Hazardous substances at work

Last updated: 17 Jun 2024

This article explains the risk posed by exposure to hazardous substances in the workplace and your employer’s responsibility to protect you.

The health risk posed by hazardous substances

There are many materials or substances used at work, or created by work processes, that can damage health. Exposure to hazardous substances can lead to a range of diseases and conditions. Some might develop quickly, while others can take years to emerge.

The nature of health conditions that exposure can cause will depend on the substance, the form it is in and the duration of exposure.

Ill health caused by these substances is preventable if they are managed appropriately, and employers have responsibilities to control workers’ exposure.

Exposure can occur through four routes, depending on the form of the substance: inhalation; skin or eye contact/absorption; injection (penetrating the skin); and ingestion.

Hazardous substances come in a number of forms, including:

  • chemicals, or mixtures of chemicals, such as bleach, acid, solvents or adhesives (which can come in a number of forms);
  • fumes or gases, such as those produced by welding or soldering, chlorine, carbon monoxide, paints or inks;
  • liquids or mists, such as those used in metalworking, solvents, cleaning chemicals and even water;
  • dusts, such as respirable crystalline silica, wood, flour, cement or metal; and
  • biological agents, such as fungi, bacteria and viruses.


What your employer should do about hazardous substances

The Control of Substances Hazardous to Health Regulations 2002, known as the COSHH Regulations, are the main regulations governing how employers manage harmful substances. The regulations cover all substances that can damage health.

The COSHH Regulations do not cover work with asbestos, lead or radiation because these substances are governed by their own sets of regulations.

Much like other health and safety regulations, COSHH requires employers to either prevent exposure to hazardous substances altogether or, where that is not possible, reduce it to as low as is reasonably practicable.


COSHH risk assessment

To work out how to protect workers, employers must carry out a COSHH risk assessment, and implement the controls it identifies, before anyone starts work with any hazardous substance.

This COSHH risk assessment must consider:

  • the processes that involve or create hazardous substances
  • how these cause harm
  • how this harm can be stopped at source or, if that’s not possible, reduced.

To gauge how dangerous processes are, employers will need to gather information on the substances that are used in or created by work processes. This can come from a variety of sources, such as the Health and Safety Executive (HSE), the internet, suppliers or staff who work with the substances.

Chemical products should be supplied with a safety data sheet. This document describes the hazards the chemical presents, and gives information on handling, storage and emergency measures in case of accident. This is not a risk assessment but will help with preparing the assessment.

First, employers must work out if it is possible to prevent exposure by eliminating the risk at source. This might involve adopting a different work process which doesn’t create a hazardous form of that substance, or swapping the substance for one that isn’t hazardous.

If it is not possible to eliminate the risk, steps should be taken to reduce exposure. This might involve:

  • swapping the substance for something less hazardous
  • enclosing the process or substance in a way that prevents fume and/or the substance escaping, for example a closed transfer system
  • installing a properly designed ventilation system, known as local exhaust ventilation (LEV), which extracts dust, fume, mist, gases or vapour through a hood or booth, reducing workers’ exposure
  • introducing systems of work which mean the process isn’t as dangerous – for example, minimising handling of the materials, ensuring materials are stored appropriately and that storage containers are correctly labelled, restrict access to those people who need to be there, produce a procedure for the task
  • Providing workers with appropriate supervision and training.

Personal protective equipment, like masks or gloves, should be used only as a last resort if other methods of reducing exposure cannot adequately control the risk. This is because if it fails, for example if it is not worn correctly or it breaks, it will offer no protection.

In some cases, employers have to monitor the health of employees who work with hazardous substances. This is to check whether the steps they are taking to reduce exposure are effective. This is necessary if there have been previous cases of work-related ill health in the workplace or industry; or where there is still some risks posed by the hazardous substances, despite the steps taken to reduce them.

Employers must tell workers about the hazards and risks of any substances they are required to work with, and how to keep themselves safe.


Exposure limits

For some substances, there are a “workplace exposure limit”, often abbreviated to WEL. These are maximum concentrations of substances in the air, averaged over a period of time. They are intended to prevent excessive exposure. These WELs provide an additional layer of legal protection to the steps outlined above and must be complied with.

However, it is usually possible for employers to reduce employees’ exposure beyond them. When it is, employers must do so.


The self employed

If you’re self employed, you must comply with the requirements of the COSHH Regulations if you employ others, if you take hazardous substances onto site with you, or if there is a chance that the substances you use could harm others.

The person or organisation that has contracted you must consider how hazardous substances could harm you and other contractors. If you are working on site, they must co-operate and co-ordinate activities with you to keep everyone safe.


If you’re concerned about hazardous substances

If you are concerned about the managing of harmful substances at work, you can take the following steps:

  • Report defects and failures in the control measures to your employer or your safety rep.
  • Remove any clothing or PPE which could cause contamination before eating or drinking.
  • Make use of washing facilities.
  • If you’re a safety rep and concerned about your employer’s control of hazardous substances, ask to see their COSHH risk assessment.