Work related asthma is a major cause of occupational lung disease. Exposure to various irritants at the work place is responsible for new onset of asthma as well as exacerbation of existing bronchial asthma. Both of them are equally important. New onset of asthma results in increased incidence and prevalence of this disease while exacerbation results in increased morbidity thus affecting normal life. The term occupational asthma refers to new onset asthma resulting from workplace exposure. A patient with this illness shows variable airflow obstruction or airway hypersensitivity or both to a specific agent which is present at the workplace.
Types Of Workplace Asthma
There are two terminologies commonly used for work related asthma. They are work caused asthma and work aggravated asthma or exacerbation of pre-existing asthma. Work aggravated asthma accounts for more number of cases than work caused asthma.
Occupational Asthma – Who Is At risk?
Dust, fumes, cotton, hemp, grain, jute, vapors, cold, ammonia, chlorine and organophosphate pesticides can cause asthma without sensitization by irritant, inflammatory or other effects. Animals, plants, bacterial proteins, antibiotics, metal, etc., develop asthma after sensitization by allergen or its components. There are a large number of materials suspected as causative agents for occupational asthma. Metals such as chromium, platinum, nickel and cobalt can cause asthma in people having occupations such as welders, platinum refiners and diamond polishers. Various drugs and pesticides cause symptoms in pharmaceutical workers and fumigators. A large number of professionals exposed to chemicals like laboratory workers, hospital staff, painters, photographic processors, beauticians etc. are also at risk. Farmers and veterinarians, meat processors are also at risk due to animals and birds.
Diagnosis Of Work Related Asthma
The important thing in this disease is to diagnose asthma and establish its relation to the patient's occupation. Asthma is diagnosed on the basis of intermittent respiratory symptoms and reversible airways obstruction or hyper-responsive airways condition. Clinically, occupational asthma shows symptoms such as wheezing, coughing, chest tightness, shortness of breath and dypsnoea, which are similar to that of non-occupational asthma. Some patients develop bronchitis, i.e. cough with sputum, ocular and nasal discharge and sneezing as well.
In order to establish the relationship between occupation and asthma, the following points are considered:
1) Assessment Of History And Exposure – It is important to know the occupational history in order to find out the precise exposure to irritants. If it is observed that symptoms develop at the workplace, improve over weekends and vacations, symptoms increase at the workplace or change after altering the work environment, then there exists a relation between asthma and the patient's occupation.
2) Objective Tests – Repeated Pulmonary Function Test (PFT), both at the workplace and home is done to diagnose occupational asthma. Airflow limitation is also assessed by Peak Expiratory Flow (PEF). It is measured at least four times a day i.e. prior to work, during work shift, after work and finally before going to bed. Specific inhalation challenge test can also be performed to determine the precise etiology. Extracts are also available to diagnose immediate hypersensitivity to some occupational sensitizers like animal protein and coffee.
Diagnostic Criteria
The American College of Chest Physicians had established the following criteria for diagnosis of occupational asthma:
1) History compatible with occupational asthma
2) Presence of airflow limitation and its reversibility
3) Presence of non-specific airway hypersensitivity
4) Demonstration of work-related asthma by objective tests
Occupational Asthma can be a disabling disease, resulting in long term illness. A common outcome of this disease is reduced working efficiency. But people with this disease can work normally with proper precautions and with or without medication. Occupational asthma needs a special approach for epidemiologic disease surveillance and medico-legal purposes.