Exposure history and assessment
Many respiratory diseases, such as lung cancer, interstitial lung disease, asthma and COPD, can be caused by both nonoccupational and occupational factors. Therefore, an occupational exposure history is crucial in assessing the respiratory risks of a worker and in establishing a diagnosis of occupational lung disease. Unfortunately, many physicians do not have adequate knowledge and/or do not take the time to take an adequate exposure history.
Some occupational lung diseases have a long latency and a critical cumulative level of exposure (for instance, lung cancer and interstitial lung diseases). Other conditions have short latency and thus the timing of symptom onset is critical. Particularly for the former group, an occupational exposure history should include every job since the patient started work.
High levels of dust over a long period are necessary to cause, for example, pneumoconiosis and COPD. Conversely, only a few weeks of asbestos exposure may lead to malignant mesothelioma 50 years later. Some allergic occupational diseases may occur even when exposure levels are within regulatory limits, because these limits are generally not defined to exclude sensitisation.
Smoking enhances the risk not only of occupational lung cancer, but also of some forms of occupational asthma and occupational COPD. Pre-existing allergies may increase the risk of becoming sensitised to occupational agents. Respiratory protective equipment, if used properly, can reduce the risk for some occupational lung diseases but efficacy is very limited with regard, for example, to protection against occupational asthma. In general, individual protective equipment is only the ‘third line of defence’ after technical and organisational approaches to reduce exposure to workplace agents.
The components of a thorough occupational exposure history include:
- Job type and activities: employer, what products the company produces, job title, years worked, description of job tasks or activities, description of all equipment and materials the patient used, description of process changes and dates they occurred, any temporal association between symptoms and days worked.
- Exposure estimate: visible dust or mist in the air and estimated visibility, dust on surfaces, visible dust in sputum (or nasal discharge) at end of work shift, hours worked per day and days per week, open or closed work process system, presence and description of engineering controls on work processes (for instance, wet process, local exhaust ventilation), personal protective equipment used (type, training, testing for fit and comfort and storage locations), sick co-workers.
- Bystander exposures at work: job activities and materials used at surrounding work stations, timing of worksite cleaning (during or after shift), individual performing cleanup and process used (wet versus dry).
- Bystander exposure at home: spouse’s job, whether spouse wears work clothes at home and who cleans them, surrounding industries.
- Other: hobbies, pets, problems with home heating or air-conditioning, humidifier and hot tub use, water damage in the home.