Control of Substances Hazardous to Health

People come into contact with a wide range of hazardous substances at work that may arise from a number of sources, for example:

  • Solvents, acids and lead, used directly in processes
  • Fungus, mites, that arise naturally
  • Cleaning chemicals used in services
  • Exhaust fumes, dust, gases, given off as by-products

The risk to the employee when coming into contact with a hazardous substance is dependent on the route of exposure. There are a number of routes through which a person may become exposed and substances may prove hazardous through only one or several of these routes:

  • Inhalation of dusts, fungus, solvents, paints, exhaust fumes, organisms
  • Ingestion of heavy metals, organisms
  • Contact with the skin with cleaning chemicals, solvents, used engine oil
  • Absorption through the skin - solvents
  • Injection into the body - drugs
  • Introduction into the body via wounds - hepatitis, Weil's disease

In many cases exposure to work related substances may, if it remains uncontrolled, lead to illness or even death in severe cases.

Consequently the Control of Substances Hazardous to Health (COSHH) Regulations have been formatted to ensure that employers take reasonable steps to reduce the risk to employees from exposure to hazardous substances in their working environment.

Risk Assessment

An employer must assess the risks associated with the use of a substance before they allow employees to be exposed to it.

Similar to the Management of Health and Safety at Work Regulations risk assessments, the Control of Substances Hazardous to Health assessments are carried out to determine whether the exposure of a person to certain substances is acceptable. There are a number of information sources that you can refer to to find out if the substances being used are potentially hazardous:

  • The label on the container
  • Labels and data sheets provided by the supplier of the substance (suppliers and manufacturers are required to give you this information by law)
  • The COSHH Regulations and the HSE Guidance EH40 (
  • The HSE publication - The Approved Supply List
  • Information from trade associations and similar businesses
  • The existing knowledge you have yourself and that of your employees

The COSHH assessment is a systematic review of the use of the substance present:

  • its form and quantity
  • possible harmful effects
  • how it is stored
  • handled
  • used
  • and if appropriate transported, the people who may be affected by it and the controls that are appropriate

The first aim of the assessment should be to eliminate the use of a hazardous substance or, if this is not possible, ensure that exposure is adequately controlled.

Sample COSHH Assessment

Control Measures

In certain circumstances it may be necessary to put control measures in place to ensure that exposure to a substance is minimised. In deciding on the control measure to be taken the following hierarchy should be followed:

  • Eliminate the hazard altogether
  • Use a safer substance (substitution)
  • Enclose the process
  • Use engineering systems such as extraction or ventilation
  • Safe systems of work
  • Personal protective equipment (this is the last resort)

When using control measures and / or personal protective equipment it is necessary to meet certain requirements of the COSHH Regulations:

  • Employers must take all reasonable steps to ensure that employees are using the control measures and the personal protective equipment (PPE) provided
  • Employers must take all reasonable steps to ensure that the control system or PPE are being maintained and are working efficiently. This includes keeping suitable maintenance records
  • PPE must be suitable for the purpose for which it is provided
  • PPE must comply with any design standards laid down
  • Employees have a duty to make full and proper use of any control measures and the PPE provided

Monitoring Exposure

In addition to the initial assessment and provision of controls it may be necessary to monitor the exposure of employees to certain substances.

Monitoring would be required where:

  • There could be serious risks to health if control measures should deteriorate
  • It cannot be guaranteed without measurement that exposure limits are not being exceeded, or control measures are working properly

In addition the use of certain chemicals means that employees must undergo health surveillance to allow a record of exposure and effects to be kept. Those liable to these requirements are detailed in Schedule 5 to the COSHH Regulations. Where health surveillance is carried out records or copies of them must be kept for 40 years from the date of the last entry.

Information, Instruction and Training

If employees are, or may be exposed to, substances hazardous to health the employer must provide suitable and sufficient information, instruction and training for employees to know the health risks created by the exposure and the precautions which should be taken.
The information must include the results of any monitoring and the collective (non-personalised) results of health surveillance.