Occupational Asthma (cont.)

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What causes occupational asthma?

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Occupational asthma is caused by exposure to particular inhaled chemicals in the workplace that cause the airways to become excessively responsive. The likelihood of developing occupational asthma seems to be related to the intensity of the exposure to the causative agent. However, it remains unclear whether the intensity of the exposure, the duration of the exposure, or the combination of the two is most important.

There are numerous agents that can cause occupational asthma. Inhalations of isocyanates, cereal dust, or flour are currently the most common causes of occupational asthma. Agents that cause occupational asthma are usually divided into two different groups: smaller molecules (low molecular weight chemicals), such as isocyanates used in rubber manufacturing, and larger molecules, typically organic substances such as flour. You can find lists of known agents at http://www.hse.gov.uk/asthma/substances.htm.

What are risk factors for occupational asthma?

Occupational asthma should be suspected in any adult with new asthma, but most workers who are exposed to potential asthma-causing agents in the workplace do not go on to develop occupational asthma. The patient's individual characteristics, as well as other factors in the workplace environment play a role in the development of the disease.

One of the main risk factors for occupational asthma is atopy. Atopy is a syndrome characterized by sensitivity to allergens that predisposes an individual to develop occupational asthma. People with atopy often have seasonal allergies or hay fever (allergic rhinitis), chronic inflammation of the nose and sinuses (sinusitis), allergic skin rashes (eczema), and food allergies. People with atopy are not only predisposed to occupational asthma, but they often have non-work-related asthma as well, and their preexisting asthma can be exacerbated by workplace agents (work-aggravated asthma).

Scientists have also discovered specific genes involved with the immune system that may be associated with a person's risk of developing occupational asthma in response to specific agents, such as isocyanates and dust from western red cedar trees. However, these correlations do not appear to be strong enough to warrant a general screening of people for these genes.

An important risk factor for occupational asthma, which fortunately can be eliminated, is cigarette smoking.

If possible, improving ventilation in the workplace may also have a positive impact on the levels of exposures to agents that cause occupational asthma. Although the intensity of exposure is important in the development of occupational asthma, it is less clear if it is the level of agent, duration of exposure, or frequency of exposures that represents the most important factor. Therefore, for most agents, it is difficult to determine what concentration of agent in the air is considered "safe."

Medically Reviewed by a Doctor on 1/15/2014

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Occupational Asthma - Causes and Risks Question: If known, what was the cause of your occupational asthma? Do you work in an environment that puts you at risk?
Occupational Asthma - Signs and Symptoms Question: Please describe the signs and symptoms associated with your occupational asthma.
Occupational Asthma - Treatment Question: What was the treatment for your occupational asthma?
Occupational Asthma - Prevention Question: If you've had occupational asthma, how do you prevent a recurrence? Did you leave your job?