The United States’ Occupational Safety and Health Administration (OSHA) has published information on its new standard for exposure to respirable crystalline silica for general industry and maritime[i]. The maximum exposure limit is now half of the maximum exposure allowed in the UK.
Crystalline silica is a common material that is found in materials such as stone, artificial stone, and sand. When workers use and manipulate these materials, dusts of fine particles are produced. The tiny particles, known as respirable particles, can penetrate deeply into the lungs and cause diseases such as silicosis, lung cancer, chronic obstructive pulmonary disease and other respiratory diseases. Workers can be exposed to crystalline silica during the manufacture of glass, pottery, ceramic, brick, concrete and other products, during the use of sand in maritime operations, and by the use of sand in operations such as foundry work and hydraulic fracturing.
The new standard for exposure to crystalline silica in general industry and maritime[ii] includes:
- An action level of 25 micrograms of silica per cubic metre of air, averaged over an 8-hour day;
- A permissible exposure limit (PEL) of 50 micrograms of silica per cubic metre of air, averaged over an 8-hour day.
The action level is the level above which action must be taken to reduce or limit exposure, and the PEL is the maximum ‘allowed’ exposure. The standard requires employers to take actions such as:
- Limit access to areas where workers may be exposed above the PEL;
- Provide respirators when dust controls and safer work methods cannot limit exposure to the PEL;
- Offer medical exams, including chest X-rays and lung function tests, every 3 years to workers exposed at or above the action level for 30 or more days a year.
OSHA also offer advice on housekeeping practices and dust control methods that can help to reduce workers’ exposure.
The previous PELs for crystalline silica were 100 mg/m3 for general industry and 250 mg/m3 for construction and shipbuilding[iii]. These limits were adopted in 1971, and OSHA found that they did not adequately protect workers, and were outdated, inconsistent and difficult to understand. The limits were based on research from the 1960s and did not reflect more recent scientific evidence; since the limits were adopted, the U.S. National Toxicology Program, the International Agency for Research on Cancer, and the National Institute for Occupational Safety and Health have all identified respirable crystalline silica as a human carcinogen[iv].
In December, OSHA published guidance[v] on the respirable crystalline silica standard for work in the construction industry[vi]. The action level and PEL are the same as those in the general industry and maritime standard, and control methods are required.
In the USA, about 2.2 million workers are exposed to crystalline silica. OSHA predicts that the new standards will save nearly 700 lives and prevent 1600 new cases of silicosis per year once they are fully implemented[vii]. General industry and maritime employers must comply with all requirements of the standard by 23rd June 2018, with two exceptions: hydraulic fracturing operators, who must implement dust control measures to limit exposures to the new PEL by 23rd June 2021; and medical surveillance of those exposed above the action level for 30 days or more must be offered by 23rd June 2020.
For comparison, in the UK, the workplace exposure limit for respirable silica dust is 0.1 mg/m3, averaged over 8 hours, which is equivalent to 100 mg/m3 [viii]. This is the same as the old United States limit for general industry.
[ii] 1910.1053 Respirable crystalline silica. https://www.osha.gov/silica/SilicaGeneralIndustryRegText.pdf (Accessed 26 February 2018)
[iii] OSHA releases first new PELs for silica in more than 40 years. MSDSOnline. 24 March, 2016 https://www.msdsonline.com/2016/03/24/osha-releases-first-new-pels-for-silica-in-more-than-40-years/ (Accessed 26 February 2018)
[iv] OSHA’s proposed Crystalline Silica Rule: Overview. OSHA Fact Sheet. August 2013. February 2018)
[vi] 1926.1153 Respirable crystalline silica. https://www.osha.gov/silica/SilicaConstructionRegText.pdf (Accessed 26 February 2018)
[vii] OSHA’s proposed Crystalline Silica Rule: Overview. OSHA Fact Sheet. August 2013. https://www.osha.gov/silica/factsheets/OSHA_FS-3683_Silica_Overview.pdf (Accessed 26 February 2018)
[viii] Silicosis. Health and Safety Executive. http://www.hse.gov.uk/lung-disease/silicosis.htm (Accessed 26 February 2018)