Why It Can Be Harder To Breathe In The Summer

Summer days are sometimes muggy and almost always uncomfortably hot. For anyone daring enough to leave their home, those two conditions can be discouraging enough. But, as it turns out, summer is also a key time for another phenomenon: air pollution, chiefly ozone. Ozone becomes particularly problematic in hotter months because the atmospheric reactions that produce ozone are actually accelerated by the warm temperatures.[1]


What is ozone?

GreenFacts.org defines ozone (O3) as a gas that can form and react under the action of light, and is present in two layers of the atmosphere. High up in the atmosphere, ozone forms a layer that shields the Earth from ultraviolet rays; this is considered “good” ozone. However, ground level ozone — where humans are susceptible — is formed from other pollutants and can react with other substances, in both cases under the action of light. It also forms when emissions by cars, power plants, refineries, chemical plants and other sources react chemically with sunlight.[2] Under these circumstances, ozone is considered a major air pollutant.[3]

Ozone is not emitted directly into the air, but is formed by gases called nitrogen oxides (NOx) and volatile organic compounds (VOCs) that, in the presence of heat and sunlight, react to form ozone.[4]

What are the effects of ozone?

According to the EPA, ozone – when inhaled (even at very low levels) – can:

  • cause acute respiratory problems
  • aggravate asthma
  • cause significant temporary decreases in lung capacity of 15 to 20 percent in some healthy adults
  • cause inflammation of lung tissue
  • lead to hospital admissions and ER visits (10 to 20 percent of all summertime respiratory-related hospital visits in the northeastern US are associated with ozone pollution)
  • impair the body’s immune system defenses, making people more susceptible to respiratory illnesses, including bronchitis and pneumonia[5]
  • Breathing other pollutants in the air may make your lungs more responsive to ozone – and breathing ozone may increase your body’s response to other pollutants.[6]

Who’s the most vulnerable to ozone-related air pollution?

  • Children, as their airways are not fully developed
  • Adults exercising outdoors: otherwise healthy people engaged in physical activity breathe faster and more deeply, which increases the amount of ozone flowing into the lungs
  • People with existing respiratory disease, for whom added ozone exposure can further irritate their airways[7]
  • If you live near a busy roadway or spend a significant amount of time commuting by car, your chances of being exposed to air pollution is also greater. The EPA’s website details the increased risks associated for people in close proximity to high traffic areas: “Air pollutants from cars, trucks and other motor vehicles are found in higher concentrations near major roads. People who live, work or attend school near major roads appear to have an increased incidence and severity of health problems associated with air pollution exposures related to roadway traffic.”[8]

What proactive steps can you take to minimize your exposure and symptoms of ozone?

  • Do outdoor activities early in the morning and after 6 p.m., when ozone levels are at their lowest
  • Check the Air Quality Index (AQI– see chart below), which uses colors and numbers to tell you how much pollution is in the air; on more severe days, consider limiting outdoor activities altogether
  • If you live near a busy roadway or in an urban area, keep windows shut during the day; for those with respiratory sensitivities, using an air purifier in your home can reduce the effects of outdoor air pollution that’s found its way inside your home





[1] http://www.noaca.org/modules/showdocument.aspx?documentid=495
[2] https://www.houstontx.gov/health/Environmental/protection_from_ozone.htm
[3] http://www.greenfacts.org/en/ozone-o3/
[4] http://www.epa.gov/region07/air/quality/o3health.htm
[5] ibid
[6] http://www.stateoftheair.org/2013/health-risks/health-risks-ozone.html
[7] http://www.airinfonow.org/html/ed_ozone.html
[8] http://www.epa.gov/otaq/nearroadway.htm