By Roberta Attanasio
“I explain it to people like you are breathing through a coffee stirrer straw, and you just can’t get enough breath. The attacks can happen so quickly and out of nowhere, so I feel like I’m really not in control of my own body. Not being able to breathe in and out the way my body is designed to do is quite scary” says one of the 19 million adults who currently have asthma in the US.
Asthma is a chronic disorder that causes swelling and inflammation in the lungs—the airways narrow and produce extra mucus, making breathing difficult and causing coughing, shortness of breath and wheezing, a high-pitched whistling sound made while breathing. Asthma attacks, in absence of appropriate treatment, can be life-threatening. Exposure to various irritants and substances that trigger allergies—as for example pollen, dust mites, mold spores, pet dander, smoke and certain medications—can also trigger signs and symptoms of asthma. However, asthma triggers are different from person to person.
According to the National Center for Health Statistics, asthma also affects 6.2 million children in the US. Indeed, childhood asthma is the most common serious chronic disease in infants and children. Alarmingly, asthma is now the most commonly reported non-communicable disease among children worldwide.
Children are especially vulnerable to air pollution, one of the major triggers of asthma attacks. Research indicates that air pollutants suppress genes that regulate the immune system’s ability to differentiate harmless substances from dangerous viruses or bacteria. The immune system then sets up an inflammatory response which leads to asthma.
Notably, results from a recent study show that millions of children worldwide develop asthma annually due to a specific type of pollution—traffic-related air pollution. The study, based on data from 2010 to 2015, focuses on a particular type of traffic-related pollutant—nitrogen dioxide, or NO2—and estimates that 64 percent of these new cases of asthma occur in urban areas. NO2 is one of a group of gases called nitrogen oxides. While all of these gases are harmful to human health and the environment, NO2 is of greater concern. It forms from emissions from cars, trucks and buses, power plants, and off-road equipment, and irritates airways in the human respiratory system. For the study, researchers used a method that takes into account high NO2 exposures occurring near busy roads. They were then able to estimate the number of new pediatric asthma cases attributable to NO2 pollution in 194 countries and 125 major cities worldwide.
Of the 125 major cities, the highest traffic-related air pollution effects on asthma were found in Lima, Peru; Shanghai, China: Bogota, Colombia; Beijing, China; and Toronto, Canada. However, the problem also concerns cities in the US—Los Angeles, New York, Chicago, Las Vegas and Milwaukee were the top five cities with the highest percentage of pediatric asthma cases linked to polluted air.
Susan Anenberg, senior author of the study, said: “Our findings suggest that millions of new cases of pediatric asthma could be prevented in cities around the world by reducing air pollution. Improving access to cleaner forms of transportation, like electrified public transport and active commuting by cycling and walking, would not only bring down NO2 levels, but would also reduce asthma, enhance physical fitness, and cut greenhouse gas emissions.”
The World Health Organization (WHO) calls air pollution “a major environmental risk to health” and has therefore established Air Quality Guidelines for NO2 and other air pollutants. The study findings suggest that the WHO guideline for NO2 may need to be re-evaluated to make sure it is sufficiently protective of children’s health.
For their study, the researchers used NO2 as a marker of the complex mixture of emissions from traffic. They believe that additional studies must be done to more conclusively identify the causative agent within this complex mixture.