Editing Chalcogen (section)

==Toxicity==
{{NFPA 704|Health = 2|Flammability = 0|Reactivity = 0|S=
|caption=Fire diamond for selenium}}
Oxygen is generally nontoxic, but [[oxygen toxicity]] has been reported when it is used in high concentrations. In both elemental gaseous form and as a component of water, it is vital to almost all life on Earth. Despite this, liquid oxygen is highly dangerous.<ref name = "The Elements"/> Even gaseous oxygen is dangerous in excess. For instance, [[Underwater diving|sports divers]] have occasionally drowned from [[convulsion]]s caused by breathing pure oxygen at a depth of more than {{convert|10|m|ft|abbr=off|sp=us}} underwater.<ref name = "ReferenceB"/> Oxygen is also toxic to some [[bacteria]].<ref name = "Structure of Matter"/> Ozone, an allotrope of oxygen, is toxic to most life. It can cause [[lesion]]s in the respiratory tract.<ref>{{Cite journal|last = Menzel|first = D.B.|pmid=6376815|title = Ozone: an overview of its toxicity in man and animals|year = 1984|doi=10.1080/15287398409530493|journal = Journal of Toxicology and Environmental Health|volume = 13|issue = 2–3|pages = 183–204| bibcode=1984JTEH...13..181M }}</ref>

Sulfur is generally nontoxic and is even a vital nutrient for humans. However, in its elemental form it can cause redness in the eyes and skin, a burning sensation and a cough if inhaled, a burning sensation and diarrhoea and/or [[catharsis (medicine)|catharsis]]<ref name = EPA-sulfur /> if ingested, and can irritate the mucous membranes.<ref>{{Cite web |url=http://npic.orst.edu/factsheets/sulfurgen.html |title=Sulfur General Fact Sheet |website=npic.orst.edu |access-date=2019-01-23}}</ref><ref>{{cite web|author = Extension Toxicology Network |url = http://pmep.cce.cornell.edu/profiles/extoxnet/pyrethrins-ziram/sulfur-ext.html |title = Sulfur|date = September 1995 |access-date=November 25, 2013}}</ref> An excess of sulfur can be toxic for [[Cattle|cows]] because microbes in the [[rumen]]s of cows produce toxic hydrogen sulfide upon reaction with sulfur.<ref>{{cite web|author = College of Veterinary Medicine, Iowa State University|url = http://vetmed.iastate.edu/diagnostic-lab/diagnostic-services/diagnostic-sections/chemistry-/-toxicology/polio-cattle-can-be-ca|title = Sulfur Toxicity|year = 2013 |access-date=November 25, 2013}}</ref> Many sulfur compounds, such as [[hydrogen sulfide]] (H<sub>2</sub>S) and [[sulfur dioxide]] (SO<sub>2</sub>) are highly toxic.<ref name="ReferenceB"/>

Selenium is a trace nutrient required by humans on the order of tens or hundreds of micrograms per day. A dose of over 450 micrograms can be toxic, resulting in bad breath and [[body odor]]. Extended, low-level exposure, which can occur at some industries, results in [[weight loss]], [[anemia]], and [[dermatitis]]. In many cases of selenium poisoning, [[selenous acid]] is formed in the body.<ref>{{cite journal|last = Nutall|first = Kern L.|url = http://www.annclinlabsci.org/content/36/4/409.full|title = Evaluating Selenium Poisoning|year = 2006|pmid = 17127727|volume = 36|issue = 4|pages = 409–20|journal = Annals of Clinical and Laboratory Science}}</ref> [[Hydrogen selenide]] (H<sub>2</sub>Se) is highly toxic.<ref name="ReferenceB"/>

Exposure to tellurium can produce unpleasant side effects. As little as 10 micrograms of tellurium per cubic meter of air can cause notoriously unpleasant breath, described as smelling like rotten garlic.<ref name="The Elements"/> Acute tellurium poisoning can cause vomiting, gut inflammation, internal bleeding, and respiratory failure. Extended, low-level exposure to tellurium causes tiredness and indigestion. [[Sodium tellurite]] (Na<sub>2</sub>TeO<sub>3</sub>) is lethal in amounts of around 2 grams.<ref name="ReferenceB"/>

Polonium is dangerous as an [[alpha particle]] emitter. If ingested, [[polonium-210]] is a million times as toxic as [[hydrogen cyanide]] by weight; it has been used as a murder weapon in the past, most famously [[Death of Alexander Litvinenko|to kill]] [[Alexander Litvinenko]].<ref name="ReferenceB"/> Polonium poisoning can cause [[nausea]], [[vomiting]], [[anorexia (symptom)|anorexia]], and [[lymphopenia]]. It can also damage [[hair follicle]]s and [[white blood cell]]s.<ref name = "ReferenceB"/><ref>{{cite journal|author1=Jefferson, R.D. |author2=Goans R.E. |author3=Blain, P.G. |author4=Thomas, S.H. |pmid=19492929|title = Diagnosis and treatment of polonium poisoning|year = 2009|volume = 47|issue = 5|pages = 379–92|doi = 10.1080/15563650902956431|journal = Clinical Toxicology|s2cid=19648471 }}</ref> Polonium-210 is only dangerous if ingested or inhaled because its alpha particle emissions cannot penetrate human skin.<ref name="Factsheets">{{cite web|url=http://www.iaea.org/Publications/Factsheets/English/polonium210.html |title=Polonium-210 |publisher=International Atomic Energy Agency |year=1998 |access-date=February 11, 2013  |archive-url=https://web.archive.org/web/20120126084112/http://www.iaea.org/Publications/Factsheets/English/polonium210.html |archive-date=January 26, 2012 |df=mdy }}</ref> Polonium-209 is also toxic, and can cause [[leukemia]].<ref>{{cite web |last=Freemantle|first=Michael|title=Yasser Arafat, Polonium Poisoning and the Curies|date=November 28, 2012 |url=http://www.huffingtonpost.co.uk/michael-freemantle/yasser-arafat-polonium-poisoning_b_2199903.html |access-date=November 25, 2013}}</ref>