Crystalline silica: the next asbestos?
Marchwood
Environment
Go back thousands of years, and you’ll find that some workplace hazards have stood the test of the time. Hippocrates, the ancient Greek philosopher, described how miners became breathless as a result of inhaling dust. Bernardo Ramazzini, the physician, described a similar ailment found in Italian Renaissance artisans. What were they depicting?
Today, we know these symptoms were a sign of silicosis, which is caused by exposure to respirable crystalline silica (RCS). As one of the oldest workplace hazards, this substance causes hundreds and thousands of deaths across the world every year. This makes RCS exposure comparable to that of asbestos, particularly as these substances affect workers in similar industries and target the lungs.
Marchwood is UKAS accredited for crystalline silica analysis with a low limit of detection of 0.005mg—the lowest in the industry. Read on to find out more about crystalline silica, why it’s important to test crystalline silica exposure levels, a comparison of crystalline silica and asbestos, and how Marchwood can help.
What is crystalline silica?
The minerals quartz, cristobalite and tridymite are forms of silicon dioxide. This can exist either in an unstructured amorphous form, or in the form of a crystal, where the atoms are arranged in a regular lattice structure. This is called crystalline silica, which is insoluble in water, doesn’t evaporate, and melts at around 1700oC.
Crystalline silica is found around the world in rocks, stones, sand, and clay, as well as in products including bricks, tiles, concrete, and some plastic composites. In fact, yellow sand is actually quartz, but sitting on a sandy beach won’t harm you. Any particles breathed in will be much too big to pass through your nose or upper airways.
When these products are worked, crystalline silica is released as a very fine dust. These respirable particles are typically less than 5 microns in size. To compare, the smallest grain of sand is around 50-70 microns. As these individual particles are so small, there may be relatively high airborne concentrations without you being aware that you are inhaling the dust.
Heating amorphous silica above 1000oC can cause some of it to transform to a more dangerous crystalline form. Burning agricultural waste or products such as rice hulls can turn amorphous silica into cristobalite.
| HSE data on the amount of silica in different substances | |
| Sandstone | 70-90% |
| Plastic composites | 10-90% |
| Concrete/mortar | 25-70% |
| Shale | 40-60% |
| China Stone | Up to 50% |
| Granite | 20-45% |
| Tile | 30-45% |
| Slate | 20-40% |
| Brick | Up to 30% |
| Ironstone | Up to 15% |
| Basalt/dolerite | Up to 5% |
| Limestone | Up to 2% |
Why is it important to test for crystalline silica?
Silica dust is only harmful as a very fine dust, as it can be breathed deep into the lungs. Other forms of silicon dioxide, called amorphous silica, do not have crystal structures. As such, these forms are less hazardous than crystalline silica as they do not scar the lungs over time.
Crystalline silica causes many adverse health effects, including asthma, chronic obstructive pulmonary disease (COPD), and silicosis. Silicosis is a lung disease that results in a hardening or scarring (fibrosis) of lung tissue with loss of function. It usually develops 10 years after RCS exposure, showing no symptoms initially other than changes in the lungs that are shown via x-ray.
In 1996, the International Agency for Research on Cancer classified crystalline silica in the form of quartz or cristobalite dust as a Group 1 carcinogen. In fact, there are around 900 new cases of lung cancer each year due to past exposure to respirable crystalline silica (RCS). Around 500 UK construction workers are believed to die from RCS every year. In light of these statistics, the importance of monitoring exposure to crystalline silica to safeguard workers and public health is clear.
Due to these health risks, taking steps to monitor and control the risks of RCS exposure, as well as to review control methods, is required by law. To ensure full compliance, occupational hygienists and businesses must test regularly to ensure the workplace exposure limit (WEL) does not exceed 0.1mg/m3 in the UK, or 0.05mg/m3 in Ireland.
Is silicosis the next asbestos?
As you can see, it’s easy to compare crystalline silica to asbestos. It is only dangerous when disturbed, it affects health in similar ways, and is often found in similar industries and scenarios to asbestos, such as in construction, stonecutting, cement laying, and excavation.
However, some clinicians assert that RCS is worse than asbestos. The latter tends to affect people at the end of their working life and into retirement, whilst RCS is affecting young workers with dependent children who have their whole working lives ahead of them. This is because asbestos exposure symptoms can take 20-30 years to appear, whilst symptoms of chronic silicosis can manifest in as little as 10 years. Acute and accelerated silicosis can cause a person to develop symptoms even faster, leading to auto-immune conditions and even death within a few short years.
How Marchwood can help
The hazardous health issues surrounding exposure to a substance less well-known but just as dangerous as asbestos means that analysis is crucial to help businesses safeguard employees and meet HSE regulations.
Marchwood is the UK’s leading specialist laboratory for occupational hygiene and air quality analysis. We work with occupational health professionals, offering a range of UKAS accredited services to help businesses maintain compliance and safeguard employees, customers, and the environment. Our expertise and investment in state-of-the-art instrumentation means that our limit of detection (LOD) of 0.005mg is the lowest commercially available in the UK, resulting in less time required for sampling.
For more information or to book your tests now, contact us.