Editing Ground-level ozone (section)

==Health effects==
{{See also|Ozone#Health effects}}
Health effects depend on ozone precursors, which is a group of pollutants, primarily generated during the combustion of fossil fuels. Ground-level ozone is created by nitrous oxides reacting with organic compounds in the presence of sunlight.<ref name="cfpub.epa.gov">{{cite web |title=Ozone: Good Up High Bad Nearby |website=epa.gov |url=https://www.epa.gov/sites/default/files/documents/gooduphigh.pdf |access-date=2019-10-26}}</ref> There are many man-made sources of these organic compounds including vehicle and industrial emissions, along with several other sources.<ref name="cfpub.epa.gov"/> Reaction with daylight ultraviolet (UV) rays and these precursors create ground-level ozone pollution. Ozone is known to have the following health effects at concentrations common in urban air:
* Irritation of the [[respiratory system]], causing coughing, throat irritation, and/or an uncomfortable sensation in the chest. Ozone affects people with underlying respiratory conditions such as [[asthma]], [[chronic obstructive pulmonary disease]] (COPD), and [[lung cancer]] as well those who spend a lot of time being active outdoors.<ref name="epa.gov">{{cite web |title=Health Effects of Ozone Pollution |last=US EPA |first=OAR |date=2015-06-05 |website=US EPA |url=https://www.epa.gov/ground-level-ozone-pollution/health-effects-ozone-pollution |access-date=2019-10-26}}</ref>
* Reduced [[lung]] function, making it more difficult to breathe deeply and vigorously. Breathing may become more rapid and more shallow than normal, and a person's ability to engage in vigorous activities may be limited. Ozone causes the muscles in the airways to constrict which traps air in the alveoli leading to wheezing and shortness of breath.<ref name="epa.gov"/>
* Aggravation of asthma. When ozone levels are high, more people with asthma have attacks that require a doctor's attention or use of medication. One reason this happens is that ozone makes people more sensitive to [[allergen]]s, which in turn trigger asthma attacks.
* Increased susceptibility to [[upper respiratory tract infection|respiratory infections]]. Examples of these respiratory complications include bronchitis, emphysema, and asthma.<ref>{{cite web |title=Effects of Ground-level Ozone |url=https://www.iowadnr.gov/Environmental-Protection/Air-Quality/Air-Pollutants/Effects-Ozone}}</ref>
* Inflammation and damage to the lining of the lungs. Within a few days, the damaged cells are shed and replaced much like the skin peels after a sunburn. Animal studies suggest that if this type of inflammation happens repeatedly over a long time period (months, years, a lifetime), lung tissue may become permanently scarred, resulting in permanent loss of lung function and a lower quality of life.{{citation needed|date=January 2024}}
*More recent data suggests that ozone can also have harmful effects via the inflammatory pathway leading to heart disease, type 2 diabetes, and other metabolic disorders.<ref>{{cite journal |last=Adar |first=Sara Dubowsky |title=Childhood Exposures to Ozone |date=2012-09-25 |journal=Circulation |volume=126 |issue=13 |pages=1570–1572 |issn=0009-7322 |pmid=23008468 |doi=10.1161/circulationaha.112.133207 |doi-access=free}}</ref>

It was observed in the 1990s that ground-level ozone can advance death by a few days in predisposed and vulnerable populations.<ref>{{cite journal |last1=Schlink |first1=Uwe |last2=Herbarth |first2=Olf |last3=Richter |first3=Matthias |last4=Dorling |first4=Stephen |last5=Nunnari |first5=Giuseppe |last6=Cawley |first6=Gavin |last7=Pelikan |first7=Emil |title=Statistical models to assess the health effects and to forecast ground-level ozone |date=April 2006 |journal=Environmental Modelling & Software |volume=21 |issue=4 |pages=547–558 |issn=1364-8152 |doi=10.1016/j.envsoft.2004.12.002}}</ref> A statistical study of 95 large urban communities in the United States found significant association between ozone levels and premature death. The study estimated that a one-third reduction in urban ozone concentrations would save roughly 4000 lives per year (Bell et al., 2004). Ground-level ozone causes approximately 22,000 premature deaths per year in 25 countries in the European Union. (WHO, 2008)