Hazardous Substances

Last reviewed on 19/04/2016 10:32

This page gives an overview on the safe handling, use and storage of hazardous substances in the workplace with links to further information and advice.

You will also find details of legal duties and obligations and advice on how to reduce risks from hazardous substances.

Quick links:

What do we mean by 'Hazardous Substances'?

Hazardous Substances are used in many workplaces and take many different forms. Solids, liquids, gases, mists and fumes can be present in the workplace.

Exposure to hazardous substances can affect the body in many different ways. Skin contact, inhalation and ingestion can cause damage.

In legislation, Hazardous Substances are defined in a number of ways. In The Control of Substances Hazardous to Health Regulations 2002 (COSHH), for example, they are those substances classified as toxic, very toxic, corrosive, harmful or irritant. Biological agents and dusts in substantial concentrations are also classified as hazardous substances.


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What risks do Hazardous Substances present?

Hazardous Substances can cause short- and long-term health problems.

They can cause serious ill health including cancers, dermatitis and asthma.

A cleaner splashing bleach on their skin could cause a burn or inflammation, which will have little long-term effect in most cases. However, a splash in the eye could cause permanent damage to their sight.

A joiner suffering years of exposure to wood dust could have long-term health problems – the dust could affect his lungs and cause health problems for the rest of his life.

There are legal obligations on employers to control exposure to Hazardous Substances to preserve the health of their employees.


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Who is at risk from Hazardous Substances?

Anyone who works with or is exposed to hazardous substances is at risk. Those exposed to more hazardous substances for long periods of time are more at risk than those exposed for short periods or to less hazardous substances.

The aim should be to prevent exposure to hazardous substances. Where exposure cannot be avoided, then adequate controls should be put in place.

Examples of those who could be exposed to hazardous substances include:

  • cleaners – common-cleaning materials can cause localised burns and skin complaints
  • hairdressers – a number of hairdressing products can damage their skin
  • welders – dangerous fumes from welding can damage their lungs
  • bakery workers – flour and bakery dust can cause irritation of eyes and nose, skin problems and asthma
  • garage workers – paints, solvents, oils and grease, and exposure to exhaust fumes can all damage their health
  • healthcare staff – exposure to biological agents can cause infection.

In reality, the list is endless and most workers will be exposed to hazardous substances at some time.


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Legal duties and obligations around Hazardous Substances

As well as a common law duty of care on employers to protect employees and members of the public, General Health and Safety Legislation covers all employers and workplaces.

In addition, there are specific regulations relating to Hazardous Substances:

The Control of Substances Hazardous to Health Regulations (COSHH) 2002 These regulations apply to activities involving the use of Hazardous Substances.

Substances hazardous to health are defined under COSHH as those that are: 'Very Toxic, Toxic, Corrosive, Harmful or Irritant.'

They include all substances allocated a Workplace Exposure Limit (WEL) in EH40, substantial quantities of dust and certain biological agents connected with work.

The Control of Substances Hazardous to Health (Amendment) Regulations 2004 These updates to the 2002 regulations came into effect on 6 April 2005. The amendments give a new focus on good practice and help employers meet their duties under COSHH legislation

To view the full text of the above legislation online, please follow the links under Legislation.


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Principles of COSHH

Under COSHH regulations, eight principles apply regardless of whether a substance has a Workplace Exposure Limit.

These are:

  • design and operate processes and activities to minimise emission, release and spread of substances hazardous to health
  • take into account all relevant routes of exposure – inhalation, skin absorption and ingestion – when developing control measures
  • control exposure by measures that are proportionate to the health risk
  • choose the most effective and reliable control options, which minimise the escape and spread of substances hazardous to health
  • where adequate control of exposure cannot be achieved by other means, provide, in combination with other control measures, suitable personal protective equipment
  • check and review regularly all elements of control measures for their continuing effectiveness
  • 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
  • ensure that the introduction of control measures does not increase the overall risk to health and safety.


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Workplace Exposure Limits

Workplace Exposure Limits (WELs) have now replaced Maximum Exposure Limits (MELs) and Occupational Exposure Standards (OESs).

The OESs for around 100 substances have been deleted as the substances are now banned, scarcely used, or there is evidence to suggest adverse health effects close to the old limit value.

Two new limits have been introduced for Refractory Ceramic Fibres and Subtilisins.

As the numerical values of the other limits transferred to the new system are unchanged, suppliers can finish stocks of safety data sheets that refer to MELs and OESs before producing new ones that refer to WELs.

Similarly, COSHH assessments can be updated as part of duty holders’ periodic reviews.

Adequate control of exposure requires employers to:

  • apply the eight principles of good practice for the control of substances hazardous to health
  • ensure that the WEL is not exceeded
  • ensure that exposure to substances that can cause occupational asthma, cancer, or damage to genes that can be passed from one generation to another, is reduced as low as is reasonably practicable.

Good practice advice on controlling chemicals is available at HSE’s COSHH Essentials website (external site).


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Assessing risks from Hazardous Substances in your workplace

The risks associated with the hazardous substances present in your workplace must be assessed. The employer has the responsibility for the risk assessment. They may call on assistance if it is required.

The person conducting the assessment must have a knowledge and understanding of the process and the requirements of the COSHH regulations. Make use of the existing knowledge within the workplace before deciding whether outside assistance is needed.

Most simple assessments can be carried out in-house:

  • make a list of all the substances and products in the workplace
  • gather as much information as you can on each substance and the risks associated with them
  • look at information on labels, in suppliers' catalogues and material safety data sheets.

You then need to assess how these risks relate to the specific circumstances of your workplace.


How much of each substance is used and how often? Larger quantities or substances that are used often will increase the risk of exposure.

How is each substance used? Are the substances mixed, poured, sprayed, piped, heated, cooled, etc.? The way they are used will determine how you will control exposures.

How could people be exposed and what effect could it have on their health?Is the substance a solid, liquid, gas, mist or fume? Will the substance damage their skin, lungs, eyes through skin contact, absorption, ingestion, inhalation or injection?

Answering these questions will help you carry out the risk assessment and determine the measures you need to take to protect the health of those people who could be exposed.


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Good practice around Hazardous Substances

The COSHH Approved code of Practice (ACoP) recommends that exposure be prevented by:

  • altering work methods so that the task that causes exposure is no longer carried out
  • modifying the process to remove Hazardous Substances including by-products or waste
  • substituting the hazardous substance with a less hazardous type or form of the substance, e.g. using granules instead of powder to reduce dust levels or a less volatile solvent in a process.

If exposure cannot be prevented, it must be adequately controlled. The hierarchy of control measures can be summarised as follows.

Eliminate Don’t use the hazardous substance or avoid the procedure which causes exposure.

Substitute Change the material or working practice to one less hazardous.

Enclose Enclose the hazardous substances or process in a closed system.

Control Control exposure to the hazardous substance by using one of the following methods:

  • Engineering Controls: Control the exposure at source with local exhaust ventilation or increased dilution ventilation to lower concentrations in the atmosphere.
  • Procedural Controls: Reduce the numbers exposed or the time spent on the procedure, carry it out in specified areas and carry out routine monitoring and health and medical surveillance if needed.
  • Personal Protective Equipment: Provide gloves, impervious aprons or overalls and/or respiratory protection to minimise the effects of exposure to hazardous substances.


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Respiratory Protective Equipment

In the COSHH hierarchy of controls, use of Respiratory Protective Equipment (RPE) is considered to be the last resort. RPE must only be considered when exposure cannot be adequately reduced by other means.

It is vital that the RPE selected is adequate for the purpose. It must reduce exposure as low as reasonably practicable, and in any case, to below any applicable Workplace Exposure Limits or other Control Limits.

RPE must fit the face of the wearer properly to be effective. To make sure that this is the case, the Approved Codes of Practice for The Control of Asbestos at Work and The Control of Lead at Work that support COSHH recommend that face-fit testing of all RPE be carried out before use. This includes testing of full-face masks, half-face masks and disposable masks.

Face-fit testing helps ensure that inadequately fitting face-pieces are not selected.

This information was sourced form the HSE document "Fit testing of respiratory protective equipment facepieces” (external site)

For more information, please see the advice on our page on Personal Protective Equipment under fit-testing of RPE.


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Information, instruction and training

Provide everyone who is involved with, or could be affected by the use of hazardous substances with the degree of training, instruction and information required to ensure their safety.


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Emergency procedures

It is also important to put in place procedures to cope with accidents and emergencies.

The controls you have in place may be adequate for normal activities but what would you do if there were an emergency like a major spillage or release of a substance?

It is vital that there are contingencies to deal with these circumstances.


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Your questions on Hazardous Substances

Our Wood Sprayer has developed chest problems. He wears a mask but how else can we protect his health?

Further information on Hazardous Substances

External resources HSE COSHH web page (external site) This page from the Health and Safety Executive gives links to more detailed information for various industry sectors and processes, including up-dated WEL tables.

COSHH Essentials (external site) This interactive website from the HSE is designed to guide employers through the risk assessment and control process for many common tasks and substances.

Free resources from Healthy Working Lives Links below are to publications pages giving options to download these resources:

Free COSHH Guidance from the Health and Safety Executive Note – all links are to external pages on the HSE website giving options to download or order these resources:

HSE priced publications: Note - all links are to external pages on the HSE website giving options to order these resources:


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→ View The Control of Substances Hazardous to Health Regulations 2002 (external site)

→ View The Control of Substances Hazardous to Health (Amendment) Regulations 2004 (external site)


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