. This can create quite a lot of overspray / mist in the air that can travel significant distances. You may improve this by using high-volume low-pressure (HVLP) spray guns.  

Alternatively, airless spraying forces paint through a nozzle under high pressure. There is less overspray / mist travel with this method as the speed of the paint droplets quickly falls after leaving the nozzle. However, there is risk of injecting paint etc into the skin if the spray tip is not properly guarded. Use the correct tip sizes and pressure. 

Some sites have specific enclosed spray booths for the use of isocyanate sprays, these are best practice in terms of control of isocyanate spray. You should consider measures to control exposure, such as selecting the correct spray equipment. You should be aware of issues associated with different types of spray equipment.  

Spraying isocyanate-based paints should be carried out in an enclosed area with local exhaust ventilation (LEV) where possible. Engineering controls including using closed systems and ventilation. Spray booths and rooms are referred to as local exhaust ventilation (LEV) systems which are designed to take harmful vapours, aerosols and mists away from a person’s breathing zone. 

Administrative Controls 

Where spray booths are used, these must be tested by a competent person on an annual basis, and the clearance time should be clearly displayed externally. Any design for spray booths should be done by a competent LEV (Local Exhaust Ventilation) engineer.  

Operators should be given information, instruction, and training in the safest means of carrying out the work and be instructed to wash hands prior to rest breaks, eating, drinking, smoking and at the end of the workday. 

PPE and RPE 

The final line of defence is personal protective equipment (PPE), PPE alone is not sufficient to protect against isocyanates but can be useful when used in conjunction with the controls discussed above. Where spray painting is carried out, operators should use respiratory protective equipment (RPE) such as constant flow air fed breathing apparatus (BA). In most instances this should have an assigned protection factor of at least 40 (e.g. a visor / hood type air-fed BA) and a low flow indicator. Make sure the breathing air is uncontaminated and meets ‘minimum flow conditions’ in terms of tubing length / internal bore and air pressure. Improve visibility by using tear-off visor protectors if needed. 

Operators should be trained in the use of respirators, and for close-fitting RPE they should be fit tested to ensure an adequate seal. Operators in non-spraying environments should wear respirators with ABEK1 and FFP3 filters. All operators handling isocyanates should be issued and wear overalls, chemical-protective gloves, and safety glasses. 

What are UK Isocyanate exposure limits? 

The UK exposure limit for isocyanates is currently 0.02 milligrams per cubic metre of air (mg/m3) as an eight-hour time-weighted average (TWA).  

The short-term exposure limit (STEL) is 0.07 mg/m3.  

These limits are set by the Health and Safety Executive (HSE) under the Control of Substances Hazardous to Health Regulations (COSHH) and are presented in the HSE EH40 document, which is regularly checked and updated. 

Every operator who comes into contact with isocyanates should undergo annual biological monitoring for isocyanates in urine as part of their regular health screening. At the same time, it is recommended that operators also undergo Spirometry (Lung Function) Testing. 

In addition to the health surveillance, it is recommended that sites where isocyanates are used undergo regular air monitoring, to compare levels in the workplace with the relevant Workplace Exposure Limits (currently 0.02 mg/m3 over 8 hours). 

Both air monitoring and health surveillance results should be retained and used to update COSHH Assessments

You are likely to need: 

  • Health Surveillance – this includes surveillance for asthma as well as dermatitis (PDF) . For asthma, you should perform annual lung function testing and a questionnaire (PDF) . For new employees carry this out on beginning work; after 6 weeks; 6 months and then yearly. 
  • Exposure Monitoringurine sampling (PDF) checks the effectiveness of your controls. Carry it out during the first few months of someone’s employment to determine whether workplace controls and practices are providing enough protection. You are likely to need to repeat the monitoring at appropriate intervals, unless it is clear from the results that exposure is well controlled. 

There are a series of videos on the HSE website showing how exposure occurs in paint spraying.   More general information about spraying isocyanates can be found in the motor vehicle repair section of the HSE website.

Experts in Isocyanate monitoring and Isocyanate exposure

Envirocare offers a thorough Local Exhaust Ventilation Examination and Testing service including visual inspection, measurement, and qualitative assessment; which helps to determine whether your LEV system can provide satisfactory control of the hazardous substances as required by COSHH regulations.

Envirocare also provides comprehensive and easy to read reports for Local Exhaust Ventilation Examination and Testing; and as we are independent of any LEV system provider we can provide unbiased reports.

  • comprehensive COSHH Workplace Air Monitoring and COSHH Risk Assessment advice to ensure compliance with the relevant exposure limits.
  • aid your COSHH risk assessment by carrying out COSHH air monitoring to determine the levels of substances in the workplace and ensure the WEL (Workplace Exposure Limits) value is not exceeded for the substances you use.
  • detailed report on work practices and findings together with recommendations for remedial action.

We service a wide range of industries from large to small companies in chemical, woodworking, engineering, and printing industries as well as in schools and colleges.

Call us on 01274 738668 or fill out our enquiry form for any queries regarding isocyanate monitoring, isocyanate exposure, workplace exposure limits, COSHH risk assessments.