Occupational asthma claims: compensation for work-related breathing conditions

What are occupational asthma claims?

Occupational asthma claims are civil compensation claims brought by workers whose asthma was caused, or permanently worsened, by exposure to a recognised sensitising substance at work. They differ from claims where a worker's pre-existing asthma is merely aggravated by a dusty environment: in a true occupational asthma case, the employer's failure to control a specific hazardous substance has permanently changed the claimant's respiratory system.

The distinction matters because the medical evidence required is different, the legal argument on causation is different, and the value of the claim is usually higher where the asthma was caused entirely by the work rather than simply worsened.

For a broader guide to all types of industrial disease claim, including industrial deafness and HAVS, see our industrial injury compensation page.

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How does occupational asthma develop?

Sensitiser asthma develops when repeated exposure to a specific substance causes the immune system to treat it as a threat. The first exposures may produce only mild or no symptoms. After sensitisation is complete, even a tiny quantity of the substance can trigger a severe bronchospasm. The process is typically gradual and may take months or years of exposure to complete.

Once sensitisation has occurred, it is permanent and irreversible. A worker who leaves the job where they were exposed and avoids further contact may find their asthma improves, but they can never return to any environment where the causative substance is present. A spray painter sensitised to isocyanates, for example, cannot safely return to bodyshop work at any level of exposure.

Irritant-induced asthma, sometimes called Reactive Airways Dysfunction Syndrome, is caused by a single high-level exposure to a corrosive or irritant gas or chemical, such as chlorine or ammonia, that directly damages the airway lining without the gradual sensitisation process. These cases are less common but equally compensable.

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Which substances cause occupational asthma?

The Health and Safety Executive recognises over 400 substances capable of causing occupational asthma. The substances most commonly linked to occupational asthma claims in the UK are:

• Isocyanates (vehicle body repair, polyurethane foam manufacture, spray coating) -- the single most common cause of work-related asthma in the UK
• Flour and grain dust (bakeries, food processing, grain handling)
• Latex (healthcare workers, dental nurses, laboratory staff)
• Colophony fumes (electronics assembly soldering, flux fumes)
• Wood dust (carpentry, joinery, timber processing, furniture manufacture)
• Epoxy resins (aerospace manufacture, electronics, construction adhesives)
• Animal proteins (laboratory animal workers, veterinary practice, farming)
• Glutaraldehyde (healthcare sterilisation and disinfection)
• Persulphate salts (hairdressing, bleaching agents)

Where a worker has been regularly exposed to any of these substances without adequate controls, an occupational asthma claim is likely to be viable. The HSE has published detailed guidance on every substance listed above, so an employer who failed to act on publicly available risk information faces a strong liability argument.

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COSHH Regulations 2002 and occupational asthma claims

The COSHH Regulations 2002 require employers to:

• Carry out a suitable and sufficient assessment of the health risks from any hazardous substance used or produced at work
• Prevent or adequately control exposure, applying controls in a defined order of priority: eliminate the substance if possible, substitute it for a safer alternative, use engineering controls such as local exhaust ventilation (LEV) or enclosure, and use respiratory protective equipment only as a supplementary measure of last resort
• Provide health surveillance for workers exposed to substances known to cause occupational asthma, including regular peak flow monitoring, so that early sensitisation can be detected before it becomes permanent
• Keep health surveillance records for 40 years

COSHH applies to every substance on the HSE's list of known respiratory sensitisers. An employer who uses isocyanates in a bodyshop without isocyanate-resistant respirators, without LEV at the spray booth, and without annual peak flow monitoring for affected workers has almost certainly breached COSHH. Each breach provides a separate legal basis for occupational asthma claims alongside the general duty under section 2 of the Health and Safety at Work etc. Act 1974.

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How are occupational asthma claims valued?

General damages in occupational asthma claims are assessed using the Judicial College Guidelines (17th edition, April 2024). The relevant brackets for lung conditions are approximately:

• Severe occupational asthma: £38,780 to £72,340. Permanent severe condition, significantly restricted lung function, substantial effect on daily activities and employment.
• Moderate occupational asthma: £26,290 to £38,780. Significant functional limitation but some residual capacity to work in a controlled environment.
• Mild occupational asthma (well controlled with medication): £18,680 to £26,290. Breathing capacity not substantially impaired; condition manageable with ongoing treatment.

Special damages in occupational asthma claims often include:

• Lost earnings during any period of inability to work in the affected occupation
• Future lost earnings where the worker cannot return to the same job or industry due to the risk of re-exposure to the sensitising substance
• The cost of ongoing medication, inhalers, and hospital treatment
• Care provided during acute episodes

Career change losses are frequently the most significant element. A paint sprayer sensitised to isocyanates can never again work in any environment where isocyanates are used. Where their wages and skills were tied to that trade, future lost earnings may far exceed the general damages award. For a guide to how lost earnings are calculated in a compensation claim, see our how claims work page.

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The time limit for occupational asthma claims

The three-year time limit for occupational asthma claims runs from the date the claimant first knew that their asthma was caused or materially contributed to by their work, not from the date of first exposure to the hazardous substance. This is the date-of-knowledge rule, which applies to all industrial disease cases under the Limitation Act 1980.

In practice, the clock typically starts from the date a respiratory specialist or occupational health physician formally diagnoses occupational asthma and identifies the occupational origin. Symptoms of occupational asthma may develop over several years before the connection to work is recognised. Workers who leave the job where the sensitisation occurred may find their symptoms improve, which can further delay diagnosis.

Acting promptly after diagnosis still matters. Evidence of the working conditions at the time of exposure, including air monitoring records, health surveillance results, employer risk assessments, and COSHH documentation, is more readily available soon after the worker leaves the role. For a full guide to time limits in industrial disease cases, see our time limits page.

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IIDB alongside civil occupational asthma claims

Industrial Injuries Disablement Benefit is payable for occupational asthma as prescribed disease D7, where the condition was caused by exposure to a substance listed as a respiratory sensitiser in the prescribed disease schedule. The IIDB eligibility page on GOV.UK sets out the qualifying substances and the application process.

IIDB is assessed entirely independently of any civil compensation claim. Receiving IIDB does not reduce any civil award, and pursuing civil compensation does not affect IIDB entitlement. Both routes should be considered where occupational asthma has caused significant disability.

Most occupational asthma claims are run on a Conditional Fee Agreement. The success fee is capped at 25% of general damages and past financial losses. Future earnings and future care awards are excluded from the success fee cap. For a guide to no-win-no-fee funding, see our no-win-no-fee page.