Occupational Asthma – Work-exacerbated asthma

Around a fifth of employees who have asthma report that their symptoms are worse when they are at work.

Some validity to this figure is provided by the observation that the proportion is higher among those who work in jobs where such a direct relationship is plausible; that is, in jobs where there is a likelihood of exposure to irritant dusts or fumes.

At face value this figure is worryingly high. Research in this area, however, is deficient in several important respects.

First, it provides no information on how much worse any symptoms are, nor whether there is any relationship with asthma severity.

Second, and critically, the findings are not accompanied by any estimate of how many people without asthma, indeed how many without any chronic disease at all, would report feeling ‘worse’ when they are at work.

General experience, and what evidence there is on sickness absence, suggests that far less than a third of employees with asthma experience significant difficulties at work.

Work-exacerbated asthma
Asthma which is causally unrelated to, but provoked by work is termed work-exacerbated asthma (WEA). It needs to be distinguished, conceptually and as far as possible practically, from true occupational asthma (OA), which arises directly from exposure encountered in the workplace.

The management, implications and legal consequences of WEA and OA are very different and confusion of the two may be disastrous.

Dozens of factors at work may exacerbate pre-existing asthma. Commonly they include non-specific dusty or irritant atmospheres, cold temperatures, dry air, heavy physical demands and even early morning shift work.

Making the diagnosis
Every practitioner will consider their patient’s occupation in the context of their illness. It is often valuable to make enquiries of patients who have asthma into whether they are struggling in their work. Where there are such difficulties, the distinction between WEA and OA needs to be considered.

Managing the condition
If the problem is one of work-exacerbated asthma then it is helpful to establish a relationship with the patient’s occupational health service if possible (barely 20 per cent of employees have access to such a service).

Most cases of WEA can be effectively managed with enhanced pharmaceutical control and expert attention to troublesome exposures. It should be rare for all but very few patients with WEA to require a change in occupation.

Patients with WEA are not eligible to claim statutory industrial disease benefit.

Agents that commonly cause occupational asthma
High molecular mass* Low molecular mass
Agent(s) Occupation Agent(s) Occupation
Flour
Alpha-amylase
(‘improver’)
Baker Colophony (‘rosin’) Electronic soldering
Animal proteins Any work with animals Diisocyanates
Anhydrides
Amines
Paint spraying
Foam/plastic manufacture
Other chemical processing
Enzymes Detergent manufacturing
Food processing
Tropical wood dusts Wood work
Pollens Any work with plants Persulfate salts (hair bleach) Hairdressing
Seafood proteins
Seafood and fish
Seafood and fish processing Antibiotics
Other drugs
Drug manufacturing
Latex Factory workers
Mechanics
Reactive dyes Textile workers
* these agents induce a specific IgE response

By Professor Paul Cullinan

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