Editing Group 4 element (section)

==Precautions==
Titanium is non-toxic even in large doses and does not play any natural role inside the [[human body]].<ref name="Emsley2001">{{cite book |last=Emsley |first=John |url=https://archive.org/details/naturesbuildingb0000emsl |title=Nature's Building Blocks: An A-Z Guide to the Elements |publisher=Oxford University Press |year=2001 |isbn=978-0-19-850341-5 |location=Oxford, England, UK |pages=[https://archive.org/details/naturesbuildingb0000emsl/page/457 457–458] |chapter=Titanium |url-access=registration}}{{vn|date=June 2020}}</ref> An estimated quantity of 0.8 milligrams of titanium is ingested by humans each day, but most passes through without being absorbed in the tissues.<ref name="Emsley2001" /> It does, however, sometimes [[bioaccumulation|bio-accumulate]] in tissues that contain [[silica]]. One study indicates a possible connection between titanium and [[yellow nail syndrome]].<ref>{{cite journal|last=Berglund|first=Fredrik|author2=Carlmark, Bjorn |title=Titanium, Sinusitis, and the Yellow Nail Syndrome|journal=Biological Trace Element Research|date=October 2011|pmc=3176400|volume=143|issue=1|pages=1–7|doi=10.1007/s12011-010-8828-5|pmid=20809268|bibcode=2011BTER..143....1B }}</ref> 

Zirconium powder can cause irritation, but only contact with the eyes requires medical attention.<ref>{{cite web |title=Zirconium |website=International Chemical Safety Card Database |date=October 2004 |publisher=International Labour Organization |url=http://www.ilo.org/legacy/english/protection/safework/cis/products/icsc/dtasht/_icsc14/icsc1405.htm |access-date=2008-03-30}}</ref> OSHA recommendations for zirconium are 5&nbsp;mg/m<sup>3</sup> [[permissible exposure limit|time weighted average]] limit and a 10&nbsp;mg/m<sup>3</sup> short-term exposure limit.<ref>{{cite web|title=Zirconium Compounds|publisher=National Institute for Occupational Health and Safety|date=2007-12-17|url=https://www.cdc.gov/niosh/pel88/7440-67.html|access-date=2008-02-17}}</ref> 

Only limited data exists on the toxicology of hafnium.<ref name = hafniumtox >{{cite web|url =https://www.osha.gov/SLTC/healthguidelines/hafnium/index.html|title= Occupational Safety & Health Administration: Hafnium|publisher=U.S. Department of Labor|access-date=2008-09-10|archive-url= https://web.archive.org/web/20080313003040/https://www.osha.gov/SLTC/healthguidelines/hafnium/index.html <!-- Bot retrieved archive --> |archive-date=2008-03-13}}</ref> Care needs to be taken when [[machining]] hafnium because it is [[pyrophoric]]—fine particles can spontaneously combust when exposed to air. Compounds that contain this metal are rarely encountered by most people. The pure metal is not considered toxic, but hafnium compounds should be handled as if they were toxic because the ionic forms of metals are normally at greatest risk for toxicity, and limited animal testing has been done for hafnium compounds.<ref name= hafniumtox />