Biological Monitoring for Isocyanates in Motor Vehicle Repair

Isocyanates are highly reactive chemicals used in making a variety of products, including paints, foams and glues. They are often used in the motor vehicle repair (MVR) industry, for example:

• two-pack spray paints, e.g. hexamethylene diisocyanate (HDI);
• some glues and hard wearing plastics, e.g. toluene diisocyanate (TDI);
• making, cutting, grinding or heating polyurethane foams, e.g. methylene diphenylene diisocyanate (MDI);
• production of polyurethane paints, varnishes and elastomers, e.g. isophorone diisocyanate (IPDI).

Breathing in isocyanate is the top cause of work-related asthma in Britain. Anyone getting asthma from isocyanates will be unable to work with them again and so exposure to isocyanates needs to be well controlled. This may involve ventilated spray booths and air-fed breathing apparatus. But how can you prove that your controls are working and your employees are safe, particularly as you are relying on correct behaviour as well as equipment maintenance to prevent exposure? The simplest way to do this is by analysing workers’ urine for traces of isocyanates (biological monitoring).

If you use isocyanate-based products, you normally need a health surveillance scheme. We recommend your surveillance scheme provider helps you with biological monitoring. There is a biological monitoring guidance value for isocyanate traces in urine. The value is “1 micro mol urinary di-amine per mol creatinine” for a urine sample collected at the end of the task and most companies using good control can get below this value.

The guidance value is about exposure control: it has no direct meaning for health.

Further information for employers is available by downloading the following documents:
  Why is it necessary?
  How is it carried out?
  What do the results mean?

Further information for workers is available by downloading the following documents:
  Why is it necessary?
  How is it carried out?
  What do the results mean?

Further information can be found on HSE’s web site at www.hse.gov.uk/mvr/nco/index.htm.

The law requires employers to control exposure to isocyanates to a level that is as low as is reasonably practicable. Further information can be obtained from www.hse.gov.uk/asthma. HSE has also issued a Sector Information Minute (SIM 03/2006/04), which recommends using biological monitoring to assess control of isocyanates. A CoSHH Essentials guidance sheet is also available (www.hse.gov.uk/pubns/guidance/g408.pdf).

The HSL offers a commercial biological monitoring service for isocyanates. A monitoring service for airborne isocyanates is also available.

  To contact the Sample Reception, please click here

  Exposure to isocyanates - further information

A website providing a range of information regarding health and safety issues in the motor vehicle repair industry has been launched by the Health and Safety Executive (HSE) and can be found at:

  www.hse.gov.uk/mvr/index.htm

What is Biological Monitoring?
Biological monitoring (BM) is used to assess exposure by the measurement of a chemical or its breakdown products in blood, urine or breath. For isocyanates, a urine sample from a person is all that is needed for BM.

Why use BM for isocyanates?
BM is unique because it can measure how much of a chemical has actually entered a person's body, rather than how much is in the environment around them. Control of exposure to isocyanates usually relies on engineering controls such as spray booths and respiratory protective equipment such as air-fed breathing apparatus (visors). By using BM you can tell whether control measures like these are working and being used correctly. The case studies below show how useful BM can be.

Urine sampling
HSL has developed a method for analysing breakdown products of isocyanates in urine. The method can measure exposure to HDI, TDI, MDI and IPDI, either separately or as mixed exposures. Samples should be taken immediately post-shift (or post-exposure, if exposure is intermittent or 'task-based'). If sampling is for TDI or a mixture of isocyanates, samples should be collected in special bottles containing citric acid.

Sprayers should not lift their visor to check on the job	Sprayers should always know and observe clearance times for booths and ventilated spaces	Never allow an unprotected person to approach a sprayer

HSL can provide sample collection kits (including special citric acid bottles) and packaging materials. We also supply full instructions for sending samples through the post in accordance with legal requirements. This is all included in the standard price of the analysis.

What do these results mean?
It is important to realise that BM analysis does not give any information about health effects, instead it is a measure of the overall effectiveness of exposure control measures. Nevertheless it is important that the purpose of BM is clearly explained to each individual taking part and that their informed consent is obtained. HSL can advise on simple, practical ways of setting up a BM programme, and can assist in the interpretation of results - a key part of any BM strategy. You will need to consider health surveillance as part of your control strategy.

In October 2005, HSE endorsed a Biological Monitoring Guidance Value of 1 µmol isocyanate-derived diamine/mol creatinine (Method for Isocyanate Metabolites in Urine). Any BM results should be below this value.  If BM results exceed this, you should look at your control measures (booths, masks, filters) and working practices and make any necessary improvements and re-test.  If BM results are below the guidance value, annual testing is recommended.

Case Studies

Case Study A
An MVR site was investigated because there were reports of occupational ill heath amongst workers there. BM showed that all staff, including administrative staff, who never did any painting, had been exposed to isocyanates from the spray paints in use at the factory. An investigation showed that the spray booth at the site was leaking. Isocyanates from the leaking booth were able to spread throughout the building, so everybody who worked there was exposed to them. This was an unexpected finding because the spray booth had been recently serviced, inspected and tested, and was thought to be working properly.

The leaking spray booth was then repaired and further BM showed that the spray booth was working properly. However one of the paint sprayers was still exposed to isocyanates. Further investigations revealed that he had not received proper instructions and was not using his breathing apparatus correctly, as a result his exposure was not as low as it could have been.

In this case, BM revealed problems with both equipment and training that, if undetected, could have resulted in employees becoming ill.

Case Study B
A BM survey of a variety of MVR companies, ranging from national dealerships to 'one man' operations, was carried out. Factors that might lead to isocyanates exposure were identified. These included:

• spraying above head height because respiratory protective equipment sometimes does not fit properly when people look upwards;
• briefly lifting visors to take a closer look at the job, wearers are then not protected;
• entering a spray booth soon after spraying without observing the correct 'clearance time';
• entry of unprotected workers into spray areas to speak to protected colleagues during spraying.

BM allowed these risk factors, which might otherwise have gone unnoticed, to be identified and highlighted areas where improved health and safety procedures were needed.

Further Details
Contact our Sample Reception Office for sample bottles and testing kits on tel: 00 44 (0)1298 218099.  For technical advice contact Dr John Cocker, tel 00 44 (0)1298 218429, email john.cocker@hsl.gov.uk) or Kate Jones, tel 00 44 (0)1298 218435, email kate.jones@hsl.gov.uk).

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