Silica dust is the second biggest cause of lung disease in workers after asbestos, killing around 800 people in the UK every year. Yet, even with such a high level of fatalities, many construction workers are unaware when they cut into kerbing, paving and other concrete, stone or masonry materials, harmful silica particles are being released.
Silica is one of the most abundant elements on Earth, second only to oxygen. It is a mineral (silicon dioxide) found in sand and soil. Many forms of silica exist, and you may find it in water, food, toiletries and other products.
Silica dust is the creation of fine particles of a type of silica known as crystalline silica, which can be found in stone, rocks, sand and clay. When these materials are disturbed, they release a dust that is dangerous to inhale. When we talk about silica dust, we are referring to crystalline silica.
In many ways, silica-containing construction products are like asbestos-containing construction products. Silica is also a naturally occurring material and the products containing it are not harmful unless disturbed.
Many building products including concrete, tiles, cement products and clay bricks contain silica. Silica is a primary component in sand and rocks like sandstone and granite. Silica dust is usually created when these building products are cut, drilled or otherwise worked on to release fine particles, this crystalline form of silica ‘dust’ when breathed in can cause health problems which we cover in the next section of this post.
Different building products can contain different levels of silica, here are some approximate percentages of silica content (based on Health and Safety Executive data).
Plastic Composites: 20-90%
China Stone: Up To 50%
Brick: Up To 30%
Ironstone: Up To 15%
Basalt/Dolerite: Up To 5%
Limestone: Up To 2%
Marble: Up To 2%
High-risk activities include tunnelling and excavation work, road building, demolition work and explosive blasting work, as well as work in slate, granite cutting and glass manufacturing industries, brick making and some manufacturing processes.
Now we know what silica dust is, and where to find it, but why do you need to know about silica dust at all? Because, unfortunately, silica dust is bad for you, it can cause lung problems, and a silica specific disease called silicosis. Crystalline silica is classified as a group 1 carcinogen, meaning it causes cancer in humans.
Silica dust can cause lung problems such as:
Silica dust is only harmful when it is inhaled deep into your lungs, and when silica-containing products are drilled, cut or otherwise disturbed, the fine particles released are so small that they can easily be breathed in. The silica dust particles are so small you can't even see them.
It’s estimated that nearly 800 people die each year in the UK from lung cancer caused by silica exposure at work.
You have probably heard of lung cancer, but what is silicosis. If you're thinking it sounds like silica, you would be right. Silicosis combines the words silica and osis (meaning disease), so in simple terms, it means silica disease.
The development of silicosis is directly related to exposure to silica dust, and similar to asbestos-related lung disease, silicosis can remain free of symptoms for 10-20 years after exposure. The disease causes damage to lung tissue leading to breathing problems and also puts those affected at greater risk of lung cancer.
There is no medical treatment for silicosis. In the chronic form of the disease symptoms develop over time and the illness is usually caused by prolonged exposure. The acute form of the disease, caused by exposure at high levels, can lead to rapid progression of breathlessness and death within months.
We can't exactly ban silica, it's found in many building products that we use every day, including bricks and concrete. So if we can't ban it, is there anything we can do to protect the health of construction workers?
Exposure should be prevented where possible through substitution of materials to eliminate the risk entirely. Where this is not possible the dust should be controlled through dust suppression techniques or local exhaust ventilation.
As the last line of defence appropriate personal protective equipment (PPE) and respiratory protective equipment (RPE) should be worn at all times when dealing with silica dust. A high level of training and supervision will be required to ensure its proper use.
Protective clothing should also be provided to prevent contamination of the workers own clothing, and prevent the dust being transported off-site. Welfare facilities for washing and changing should be available on site and hands washed before eating, drinking, smoking or going to the toilet – which should take place away from the contaminated area.
Small changes can make a big difference when it comes to silica dust. In fact, a recent study by IOSH estimated that with better compliance the number of deaths from silica-related lung cancer could reduce by over 75%.
Silica lung cancer cases in Britain could drop to 100 a year if we improve legal compliance.
Did you know that there are legal limits to the amount of silica dust you can be exposed to at work?
Silica dust has a workplace exposure limit (WEL) of 0.1 mg/m3, expressed as an 8-hour time-weighted average (TWA). Exposure should be reduced as low a reasonably practicable, and at least below the WEL.
Workers regularly exposed to respirable crystalline silica (dust) should have health surveillance which includes a respiratory questionnaire, lung function testing and chest X-rays.
The HSE regularly arranges events to raise awareness of the dangers of silica dust, however many in the construction professionals still appear unaware of this site hazard. With many workers and management in the industry unaware of the risk, it's important to spread the message to anyone you work with, and make sure they know the risks.
Make sure your team know about the invisible hazard on your sites, give a silica safety talk, and if you need help you can download the silica dust toolbox talk to use as a handout.