Air Quality: Warm, Humid Days and the Risk of Asthma

Warm, Humid Days and the Risk of Asthma

For most of us, the thought of a warm summer day spent on a bicycle or rollerblading is enough to warm us up even on the coldest winter night. But those hot, sticky days that have us clamouring for the cool relief of an air-conditioned house can be dangerous for those with asthma.

Asthma is an inflammation of the breathing tubes that make up our lungs. These tubes, or bronchi, are lined with mucus-producing cells. This mucus traps airborne particles that we inhale. A network of tiny hairs also lines the bronchi, and these hairs are in constant, coordinated motion, to sweep the mucus along, taking all those nasty particles out of our lungs. Inflammation of the bronchi leads to increased mucus production and swelling of the lining of the bronchi. This swelling reduces the inner diameter of the bronchi, making it more difficult to breathe. It’s like trying to breathe through pursed lips instead of with your mouth wide open. Try it and you’ll see.

The bronchi are surrounded by a layer of muscle, which when inflamed can go into spasm, causing coughing and further difficulty breathing. Medications to treat asthma address both inflammation as well as this bronchial muscle spasm.

Inflammation of the bronchi can be triggered by a variety of causes: allergy-inducers like pollen, dust or animals; cold, dry air; cold viruses or other infections; or warm, humid air, and pollution.

In summer, there are hundreds of thousands of visits to emergency rooms across North America each year for asthma symptoms. More of these visits, and more admissions to hospital for asthma, occur on days with high humidity or pollution. If untreated, asthma can be deadly.

But in many people, asthma "attacks" never happen. Try to erase the picture in your head of a kid in the playground suddenly having trouble breathing and having to sit down to use an inhaler. Asthma comes in many different degrees of severity, and in many people, the only symptom is coughing. In this group of asthmatics, symptoms are mild, occur very infrequently, and often only require medication for a short period of time.

Asthma is not a reason to stop participating in sports. Studies have shown that in Olympic athletes, the incidence of asthma is as high as 15%, about double that of the general population. So you can have asthma and still perform at an extremely high level.

If you are asthmatic, watching the pollen index, the relative humidity, and the pollution index can help you decide if that particular day poses a risk of worsening your asthma. You should avoid heavy physical activity on days when those counts are up.

If you haven’t been diagnosed, but notice a change in your breathing with any of these environmental conditions, a simple test in your doctor’s office might lead to a diagnosis, and perhaps could even save your life.

Dr. Grant Lum is a sports medicine physician in Toronto, Ontario, Canada. He is a consultant for the National Hockey League Players’ Association, and a Lecturer at the University of Toronto, in the Faculty of Medicine. He is the medical director and founder of Athletic Edge Sports Medicine. You can find out more about his practice at www.drgrantlum.com.