Editing Sievert (section)

==History==
The sievert has its origin in the [[roentgen equivalent man|röntgen equivalent man]] (rem) which was derived from [[CGS units]]. The [[International Commission on Radiation Units and Measurements]] (ICRU) promoted a switch to coherent SI units in the 1970s,<ref>{{cite conference |last=Wyckoff |first=H. O. |title=Round table on SI units: ICRU Activities |conference=International Congress of the International Radiation Protection Association |date=April 1977 |url=http://www.irpa.net/irpa4/cdrom/VOL.2/P2_101.PDF |access-date=18 May 2012 |location=Paris, France }}</ref> and announced in 1976 that it planned to formulate a suitable unit for equivalent dose.<ref>{{cite journal |last1=Wyckoff |first1=H. O. |title=The New Special Names of SI Units in the Field of Ionizing Radiations |journal=British Journal of Radiology |date=May 1976 |volume=49 |pages=476–477 |url=http://bjr.birjournals.org/content/49/581/476.2.full.pdf |access-date=18 May 2012 |issn=1748-880X |pmid=949584 |last2=Allisy |first2=A. |last3=Lidén |first3=K. |issue=581 |doi=10.1259/0007-1285-49-581-476-b}}</ref> The ICRP pre-empted the ICRU by introducing the sievert in 1977.<ref name="ICRP26">{{cite journal |title=Recommendations of the ICRP |journal=Annals of the ICRP |year=1977 |volume=1 |series=ICRP publication 26 |issue=3 |url=http://www.icrp.org/publication.asp?id=ICRP%20Publication%2026 |access-date=17 May 2012 }}</ref>

The sievert was adopted by the [[International Committee for Weights and Measures]] (CIPM) in 1980, five years after adopting the gray. The CIPM then issued an explanation in 1984, recommending when the sievert should be used as opposed to the gray. That explanation was updated in 2002 to bring it closer to the ICRP's definition of equivalent dose, which had changed in 1990. Specifically, the ICRP had introduced equivalent dose, renamed the quality factor (Q) to radiation weighting factor (W<sub>R</sub>), and dropped another weighting factor "N" in 1990. In 2002, the CIPM similarly dropped the weighting factor "N" from their explanation but otherwise kept other old terminology and symbols. This explanation only appears in the appendix to the SI brochure and is not part of the definition of the sievert.<ref name="SI">{{SIbrochure}}</ref>