Painters are exposed to dangerous vapours.
To ensure that workers are not breathing in unhealthy levels of volatile carcinogens such as
benzene, accurate air tests must be relied upon. The project participants worked together to develop a reference material to be used to monitor workplace air all over Europe. By working together, they perfected their measurement techniques and formed laboratory networks.
The effects of working in polluted air has begun to take its toll on the European workforce. One only needs to look at the case of asbestos; thousands of workers' health was compromised. The human and monetary cost of this is only now being realised. However, with increased legislation and improved methods for monitoring exposure to harmful substances, workers are now more than ever protected from these dangers.
Protecting the many people who work with toxic and carcinogenic chemicals everyday is not an easy task. European legislation introduced in 1980 and national legislation states that the exposure of individual workers to certain potentially harmful vapours must be assessed. These vapours include volatile organic hydrocarbons such as benzene and its relatives. Benzene is known to be a carcinogen. If the worker is in an environment where exposure could be significant, they must be monitored periodically.
Tiny tubes collect the samples
Monitoring can be can be achieved without scientists visiting to take air samples.
A small tube of charcoal is attached to the worker's clothes and the charcoal absorbs the vapours. The tube is then taken to the lab where analysts measure the levels of harmful chemicals absorbed by the charcoal. This is done by using a solvent that desorbs the chemicals and so separates them from the graphite. Gas chromatography is a key technique used to separate and detect the trapped air components.
This method is used world wide as a standard method for measuring workplace vapours. However, in the past, various quality checks showed that when measuring levels of benzene and other compounds, results varied tremendously from laboratory to laboratory and country to country. This is unacceptable because it is difficult to know which measurement is the correct one and this means the test results cannot be trusted. The consequences of false results are drastic; if a worker thinks the levels of benzene are lower than they are in reality, his or her health is at risk. Conversely, if the result shows levels above the true levels, companies may be wrongly accused of breaking the law. Either way, the cost is great.
As a result, the Standards, Measurements and Testing programme, then known as the BCR, initiated a project in order to rectify this troubled state-of-affairs. This project has improved measurement methods so much that less than 2% variation in results can now be achieved.
Collaborating is the key to quality work
How did the thirteen participating laboratories achieve this? Through much collaborative study, they analysed the method in great detail. Each partner tested a charcoal sample using their version of the standard method and then the group met to discuss the results and the reasons for the variation. Returning to the laboratories, they would perform the tests again, implementing any improvements. Another meeting was held to discuss any new problems. Carrying on this process led to each laboratory optimising the way they performed the measurements.
The next step in the project, which was co-ordinated by Prof Kettrup at GSF in Germany, was to develop a Certified Reference Material. Samples of this material were prepared to become available to any laboratory performing occupational air quality tests. The "material" is in fact a tube containing charcoal, just like those used to sample air in the workplace. The only difference is that these tubes have been charged with a specific and known -"Certified"- level of benzene. They provide the laboratories with a means of checking that their techniques are correct and the results are reliable.
Thorough testing provides accurate results
Because thousands of tubes of the CRM would be widely distributed and relied upon to verify measurements, it was important that it was prepared carefully. The charcoal in all of the tubes was "charged" with precise amounts of vapours before being sealed. Random tubes were chosen for analysis to ensure that the amount of harmful vapours in each tube was in fact the same. The tubes were also tested over two and three years to check that there was no variation of the vapour levels. This is important because the CRMs are produced en masse to meet the demand arising for five years or more. They are produced this infrequently because their production is highly specialised and costly. It is therefore imperative that they can be used confidently for this amount of time.
To assign accurate values for the vapour levels, the laboratories again teamed up to produce quality results. The laboratories went on to use their perfected measurement methods to determine the precise amount of vapour the tubes hold. They found results which agreed very well with each other and this allowed them to guarnatee the exact levels in the reference material with great confidence.
Working together to produce such precise results allows other laboratories all over the world to check their own measurements for quality. They can all use the CRM to calibrate their methods and equipment. The accuracy is transferred and reliable results abound. Monitoring the levels of dangerous chemicals is more likely to produce accurate results and companies' awareness of these health risks is heightened.