Editing Pollution (section)

==Natural causes==
[[File:Ship Tracks Reveal Pollution's Effects on Clouds.ogv|thumb|left|Air pollution produced by ships may alter clouds, affecting global temperatures.]]

One of the most significant natural sources of pollution are [[volcano]]es, which during eruptions release large quantities of harmful gases into the atmosphere. Volcanic gases include carbon dioxide, which can be fatal in large concentrations and contributes to [[climate change]], hydrogen halides which can cause [[acid rain]], sulfur dioxides, which are harmful to animals and damage the [[ozone layer]], and [[hydrogen sulfide]]s, which are capable of killing humans at concentrations of less than 1 part per thousand.<ref>{{Cite web |title=Volcanic gases can be harmful to health, vegetation and infrastructure |url=https://www.usgs.gov/programs/VHP/volcanic-gases-can-be-harmful-health-vegetation-and-infrastructure |access-date=7 May 2022 |website=United States Geologic Survey}}</ref> Volcanic emissions also include fine and ultrafine particles which may contain toxic chemicals and substances such as [[arsenic]], [[lead]], and [[Mercury (element)|mercury]].<ref>{{Cite journal |last1=Trejos |first1=Erika M. |last2=Silva |first2=Luis F. O. |last3=Hower |first3=James C. |last4=Flores |first4=Eriko M. M. |last5=González |first5=Carlos Mario |last6=Pachón |first6=Jorge E. |last7=Aristizábal |first7=Beatriz H. |date=1 March 2021 |title=Volcanic emissions and atmospheric pollution: A study of nanoparticles |journal=Geoscience Frontiers |language=en |volume=12 |issue=2 |pages=746–755 |doi=10.1016/j.gsf.2020.08.013 |bibcode=2021GeoFr..12..746T |s2cid=224936937 |issn=1674-9871|doi-access=free |hdl=11323/7574 |hdl-access=free }}</ref>

[[Wildfire]]s, which can be caused naturally by [[lightning strike]]s, are also a significant source of air pollution. Wildfire smoke contains significant quantities of both carbon dioxide and carbon monoxide, which can cause [[suffocation]]. Large quantities of [[Particulates|fine particulates]] are found within wildfire smoke as well, which pose a health risk to animals.<ref>{{Cite web |title=Wildfires |url=https://www.who.int/health-topics/wildfires |access-date=8 May 2022 |website=[[World Health Organization]]}}</ref>