Editing Halogen (section)

== Toxicity ==
The halogens tend to decrease in toxicity towards the heavier halogens.<ref name = "The Elements"/>

Fluorine gas is extremely toxic; breathing in fluorine at a concentration of 25 parts per million is potentially lethal.  [[Hydrofluoric acid]] is also toxic, being able to penetrate skin and cause [[Hydrofluoric acid burn|highly painful burns]]. In addition, fluoride anions are toxic, but not as toxic as pure fluorine. Fluoride can be lethal in amounts of 5 to 10 grams. Prolonged consumption of fluoride above concentrations of 1.5&nbsp;mg/L is associated with a risk of [[dental fluorosis]], an aesthetic condition of the teeth.<ref>{{cite book|chapter=Guidelines and standards|title=Fluoride in Drinking-water|last1=Fawell | first1=J.|last2= Bailey |first2=K.|last3 =  Chilton |first3= J. |last4=Dahi |first4=E. |last5=Fewtrell |first5=L. |last6=Magara |first6=Y.|publisher=World Health Organization|isbn=978-92-4-156319-2|year=2006|chapter-url=https://www.who.int/water_sanitation_health/publications/fluoride_drinking_water_full.pdf|pages=37–9}}</ref> At concentrations above 4&nbsp;mg/L, there is an increased risk of developing [[skeletal fluorosis]], a condition in which bone fractures become more common due to the hardening of bones. Current recommended levels in [[water fluoridation]], a way to prevent [[dental caries]], range from 0.7 to 1.2&nbsp;mg/L to avoid the detrimental effects of fluoride while at the same time reaping the benefits.<ref>{{cite web|url=https://www.cdc.gov/fluoridation/safety/nrc_report.htm|title=CDC Statement on the 2006 National Research Council (NRC) Report on Fluoride in Drinking Water|date=July 10, 2013|publisher=Centers for Disease Control and Prevention|access-date=August 1, 2013|archive-url=https://web.archive.org/web/20140109183156/http://www.cdc.gov/fluoridation/safety/nrc_report.htm|archive-date=January 9, 2014|url-status=dead|df=mdy-all}}</ref> People with levels between normal levels and those required for skeletal fluorosis tend to have symptoms similar to [[arthritis]].<ref name = "Nature's Building Blocks"/>

Chlorine gas is highly toxic. Breathing in chlorine at a concentration of 3 parts per million can rapidly cause a toxic reaction. Breathing in chlorine at a concentration of 50 parts per million is highly dangerous. Breathing in chlorine at a concentration of 500 parts per million for a few minutes is lethal. In addition, breathing in chlorine gas is highly painful because of its corrosive properties. Hydrochloric acid is the acid of chlorine, while relatively nontoxic, it is highly corrosive and releases very irritating and toxic hydrogen chloride gas in open air.<ref name="The Elements">{{cite book|last=Gray|first=Theodore|title=The Elements|year=2010 |publisher=Running Press | isbn= 9781579128951 }}</ref>

Pure bromine is somewhat toxic but less toxic than fluorine and chlorine. One hundred milligrams of bromine is lethal.<ref name = "Nature's Building Blocks"/> Bromide anions are also toxic, but less so than bromine. Bromide has a lethal dose of 30 grams.<ref name = "Nature's Building Blocks"/>

Iodine is somewhat toxic, being able to irritate the lungs and eyes, with a safety limit of 1 milligram per cubic meter. When taken orally, 3 grams of iodine can be lethal. Iodide anions are mostly nontoxic, but these can also be deadly if ingested in large amounts.<ref name = "Nature's Building Blocks"/>

Astatine is [[radioactive]] and thus highly dangerous, but it has not been produced in macroscopic quantities and hence it is most unlikely that its toxicity will be of much relevance to the average individual.<ref name = "Nature's Building Blocks"/>

Tennessine cannot be chemically investigated due to how short its half-life is, although its radioactivity would make it very dangerous.