Thousands of asthmatics are taken to the emergency room every day. As this disease becomes a national epidemic, a growing question arises – what is making us sick?
Some of the most common triggers, including -- smog and soot from tailpipe exhaust and power plants -- are in the air we breathe every day. Because of this, 17 million people with breathing difficulties in the United States, have a challenge controlling their air space for easy breathing.
It's possible that air pollution is doing more than just triggering asthma attacks. It may also be one element in the development of the disease.
According to the American Lung Association, asthma is described as a chronic condition involving the respiratory system in which the airways occasionally constrict, become inflamed, and are lined with excessive amounts of mucus, often in response to one or more triggers.
These episodes may be triggered by such things as exposure to environmental stimulants such as:
• allergens,
• tobacco smoke (including second hand smoke),
• cold or warm air,
• perfume,
• pet dander,
• moist air,
• exercise or exertion
• and emotional stress.
In children, the most common triggers are viral illnesses such as those that cause the common cold.
Symptoms such as wheezing, shortness of breath, chest tightness, and coughing are caused by the narrowing of the airways. The airway constriction responds to bronchodilators.
Between episodes, most patients feel well with only mild symptoms. They may remain short of breath after exercise for longer periods of time than the unaffected individual. The symptoms of asthma, which can range from mild to life threatening, can usually be controlled with a combination of drugs and environmental changes.
In industrialized countries, asthma is becoming more common and more severe. Five thousand people die of it every year in the United States.
Currently it's the sixth most common chronic condition in the nation. Three times as many people have it now as in 1980.
Some 6 million of them are children. For children, this disease is the most common chronic disorder, the leading cause of
missed school,
and the leading cause of hospitalization.
Is polluted air helping to drive this epidemic? As yet, there's no scientific consensus. But the evidence pointing to air pollution as one major culprit is getting harder and harder to dispute.
What makes the asthmatic's airways hypersensitive to the environment? Genetics can play a part but DNA isn't the whole story.
"Genetic changes haven't occurred rapidly enough to account for the global increase in asthma," says Anne Wright of the Arizona Respiratory Center at the University of Arizona in Tucson. "It pretty clearly has something to do with our interaction with the environment."
Wright and other researchers agree that asthma, like cancer, has no single cause.
"We won't find treatments and cures and preventive measures if we don't address the disease from different points of view -- environmental, genetic, molecular, biological," says Fernando Martinez, director of the Arizona Respiratory Center.
Children and adults who have been frequently exposed to tobacco smoke and to indoor allergens from cats, cockroaches, and household dust mites have more asthma than those who haven't.
The disease is more prevalent and more severe among poor people. It's more common in inner cities. Stress may be a leading contributor. Sedentary lifestyles and unhealthy diets have also been associated with the disease.
On pollution, scientists are making progress. Several long-term, multimillion-dollar studies are now underway to track children from the womb onward, measuring precisely what contaminants they're exposed to through blood tests and recording who develops asthma and who doesn't.
One study will investigate effects of the mix of air pollutants and pesticides that are breathed by children in central California. In the next few years, this research should start to shape concrete answers.
Last February, researchers from the University of Southern California published the most persuasive evidence yet linking asthma and air pollution.
The study followed more than 3,500 children from twelve Southern California communities, six of which endured the kind of smog for which the Los Angeles region is notorious, and six of which had fairly clean air.
Smog's primary ingredient is ozone, a caustic gas formed when sunlight and heat acts on certain air pollutants -- namely, nitrogen oxides and hydrocarbons. In Southern California, by far the largest source of these pollutants is tailpipes.
None of the children had the disease when the study began. After five years, 265 were diagnosed with it. But the critical finding was that children who lived in high-ozone areas and were involved in several team sports were three times more likely to develop asthma than less active children living in less polluted communities.
"Kids playing three or more sports are likely to be outdoors ventilating at high rates, and are therefore being exposed to higher levels of air pollution," explains James Gauderman, one of the study's authors.
"Frequent use of household cleaning sprays may be an important risk factor for adults," wrote lead author Jan-Paul Zock, Ph.D., of the Centre for Research in Environmental Epidemiology at the Municipal Institute of Medical Research in Barcelona, Spain.
The epidemiological study, the first to investigate the effects of
cleaning products
on occasional users rather than occupational users, appeared in the second issue for October of the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.
The investigators used baseline data from the first phase of the European Community Respiratory Health Survey (ECRHS I), one of the world's largest epidemiologic studies of airway disease, and interviews conducted in the follow-up phase, ECRHS II.
Altogether, the study included more than 3,500 subjects across 22 centers in 10 European countries. Subjects were assessed for current asthma, current wheeze, physician-diagnosed asthma and allergy at follow-up, which took place an average of nine years after their first assessment. They were also asked to report the number of times per week they used cleaning products.
Two-thirds of the study population who reported doing the bulk of cleaning were women, about six percent of whom had the disease at the time of follow-up. Fewer than ten percent of them were full-time homemakers.
The risk of developing breathing problems increased with frequency of cleaning and number of different sprays used, but on average was about thirty to fifty percent higher in people regularly exposed to cleaning sprays than in others.
The researchers found that cleaning sprays, especially air fresheners, furniture cleaners and glass-cleaners, had a particularly strong effect.
"Our findings are consistent with occupational epidemiological studies in which increased asthma risk was related to professional use of sprays among both domestic and non-domestic cleaning women," wrote Dr. Zock. "This indicates a relevant contribution of spray use to the burden of asthma in adults who do the cleaning in their homes."
This study was not designed to determine the biological mechanism behind the increase with exposure to cleaning sprays. But Dr. Zock and colleagues propose a number of possible explanations, including the possibility that asthma is partially irritant-induced, that sprays contain sensitizers that are specific to the disease, and/or that an inflammatory response is involved in the development of the disease.
"There is a need for researchers to conduct further studies to elucidate both the extent and mechanism of the respiratory toxicity associated with such products," noted Dr. Zock.
Though the biological mechanism is still unknown, the findings have important clinical relevance. "Clinicians should be aware of the potential for cleaning products used in the home to cause respiratory symptoms and possibly asthma," wrote Kenneth D. Rosenman, M.D., professor at Michigan State University, in an editorial in the same issue of the journal.
The research may have also significant implications for public health. "The relative risk rates of developing adult asthma in relation to exposure to cleaning products could account for as much as 15 percent, or one in seven of adult asthma cases," wrote Dr. Zock.
If you have "tight lungs" or trouble breathing, here are the basic steps to take:
Get a medical diagnosis and advice from your physician. If you have asthma, a doctor can help you control attacks with medication, track your breathing regularly to prevent acute attacks, and design a healthy exercise program.
