UPDATE: HSE Chemical Exposure Limits


The Health and Safety Executive (HSE) have updated an important document outlining safe exposure limitations for hazardous chemicals – altering regulatory guidelines for 31 chemicals/gases.

HSE’s EH40 document is the official reference text for Workplace Exposure Limits (WML) across the UK. Last updated in 2011, this revisited publication describes WELs for some 500 hazardous substances and is an essential document for ensuring respiratory safety in the workplace.


An HSE spokesperson commented: “The HSE publication EH40 has been updated to include 31 new and revised workplace exposure limits (WELs) for hazardous substances. These limits were included in the 4th Indicative Occupational Exposure Limit Values (IOELV) Directive on the recommendation of the European Scientific Committee on Occupational Exposure Limits (SCOEL) on the basis that ill-health effects are unlikely to occur for occupational exposures at these limits and were agreed by the Advisory Committee on Safety and Health.

The introduction of these [new] limits should not require businesses to undertake any significant changes if they are already complying with Control of Substances Hazardous to Health (COSHH) Regulations.”


Exposure routes

People are exposed to a variety of substances every day that, given the wrong circumstances, could be hazardous to their health. Exposure to hazardous substances can be through numerous means:

  • Inhalation through breathing
  • Absorption through skin contact
  • Consumption through swallowing

While exposure to some hazardous substances will show reactions immediately, in many cases symptoms may not occur for many years – such as with most occupational diseases such as COPD and silicosis.

To ensure worker safety, employers must comply with HSE / COSHH regulations.

COSHH Regulation 7 states that employers have a duty of care to ensure that every employee is no exposed to any concentration of hazardous substance that would be dangerous to their health. To control this, the HSE produce a list of Workplace Exposure Limits (WELs) in document EH40.


Making sense of Workplace Exposure Limits

Calculated by measuring the concentration of chemical per meter cubed of air, WELs are given as Time Weighted Averages (TWA) and divided into Long Term Exposure Limits (LTEL) and Short Term Exposure Limits (STEL).

  • LTEL = maximum exposure permitted during an 8 hour period
  • STEL = maximum exposure permitted during a 15 minute period

Distinguishing between the two exposure periods allows different regulations for the same hazardous substance. For example, chemical x may be completely safe in short, while prolonged exposure could be harmful.


Still not sure?

If you’re struggling to tell your WELs from your STELs then get in touch with one of our RPE Experts. With over 50 years’ experience in the field, our specialists offer comprehensive auditing and consultancy services.

For more information, please email: info@fullsupporthealthcare.com or call 01933 672180.