Editing Group 4 element (section)

==Biological occurrences==
The group 4 elements are hard refractory metals with low aqueous solubility and low availability to the biosphere. Titanium and zirconium are relatively abundant, whereas hafnium is rare in the environment, and rutherfordium non-existent.

Titanium has no known role in any organism's biology. However, many studies suggest that titanium could be biologically active. Most titanium on Earth is stored within insoluble minerals, so it is unlikely to be a part of any biological system in spite of being potentially biologically active.<ref>{{Cite web |title=Contemplating a role for titanium in organisms |url=https://academic.oup.com/metallomics/article/8/1/9/6000637 |access-date=2023-09-23 |website=academic.oup.com}}</ref>

Zirconium plays no known role in any biological system,<ref>{{Cite web |title=Zirconium - Element information, properties and uses {{!}} Periodic Table |url=https://www.rsc.org/periodic-table/element/40/zirconium#:~:text=Zirconium%20has%20no%20known%20biological,It%20has%20low%20toxicity.&text=Zirconium%20occurs%20in%20about%2030,ones%20being%20zircon%20and%20baddeleyite. |access-date=2023-09-23 |website=www.rsc.org}}</ref> but is common in biological systems. Certain antiperspirant products use [[Aluminium zirconium tetrachlorohydrex gly]] to block sweat pores in the skin.<ref>Karl Laden, 1999, Antiperspirants and Deodorants, CRC Press, {{ISBN|0-8247-1746-5}}</ref>

Hafnium plays no known role in any biological system, and has low toxicity.<ref>{{Cite web |title=Hafnium - Element information, properties and uses {{!}} Periodic Table |url=https://www.rsc.org/periodic-table/element/72/hafnium#:~:text=Hafnium%20has%20no%20known%20biological%20role,%20and%20it%20has%20low%20toxicity. |access-date=2023-09-23 |website=www.rsc.org}}</ref>

Rutherfordium is synthetic, expensive, and radioactive: the most stable isotopes have half-lives under an hour. Few chemical properties and no biological functions are known.