Excessive x-rays in pre-1968 TVs

[jiHymas]

The master makes the comment that “Prior to 1968 or so some [TV] sets emitted excessive X-rays, but that problem has now been eliminated.” (http://www.straightdope.com/classics/a920724.html, repeated as http://www.straightdope.com/classics/a5_105.html).

What does “some” mean? What does “excessive” mean? How would an hour’s TV watching compare in exposure to, say, a dental x-ray?

[samclem]

When the TV x-ray problem first became a public concern in 1966, the Surgeon General recommended that viewers sit at least six feet from an operating receiver to reduce the quite low potential of biological damage.

Bolding is mine.

From http://www.fda.gov/cdrh/consumer/TVRad.html

So I doubt that it was significant, but this will get things started.

[samclem]

When the TV x-ray problem first became a public concern in 1966, the Surgeon General recommended that viewers sit at least six feet from an operating receiver to reduce the quite low potential of biological damage.

Bolding is mine.

From http://www.fda.gov/cdrh/consumer/TVRad.html

So I doubt that it was significant, but this will get things started.

[jiHymas]

http://www.cco.caltech.edu/~safety/trm.html#A4
**Caltech’s whole body dose limit for planned exposures is 500 mrem/year (5 mSv/yr). If a Caltech worker were to receive the maximum allowable planned dose each year for twenty years, the total dose received would be 10 rem (0.1 Sv). According to the BEIR V report, the worker’s chance of death from cancer would increase by approximately 0.4%. This is fairly small compared to the normal chance of death from cancer in the U. S. of about 20%.
**Note: for x-rays, 1 Rem = 1 Roentgen, ibid.

http://www.ccnr.org/radiation_standards.html**
With one more important piece of information, namely that medical X-ray is measured by the mR in air at skin entrance (rather than by tissue or bone marrow dose as used by the physicist), I will telescope some ten years of research into a few short conclusions:

For X-ray of arms or legs, and dental X-ray, it requires an accumulated dose of 4000 mR to increase the risk of non-lymphatic leukemia the same amount as one year of natural aging.

For chest X-ray, it requires an accumulated dose of 1670 mR at skin entrance to simulate one year’s natural aging for increasing non-lymphatic leukemia rate. **

The source provided by samclem (http://www.fda.gov/cdrh/consumer/TVRad.html) states that the current standard (mandatory in the US from June 1, 1971) was 0.5 milliRoentgen/hour; but it doesn’t state how far away from the set this is measured (important due to inverse-square law) or what the situation was prior to 1968.

But we’re on the right track.