Workplace exposure limits

As an employer, you must protect workers from exposure to hazardous substances, including dust, fumes, chemicals, vapours, mists, nanotechnology, gases, biological agents and germs that cause disease.

Where substances have been classified as carcinogens, mutagens or asthmagens, to comply with the Control of Substances Hazardous to Health Regulations 2002 (COSHH), exposure must be controlled to as low as is reasonably practicable (ALARP).

Exposure to a substance is uptake into the body by:

  • breathing fume, dust, gas or mist
  • skin contact
  • injection into the skin
  • swallowing

Workplace exposure limits (WELs) are GB occupational exposure limits approved by HSE. They are set to help protect workers’ health. WELs are concentrations of hazardous substances in the air, averaged over a set period of time.

Find WELs in EH40

Many thousands of substances are used at work but only about 500 substances have WELs. EH40 Workplace exposure limits is a publication which contains a list of all current GB WELs. The list is legally binding under COSHH.

The list is amended when new or revised WELs are approved.

Monitor WELs

You can check that exposure to hazardous substances is below their WEL by monitoring. This means measuring the substance in the air that a worker breathes while they are doing a task.

You may get a consultant to monitor substances in your workplace. Exposure measurement: Air sampling G409 tells you what to expect from a competent consultant who provides monitoring services.

Monitoring can be a useful indicator to check whether the control measures you have in place are effective. If they are, exposures are likely to be below the WEL.

Go to COSHH essentials for more guidance on this.

How WELs are set

When Great Britain was part of the EU, HSE was involved in the EU regime for setting WELs. We are no longer part of the EU regime, we have a blended approach to controlling exposures, such as communicating what proportionate control measures we expect rather than solely introducing a WEL, as directed by evidence.

Where there is evidence to support the introduction of a new/revised WEL, HSE will follow its own approach for GB workplaces:

  • the substance will be assessed and analysed by relevant specialists, including an economic assessment
  • the Workplace Expert Health Committee (WHEC) will act as independent experts to review the scientific basis for any WEL proposed
  • there will be a public consultation on the updates
  • they will be approved by the HSE Board

HSE has considered the evidence on all outstanding EU limits and will introduce a revised limit for 3 of them. These are specific to underground mining and tunnelling and already published in EH40/2005, which contains all updated limits.

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