Ozone

Ozone is a colorless gas with a noticeable odor. When inhaled, it can damage the lungs and irritate the throat. Although ozone is found and is naturally produced in the atmosphere, it is also a main part of air pollution called smog. In the upper layer of the atmosphere, ozone is helpful in protecting us from some of the effects of the sun harmful radiation. However, when it exists outdoors and in our homes, it can be harmful if we inhale it.

Breathing in fairly low levels of ozone can result in signs and symptoms such as coughing, congestion, wheezing, shortness of breath, and chest pain in otherwise healthy people. People with already existing asthma, bronchitis, heart disease, and emphysema may find their conditions worsen while inhaling ozone. Breathing in ozone may also increase the risk of getting certain lung diseases and at high levels, over long periods of time, may have more damaging and longer-lasting effects.

Although some manufacturers of air cleaning equipment have claimed that ozone generators can decrease volatile organic compounds (VOCs) in the air, recent research has shown that such devices may, in fact, increase some types of VOCS.  If an air cleaning device produces ozone at a level that is effective in killing molds and viruses, then it is also at a level that can be harmful to you and your pets.

Daily inhalation intakes of indoor ozone (micrograms per day) are estimated to be between 25 and 60% of total daily ozone intake. This is especially noteworthy in light of recent work indicating little, if any, threshold for ozone’s impact on mortality. Additionally, ozone oxidation products are roughly one-third to twice the indoor inhalation intake of ozone alone. Some of these oxidation products are known or suspected to adversely affect human health (e.g., formaldehyde,  fine and ultrafine particles). Indirect evidence supports connections between morbidity/mortality and exposures to indoor ozone and its oxidation products. For example, cities with stronger associations between outdoor ozone and mortality tend to have residences that are older and less likely to have central air conditioning, which implies greater transport of ozone from outdoors to indoors.

Indoor exposures to ozone and its oxidation products can be reduced by filtering ozone from ventilation air and limiting the indoor use of products and materials whose emissions react with ozone. Such steps might be especially valuable in schools, hospitals, and childcare centers in regions that routinely experience elevated outdoor ozone concentrations.