Occupational asthma is defined as an asthma that is caused by a particular exposure to a substance in a work-place. It is different than the other common variety of asthma which can also worsen at the work place.
Occupational asthma is caused by repeated and continuous exposure to a particular allergic substance. This repeated exposure gradually leads to development of hypersensitivity of the individual to that substance. The pathophysiology or the mechanism of causation of occupational asthma is different than usual form of asthma. In usual form of asthma, on exposure to an allergen, certain type of white blood cells called ‘mast cells’ and ‘macrophages’ to which Immunoglobulin-E if bound, react with the allergic substance and release chemicals like leukotrienes and histamine which cause inflammation and constriction of airways. On the other hand, the occupational asthma involves type-III and type-IV hypersensitivity reactions which do not involve immunoglobulin-E. These reactions develop gradually over a longer period of up to five years.
Another feature of occupational asthma is that it is triggered only by very specific substances, which are usually present in the workplace and not commonly found everywhere. This has an important repercussion as it means that a change in the working environment or change of work-place will significantly reduce the progression of the disease.
A very wide variety of allergic substances can lead to occupational asthma. Primary among them are mineral and inorganic dust, chemicals used in industry, organic particles, fumes, polymers, metal welding and latex industry. In addition to them, farming, food packaging and other industries can also cause occupational asthma, though the frequency is lower.
The usual symptoms of occupational asthma are same as those of asthma and involve a cough, shortness of breath and restlessness. While some extent of these symptoms may be present otherwise too, they become worse once in a while during acute attacks.
The classical presentation of occupational asthma is a history which suggests that the patient never had any asthmatic attack prior to joining the work-place. Typically, the asthmatic episodes begin to appear after a gap of time, and gradually increases in frequency and intensity. Usually the attacks are observed only on the day the person is working and are not seen on weekends and holidays. Typically, taking leave from work relieves the symptoms, which are also relieved if a weekend falls immediately after the worsening episode.
The most important part of treatment is the diagnosis itself. The reason for this lies in the difficulty in differentiating a case of occupational asthma from common asthma. The important implication of the difference between the two is in making the decision regarding continuing or not in the same job. In the case of occupational asthma, the degree of the disease keeps worsening with time and a time comes, when the changes begin to become irreversible, which means that once that point is crossed, even leaving the work-place does not provide relief because of the underlying damage to the respiratory apparatus.
The medicinal treatment is same as asthma, and involves inhaled corticosteroids and beta agonists like albuterol (salbutamol). In the case of asthmatic attacks, usually albuterol is given, often along with a long acting steroid, by inhaler. In case symptoms worsen, oral steroids may be required. Once symptoms stabilize, the person is shifted to daily inhalations, while other investigations are undertaken to finalize the diagnosis.
In case the diagnosis is that of occupational asthma, a change of work-place is advised. Employer can be advised and together a possibility of a change of workplace and exposure without a change of employer can be considered, and if possible, it is the best option. When it is not possible, there are important social and financial implications which often become the decisive factors. Till the time it is not possible to change work, one should try to minimize exposure by undertaking more outdoor activities, using masks and other protective gear, frequent movements away from source of exposure and frequent gargling and rinsing of mouth can all make minor differences, but not prevent the disease. It is also advisable to have a long term treatment plan properly chalked out and carry short term relief medicines for the occasional worsening.