A small number of people with asthma--about 2 percent--develop the condition at work. While anyone can get "occupational asthma," you’re at highest risk if your family has a history of asthma (or allergies) and you frequently encounter irritating substances. A few of these irritants are:

Chemical fumes or dust. These come from paint, insulation, furniture, foam mattresses, or packing materials. Two groups of asthma-causing chemicals are isocyanates and anhydrides. Workers in manufacturing and processing plants may inhale them.

Animal dander, hair, or mites. Almost every animal carries allergens like these. You get hefty exposure to the irritants if you work at a kennel or farm. Veterinarians and animal groomers are also at asthma risk.

Dust from flour, grains, cereals, coffee, or tea. So-called "baker’s asthma" can affect anyone working in a kitchen, mill, or other food-processing job.

Industrial materials, like cotton, and certain metals. Employees in refining or textile jobs bump into these irritants every day.

How can you tell if your job is causing asthma? It’s not always easy. You might start to cough, wheeze, or feel breathless hours after you arrive at work--or even after you leave. If you have bouts of asthma symptoms, pay attention to when they occur. Do you feel much better on the weekend or during vacation? That could indicate on-the-job asthma. Keep in mind that occupational asthma can take years to develop. Once it does, you may become sensitive to a host of substances--like cigarette smoke or cold air--even away from work.