Editing Smog (section)

== Health effects ==

[[File:LA smog masks.jpg|thumb|Highland Park [[Optimist International|Optimist Club]] wearing smog-gas masks at banquet, [[Los Angeles]], circa 1954]]
Smog is a serious problem in many cities and continues to harm human health.<ref>{{cite news | url = https://www.usatoday.com/weather/news/2004-04-15-air-quality-ap_x.htm | date = 16 April 2004 | title = EPA: Half of USA breathing illegal levels of smog | first = Traci | last = Watson | location = Washington | work = USA Today}}</ref><ref>{{cite web|last1=Marziali|first1=Carl|title=L.A.'s Environmental Success Story: Cleaner Air, Healthier Kids|url=https://news.usc.edu/76761/las-environmental-success-story-cleaner-air-healthier-kids/|website=USC News|access-date=16 March 2015|date=4 March 2015}}</ref> [[tropospheric ozone|Ground-level ozone]], [[sulfur dioxide]], [[nitrogen dioxide]] and [[carbon monoxide]] are especially harmful for senior citizens, children, and people with heart and lung conditions such as [[emphysema]], [[bronchitis]], and [[asthma]].<ref name=epa/> It can inflame breathing passages, decrease the lungs' working capacity, cause shortness of breath, pain when inhaling deeply, wheezing, and coughing. It can cause eye and nose irritation and it dries out the protective membranes of the nose and throat and interferes with the body's ability to fight infection, increasing susceptibility to illness.<ref>{{Cite journal|last1=Kurt|first1=Ozlem Kar|last2=Zhang|first2=Jingjing|last3=Pinkerton|first3=Kent E.|date=March 2016|title=Pulmonary Health Effects of Air Pollution|journal=Current Opinion in Pulmonary Medicine|volume=22|issue=2|pages=138–143|doi=10.1097/MCP.0000000000000248|issn=1070-5287|pmc=4776742|pmid=26761628}}</ref> Hospital admissions and respiratory deaths often increase during periods when ozone levels are high.<ref>{{cite web | url = http://www.cleanwateractioncouncil.org/issues/air-quality/ozone-pollution/ | title = Ozone Pollution | publisher = Clean Water Action Council of Northeast Wisconsin}}</ref><ref>{{cite web | url = http://www.epa.gov/apti/ozonehealth/population.html | title = Health Effects of Ozone in the General Population | work = Ozone and Your Patients' Health: Training for Health Care Providers | publisher = United States Environmental Protection Agency | date = 10 September 2013 | quote = In addition to these effects, evidence from observational studies strongly indicates that higher daily ozone concentrations are associated with increased asthma attacks, increased hospital admissions, increased daily mortality, and other markers of morbidity.}}</ref>

There is a lack of knowledge on the long-term effects of air pollution exposure and the origin of asthma. An experiment was carried out using intense air pollution similar to that of the 1952 Great Smog of London. The results from this experiment concluded that there is a link between early-life pollution exposure that leads to the development of asthma, proposing the ongoing effect of the Great Smog.<ref>{{Cite journal |first1=Prashant |last1=Bharadwaj |first2=Joshua Graff |last2=Zivin |first3=Jamie T. |last3=Mullins |first4=Matthew |last4=Neidelllast |date=8 July 2016 |title=Early life exposure to the Great Smog of 1952 and the Development of Asthma|journal= American Journal of Respiratory and Critical Care Medicine|volume=194 |pages=1475–1482 |number=12|doi=10.1164/rccm.201603-0451OC |pmid=27392261 |pmc=5440984 }}</ref>
Modern studies continue to find links between mortality and the presence of smog. One study, published in [[Nature magazine]], found that smog episodes in the city of Jinan, a large city in eastern China, during 2011–15, were associated with a 5.87% (95% CI 0.16–11.58%) increase in the rate of overall mortality. This study highlights the effect of exposure to air pollution on the rate of mortality in China.<ref>Ambient air pollution, smog episodes and mortality in Jinan, China: Jun Zhang, Yao Liu, Liang-liang Cui, Shou-qin Liu, Xi-xiang Yin & Huai-chen Li
Scientific Reports 7, Article number: 11209 (2017)
doi:10.1038/s41598-017-11338-2</ref> A similar study in Xi'an found an association between ambient air pollution and increased mortality associated with respiratory diseases.<ref>{{Cite journal|last1=Mokoena|first1=Kingsley Katleho|last2=Ethan|first2=Crystal Jane|last3=Yu|first3=Yan|last4=Shale|first4=Karabo|last5=Liu|first5=Feng|date=2019-07-05|title=Ambient air pollution and respiratory mortality in Xi'an, China: a time-series analysis|url= |journal=Respiratory Research|volume=20|issue=1|pages=139|doi=10.1186/s12931-019-1117-8|issn=1465-993X|pmc=6612149|pmid=31277656 |doi-access=free }}</ref>

===Levels of unhealthy exposure===
The [[United States Environmental Protection Agency|U.S. EPA]] has developed an [[air quality index]] to help explain air pollution levels to the general public. 8 hour average ozone concentrations of 85 to 104 [[parts per notation|ppbv]] are described as "Unhealthy for Sensitive Groups", 105 ppbv to 124 ppbv as "unhealthy" and 125 ppb to 404 ppb as "very unhealthy".<ref name=epa/> The "very unhealthy" range for some other pollutants are: 355 μg m<sup>−3</sup> – 424 μg m<sup>−3</sup> for [[PM10]]; 15.5 ppm – 30.4ppm for CO and 0.65 ppm – 1.24 ppm for NO<sub>2</sub>.<ref>{{Cite journal | url = http://www.epa.gov/ttn/oarpg/t1/memoranda/rg701.pdf | title = Guidelines for the Reporting of Daily Air Quality – the Air Quality Index (AQI) | date = May 2006 | publisher = United States Environmental Protection Agency, Office of Air Quality Planning and Standards | issue = EPA-454/B-06-001 | archive-url = https://web.archive.org/web/20060725183242/http://www.epa.gov/ttn/oarpg/t1/memoranda/rg701.pdf | archive-date = 25 July 2006 | url-status = dead }}</ref>

===Premature deaths due to cancer and respiratory disease===
In 2016, the [[Ontario Medical Association]] announced that smog is responsible for an estimated 9,500 premature deaths in the province each year.<ref>{{cite web|url=http://wheels.ca/reviews/article/256058 |publisher=Wheels.ca |title=$3.83 to power hybrid plug-in for 6 days |first=Tyler |last=Hamilton |date=9 June 2016 |url-status=dead |archive-url=https://web.archive.org/web/20100818225927/http://www.wheels.ca/reviews/article/256058 |archive-date=18 August 2010 }}</ref>

A 20-year [[American Cancer Society]] study found that cumulative exposure also increases the likelihood of premature death from respiratory disease, implying the 8-hour standard may be insufficient.<ref>[https://www.npr.org/templates/transcript/transcript.php?storyId=101694787 Smoggy Skies May Cause Respiratory Death] NPR.org</ref>

===Alzheimer risk===
Tiny magnetic particles from air pollution have for the first time been discovered to be lodged in human brains– and researchers think they could be a possible cause of Alzheimer's disease.
Researchers at Lancaster University found abundant [[magnetite]] [[nanoparticle]]s in the brain tissue from 37 individuals aged three to 92-years-old who lived in Mexico City and Manchester. This strongly magnetic mineral is toxic and has been implicated in the production of reactive oxygen species (free radicals) in the human brain, which is associated with neurodegenerative diseases including Alzheimer's disease.<ref>{{cite web|url=http://www.lancaster.ac.uk/news/articles/2016/toxic-air-pollution-nanoparticles-discovered-in-the-human-brain/|title=Toxic air pollution nanoparticles discovered in the human brain|date=5 September 2016|publisher=Lancaster University}}</ref><ref>{{cite web|last=Reuben|first=Aaron|title=The terrifying truth about air pollution and dementia|url=https://www.motherjones.com/environment/2015/06/air-pollution-dementia-alzheimers-brain/|date=24 June 2015|website=Mother Jones|language=en-US}}</ref>

===Risk of certain birth defects===
A study examining 806 women who had babies with birth defects between 1997 and 2006, and 849 women who had healthy babies, found that smog in the [[San Joaquin Valley]] area of [[California]] was linked to two types of [[neural tube defect]]s: [[spina bifida]] (a condition involving, among other manifestations, certain malformations of the [[spinal column]]), and [[anencephaly]] (the underdevelopment or absence of part or all of the brain, which if not fatal usually results in profound impairment).<ref>{{cite journal |pmid=23045474 |year=2012 |last1=Padula |first1=AM |last2=Mortimer |first2=K |last3=Hubbard |first3=A |last4=Lurmann |first4=F |last5=Jerrett |first5=M |last6=Tager |first6=IB |title=Exposure to traffic-related air pollution during pregnancy and term low birth weight: Estimation of causal associations in a semiparametric model |volume=176 |issue=9 |pages=815–24 |doi=10.1093/aje/kws148 |pmc=3571254 |journal=American Journal of Epidemiology}}</ref> An emerging cohort study in China linked early-life smog exposure to an increased risk for adverse pregnancy outcomes, in particular oxidative stress.<ref>{{Cite journal|last1=Song|first1=Jing|last2=Chen|first2=Yi|last3=Wei|first3=Ling|last4=Ma|first4=Ying|last5=Tian|first5=Ning|last6=Huang|first6=Shi Yun|last7=Dai|first7=Yin Mei|last8=Zhao|first8=Li Hong|last9=Kong|first9=Yuan Yuan|date=2017-09-03|title=Early-life exposure to air pollutants and adverse pregnancy outcomes: protocol for a prospective cohort study in Beijing|journal=BMJ Open|volume=7|issue=9|pages=e015895|doi=10.1136/bmjopen-2017-015895|issn=2044-6055|pmc=5588991|pmid=28871018}}</ref>

===Low birth weight===
According to a study published in [[The Lancet]], even a very small (5&nbsp;μg) change in [[PM2.5]] exposure was associated with an increase (18%) in risk of a low birth weight at delivery, and this relationship held even below the current accepted safe levels.<ref>{{cite journal |doi=10.1016/S2213-2600(13)70192-9 |pmid=24429273 |title=Ambient air pollution and low birthweight: A European cohort study (ESCAPE) |year=2013 |last1=Pedersen |first1=Marie |last2=Giorgis-Allemand |first2=Lise |last3=Bernard |first3=Claire |last4=Aguilera |first4=Inmaculada |last5=Andersen |first5=Anne-Marie Nybo |last6=Ballester |first6=Ferran |last7=Beelen |first7=Rob M J |last8=Chatzi |first8=Leda |last9=Cirach |first9=Marta |last10=Danileviciute |first10=Asta |last11=Dedele |first11=Audrius |last12=Eijsden |first12=Manon van |last13=Estarlich |first13=Marisa |last14=Fernández-Somoano |first14=Ana |last15=Fernández |first15=Mariana F |last16=Forastiere |first16=Francesco |last17=Gehring |first17=Ulrike |last18=Grazuleviciene |first18=Regina |last19=Gruzieva |first19=Olena |last20=Heude |first20=Barbara |last21=Hoek |first21=Gerard |last22=Hoogh |first22=Kees de |last23=Van Den Hooven |first23=Edith H |last24=Håberg |first24=Siri E |last25=Jaddoe |first25=Vincent W V |last26=Klümper |first26=Claudia |last27=Korek |first27=Michal |last28=Krämer |first28=Ursula |last29=Lerchundi |first29=Aitana |last30=Lepeule |first30=Johanna  |journal=The Lancet Respiratory Medicine |volume=1 |issue=9 |pages=695–704 |display-authors=5|arxiv=0706.4406 }}</ref>