Editing Cathode-ray tube (section)

===Ionizing radiation===
CRTs can emit a small amount of [[X-ray]] radiation; this is a result of the electron beam's bombardment of the shadow mask/aperture grille and phosphors, which produces [[bremsstrahlung]] (braking radiation) as the high-energy electrons are decelerated. The amount of radiation escaping the front of the monitor is widely considered to be not harmful. The [[Food and Drug Administration]] regulations in {{CodeFedReg|21|1020|10}} are used to strictly limit, for instance, TV receivers to 0.5 [[Roentgen (unit)|milliroentgens]] per hour at a distance of {{convert|5|cm|0|abbr=on}} from any external surface; since 2007, most CRTs have emissions that fall well below this limit.<ref>{{cite web |url=http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=1020.10 |title=Subchapter J, Radiological Health (21CFR1020.10) |publisher=U.S. Food and Drug Administration |date=1 April 2006 |access-date=13 August 2007}}</ref> Note that the roentgen is an outdated unit and does not account for dose absorption. The conversion rate is about .877 roentgen per [[Roentgen equivalent man|rem]].<ref>{{Cite web |title=Rad Pro Calculator: Frequently Asked Questions (FAQ) |url=http://www.radprocalculator.com/FAQ.aspx#:~:text=Since%201%20Roentgen%20equals%200.877,00877%20Sieverts. |access-date=2022-03-06 |website=www.radprocalculator.com}}</ref> Assuming that the viewer absorbed the entire dose (which is unlikely), and that they watched TV for 2 hours a day, a .5 milliroentgen hourly dose would increase the viewers yearly dose by 320 [[millirem]]. For comparison, the average background radiation in the United States is 310 millirem a year. Negative effects of chronic radiation are not generally noticeable until doses over 20,000 millirem.<ref>{{Cite web |title=US Department of Energy, Dose Ranges Rem/Sievert Chart |url=https://www.nrc.gov/docs/ML1209/ML120970113.pdf}}</ref>

The density of the x-rays that would be generated by a CRT is low because the raster scan of a typical CRT distributes the energy of the electron beam across the entire screen. Voltages above 15,000 volts are enough to generate "soft" x-rays. However, since CRTs may stay on for several hours at a time, the amount of x-rays generated by the CRT may become significant, hence the importance of using materials to shield against x-rays, such as the thick leaded glass and barium-strontium glass used in CRTs.<ref name="auto35"/>

Concerns about x-rays emitted by CRTs began in 1967 when it was found that TV sets made by General Electric were emitting "X-radiation in excess of desirable levels". It was later found that TV sets from all manufacturers were also emitting radiation. This caused TV industry representatives to be brought before a U.S. congressional committee, which later proposed a federal radiation regulation bill, which became the 1968 Radiation Control for Health and Safety Act. It was recommended to TV set owners to always be at a distance of at least 6 feet from the screen of the TV set, and to avoid "prolonged exposure" at the sides, rear or underneath a TV set. It was discovered that most of the radiation was directed downwards. Owners were also told to not modify their set's internals to avoid exposure to radiation. Headlines about "radioactive" TV sets continued until the end of the 1960s. There once was a proposal by two New York congressmen that would have forced TV set manufacturers to "go into homes to test all of the nation's 15 million color sets and to install radiation devices in them". The FDA eventually began regulating radiation emissions from all electronic products in the US.<ref>{{cite web | last=Murray | first=Susan | title=When Televisions Were Radioactive | website=The Atlantic | date=2018-09-23 | url=https://www.theatlantic.com/technology/archive/2018/09/when-televisions-were-radioactive/570916/ | access-date=2020-12-11}}</ref>