The legal angle on work-related exposure to silica dust
The authors, Simon Matthews and Alastair Clough, are insurance and safety, health and environmental lawyers, respectively, in the mining and minerals team at DLA Piper
Silicosis is the oldest known industrial disease. It was first recognized by legislation in the Workmen's Compensation Act 1925, which facilitated the Various Industries (Silicosis) Scheme of 1931 – a government-funded scheme to compensate for death, disability or inability to work arising from the contraction of silicosis. Dust suppression was first required by the Mines & Quarries Regulations 1938.
Prior to 1989, however, and the introduction of the Control of Substances Hazardous to Health Regulations (COSHH), only a ‘recommended’ workplace exposure limit for respirable crystalline silica (RCS) exposure existed. This recommended limit was 0.1mg/m3 (8h time weighted average). When COSHH was introduced in 1989 an Occupational Exposure Standard (OES) of the same amount was provided for, subject to further advisory review. Following this review in 1992 a Maximum Exposure Limit (MEL) of 0.4mg/m3 was implemented, which was adjusted to 0.3mg/m3 in 1997.
In 2002 the Scientific Committee on Occupational Exposure Limits, whose purpose is to provide scientific advice to the European Commission, issued a recommendation that, to control against silicosis, the occupational exposure limit would need to be below 0.05mg/m3. It should be noted, however, that this recommendation was based purely on health issues, and other matters such as practicability, cost and technical measurement constraints were not considered.
In 2005 the term Workplace Exposure Limits (WEL) replaced Maximum Exposure Limits (MEL) and Occupational Exposure Standards (OES), although the limit remained at 0.3mg/m3.
The Health and Safety Commission (HSC) consulted on proposals to amend the WEL early in 2006. The consultation stated that evidence suggested that long-term exposure at the then limit would eventually result in up to a 20% risk of developing silicosis, while exposure at 0.1mg/m3 reduced the risk to 2.5%. Following this consultation the WEL was reduced to 0.1mg/m3 from October 2006. It is interesting to note that the relevant limit for respirable dust arising from Portland cement, limestone and marble has remained at 4mg/m3, highlighting the entirely different category into which RCS is placed compared to other known quarry dusts.
Under COSHH employers need to assess the risks of their activities and ensure that the exposure of their employees to substances hazardous to health is either prevented or, where this is not reasonably practicable, adequately controlled by applying protection measures appropriate to the activity. The legislation notes that controls shall only be treated as adequate if the WEL is not exceeded and good practice principles set out within the legislation are applied.
The good practice principles include issues such as the design and operation of the processes to minimize the emission of substances; the development of control measures taking account of all potential exposure routes; the use of control measures proportionate to the health risk; the provision of suitable personal protective equipment; and informing and training employees on the risks and control measures. Specific guidance in respect of silica in quarries has been provided by the HSE in the form of good practice guidance notes, which can be found on the HSE’s website. HSE inspectors will use such guidance in assessing compliance with COSHH. As noted in Martin Isles’ article (see pages 17–21), this guidance influenced the good practice guides which were prepared as part of the Social Dialogue Agreement, which are explained further in that article.
While there have been calls from some quarters for a further reduction in the WEL, one of the key barriers to any such reduction is the ability to obtain accurate measurements, particularly in the case of relatively short-term sampling periods. At the time of the 2006 consultation the HSE acknowledged the difficulties associated with low-level exposure measurements, although the HSC did subsequently confirm that the Advisory Committee on Toxic Substances would continue to review research on exposure measurement in the context of potentially progressing towards a lower WEL. It also announced that an enforcement initiative would be undertaken, starting with the stonemasonry sector in 2006/2007. A number of enforcement notices have been served in that sector during this period, and it is understood that the HSE intends to extend the enforcement initiative into the quarrying sector from April 2008.