Mark Godden discusses preventing workplace exposure for respirable crystalline silica

Materials World magazine
4 Jul 2016

Mark Godden looks at the regulatory methods for preventing workplace exposure to respirable crystalline silica.

The cost of quartz

Silica, also known as silicon dioxide (SiO2), silex or quartz is an abundant mineral on Earth, constituting around 12% of its crustal rocks. It would be difficult to undertake any sort of mineral extraction or processing without encountering at least a small amount of silica. Sandstone typically contains 90% silica, granite 30%, slate 30%, clay 20% and limestone 2%. The recovery and processing of natural materials containing silica can potentially result in the airborne ejection of very small fractions of the mineral, which may subsequently be inhaled. This is called respirable crystalline silica (RCS).    

RCS is well known to be harmful to the health of those inhaling it, being firmly linked to lung diseases such as silicosis, chronic obstructive pulmonary disease and, with less certainty, lung cancer. Fourteen people died in the UK from silicosis during 2006.

The current UK occupational exposure limit for RCS is 0.1mg/m3 (measured over an eight-hour time weighted average). This limit was reduced from 0.3mg/m3 in 2006. The USA is about to adopt a new exposure limit of 50µg/m3 and it seems likely that the UK limit will be further reduced in the future. 

EU legislators have long been considering setting a binding RCS occupational exposure limit of 0.1mg/m3 for workers in member states via one of two different Directives. These are 98/24/EC The Chemical Agents at Work Directive and 2004/37/EC The Carcinogens and Mutagens at Work Directive. 

EUROSIL, the official body representing European industrial silica producers completed a socio-economic impact study in 2013 suggesting that if RCS is controlled via the Chemical Agents at Work Directive, the ten-year socio-economic cost will be €25 billion. Alternatively, if the Carcinogens and Mutagens at Work Directive were to be used to set RCS occupational exposure limits, the projected socio-economic cost will be €152 billion over the same ten-year period (2015-2025). 

Unfortunately, recent announcements from the EU suggest that legislators are intending to use the potentially more controversial Carcinogens and Mutagens at Work Directive to control occupational exposure to RCS within European states. 

I believe that a safe occupational exposure limit for RCS should be firmly enshrined in European law. The Chemical Agents at Work Directive is the best place to put the control because it would provide a solid legal safeguard for workers, while being the least expensive option for industry. 

How many people will be dissuaded from using beautiful natural materials because they are linked to regulations covering carcinogens and mutagens? Does crystalline silica (ubiquitous in nature) really deserve to be grouped with toxic chemical compounds such as trichloroethene, hydrazine, acrylamide and epichlorohydrin?

RCS is a problem for the extractives sector that is not going away. To reduce the human cost, the financial and engineering challenges to industry can only intensify. 

Mark Godden is Mine and Quarry Manager at Albion Stone, UK. With more than 30 years’ experience in the sector, Mark has developed new underground dimension stone mining techniques and modern open quarrying methods, been involved in the supply of Portland Stone for Buckingham Palace, and worked on the refurbishment of Green Park Tube Station.

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