What You Need to Know about Respirable Crystalline Silica
Part I: Technical, Health, and Regulatory Background
By Alexandra Serban
November 04, 2019
Exposure to crystalline silica is a serious, established occupational health and safety issue that many companies are struggling to understand and diminish. There is further pressure from governmental agencies – OSHA is tightening the 2016 silica exposure standards, and the U.S. Mine Safety and Health Administration is looking to create a new silica regulation.
Why is crystalline silica exposure a serious health and safety issue?
Find the answer to this question and more, in our comprehensive guide to understanding crystalline silica, an occupational safety hazard some companies are still struggling to keep under control.
Part I: Technical, Health, and Regulatory Background
What is crystalline silica?
Silica (silicon dioxide) is a mineral commonly found in soil, concrete, glass, sand, silicone, and other materials. It’s also a key component in a variety of applications, from fiber-optic cables and computer chips to cars and buildings.
There are two types of silica:
- Crystalline silica or quartz
- Non-crystalline silica
Crystalline silica has been classified as a group 1 human carcinogen by the International Agency for Research on Cancer (IARC). There is strong evidence that prolonged exposure to crystalline silica is responsible for lung disease and lung cancer.
Silica dust is the second biggest cause of lung disease in workers, after asbestos, killing around 800 people in the UK every year. OSHA estimates that there are more than 600 deaths from silicosis each year – and 900 new diagnoses.
Consequences of silica dust exposure
Certain construction tasks may expose workers to silica dust at levels more than 10 times the permissible exposure limit (PEL) set by OSHA, according to the results of a 2018 academic study.
Crystalline silica can become airborne during sanding, crushing, cutting, drilling, and chipping. These construction-site activities produce silica dust. Particles smaller than 4 microns inhaled by workers can lodge deep in the lungs and stay there.
Other common silica health risks include:
- Inflammation of lung tissue
- Lung cancer
- Kidney damage
A recent study links pulmonary hypertension to silica exposure-induced sarcoidosis. Researchers concluded that the pulmonary hypertension was caused by fibrosis of chest organs, a state induced by immune and inflammatory reactions to silica exposure.
Long-term exposure to silica dust can also cause chronic silicosis, an incurable disease similar to the effects of asbestos exposure. It can damage lung tissue and cause breathing problems and lung cancer. Silicosis can remain undetected for 10 to 50 years after exposure and has no known medical treatment.
Who is at risk?
OSHA estimates that some two million construction workers are exposed to crystalline silica while performing tasks such as:
- Cutting stone
- Abrasive blasting
Tuckpointing or breaking concrete with a jackhammer in poorly ventilated areas, for instance, puts construction workers at risk of high concentrations of hazardous dust.
The evolution of silica standards
Safety experts have urged a tightening of silica exposure standards since the 1970s, yet regulatory efforts officially started in 1994, when OSHA listed silica as a priority for rulemaking. In 1996, the World Health Organization’s IARC classified silica as a human carcinogen. In 1998, the ACCSH formed a Silica Work Group to hold regular meetings.
2003 saw the first draft of the standard that OSHA submitted to various organizations and committees for approval. But it wasn’t until 2013 that OSHA published a Notice of Proposed Rulemaking, followed by five months of public hearings, comments, and evidence submitted by the public.
In March 2016, OSHA published its final rule consisting of two separate standards, one for construction and one for general industry and maritime.
The respirable crystalline silica construction standard became enforceable on Sept. 23, 2017.
For the construction industry, the rule reduces the current PEL of respirable crystalline silica from 250 micrograms, or mcg, per cubic meter of air averaged over an 8-hour period to 50 mcg. The new PEL represents approximately 20% of the previous PEL for construction and is consistent with the limit recommended by NIOSH in 1974.
Companies are also required to keep records of employee exposure to silica and examine workers wearing respiratory personal protective equipment (PPE) every three years.
According to the US Labor Department, an estimated 2.3 million workers are affected by the new rule.
Companies had two years to comply with the new standard. Some industries, such as the fracking industry, had a five-year pass. Frac sand mining uses silica sand for horizontal hydraulic fracturing, a process in fossil fuel extraction. Sand dust is released at every stage of the mining and processing operations, exposing not only workers, but also residents of areas where this type of mining is present.
The General Industry standard came into effect on June 23, 2018, and includes industry-specific requirements and controls.
Crystalline silica regulations, a global concern
Apart from the U.S., Canada, and Mexico, only a handful of European countries have imposed a stringent standard.
Moreover, where standards are in place globally, occupational exposure limits vary significantly. ISHN analyzed requirements in 34 countries and found that 30 have standards for quartz and other forms of silica. The Australian Exposure Standard for airborne crystalline silica is 0.1mg/m3 over 8 hours, which equates to as little as 15 minutes of cutting or polishing reconstituted or engineered stone.
Table 3 of OSHA’s standard summarizes workplace requirements for Australia, Brazil, British Columbia, Canada, China, India, Russia, South Africa, the UK, and the U.S.
Part II is all about health and safety recommendations. Coming soon!