Guidelines on Occupational Asthma

Asthma is an inflammatory disorder of the airways. When an asthma attack
occurs, the muscles surrounding the airways become tight and the lining of the
air passages swell. This reduces the amount of air that can pass by, and can
lead to wheezing sounds. Most people with asthma have wheezing attacks
separated by symptom free periods. Other symptoms include shortness of breath,
cough and chest tightness. Asthma attacks can last minutes to days and can
become dangerous if the airflow becomes severely restricted.

What is work related asthma?

Work related asthma accounts for about 10% of all adult onset asthma. Asthma
related to the workplace can be categorized into 2 distinct subsets:

  • Work aggravated asthma and

  • Occupational asthma

Work Aggravated Asthma

Persons with work aggravated asthma usually have a history of pre existing
asthma. This usually has been symptomatic and the person may have been on
treatment but sometimes they have not. Some but not all of this latter group
may give a history of childhood asthma, that they have grown out of. They may
tell of recurrent asthmatic episodes that are triggered by cold temperatures,
excessive exertion, or exposure to irritant aerosols including dusts, fumes,
vapours, and gases. These people may get wheezy or have other symptoms at work.
The problem can often be eliminated by improving the work environment or
avoiding the irritant.

Occupational Asthma

Occupational asthma is caused as a direct result of workplace exposure. There
are 2 forms of occupational asthma:

  • Irritant Induced Occupational Asthma (previously called reactive airway
    dysfunction syndrome or RADS) and

  • Allergic Occupational Asthma. This is the cause of the vast majority of
    occupational asthma cases.

Irritant Induced Occupational Asthma usually develops after a single, very high
exposure to an irritant chemical. It is a direct burn effect on the airways and
is not related to the immune system. Examples of causal agents include ammonia,
acids and smoke. The high levels of exposure required are usually the result of
accidents or some major failure of controls, often in enclosed spaces. The
patients nearly always manifest asthma symptoms within 24 hours of the
exposure, that is, there is no latent period. Symptoms will tend to improve
over time and may go away entirely but if symptoms persist beyond 6 months
persistent problems are possible. Whether recurrent exposure to lower levels of
respiratory irritants leads to irritant induced asthma is currently a matter of
debate but the majority of experts believe it does not.

Allergic Occupational Asthma is caused by sensitisation or becoming allergic to
a specific chemical agent in the workplace over a period of time. This is the
mechanism for the vast majority (>90%) of cases of occupational asthma. The
sensitisation process does not occur after one exposure but develops over time
(i.e., latency period). Latency periods are variable and can be as short as
several weeks or as long as 30 years. If exposure is consistent, the period of
greatest risk is the first two years of exposure but the risk does not go away
after that but may reduce somewhat.

A new booklet, published by the Health and Safety Authority, informs about

What is the natural history of occupational asthma?

What are respiratory sensitisers?

What are the types of respiratory sensitisers?
What is an employer required to do?

How is a Risk Assessment carried out?

How is exposure prevented and controlled?
What do employees need to know?

What is the role of health surveillance?

How is occupational asthma evaluated?
What should be included in an occupational respiratory questionnaire?

More info

AplusA-online.de - Source: European Agency for Safety and Health at work