COSHH G402: Health Surveillance for Occupational Asthma

Early Detection of Occupational Asthma – An Essential Companion to Effective LEV Control

LEVCentral Expert Commentary

Every year, workers develop occupational asthma that could have been prevented through better exposure control or identified earlier through effective health surveillance.

G402 – Health Surveillance for Occupational Asthma is one of HSE’s COSHH Essentials General Guidance sheets. It explains when employers should implement health surveillance for workers exposed to respiratory sensitisers, what a suitable programme should include, and the role of occupational health professionals in identifying disease at an early stage.

Importantly, the guidance makes a distinction that every employer and LEV engineer should understand:

Health surveillance is not a substitute for controlling exposure.

Its purpose is to verify that exposure controls—such as Local Exhaust Ventilation (LEV), process enclosure and safe systems of work—are protecting workers as intended. Where health surveillance identifies early signs of occupational asthma, employers must review their COSHH risk assessment and determine whether existing control measures remain adequate.

For occupational hygienists, LEV professionals and Duty Holders, G402 reinforces the principle that protecting health requires both effective engineering controls and ongoing verification of worker health.

View HSE Guide

HSE Guide

Key Learning Points

G402 explains:

What occupational asthma is.
The difference between irritation and respiratory sensitisation.
When health surveillance should be considered.
The role of occupational health professionals.
Baseline respiratory assessments.
Ongoing health surveillance programmes.
Respiratory questionnaires.
Lung function testing (spirometry).
Health records.
Early reporting of symptoms.
Worker education.
Review of COSHH risk assessments.
The relationship between health surveillance and exposure control.
Employer responsibilities under COSHH.

Common Causes of Occupational Asthma

The guidance identifies a wide range of substances capable of causing occupational asthma, including:

Respiratory Sensitiser	Typical Industries
Isocyanates	Vehicle refinishing, spray painting, polyurethane manufacture
Wood dust	Joinery, furniture manufacture, woodworking
Flour and grain dust	Bakeries, flour mills, food manufacture
Rosin (colophony) solder fume	Electronics manufacture and soldering
Laboratory animals	Research laboratories and universities
Latex	Healthcare and laboratories
Glues and resins	Manufacturing and composites
Cleaning chemicals and enzymes	Healthcare, food manufacture and cleaning services
Stainless steel welding fume	Fabrication and engineering

These examples illustrate that occupational asthma affects a diverse range of industries and is not confined to traditional manufacturing environments.

When is Health Surveillance Required?

Health surveillance should be considered where there is:

Exposure to recognised respiratory sensitisers.
Exposure to substances carrying the hazard statement H334 – “May cause allergy or asthma symptoms or breathing difficulties if inhaled.”
Reliance on Respiratory Protective Equipment (RPE) to control exposure.
A known history of occupational asthma associated with the process.
A confirmed case of occupational asthma within the workforce.

The guidance recommends involving a suitably competent occupational health professional to determine the appropriate surveillance programme.

Source Information

Organisation: Health and Safety Executive (HSE)

Publication: G402 – Health Surveillance for Occupational Asthma

Series: COSHH Essentials – General Guidance

Document Type: HSE Guidance Sheet

Primary Topics: Occupational Asthma, Respiratory Sensitisers, Health Surveillance, Spirometry, COSHH, Occupational Health.

LEVCentral Perspective

From an LEVCentral perspective, G402 reinforces one of the most important concepts in occupational hygiene:

Health surveillance verifies the outcome of exposure control—it does not replace it.

An employer cannot rely on health surveillance instead of providing effective LEV or other engineering controls.

Instead, health surveillance acts as an early warning system.

If workers begin to develop symptoms despite apparently effective control measures, employers should ask fundamental questions:

Is the LEV system performing as designed?
Has the process changed?
Are work practices allowing exposure?
Is the LEV being used correctly?
Is maintenance adequate?
Are Thorough Examination and Testing intervals appropriate?
Is RPE suitable and correctly worn?

Health surveillance therefore provides valuable feedback into the entire COSHH management system.

The guidance also highlights the importance of baseline assessments before, or as soon as possible after, exposure begins. Without a baseline, it becomes much more difficult to identify subtle changes in respiratory health over time.

Further Resources

Recommended Learning

Thought Leadership

One of the most important messages within G402 is that occupational asthma is often preventable—but it is not always reversible.

Once a worker becomes sensitised to a substance such as isocyanates, flour dust or wood dust, even very low future exposures may trigger asthma symptoms. This is why COSHH places such emphasis on preventing exposure through engineering controls rather than relying on medical monitoring alone.

From a LEVCentral perspective, G402 highlights the close relationship between LEV engineering and occupational health. A well-designed, well-commissioned and properly maintained LEV system should minimise exposure to respiratory sensitisers.

Health surveillance then provides independent confirmation that those controls continue to protect the workforce. Together, they provide employers with a robust and defensible approach to managing one of the most significant occupational diseases still encountered in UK workplaces.