COSHH (Control of Substances Hazardous to Health)

Summary of Requirements

Key Points

Significant changes were introduced to the Control of Substances Hazardous to Health Regulations 2002 on 6 April 2005:

  • Maximum Exposure Limits (MELs) and Occupational Exposure Standards (OESs) were replaced, although suppliers may exhaust stocks of Safety Data Sheets that refer to MELs and OESs.
  • Workplace Exposure Limits (WELs) were introduced which replaced the previous two-tier system of limits. WELs are averaged over a specified period of time referred to as a time-weighted average (TWA). Two time periods are used long term (eight hours) and short term (15 minutes). The HSE's publication EH40/2005 Workplace exposure limits now includes the list of substances that have been assigned WELs. Further changes will follow in 2007 following the introduction of new WELs. This follows the implementation of the 2nd Directive on Indicative Occupational Exposure Limit Values (IOELVs) (2006/15/EC).
  • Eight principles have now been introduced which will apply regardless of whether a substance has an Occupational Exposure Limit.


  • Control of Substances Hazardous to Health Regulations 2002 (as amended) (COSHH).
  • The Classification, Labelling and Packaging of Chemicals (Amendments to Secondary Legislation) Regulations 2015 (CLP).
  • Registration, Evaluation, Authorisation and Evaluation of Chemicals (REACH) Regulation (EC) No 1907/2006.

From 6 April 2005 a new focus on good practice has been introduced. Under the eight principles, employers must:

  1. Design and operate processes and activities to minimise emission, release and spread of substances hazardous to health.
  2. Take into account all routes of exposure when developing control measures:
    • Inhalation
    • Skin Absorption
    • Ingestion
  3. Control exposure by measures that are proportionate to the health risk;
  4. Choose the most effective and reliable control options which minimise the escape and spread of substances hazardous to health.
  5. Where adequate control of exposure cannot be achieved by other means, provide, in combination with other control measures, suitable personal protective equipment.
  6. Check and review regularly all elements of control measures for their continuing effectiveness.
  7. Inform and train all employees on the hazards and risks from the substances with which they work and the use of control measures developed to minimise the risks.
  8. ensure the introduction of control measures does not increase the overall risk to health and safety.

Substances Hazardous to Health

COSHH 2002 applies to a very wide range of substances and preparations with the potential to cause harm if they are inhaled, ingested or come into contact with or are absorbed through the skin. COSHH defines a "substance hazardous to health" as anything which:

  1. Is listed in Part I of the approved supply list as dangerous for supply within the meaning of the CHIP Regulations and for which an indication of danger specified for the substance is very toxic, toxic, harmful, corrosive or irritant.
  2. The Health and Safety Commission has approved a workplace exposure limit.
  3. Is a biological agent.
  4. Is dust of any kind, except dust which is a substance within paragraph (1) or (2) above, when present at a concentration in air equal to or greater than (i) ten mg/m3, as a time-weighted average over an eight-hour period, of inhalable dust, or (ii) four mg/m3, as a time-weighted average over an eight-hour period, of respirable dust.
  5. not being a substance falling within sub-paragraphs (1) to (4), because of its chemical or toxicological properties and the way it is used or is present at the workplace creates a risk to health.

Examples would include:

  • Chemical substances or preparations such as paints
  • Cleaning materials
  • Metals
  • Pesticides and insecticides
  • Biological agents such as pathogens or cell cultures

Substances hazardous to health can occur in many forms:

  • Solids
  • Liquids
  • Vapours
  • Gases
  • Dust
  • Fibres
  • Fumes
  • Mist
  • Smoke

NOTE: The Registration, Evaluation, Authorisation and Evaluation of Chemicals (REACH) Regulation (EC) No 1907/2006 came into effect on 1 June 2007. The Regulations will fundamentally change the format and content of chemical safety information provided by suppliers. For the first time downstream users of chemicals will have specific duties placed on them that was not previously covered by legislation. (See chapter on REACH.)

To comply with COSHH you need to:

1. Assess the risks

  • Identify the hazardous substances present in your workplace.
  • Consider the risks these substances present to people's health.

2. Decide what precautions are needed

If you identify significant risks, decide on the action you need to take to remove or reduce them to acceptable levels. If you have five or more employees you must make and keep a record of the main findings of the assessment either in writing or on a computer.

3. Prevent or adequately control exposure

You are required to prevent exposure to substances hazardous to health, if it is reasonably practicable to do so. You might:

  • change the process or activity;
  • replace with a safer alternative; or
  • use it in a safer form, e.g. pellets instead of powder.

If prevention is not possible you must adequately control exposure. You should consider and put in place measures appropriate to the activity and consistent with the risk assessment. COSHH essentials ( can assist in providing advice on the controlof chemicals for a range of common tasks, e.g. mixing or drying. It is a practical interactive tool that can assist but not replace the completion of a COSHH assessment. COSHH essentials issupported by a series of general and specificguidance publications aimed at providing practical and informative advice. (

4. Ensure that control measures are used and maintained

Employees are required to make proper use of control measures and to report defects. A common failure with employers is to ignore this point. It is the employer's responsibility to take all reasonable steps to ensure that employees do this.

Some items of equipment such as local exhaust ventilation will have to be regularly checked to make sure that they are still effective. Respiratory protective equipment (RPE) should be examined and where appropriate tested at suitable intervals. The Regulations set out specific intervals between examinations and you must retain records of examininations for at least five years.

5. Monitoring exposure

You must measure the concentration of hazardous substances if your assessment concludes that:

  • there could be serious risks to health if control measures failed or deteriorated;
  • exposure limits might be exceeded; or
  • control measures might not be working properly.

Records should be kept for at least five years for general records and for at leat 40 years for personal records.

6. Carry out appropriate health surveillance

You are required to carry out health surveillance in the following circumstances:

  • Where an employee is exposed to substances listed in Schedule 6 to COSHH and is working in one of the related processes and there is a reasonable likelihood that an identifiable disease or adverse health effect will result from that exposure.
  • Where employees are exposed to a substance linked to a particular disease or adverse health effect and there is a reasonable likelihood, under the conditions of work, of that disease or effect occurring and it is possible to detect the disease or health effect.

Personal records need to be maintained for at least 40 years.

7. Prepare plans and procedures to deal with accidents, incidents and emergencies

This will apply where the work activity goes well beyond the risks associated with normal day-to-day work. If this is the case you must plan your response to an emergency involving hazardous substances before it happens.

8. Ensure that employees are properly informed, trained and supervised

This should include:

  • the names of the substances they work with or could be exposed to and the risks created by such exposure, and access to any safety data sheets that apply to those substances;
  • the main findings of your risk assessment;
  • the precautions they should take to protect themselves and other employees;
  • how to use personal protective equipment and clothing provided;
  • results of any exposure monitoring and health surveillance (without giving individual employees' names); and
  • emergency procedures which need to be followed.

Note: This requirement is regarded as vital by the HSE. Control measures will not be fully effective if employees do not know their purpose, how to use them properly or the importance of reporting faults.

Safety Data Sheets

Collecting manufactures' or suppliers' data sheets and other information does not in itself meet the COSHH requirements to carry out an assessment. (Note: REACH is likely to see more extended safety datasheets being produced by suppliers. Gathering the information is only the first stage; the information must then be used to determine the appropriate control measures needed to protect the health of employees

The assessment record has to include the following infromation:

  • the hazardous properties of the substance;
  • information on health effects provided by the supplier, including information contained in any relevant safety data sheet;
  • the level, type and duration of exposure;
  • the circumstances of the work, including the amount of the substance involved;
  • activities, such as maintenance, where there is the potential for a high level of exposure;
  • any relevant occupational exposure standard, maximum exposure limit or similar occupational exposure limit;
  • the effect of preventive and control measures which have been or will be taken in accordance with Regulation 7;
  • the results of relevant health surveillance;
  • the results of monitoring of exposure in accordance with Regulation 10;
  • in circumstances where the work will involve exposure to more than one substance hazardous to health, the risk presented by exposure to such substances in combination;
  • the approved classification of any biological agent; and
  • such additional information as the employer may need in order to complete the risk assessment.

Case Law

In the case of Bilton v. Fastnet Highlands Ltd (1997) the plaintiff, Bilton, worked in a prawn processing factory, and claimed her occupational asthma, caused by certain substances in the workplace, could have been prevented had appropriate measures been taken.

While employed in this capacity, she developed occupational asthma as a result of exposure to respirable prawn protein. Her condition was aggravated further by contact with certain substances used and produced in the processing of prawns. The appellant contended that these substances, as well as the prawn protein, fell within the definition supplied by the COSHH Regulations, and that her employer was in breach of this duty.

The employer argued that these were insufficient grounds to claim that a breach of COSHH had occurred, and that the appellant also needed to illustrate what measures should have been taken, but were not, in order to comply with the Regulations.

The court referred to the case of Nimmo v. Alexander Cowan, where the House of Lords ruled that a plaintiff need only claim that the place in which they had to work was unsafe. It was unnecessary for them to state what they believed was reasonably practicable to actually make and keep it safe.

The court held that an absolute duty lay with the employer to keep the workplace safe. The appellant need do no more than claim she has suffered injury as a result of the employer failing to discharge their duty under COSHH.

Dugmore v. Swansea NHS Trust and another, Court of Appeal (Civil Division) (2002) EWCA Civ 1689 was a further important case on the prevention and control of hazardous substances. It reinforced the authority that:

  • the primary duty under COSHH is to prevent exposure altogether where the Regulations apply, unless this is not reasonably practicable;
  • if prevention is not reasonably practicable, the secondary duty is "adequately" to control the exposure. The defence of reasonable practicability qualifies only the primary duty and for purposes of the secondary duty "adequately" is defined without reference to reasonableness;
  • the duties under the Regulationsare not subject to foreseeability of risk nor is it dependent upon what a risk assessment would have revealed; and
  • there is no common law duty to dismiss an employee with a particular sensitivity who is willing to take the risk of carrying on working in what for others is a reasonably safe environment.

Workplace Law Network. 8th January 2008