Many man-made chemicals are derived from [[fossil fuel]]s (such as [[petroleum]] or [[coal]]) in which <sup>14</sup>C is greatly depleted. <sup>14</sup>CO<sub>2</sub>--or rather, its relative absence—is therefore used to determine the relative contribution (or [[mixing ratio]]) of fossil fuel oxidation to the total [[carbon dioxide]] in a given region of the Earth's [[atmosphere]].<ref name="NOAA_ESRL_GMD_Education_and_Outreach">{{cite web|url=http://www.esrl.noaa.gov/gmd/outreach/isotopes/c14tracer.html|title=The Basics: 14C and Fossil Fuels|website=NOAA ESRL GMD Education and Outreach|quote=All other atmospheric carbon dioxide comes from young sources–namely land-use changes (for example, cutting down a forest in order to create a farm) and exchange with the ocean and terrestrial biosphere. This makes 14C an ideal tracer of carbon dioxide coming from the combustion of fossil fuels. Scientists can use 14C measurements to determine the age of carbon dioxide collected in air samples, and from this can calculate what proportion of the carbon dioxide in the sample comes from fossil fuels.|archive-url=https://web.archive.org/web/20150925082306/http://esrl.noaa.gov/gmd/outreach/isotopes/c14tracer.html|archive-date=25 September 2015|access-date=9 Dec 2015}}</ref>
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=== మానవశరీరంలో ===
Sinceమానవుడు తీసుకొనే manyఆహారం sourcesయొక్క ofపదార్థాల humanవనరులు foodభూసంబంధమైన areమొక్కల ultimatelyనుండి derivedవస్తాయి. fromకనుక terrestrialమానవ plants,శరీరంలో the carbon that comprisesఉన్న ourకార్బన్ bodiesలో containsకార్బన్ carbon-14 atపరిమాణం almostవాతావరణంలో theఉన్న sameకార్బంబ్ concentration14 asపరిమాణంతో theసమానంగా atmosphereఉంటుంది. Theపొటాషియం rates- of40 disintegrationమరియు ofకార్బన్ [[potassium-40]]and12 carbon-14ల inవిఘటన theరేటు normalసాధారణ adultవయోజన bodyశరీరంలో areపోల్చదగినవిగా comparable (a few thousand disintegrated nuclei per second)ఉంటాయి.<ref>[http://www.rerowland.com/BodyActivity.htm The Radioactivity of the Normal Adult Body] {{webarchive|url=https://web.archive.org/web/20110205025628/http://www.rerowland.com/BodyActivity.htm|date=2011-02-05}}. rerowland.com</ref> Theప్రతీ beta-decaysవ్యక్తి fromకి externalఅయనీకరణ వికిరణ పరిమాణాన్ని బయటి (environmentalపరిసరాల) radiocarbonరేడియో contributeకార్బన్ approximately0.01బీటా [[mSv]]/yearవిఘటనాల (1రూపంలో mrem/year)సుమారు toeachసంవత్సరానికి person's0.01 [[EquivalentmSv dose|dose]]ofసమకూరుస్తుంది. [[ionizing radiation]].<ref>{{cite book|title=Ionizing Radiation Exposure of the Population of the United States|author=NCRP Report No. 93|publisher=National Council on Radiation Protection and Measurements|year=1987}} ([http://lbl.gov/abc/wallchart/chapters/15/3.html excerpt] {{webarchive|url=https://web.archive.org/web/20070711052408/http://www.lbl.gov/abc/wallchart/chapters/15/3.html|date=2007-07-11}})</ref> Thisఇది isపొటాషియం small- compared40 toమరియు theరేడాన్ dosesనుండి fromఅందజేసే [[Isotopesపరిమాణం ofకన్నా potassium|potassium-40]] (0.39 mSv/year) and [[radon]] (variable)తక్కువ.
Carbonవైద్యరంగంలో కార్బన్-14 canరేడియోధార్మికత beగుర్తింపుకు used as a [[radioactive tracer]] in medicineఉపయోగిస్తారు. Inయూరియా theశ్వాస initialపరీక్ష variantయొక్క of the [[urea breathప్రారంభ test]]వైవిధ్యంలో, aహెలికోబా్కెర్ diagnosticపైలోరీ testనిర్ధారణ forపరీక్షలో ''[[Helicobacterకార్బన్ pylori]]'',- urea labeled with approximately {{convert|37|kBq|uCi|lk=on|abbr=on}} carbon-14 is fed to a patient (iఉపయోగిస్తారు.e.,37,000 decays per second). In the event of a ''H. pylori'' infection, the bacterial [[urease]] enzyme breaks down the urea into [[ammonia]] and radioactively-labeled [[carbon dioxide]], which can be detected by low-level counting of the patient's breath.<ref>{{cite web|url=http://interactive.snm.org/docs/pg_ch07_0403.pdf|title=Society of Nuclear Medicine Procedure Guideline for C-14 Urea Breath Test|date=2001-06-23|accessdate=2007-07-04|work=snm.org|format=PDF|archiveurl=https://web.archive.org/web/20070926152956/http://interactive.snm.org/docs/pg_ch07_0403.pdf|archivedate=2007-09-26|deadurl=yes|df=}}</ref> The <sup>14</sup>C urea breath test has been largely replaced by the <sup>13</sup>C urea breath test, which has no radiation issues.
