The Inspectorate SZW, the Dutch labour inspectorate, derives its enforcement policy for exposure to hazardous substances from the statutory and recommended occupational exposure limits listed on the website of the Social and Economic Council of the Netherlands (Sociaal Economische Raad, SER).
Worker exposure, as measured in the so-called “employee inhalation zone”, must not exceed the eight-hour time-weighted average Workplace Exposure Limits (GSW TGG-8u) published by the SER.
Silica and hardwood dust are the principal hazardous substances encountered in the construction industry. Both are carcinogens. For more information, see the Inspectorate SZW website.
The Workplace Exposure Limit (WEL) for silica is set using the so-called “threshold effect”. This means that there is no known adverse effect upon health from exposure to concentrations below the WEL. The current WEL for respirable crystalline silica is 0.075 mg/m³. As long as the employer can demonstrate that exposure does not exceed that limit, the inspectorate does not enforce further exposure safeguards.
But the rules are far tighter for carcinogens without a “threshold effect”, such as hardwood dust/dimethyl ether (DME). In this case, any possible reduction in exposure must be carried out. In other words, even if exposure is already below the WEL (the current WEL for respirable hardwood dust is 2.0 mg/m³) but it is still technically possible to reduce it even further – by applying state-of-the- art technology, for example – then the employer is obliged to do so.