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Occupational exposure to hazardous substances can lead to lung and skin diseases (like asthma and dermatitis respectively).

These conditions can cost millions of pounds each year to:

  • industry (to replace the trained worker);
  • society (in disability allowances and medicines); and
  • individuals (who may be unable to work).

Using hazardous substances at work, even in small quantities, can result in physical injury and or cause health problems. Those exposed for long periods of time are generally more at risk than those exposed for short periods or to less hazardous substances.

Hazardous substances can include:

  • biological agents (fungi, bacteria, viruses);
  • natural substances (grain, flour, enzyme dusts, etc.);
  • substances generated by work (e.g. soldering/welding fumes or wood dust); and
  • chemical products used or produced at work (e.g. adhesives or cleaning agents).

This topic page focuses on the risk of illness and disease as a consequence of contact with hazardous substances via skin, inhalation or ingestion. For guidance on fire and explosion hazards refer to:

Process-related fire and explosion hazards

Storage and use of flammables and explosives

  • Identify situations where there might be a risk of exposure to your workers so you can begin considering control measures. Controls should be approached in the following order (known as a hierarchy of controls):
  • Step 1: Eliminate using the substance;
  • Step 2: Replace the substance with a safer alternative (for example, a ready-made paste instead of a powder) or change the process to reduce the need for, or limit the amount of the substance (including waste streams);
  • Step 3: Enclose the process so the substance shouldn’t escape; and/or extract emissions from the substance near the source through exhaust ventilation;
  • Step 4: Minimise the number of workers who could be exposed to the hazard (even with controls in place);
  • Step 5: Provide personal protective equipment (PPE),
    such as gloves, coveralls and respirators.
  • Find out what the workplace exposure limits (WELs) are for the substances you’re working with – so you can make informed decisions about control measures.
  • Make sure using PPE is always the last resort. If PPE is used, it must fit the wearer and provide the correct protection for the task, the substance and the work environment. You should also ensure equipment provided is free of charge, workers are property trained so they know how and when to use it and that checks, maintenance and testing are completed as necessary, and records kept.
  • Introduce and sustain effective prevention or control measures based on the following eight principles of good practice:
  • Step 1: Complete a risk assessment for all substances used in, or created by, workplace activities.
  • Step 2: Avoid work that could lead to exposure without first considering the risks, and decide the necessary precautions and other measures required by the regulations.
  • Step 3: Eliminate exposure. Where this is not reasonably practicable, put appropriate controls in place.
  • Step 4: Ensure that control measures are used and maintained.
  • Step 5: Monitor the exposure of employees to hazardous substances, where necessary.
  • Step 6: Carry out health surveillance where shown to be necessary by the risk assessment or where COSHH sets specific requirements.
  • Step 7: Prepare plans to deal with accidents, incidents and emergencies.
  • Step 8: Ensure employees are properly informed, trained and supervised.


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Frequently asked questions
Find answers to some common queries about health and safety issues and related legislation.