What causes occupational asthma?
Asthma has two components: the underlying chronic inflammation and the periodic attacks. We do not know for certain what causes the underlying inflammation. What we do know is that the tendency to have asthma runs in families and that some people are born with the tendency.
We do know what causes asthma attacks: exposure to a trigger. The attack is similar in many ways to an allergic reaction.
- An allergic reaction is a response by the body's immune system to an "invader." That invader can be a substance or anything that the body senses as "different."
- When the cells of the immune system sense an invader, they set off a series of reactions that help fight off the invader.
- It is this series of reactions that causes the production of mucus and bronchospasms. These responses cause the symptoms of an asthma attack.
In occupational asthma, the trigger is a substance or condition in the workplace that causes asthma symptoms. Most of these substances and conditions are very common and are not normally considered hazardous. Although these substances and conditions can be encountered in almost any workplace, occupational asthma is most common in workers in the following industries and jobs:
- Plastics industry
- Rubber industry
- Chemical industry
- Textile industry
- Electronics industry
- Oil refining
- Baking and food processing
- Gardening, landscaping, and horticulture
- Working with animals
- Laboratory work
Triggers that are often associated with a delay in the onset of symptoms (latency period) come in two groups (characterized by the size of the molecules involved). These are either high molecular weight or low molecular weight agents.
The high molecular weight agents tend to be proteins, and polysaccharides. Examples of these agents include a variety of enzymes (used in the baking and food industry), cereals (also seen in the baking industries), animal waste and shellfish (found in laboratory technicians, farmers, food processors), and latex (found in health-care workers).
Low molecular agents often have a shorter onset of symptoms and usually do not include nasal and eye irritation. Some examples of these agents include anhydrides (often used in plastics, dyes, and epoxy), metals (used in refineries, electroplating, welding), diisocyanates (found in plastics, spray paints, foundries), specific wood dusts like red cedar (found in wood carvers, furniture makers, sawmill workers), and cleaning agents (found in maintenance workers health-care professionals).
Not everyone exposed to these conditions will develop asthma. Some people are more susceptible to asthma than others. Also, exposure to some of these substances can produce chronic lung diseases other than asthma. Risk factors for occupational asthma include the following:
If asthma is not treated, the airways gradually develop a pattern of overreacting, hence, the alternative term for asthma, reactive airways disease. Common, everyday conditions, such as cigarette smoke or cold air, may cause asthma symptoms. In fact, it is part of the normal human condition for a small degree of bronchospasm to occur when the airways are exposed to cold or dry air. Normally, the body's upper airway warms and moistens the air to prevent this from occurring.