21st June, 2023

Silica Dust Exposure Limits, Regulations And The Law

Silica dust is deadly, killing hundreds of people in the UK each year. Because silica dust is found in a lot of building materials, it's difficult to avoid. But avoid it, you must. Because the law, and your health, require you to. How much silica dust is harmful, and what are the silica dust exposure limits?

Silica Dust Exposure Limits, Regulations And The Law header image

Silica dust kills around 800 people every year in the UK. In fact, it came in 4th place among our top 5 health hazards at work.

And if you work in construction, silica dust is difficult to avoid.

If you carry out work that requires you to cut, sand, drill or carve materials containing silica, you create and release dust. This fine dust is known as respirable crystalline silica (RCS). This fine dust is what can be inhaled deeply into your lungs, causing long-term irreversible damage to your health.

Find out more about silica dust in our blog post what is silica dust and why is it bad for you?

The most at-risk work includes:

Especially if you work with sandstone, concrete, mortar, tile, granite, slate, brick, limestone and marble. Even certain types of plastic can contain silica.

Because silica dust is found in a lot of building materials, you often can't avoid working with it. But you can avoid getting exposed to silica dust. And you must - because the law, and your health, require you to.

Silica Dust Exposure Limits

The HSE publishes workplace exposure limits (WELs) for certain hazardous substances. WELs are the maximum amount of a hazardous substance that can be present in the air. A limit that should not be exceeded. WELs are a legal requirement.

The measurement for a WEL is averaged over a period of time, known as a time-weighted average (TWA). Two time periods are commonly used:

You can find out more about WELs and how to calculate them in COSHH workplace exposure limits (WELs) explained.

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 as is reasonably practicable (ALARP), and at least below the WEL.

Because the WEL for RCS is an 8-hour WEL, you can exceed it but only for a short amount of time.

As a simple example, if you had a concentration of 0.2 mg/m3 for 4 hours. You have double the WEL of 0.1 mg/m3 so you will reach the limit quicker. In this example, you have reached the 8-hour limit in 4 hours, and should not have any further exposure.

(0.2 x 4) / 8 = 0.1 mg.m-3

It's important to note that this isn't a safe level. The WEL isn't a figure to aim for, but a limit to stay under (and as far under as you can).

Any amount of silica dust exposure can be harmful. As silica dust is a substance known to cause cancer, you must reduce exposure to as far below the level as is reasonably practicable.

But how do you know what levels you are being exposed to in the first place? And how do you check if limits are being reached? The answer can be found in the law.

Silica Dust Regulations

What regulations apply to silica dust?

Silica dust has many similarities to asbestos. It's naturally occurring. It's found in hundreds of building products. It is bad for your lungs. And it kills hundreds of people every year.

But unlike asbestos, it doesn't have its own set of regulations (currently). That doesn't mean no regulations apply.

The Control of Substances Hazardous to Health (COSHH) Regulations apply to any substances that can harm health. That doesn't just mean chemicals or substances in packaging and containers that you buy in. It also includes hazardous dust that is produced as part of your work processes.

concrete wall

Concrete. Granite. Brick. Sandstone. Many natural materials contain silica. People are exposed to silica dust when they drill, saw or cut a material that contains silica. And you must apply the requirements of COSHH to any work you carry out that produces silica dust.

In fact, it's the COSHH regulations make WELs (the legal limits we discussed earlier) a legal requirement. The regulations allow WELs to be set and require that any WEL is not exceeded.

Under COSHH, control is defined as adequate only if a) the principles of good control practice are applied, b) any WEL is not exceeded, and c) exposure to asthmagens, carcinogens and mutagens are reduced to as low as is reasonably practicable.

So what does the law say about silica dust? Well, as we mentioned earlier in the post, workplace exposure limits (WELs) are legal limits. The COSHH regulations are also a legal requirement.

To comply with the law, you must carry out a COSHH assessment. This assessment should look at the level of risk and controls needed to reduce the risk.

Find out more about controlling dust in how dust hazards in the workplace can kill your future.

The control measures you develop to reduce exposure to silica dust must keep exposure below the workplace exposure limit (WEL). That's 0.1 mg/m3 respirable crystalline silica (RCS) dust, averaged over 8 hours.

When assessing your work, you need to determine the levels of exposure you are likely to be exposed to. The closer you are to a limit, the more likely you are going to need to measure and monitor exposure.

10.—(1) Where the risk assessment indicates that—

  1. it is requisite for ensuring the maintenance of adequate control of the exposure of employees to substances hazardous to health; or
  2. it is otherwise requisite for protecting the health of employees,

the employer shall ensure that the exposure of employees to substances hazardous to health is monitored in accordance with a suitable procedure.

Then think about the types of controls that will be best to protect your workforce and other people who may be exposed to silica dust during your work.

risk control infographic

Controls might include PPE, but remember that PPE is the last line of defence and only protects the wearer. You should also consider controlling dust at the source with engineering controls, like wet cutting, or ventilation systems first to reduce the amount of dust in the air.

Download the silica dust toolbox talk and make sure your team know about the dangers. Use our free COSHH assessment template, or get the pre-completed silica dust COSHH assessment template for your work.

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This article was written by Emma at HASpod. Emma has over 10 years experience in health and safety and BSc (Hons) Construction Management. She is NEBOSH qualified and Tech IOSH.

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