The spread of cities and commuter culture has naturally resulted in the growth of highways throughout the country. Unfortunately, highways have contributed to a variety of problems, including an increase in air pollution. Along with its effects on the environment, air pollution has many well-known effects on the human respiratory system. Read on to learn about some of the respiratory effects of air pollution as well as some of its lesser known effects.
Understanding Air Pollution
Burning anything naturally releases unhealthy products into the air. Burning gasoline or diesel releases nitrogen oxides, carbon monoxide, particulate matter, and volatile organic compounds (VOCs) out of a vehicle’s tailpipe. Fossil fuels also release carbon dioxide into the air. While you risk exposure to these harmful compounds whenever you hit the road or are stuck in traffic, your exposure increases exponentially if you live near a highway, where the levels of air pollution are significantly higher. A 2010 review suggests that between 30 and 45 percent of North Americans live or work close enough to a busy road or highway to experience higher air pollutant exposure.1
Air pollution can have a huge impact on health, from both short- and long-term exposure. Groups that may be at a higher risk of these health effects include:
- The elderly
- People with existing medical issues
Proven Health Effects of Air Pollution
1. Increased Asthma
Asthma is characterized by a swelling and constriction of the airways, making breathing difficult. The exact severity of asthma can range from person to person. For some, asthma may be a minor nuisance. For others, it can be a major problem with potentially life-threatening asthma attacks. The most common signs and symptoms of asthma include:
- Pain or tightness in the chest
- Shortness of breath
- Wheezing or whistling sound when exhaling
- Sudden coughing or wheezing attacks
- Sleep troubles from frequent cough, wheezing, and shortness of breath
The exact cause of asthma is not well understood, but research suggests it may come as a combination of genetic and environmental factors.2 Asthma can be exacerbated by intense physical activity as well as changes in air quality.
Air pollutants can naturally contribute to asthma attacks, and studies suggest that air pollution from traffic can significantly increase asthma issues. In a German study of over 7,500 schoolchildren, researchers found that living within 50 meters of a busy highway contributed to asthma, coughing and wheezing.3
In a similar study, researchers evaluated 12 Southern California communities that experienced different types and levels of air pollution. Results of the study found an association between increased wheezing and exposure to nitrogen dioxide among boys. Nitrogen dioxide is a common component of vehicle exhaust. Outdoor nitrogen dioxide exposure was also associated with a longer duration of symptoms.4
2. Impaired Lung Function
Even if you don’t have asthma, air pollution from highways can still contribute to lung problems and impair your basic respiratory functions. In a prospective study, researchers evaluated 3,677 children from 12 communities in California representing a wide range of regional air qualities. The study followed the children for eight years, recording their lung function measurements once per year. The researchers also identified indicators of residential exposure to traffic from large roads.
The results of the study found that children who lived within 500 meters of a freeway showed substantial deficits in forced expiratory volume (essentially, the amount of air they could exhale with a forced breath) and maximum midexpiratory flow compared to children who lived at least 1,500 meters from a freeway. This suggests that local exposure to freeway traffic can have significant adverse effects on lung development in children, which may result in impair lung function later in life.5
In a similar study, researchers evaluated the respiratory health of children in six areas near major motorways in the Netherlands. The study assessed the children’s lung function and exposure to traffic-related air pollution. The results suggested impaired lung function was associated with truck traffic density. This association was stronger for those who lived less than 300 meters from a major motorway. Impaired lung function was also associated with concentrations of black smoke, a proxy for diesel exhaust particles.6
3. Increased Risk of Lung Cancer
Along with its potential effects on general lung function, air pollutants can potentially contribute to lung cancer. In a cohort study of 6,338 Californian adults, researchers evaluated the relationship between long-term concentrations of ambient air pollutants and lung cancer risk. Results showed that an interquartile range increase in ozone resulted in a 3.56 increased relative risk of lung cancer in men. Interquartile range increases in particulate matter also contributed to a 5.21 relative risk increase of lung cancer in men. For women, increases in nitrogen dioxide exposure resulted in a 2.14 relative risk increase, while increased particulate matter also increased relative risk of lung cancer. In both genders, elevated long-term ambient concentrations of particulate matter and nitrogen dioxide were associated with an increased risk of lung cancer.7
4. Increased Infections, Respiratory Illnesses, and Food Allergies
Air pollution can go beyond just the lungs and pose some serious problems for your general immune functions. In a cohort study from the Netherlands, researchers evaluated the association between air pollution and the development of allergies and respiratory infections among a sample of about 4,000 children during their first 4 years of life. The results of the study found that children living near major motorways had:
- 20 percent higher rate of ear, nose, and throat infections
- 20 percent higher rate of flus and serious colds
- 60 percent higher rate of food allergies
Air pollution was also associated with an increased incidence of wheezing and dry coughs at night.8
In another study from the University of British Columbia, researchers evaluated the potential association between air pollution from traffic and allergies in children in the first year of life. Using data from 2,477 children, the researchers found that exposure to air pollution in the first year of life increased children’s risk of developing allergies to food, pets, pests, and mold. The study did not find an association between mothers exposed to air pollution during pregnancy and allergy risk in their children.9
5. Decreased Fertility
Some studies even suggest that exposure to air pollution from vehicles may affect a person’s fertility. In a systematic review of female fertility and air pollution, researchers found that among the in vitro fertilization population, exposure to nitrogen dioxide and ozone was associated with a decrease in live birth rates, while exposure to particulate matter of 10 mm was associated with an increased rate of miscarriage. In the general population, exposure to particulate matter between 2.5 and 10 mm was associated with reduced pregnancy rates, while exposure to carbon monoxide, sulfur dioxide, and nitrogen dioxide was shown to potentially promote miscarriages and stillbirths. While larger trials are still necessary to determine any definitive conclusions, these studies suggest that air pollution could have an effect on female fertility.10
Air pollution may also affect male fertility. In a mouse study, researchers looked at four groups of male mice exposed to particulate matter at varying stages of their lives. The results of the study found that the group of mice that had been exposed to particulate matter before and after birth showed significantly worse quality sperm compared to the group not exposed to any particulate matter. Exposure to the particulate matter was found to cause changes at an epigenetic level that contributed to testicular function, and exposure after birth seemed to be the most harmful to testicular function.11
Protecting Yourself from Air Pollution
While the greater long-term solution would require a shift away from fossil fuels and supporting more public transit measures, you can still take some steps to protect yourself and minimize exposure to air pollution.
- Check air pollution and air quality forecasts in your area, particularly during times of high traffic and wildfire season.
- Avoid any outdoor activities when air pollution levels are forecasted to be high. Stay indoors, either at home or in public spaces where air is filtered. This is especially important for children, the elderly, and those with existing respiratory issues.
- Avoid any outdoor activities near freeways and other high traffic zones. Even if forecasts show good overall air quality, being even just a third of a mile near a freeway can expose you to high levels of air pollution.
- Make sure your home air system is in good working order to help filter air pollution. A malfunctioning HVAC system can also contribute to bad air quality on its own.
- Avoid burning wood, trash, or foliage. Burning trash and firewood are some of the major sources of particle pollution.
While it’s not feasible for everyone, if exposure to traffic pollution has contributed to health problems or exacerbated existing issues, you may have to consider moving away from highways and major motorways.
Living near busy highways has many known effects on health, and studies on air pollution are still ongoing, suggesting there may be effects that science still isn’t aware of. It is important to keep these effects in mind, especially when choosing a home, and to do your part to minimize air pollution.