This article considers what substances beyond industrial chemicals must be controlled in workplaces and the practical steps that can be taken to protect employees' health.

Published: 23 September 2026
Authors: Rubina Zaidi

What are substances hazardous to health?

Although The Control of Substances Hazardous to Health Regulations 2002 (the Regulations) are often associated with industrial chemicals, their scope is considerably wider. The Regulations also apply to substances encountered in many non-industrial workplaces, including cleaning products, dusts, fumes, vapours and biological agents.

The definition of a substance hazardous to health in Regulation 2(1) is intentionally broad. In addition to substances carrying hazard classifications, substances assigned workplace exposure limits and biological agents, COSHH applies where a substance creates a health risk because of its chemical or toxicological properties and the way it is used or present at work.

The Regulations are not limited to substances that are inhaled. Employees may be exposed through skin contact, eye contact, skin absorption or accidental ingestion. Employers should therefore consider all potential exposure routes when assessing risk.

COSHH applies to exposure arising out of, or in connection with, work. This distinction means the Regulations would not ordinarily apply simply because an employee contracts an illness from a colleague at work. The focus is on work-related exposure to hazardous substances, although biological agents at workplaces may be caught by the Regulations.

Who has duties under the Regulations?

The Regulations impose duties on employers and the self-employed.

Where an employer has duties under the Regulations to their employees, he has the same duty, so far as is reasonably practicable, in respect of others, whether at work or not, who may be affected by the employer’s work (save for duties relating to health surveillance, monitoring, information and training, and dealing with accidents). ‘Others’ might include contractors, agency workers or members of the public.

Organisations should therefore consider who beyond their direct workforce may be affected by hazardous substances.

Assessing the risk

The starting point for compliance is a suitable and sufficient assessment of the risks from substances hazardous to health (regulation 6).

COSHH assessments should include identification of:

• the hazardous substances present
• who may be exposed
• potential exposure routes
• the type and extent of exposure
• potential health effects
• any exposure limits
• the measures required to eliminate, prevent or control exposure.

COSHH assessments should not be treated as paper exercises. They should reflect how work is conducted in practice, including maintenance, cleaning operations, emergencies and foreseeable deviations from normal procedures. Assessments must be reviewed if there is reason to suspect they are no longer valid, where the work has significantly changed, or where monitoring or health surveillance indicates existing controls may be inadequate.

Employers should consider whether exposure can be eliminated before considering controls. Any assessment required should consider the effectiveness of existing controls and employers should take account of all exposure routes, including inhalation, ingestion and skin or eye contact. Failure to recognise non-inhalation exposure can result in overlooking significant risks.

While safety data sheets provide useful information about hazardous properties and recommended precautions, they should not be viewed as a substitute for workplace-specific assessments. Risks arising from substances often depends on their use, handling, storage or generation in the workplace.

New or expectant mothers and other vulnerable employees require specific consideration. COSHH assessments should, for example, identify substances that present additional risks during pregnancy or breastfeeding and controls adjusted appropriately.

Preventing or controlling exposure

A key principle of COSHH is that exposure, wherever reasonably practicable, must be prevented, otherwise it must be adequately controlled (regulation 7).

Employers may be able to prevent exposure by:

• eliminating the hazardous substance
• substituting it with a safer alternative
• changing the process to avoid its use or generation, or
• using equipment or methods that reduce exposure.

Where exposure cannot be prevented, employers should implement appropriate controls which may include local exhaust ventilation, enclosure of processes, engineering controls, safe systems of work and hygiene measures.

Personal protective equipment (PPE) should generally be used only where adequate controls cannot be otherwise achieved, or as a supplement to other controls.

Other key duties

As well as conducting an assessment and implementing controls, employers should:

• ensure control measures are properly used
• maintain, examine and test control measures
• monitor workplace exposure where necessary
• provide health surveillance where appropriate
• provide employees with information, instruction and training
• establish arrangements for dealing with accidents, incidents and emergencies involving hazardous substances.

The extent of these requirements (regulations 8-13) will depend on the nature of the substances used and the risks identified.

Principles of good practice

Schedule 2A to the Regulations describes eight principles of good practice for controlling exposure to substances hazardous to health which underpin the concept of "adequate control" and provide a practical framework for employers when devising, implementing and reviewing controls.

Employers should design and operate work activities and controls to minimise emission, release and spread of substances hazardous to health. Exposure should be reduced to the lowest level reasonably practicable, with controls applied at source wherever reasonably practicable and a hierarchy of control measures used, prioritising elimination, substitution and engineering controls before relying on PPE.

Measures adopted should be proportionate to the health risks involved, suitable for the nature and severity of the risk and capable of achieving and maintaining adequate control of exposure.

The principles also emphasise that controls should be regularly reviewed to ensure continuing effectiveness, and that employers should consider all potential exposure routes. Employees should be provided with suitable information and training so that controls are used effectively.

Compliance is therefore not achieved through a COSHH assessment alone or by demonstrating that exposure is below a workplace exposure limit. Rather, employers should adopt a preventative and systematic approach that seeks to eliminate or minimise exposure so far as is reasonably practicable and ensure that controls remain effective.

Employees' duties

Employees must use the controls provided for their protection fully and properly and report defects in those controls where appropriate (regulation 8).

Effective compliance depends on both suitable controls and employee engagement.

Training and monitoring effectiveness remain essential to ensure controls are used properly.

Practical steps for employers

• identify all substances that could create a risk to health, not just industrial chemicals
• complete and regularly review COSHH assessments
• eliminate use of hazardous substances where reasonably practicable
• substitute safer products or processes where possible
• implement appropriate engineering and organisational controls
• ensure control measures are maintained and tested
• provide suitable information, instruction and training
• consider whether health surveillance is required
• monitor compliance in practice rather than relying solely on documentation
• review arrangements following incidents, near misses, process changes or the introduction of new substances.

Comment

COSHH extends across a wide range of workplaces and to seemingly routine work.

Enforcement action frequently highlights failures to identify or adequately control less obvious hazards arising from dusts, fumes, vapours, biological agents and substances generated by the work itself. Proportionate and well-considered COSHH assessments, coupled with effective control measures and ongoing review, can significantly reduce the risk of occupational ill health and therefore of enforcement action.

As regulators continue to focus on the prevention of work-related ill health, employers should ensure that COSHH compliance forms part of their wider health and safety management arrangements rather than being treated as a standalone exercise. By adopting a proactive approach to identifying and controlling exposure, organisations can better protect employees, reduce business risk and demonstrate compliance with their legal duties.

Useful links

• The Control of Substances Hazardous to Health Regulations 2002 (legislation.gov.uk)
• HSE L5: Control of Substances Hazardous to Health (Sixth Edition) Approved Code of Practice and Guidance
• www.hse.gov.uk/pubns/indg136.htm
• HSE: Control of Substances Hazardous to Health (COSHH)
• HSE: What the law says
• HSE COSHH Essentials