Dental X-rays -- More Modern Medical Woo-woo

[Rouser2]

Study links dental X-rays, low birth weight

FINDINGS FLY IN FACE OF WHAT WAS THOUGHT

By Lindsey Tanner

ASSOCIATED PRESS

CHICAGO - "Women who undergo dental X-rays while pregnant face an increased risk of having underweight babies, a study found...."
.
"The study, which appears in today's Journal of the American Medical Association, involved 4,500 women who gave birth while enrolled in a dental insurance plan in Washington state between 1993 and 2000."

http://www.kentucky.com/mld/heraldleader/news/nation/8537035.htm


Comment: Flys in the face of what was thought, eh? Low birth babies can cause mental retardation and death. Dental X-rays -- just as safe as the X-rays you get from a flight over the Rockies -- that's the standard spiel one gets from the Modern Medical Doctors of Dentistry. Fact is, X-rays can and do kill, and not just babies, modern medical woo-woo assurances to the contrary notwithstanding.

-- Rouser

[Wrath of the Swarm]

I would want to know if there are any confounding variables involved.

[garys_2k]

Originally posted by Wrath of the Swarm
I would want to know if there are any confounding variables involved.
Absolutely, yes.

Assuming these were at least middle class people with access to health care (from the dental insurance reference) I would hope a deeper look would be taken.

[DaveW]

And there are no other numbers in the article other than 4,500 women were involved (between 1993 and 2000). Hardly an in-depth report.

[Benguin]

Yes, surely women who have dental xrays will be experiencing pain, undergoing gas or anaesthetic and all sorts of other things.

And of course dentist-induced financial stress!

Have they managed to rule that out?

[Wrath of the Swarm]

Now, there are known effects of fetal exposure to ionizing radiation, especially at certain vulnerable periods (during some stages of brain development).

I can imagine that indirect exposure might somehow be able to affect fetal growth.

I have difficulty understanding how x-rays directed at the head could affect fetal development, particularly if the mother was wearing a leaded shield (as she should).

In short, this calls for more research.

[Badly Shaved Monkey]

Originally posted by Wrath of the Swarm

In short, this calls for more research.

Really, though, it calls for a close analysis of the original study not a newspaper report to look for those confounding variables before any conclusion can be drawn at all including the conclusion that any more research is warranted.

[pgwenthold]

Originally posted by garys_2k

Absolutely, yes.

Assuming these were at least middle class people with access to health care (from the dental insurance reference) I would hope a deeper look would be taken.

Perhaps the real correlation is between low-birth weight and cavities?

[Wrath of the Swarm]

Originally posted by Badly Shaved Monkey
Really, though, it calls for a close analysis of the original study not a newspaper report to look for those confounding variables before any conclusion can be drawn at all including the conclusion that any more research is warranted. That is "more research", BSM.

[Bjorn]

The study's lead author, Dr. Philippe Hujoel, a professor of dental public health services at the University of Washington, said more research is needed to determine if dental X-rays really are the culprit.

[Wrath of the Swarm]

Well, yeah. That's the standard response to any unusual finding - and with good reason, too.

More research is almost always called for. Even if it isn't we have to support our researchers somehow!

[pupdog]

All those women were enrolled in a dental plan--how many actually went to the dentist? How many had x-rays?

[Goshawk]

Found some more actual numbers in other articles.

http://www.omaha.com/index.php?u_np=0&u_pg=1642&u_sid=1079709
A total of 1,117 low-birth-weight babies, or those weighing less than 5 pounds, 8 ounces, were born to study participants. Women who had had dental X-rays during pregnancy faced about double the risk of having a low-birth-weight baby born prematurely and more than triple the risk of having a full-term underweight baby.

Only 21 women who had low-birth-weight babies had dental X-rays in the first trimester, when they might not have known they were pregnant.

http://news.bbc.co.uk/2/hi/health/3660235.stm
A low weight baby was defined as weighing less than 2.5 kg (5lb 8oz).

The researchers examined the records of women who received dental treatment between January 1993 and December 2000.

Among women who gave birth to underweight babies, 1.9% were exposed to a relatively high (at least 0.4 mGy) cumulative level of radiation from dental X-rays.

The same level of exposure was only half as common among women who gave birth to a normal weight baby.

Overall, women who were exposed to at least 0.4 mGy of radiation from dental X-rays seemed to be more than three-and-a-half times more likely to give birth to an underweight full-term baby than women who had no dental X-rays at all during pregnancy.

[garys_2k]

Originally posted by pgwenthold


Perhaps the real correlation is between low-birth weight and cavities?
Good point! Perhaps those who eat more sugary junk tend toward more visits to the dentist and lower weight babies.

[epepke]

Originally posted by Rouser2
Study links dental X-rays, low birth weight

:con2: Ever since I was a kid, I've always asked for a lead apron when getting dental X-rays. Dentists are required by law to provide them. I ran into one or two dentists back in the 1970s who thought it was a funny request, but none since then.

[Wrath of the Swarm]

Of course, your head doesn't get an apron.

[epepke]

Originally posted by Wrath of the Swarm
Of course, your head doesn't get an apron.

Unless you count Zeus, people don't generally get born from the head. Also, heads, like hands and feet, can generally take a lot more X-ray exposure than the rest of the body. Save the nads and the lungs and the rest or the internal organs.

However, in the past there has certainly been danger from dental X-rays. They used to have assistants hold the plates in the patients' mouths. This caused the assistants to have problems from repeated exposure. It's nothing like the Japanese who painted radium on watch faces and licked their brushes, but it was still pretty bad.

Nowadays, the emulsions are super-sensitive, and the levels of X-rays are very low. It seems to me pretty unlikely that there should be any problem, but always ask for the lead apron just in case.

[Wrath of the Swarm]

The eyes have relatively little protection, and they are extremely sensitive to radiation.

The brain, while shielded by bone, is also something you don't want radiated more than necessary.

Honestly, if you have no reason to believe there are holes developing in your teeth, there's really no reason to have dental x-rays. I've heard the ADA recommends yearly scans, but not every six months.

If you refuse them, and the dentist makes a point of it, he was probably trying to pad the bill he submits to insurance.

(As you may have gathered, I don't like dentists very much. There are many honest ones, but there are many dishonest as well, and few people question them about procedures or get second opinions.)

[Ranb]

Obviously premature findings for an article like this.

The findings are probably inaccurate due to the portion of the population sampled. This reminds me of a study conducted by a doctor and an east coast newspaper concerning cancer rates of Sailors discharged from service in the ballistic missile submarine force. That they only included those Sailors who were discharged from the service, their results were inaccurate. They forgot (or maybe not) that Sailors are many times medically discharged if they have cancer. If they had included the active duty population in their sample group, then they would have found the cancer rate was about the same as the rest of the USA.

Ranb

[epepke]

Originally posted by Wrath of the Swarm
The eyes have relatively little protection, and they are extremely sensitive to radiation.

I don't think I've ever met anybody with eye cancer.

Honestly, if you have no reason to believe there are holes developing in your teeth, there's really no reason to have dental x-rays. I've heard the ADA recommends yearly scans, but not every six months.

I don't think I've ever had a dentist recomment X-rays more than once a year.

(As you may have gathered, I don't like dentists very much.

I don't think I've ever met anyone who particularly enjoyed dentists. It doesn't seem to be in the job description. When I was a kid, I kinda liked my dentist, because he let me mix the amalgum.

[Badly Shaved Monkey]

Originally posted by Wrath of the Swarm
That is "more research", BSM.

OK, I thought you meant more studies should be done, which would be a be premature. It's not clear from that press snippet why the hypothesis was even generated. One presumes that the JAMA paper explains it.

[Agammamon]

Hold on a minute here!

A pregnancy last nine freaking months, how many dental x-rays do you get in nine freaking months? One set, maybe. Quite a few don't get checkups at all and for others the checkup window will be before or after the pregnancy.

So if one set of x-rays has such a pronounced effect that it shows up even in such a small subset of the population, how come the roughly 20 something other xrays you'll get before you get pregnant don't do anything to the other women?

Then there's the question of how an exposure to the JAW affects a fetus 3 feet outside the exposure area and under a lead blanket.

If a single exposure is enough to cause low birth weight then there should be an enormous incidence of low birth weight and birth defects/mutations in general, because it would have to have a significant effect on men as well as unpregnant women.

[Wrath of the Swarm]

Originally posted by epepke
I don't think I've ever met anybody with eye cancer. Why do people make the assumption that the only consequence of radiation exposure is cancer?

With the eye, it also damages the retina (which cannot repair itself, and slowly loses resolution as parts of it die) and clouds the lens, hastening the onset of cataracts.

[Dancing David]

Originally posted by pgwenthold


Perhaps the real correlation is between low-birth weight and cavities?

I was thinking a similar scenario:

A person becomes pregnant who has no or little health insurance. Because they are pregnant they qualify for Medical Assistance under the Medicaid program for thier state.

They have poor health, which is associated with poverty, and they have extremely poor dental health associated with poverty.

They get a dental exam because they have tooth pain. The low birth weight is associated with more than the dental exam, it is associated with poverty.

The questions is this, what are the proportions of women in the study who didn't get a dental exam during pregnancy. And if we match the demographics for
a. poverty
b. prior health insurance
c. age of mother

Does the effect still exist?

[ca3799]

There is a correlation between gum disease and premature birth (thus low birth weight babies). There are also some dental problems associated with or aggravated by pregnancy such as bleeding gums.

Perhaps the mothers were being treated for gum disease.

[pgwenthold]

Originally posted by ca3799
There is a correlation between gum disease and premature birth (thus low birth weight babies). There are also some dental problems associated with or aggravated by pregnancy such as bleeding gums.

Perhaps the mothers were being treated for gum disease.

People with gum disease/bleeding gums will be more likely to go to the dentist. People who go to the dentist are far more likely to have dental x-rays than those who don't. Therefore, if gum disease is correlated with low-birth weight babies, we should not be surprised to see the correlation between dental x-rays and low birth weight.

[Wrath of the Swarm]

Here's a quick thought: if gum disease is correlated less strongly with low birth weights than x-rays were in this study, that is moderate evidence that our explanation is actually wrong and that there's another factor involved.

However, if gum disease is correlated more strongly than low birth weights, then given our current information, we have no reason to presume that dental x-rays in themselves have any effect on birth weight.

So: how strongly have gum diseases been linked with low birth weight?

[ca3799]

I didn't look very much, but here is one statement that refers to a study and has some numbers:

"New research suggests a link between gum disease in pregnant women and premature low birth weight babies. Conducted by researchers at the University of North Carolina School of Dentistry, this recent study suggests that every year as many as 45,500 premature births may be linked to gum disease. That's 18% of the 250,000 premature babies born every year, which is more than those attributed to smoking and alcohol use combined.

What the research shows:
The bacteria P. gingivalis is known to be the primary cause of gum infection. This organism can travel via your blood stream to sites far from the mouth, even to the uterus. P. gingivalis carries substances that can trigger the production of chemicals called "prostaglandins" in the reproductive tract. These prostaglandins are suspected to induce premature labor, resulting in low birth weight babies."


I think there is some extrapolation in that article as the study only involved about 124 participants.

[TillEulenspiegel]

OH fer cryin out loud , my closest friend is a dentist. The exposure to dental X-Rays as a source of genetic effects is such BS. The normal picture taking of a dental patient, called a "Bitewing " is about .5 MRems That ain't dik. Most dentists use multiple lead aprons on their patients who are pregnant.
It is probably more relevant to the basic lack of comprehensive medical care the X-Rays or the easter bunny.

I mean I realize that this is the 12th century.................

[Dancing David]

Originally posted by TillEulenspiegel
OH fer cryin out loud , my closest friend is a dentist. The exposure to dental X-Rays as a source of genetic effects is such BS. The normal picture taking of a dental patient, called a "Bitewing " is about .5 MRems That ain't dik. Most dentists use multiple lead aprons on their patients who are pregnant.
It is probably more relevant to the basic lack of comprehensive medical care the X-Rays or the easter bunny.

I mean I realize that this is the 12th century.................

;) You have merely bought the message that our communist government wants you to buy. Dental exams are part of mind control!
:)

[Goshawk]

Originally posted by Wrath of the Swarm
Of course, your head doesn't get an apron....

The eyes have relatively little protection, and they are extremely sensitive to radiation...

Why do people make the assumption that the only consequence of radiation exposure is cancer?

With the eye, it also damages the retina (which cannot repair itself, and slowly loses resolution as parts of it die) and clouds the lens, hastening the onset of cataracts.
Er...they actually use X-rays as a diagnostic tool for eyes. With no apparent ill effects.

There is no evidence that normal, routine, occasional low-dosage x-rays as used by medical professionals cause cataracts. There IS evidence that excessive exposure to x-rays can cause cataracts, excessive exposure such as that experienced by x-ray technicians, who are exposed to x-rays all day every day. Which is why they have all kinds of safety protocols to make sure they aren't exposed to excessive x-rays on the job.

Your head doesn't need an apron in the dentist's chair.

Sorry.

http://hps.org/publicinformation/ate/q1520.html
The radiation dose that leads to the production of cataracts in humans is in excess of 1 gray (100 rad). It is highly unlikely that the procedure performed on you resulted in a dose to the eye that was anywhere near this level. Without knowing any more than what you have stated, my guess would be that the radiologist rejected the x ray of the eye because it did not have the capability of providing the information required by the eye surgeon rather than concern over radiation dose and any possibility of producing a cataract.


http://www.healthatoz.com/healthatoz/Atoz/ency/x_rays_of_the_orbit.html
Orbital x rays are studies of the area and structures containing the eye. The orbit is the circle of thin bones that houses and protects the eye, even extending behind the eye and nearly wrapping around it. The orbit includes the eyebrow, the bridge of the nose and the cheekbone. X rays are a form of radiation (like light) that can penetrate body tissues.

Orbital x ray, or orbital radiography, is often used to detect problems resulting from injury or trauma to the eye. The exam may also detect changes to the structure of the eye, which may indicate various diseases. An ophthalmologist may also order an orbital x ray if there is concern that foreign bodies may be present in the eye that cannot be detected with an instrument called an ophthalmoscope.

Pregnant women and women who could possibly be pregnant should only receive orbital x rays when absolutely necessary. If the patient is in severe pain due to injury or trauma, a painkiller may be given to help ease discomfort during positioning of the head throughout the exam. No other precautions are necessary for orbital x rays.
http://www.cancerbacup.org.uk/Cancertype/Eye/Melanomaoftheeye
Tests

A number of tests may be done to diagnose ocular melanoma, including:

< snip >

Fluorescein angiography. A dye (injected into a vein in your arm) flows through the blood stream to the eye, where it highlights any growths or damage. X-rays are taken and the highlighted areas show up clearly on the film.
http://www.szp.swets.nl/szp/journals/op071061.htm
Exposure to diagnostic x-rays and incident age-related eye disease

Barbara E.K. Klein 1 , Ronald Klein 1 and Scot E. Moss 1
1 University of Wisconsin Medical School, Department of Ophthalmology and Visual Sciences, Madison, USA

OBJECTIVE. The purpose of this study was to evaluate whether a self-reported history of computed tomography or other x-rays of the head were associated with the incidence of age-related cataracts and maculopathy five years later.

METHOD. A 5-year longitudinal follow-up of the Beaver Dam Eye Study cohort (n=3,684, 43-86 years at baseline).

RESULTS. There was no evidence of a relationship between the x-ray exposures and the incidence of nuclear or cortical cataracts, or early maculopathy. There was a significant relationship to the incidence of posterior subcapsular cataract after adjusting for age only.

CONCLUSIONS. Adult patients in whom medical conditions warrant diagnostic x-rays of the head appear to be at little or no increased risk of age-related cataract or maculopathy. However, research efforts with more precise measures of x-ray exposure, longer follow-up, and further attempts to define uncontrolled confounders are warranted.

[Mahatma Kane Jeeves]

Originally posted by Rouser2
Low birth babies can cause mental retardation and death.
Holy Pickles! I had no idea "low birth babies" were so dangerous. I'll be sure to steer clear of them from now on. Thanks for the tip!

[Goshawk]

The possible correlation that popped out at me from the study would be, "the kind of woman, health-wise, who has dental problems that are so severe that they require x-rays is perhaps also the kind of woman, health-wise, who has low birth weight babies". There's a certain socioeconomic profile that tends to go along with "bad teeth"--poor diet mainly. And poor diet also causes low birth weight babies.

So it would be just a statistical skew, not a cause-and-effect thing.

[Wrath of the Swarm]

Originally posted by Goshawk

Er...they actually use X-rays as a diagnostic tool for eyes. With no apparent ill effects. Not quite true. One or two scans don't produce readily noticable effects. People who have such scans repeatedly often begin having problems with their eyes - and the damage doesn't not exist just because it's not obvious.

I believe there was some work on making shields for the eyes a while ago... not sure how that turned out.

[Goshawk]

First, I need to correct something. Researching fluorescein angiography, I discovered that x-rays are not in fact used in the procedure, so the link (http://www.cancerbacup.org.uk/Cancertype/Eye/Melanomaoftheeye) I quoted was, surprisingly, 100% wrong. I have sent their webmaster an e-mail concerning this. One opthamalogy website noted, however, that this was a "common misconception", that x-rays are used in the procedure.

One or two scans don't produce readily noticable effects. People who have such scans repeatedly often begin having problems with their eyes
Right. That's exactly the point I just got done making. :rolleyes:

Excessive (meaning "repeated") exposure can cause cataracts. Right. But an annual dental x-ray doesn't count as "excessive" or "repeated" exposure.

If you have a cite that shows that routine dental x-rays, accumulated over many years, cause cataracts, then by all means, trot it out.

And we're not talking about people who are experiencing repeated exposure to x-rays. We're talking about people who are experiencing one-time-only, and limited, exposure to x-rays, ("one or two scans"), such as people who are going in for x-rays of an orbital fracture, or an annual dental x-ray.

And if you have a cite that shows that repeated orbital x-rays, causes people to "have trouble with their eyes", let's see that, too.

Dentists have been using x-rays for over 100 years.

http://www.dentistry.vcu.edu/departments/opath/newslets/nl196.html
ORAL PATHOLOGY DIAGNOSTIC SERVICE
January 1996

DENTAL RADIOLOGY: THE QUESTIONS
THAT PATIENTS ASK

X-rays were discovered 100 years ago and within weeks the first dental radiographs were produced by Dr. Otto Walkhoff. The equipment was crude, the exposure time long (approximately 25 minutes), and the diagnostic quality of the early radiographs was poor, but the importance of this diagnostic tool to dentistry was readily apparent.
Early photos depicting the procedures.
http://www.xray.hmc.psu.edu/rci/ss6/ss6_1.html

Now, they've been doing dental x-rays for 100 years--don't you think someone would have noticed that it was damaging people's eyes? It sure didn't take them long to figure out that the dental x-ray radiation was harmful to hands, arms, etc. Many of the early dental x-ray pioneers died themselves of radiation injuries on their hands and arms, as outlined in the PSU link.

Especially since the 1960s, when the scientific community started to realize just how dangerous radiation was (back in the 1930s, 40s, and 50s, people used to think it was "cool" and "fun", you know), and scientists started looking at radiation and re-evaluating it, why wouldn't anyone have noticed, "Hey, if you go in for x-rays of your teeth, you'll go blind"?

With more and more people going to the dentist, and more and more people having dental x-rays, every year during the 20th century, why is there no corresponding rise in the incidence of cataracts? I mean, everybody goes to the dentist and gets x-rays, ever since at least about, say, the 1930s. Why aren't there cataracts cases everywhere?

I can't find anything on Google linking dental x-rays and cataracts.

I can, however, find information linking inhaled corticosteroids and cataracts. Why is there no corresponding information for dental x-rays?

http://content.nejm.org/cgi/content/short/337/1/8

A list of risk factors for cataracts says nothing about dental x-rays.

http://www.ucdmc.ucdavis.edu/ucdhs/health/a-z/26Cataracts/doc26risk.html

In that list, "age" is the #1 risk factor for cataracts. It says:
About 40% of people between 55 and 64 years old had some opaque areas in their lenses, and 5% had fully-developed cataracts.

About 70% of people between 65 and 74 years old had opaque areas, and 18% had cataracts.

More than 90% of people between 75 and 84 had opaque areas, and almost half had cataracts.
Now, let's assume that the 5% of those 55-year-olds who had fully developed cataracts had one dental x-ray a year for, say, 50 years. How much x-ray radiation would that have subjected them to?

Here is a physicist addressing the issue of how much radiation is in a dental x-ray.

http://www.physics.isu.edu/radinf/dental.htm
...Advances in x-ray equipment, especially film technology, allow your dentist to get a good x-ray image using much less radiation than was previously required. A typical dental x-ray image exposes you to only about 2 or 3 mrem. The National Council on Radiation Protection (NCRP) says that the average resident of the U.S. receives about 360 mrem every year from background sources. This comes from outer space, radioactive materials in the earth, and small amounts of radioactive material in most foods we consume.

Some typical sources that may expose you to radiation also include smoke detectors (less than 1 mrem per year), living in a brick house instead of a wood one (about 10 mrem per year due to radioactive materials in the masonry), cooking with natural gas (about 10 mrem per year from radon gas in the natural gas supply), reading a book for 3 hours per day (about 1 mrem per year due to small amounts of radioactive materials in the wood used to make the paper), and even from flying in an airplane (about 5 mrem for one cross-country flight because of the increased altitude.) In fact, you receive about 2 mrem per year from sleeping next to someone! This is because all of us have very small amounts of naturally occurring radioactive materials in our bodies. Now, according to this site, (http://hps.org/publicinformation/ate/q1173.html) dosages in the past may have been as much as 10 times the amount as currently. So, 30 mrem a year for 50 years equals 1500 mrem, still only as much as you'd get from background sources in the world for 5 years.

[Wrath of the Swarm]

I'm not suggesting that people will suddenly go blind.

But the eyes are particularly sensitive to x-rays - this is a factor with people who undergo repeated CAT scans, for example. Also, the effects tend to be delayed. If a person's eyesight begins deteroriating faster than it would have otherwise, but twenty years after exposure, it's hard to link it to exposure.

Dental x-rays are a lot less potent, so any damage is minor, but it would be nice if it were eliminated alltogether. It's probably not even worth thinking about normally, although not when performing a price/benefit summation.

Anyway, we seem to have concluded that, although there may indeed be a correlation between x-rays and low birth weight babies, there's little reason to think there's causation.

[Goshawk]

Originally posted by Wrath of the Swarm
But the eyes are particularly sensitive to x-rays - this is a factor with people who undergo repeated CAT scans, for example.
I'll grant you the possible CAT scan/cataracts connection, as evidenced by the Beaver Dam study.

http://www.ajph.org/cgi/content/abstract/83/4/588
Diagnostic x-ray exposure and lens opacities: the Beaver Dam Eye Study
BE Klein, R Klein, KL Linton and T Franke
Department of Ophthalmology, University of Wisconsin, Madison 53792.

The Beaver Dam Eye Study is a population-based study of common age-related eye diseases. During the standardized medical history, the 4926 subjects were asked whether they had ever had a chest x-ray, computerized axial tomography (CAT) scan of the head, other x-rays of the head, x-rays of the abdomen, or other diagnostic x-rays. The eye examination included photographs of the lenses of the eyes, which were subsequently graded according to protocol. Nuclear sclerosis and posterior subcapsular opacity were significantly associated with CAT scans. If these relationships are causal, it would highlight the importance of minimizing such exposure to the lens of the eye. However.

According to this, (http://www.nsc.org/issues/rad/exposure.htm) a CAT scan gives you 110 mrems, and dental x-rays are only 1 mrem. So a CAT scan would be the equivalent of 110 dental x-rays (let me repeat that: one hundred and ten dental x-rays), and yes, repeated CAT scans would expose your eyes to some serious radiation, comparatively speaking.

But.

But--we're not talking about CAT scans here.

We're talking about dental x-rays, which are much less mrems to begin with. You'd need to have 110 (again, let me repeat that: one hundred and ten) dental x-rays to equal one CAT scan.

Also, a CAT scan applies the whole x-ray dosage to your entire head as it moves down your body--your entire eyeball and the sockets, everything. A dental x-ray, however, is pointed like a gun directly at your jaw, away from your eyes. There is a certain amount of leakage and scatter, (http://hps.org/publicinformation/ate/q889.html) but for the most part the x-rays are focused right at your teeth. Here's (http://www.hc-sc.gc.ca/hecs-sesc/ccrpb/publication/99ehd177/chapter5.htm)how much leakage is allowed in Canada, for example:
X-ray tube shielding - The X-ray tube must be enclosed within a shielded housing. The housing must be constructed so that the leakage radiation, measured at a distance of one metre in any direction from the focal spot of the X-ray tube, does not exceed 0.87 mGy (100 mR) in one hour for any specified rating of the tube. The tube can only leak 100 mrems every hour. And since a dental x-ray takes, like, what, one second, your eyeballs aren't at risk from that brief "blip" of leakage. You'd have to sit there in the chair with the machine running for an hour in order to get 100 mrems of x-ray leakage--the amount that a CAT scan gives--zapping into your eyes.

And it's not fair--not scientific--to say, "Well, if CAT scans can give you cataracts, then dental x-rays can give you cataracts, too. After all, they're both radiation, and they're both close to your eyes."

It simply doesn't follow. There's a huge difference between 110 mrems and 1 mrem, and between having the x-rays aimed directly at your eyes, and having the x-rays being carefully shielded and aimed away from your eyes.

If dental x-rays could give you cataracts, why are only 5% of those 55-year-olds showing cataracts? If the effect were that far-reaching and well-established, the number ought to be closer to 80-90%, because "everybody" goes to the dentist and has x-rays, especially Baby Boomers, who comprise that demographic. So "everybody" (i.e. all the Boomers) ought to be coming down with cataracts, too, having had annual, and sometimes semi-annual dental x-rays ever since they were kids, for the last 40 years.

And they're not.

You're welcome to speculate all you like that dental x-rays might cause cataracts, but there's not a shred of scientific evidence for it.

[Wrath of the Swarm]

The intensity of the x-rays doesn't matter so much as their energy. The x-rays will damage eye tissue. Whether that damage is extensive enough to notice depends on how much exposure to such x-rays takes place.

[Goshawk]

Originally posted by Wrath of the Swarm
The intensity of the x-rays doesn't matter so much as their energy.

If you are using the words "intensity" and "energy" in a physics context, then this statement makes no sense, as all dental x-rays are, by the physics definition, "low-energy" and "low intensity".

http://ehs.unlv.edu/newsletter08.html
Dental x-ray machines make pictures of the internals of our teeth. They are low energy and low dose rate machines where the distance from the source to film is small and the resulting picture is small.

Medical diagnostic x-ray machines may be used to evaluate our internal bone structures or other structures in our bodies. They are typically higher in energy than dental machines because they have to penetrate a larger depth of the body (and bigger bones) than dental x-rays.
http://www.ecomass.com/xray.html
Dental X-rays are exposed onto small plastic-encased X-ray film packages commonly known as bitewings. In the package, behind the film, is a thin lead foil shield that prevents the low intensity X-rays from imaging teeth on the opposite side of the mouth.
http://encarta.msn.com/media_461554983_761579196_-1_1/Uses_of_X_Rays.html
While diagnostic dental and medical X rays are low-intensity beams, high-intensity X rays, capable of destroying tissue, are used in the treatment of tumors.
There would appear to be no such thing as variability as to "energy" and "intensity" when it comes to dental x-rays, so your statement that "their intensity doesn't matter, it's their energy that counts", is meaningless.

The x-rays will damage eye tissue. Whether that damage is extensive enough to notice depends on how much exposure to such x-rays takes place.
So, your position is that dental x-rays do damage the eyes--but that the damage is so miniscule that it's not noticeable?
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Huh??

I mean, I beg your pardon, but if the "damage" isn't even noticeable, then so what?

Cataracts that aren't "noticeable"? Cataracts that the opthamologist somehow can't detect?

We're talking "hypochondria" here.

Or paranoia, a la, "I know those rays are beaming into my head and damaging my eyes!" :rolleyes:



Also, I found this, on exposure times.
http://www.xray2000.f9.co.uk/Site3/history/history.htm
The modern diagnostic X-ray equipment uses a rotating anode tube which may have a power rating of fifty kilowatts or more, but the exposure times required are only a small fraction of a second. This may be contrasted with the long exposures, sometimes half an hour or more, required in the early months of radiography.
A fraction of a second's exposure to the tiny amount of low-energy, low-intensity leakage generated by a low-energy, low-intensity x-ray device--even if that fraction of a second's exposure is accumulated over a lifetime, thus adding up to, say, a total of a few seconds' exposure over a lifetime--is not going to cause cataracts, no matter how much you may want to believe it, sorry.

[Wrath of the Swarm]

They're low-energy only in a relative sense. They're still highly energetic ionizing radiation - I doubt their effects on the eyes are particularly dependent on their wavelengths.

Just like the photoelectric effect, high-energy photons will do damage to what they hit, regardless of whether they're part of an intense burst or a dim exposure. The total number of photons will determine the total damage, of course, but individual "units" of damage will occur with each and every photon.

I'm sure the effect is quite small; nevertheless, it's still there.

[Badly Shaved Monkey]

Originally posted by Wrath of the Swarm
They're low-energy only in a relative sense. They're still highly energetic ionizing radiation - I doubt their effects on the eyes are particularly dependent on their wavelengths.

Just like the photoelectric effect, high-energy photons will do damage to what they hit, regardless of whether they're part of an intense burst or a dim exposure. The total number of photons will determine the total damage, of course, but individual "units" of damage will occur with each and every photon.

I'm sure the effect is quite small; nevertheless, it's still there.

I've lost track of this now. Is it your opinion that the hypothesis that dental X-rays causes fetal problems is reasonable i.e. they cause a lot of damage, or merely that dental radiography must in principle cause some radiation damage outside the beam focus though it will be vanishingly small?

[Wrath of the Swarm]

The second statement. I would be quite surprised if dental x-rays were directly linked with fetal development problems.

[Badly Shaved Monkey]

Originally posted by Wrath of the Swarm
The second statement. I would be quite surprised if dental x-rays were directly linked with fetal development problems.

Fair enough.

[Dancing David]

The energy of the photons would be dependant upon thier frequency. I would asume that you can really charge up the emitter so that it creates x-rays that are close to gamma radiation and are very dangerous.

So yes, in one way WotS is correct in that X-rays are very high in energy compared to microwaves, in that the energy carried by a single photon is very high.

So no WotS is inexact in saying that there is not variability in the energy level of individual photons of 'x-rays' there are those with longer wavelenths and those with higher frequencies, and the higher the frequecy ones can contain much more energy.

What is the relationship bewteen dose amount and frequency and potential damage I don't know. I would asume that the rate of damage is dependant upon the frequency of the photon and that the more there are the more damage is likely.

[Wrath of the Swarm]

As far as I can tell, there's no practical difference between the damage caused by high-energy x-rays and low-energy x-rays when we're talking about biological systems. The energy contained in one photon of either type is far more than is necessary to ionize molecules. There may be minor penetration and absorption differences, but I don't think there are many.

[Goshawk]

As far as I can tell, there's no practical difference between the damage caused by high-energy x-rays and low-energy x-rays when we're talking about biological systems.
You're probably right, but...since there's no evidence that dental x-rays, whether of high-energy or low-energy, are causing eye damage, the point seems moot.

I doubt their effects on the eyes are particularly dependent on their wavelengths.
Actually, a standard x-ray tube gives out a spectrum of frequencies, so in that respect you're right--wavelength has nothing to do with it.

http://www.exploration.vanderbilt.edu/news/news_fel_monox_nsv.htm
The standard X-ray tube used in hospitals produces a beam that contains a broad spectrum of frequencies. It generates "soft" X-rays that barely penetrate the skin at the low end of the spectrum. At the high end, it produces "hard" X-rays that ricochet off bone and tissue, creating a fog that obscures subtle features in X-ray images

Except that...it doesn't matter what wavelength they are--there's no scientific evidence that shows that dental x-rays cause eye damage. There isn't even any anecdotal correlation between "I had these dental x-rays" and "Now I have cataracts". Nobody anywhere is reporting this "phenomenon", this non-event. You seem to be the only one worried about it. Even the "transmission towers cause cancer" people, and the "cell phones cause tumors" people, and the "fluoridated water causes everything" people, and the "mercury amalgam fillings cause everything else" people have more Google hits, more websites, more articles out there.

But there's a deafening silence on the subject of "dental x-rays cause eye damage". Apparently you are a quorum of one.

I'm sure the effect is quite small; nevertheless, it's still there.

Again, if the effect is "quite small", so small in fact as to be invisible to everybody else in the whole wide world, what difference does it make?

No matter how hard you wanna believe that the "rays" are beaming into your head and damaging your eyes: there is no evidence that it's happening. Nobody is reporting any symptoms, nobody is doing research to find out why dental patients are reporting vision problems. There are no vision problems associated with dental x-rays, and therefore your insistence that "there must be some damage" is beginning to qualify you for a tinfoil hat. ;) If "there must be some damage", but nobody can tell, what difference does it make?

[Wrath of the Swarm]

While I'm as much a fan for evidence as anyone, I don't think you're relying on it properly.

We can use logic, applied to known facts, to produce meaningful statements about the world. We should keep in mind that these conclusions are only preliminary, and that we might be missing information that's vitally important, but we can still draw them.

Given certain facts about the effects of x-rays, we can reach certain conclusions about the total effect of dental x-rays on the eyes. We don't need direct evidence of these effects in the case of dental x-rays, as we have plenty of evidence dealing with x-rays in general.

[Goshawk]

We don't need direct evidence of these effects in the case of dental x-rays, as we have plenty of evidence dealing with x-rays in general.
Errr...

Excuse me? [jaw drops in amazement]

"WE. DON'T. NEED. DIRECT. EVIDENCE"???

WTF??

Do you realize what you're saying here?

You're saying exactly the same thing as...

"We don't need direct evidence of these effects in the case of fluoridation, as we have plenty of evidence dealing with the toxic effects of fluoride in general."

"We don't need direct evidence of these effects in the case of power transmission lines and cell phones, as we have plenty of evidence dealing with electromagnetism in general."

"We don't need direct evidence of these effects in the case of mercury amalgam in fillings, as we have plenty of evidence dealing with the toxicity of mercury in general."

Do you listen to yourself? You just said that we don't need evidence in order to "know" that something is there. Did you realize that that's what you just said?

Do you realize where you are? Perhaps you have become confused and you thought you were on TimeBomb2000, or Godlike, where they welcome paranoia coupled with a complete lack of evidence?

Geeeeez. :rolleyes:

You are hereby awarded a One-Size-Fits-All tinfoil hat.

Enjoy.

[Wrath of the Swarm]

I really don't think any of those examples are appropriate.

In the case of x-rays, intensity doesn't affect the damage done, just the extensiveness of the damage. The only significant difference between CAT scans and dental x-rays is their intensity and duration...

So we can reasonably conclude that dental x-rays also contribute to eye damage. Whether that contribution is even detectable is another question.

What's with the giant chip on your shoulder? I don't see why you should accuse me of being a woo. My position is quite reasonable.

[CyCrow]

Unlike the hypothetical cancer risk from low doses of ionising radiation, radiation induced cataracts are considered a determinisic effect. Below a certain threshold (1-2 Gy) which is NOT a low dose, and many orders of magnitude above a dental X-Ray, no cataracts are observed. With higher dose, all subjects get cataracts.

And now a little rant about the Linear-No-Threshold Hypothesis... It has never been proven that low-dose, low-dose-rate radiation causes cancer. In fact, the scientific evidence suggest the opposite effect. LNT is political, not scientific. I suggest reading http://www.21stcenturysciencetech.com/articles/nuclear.html for a "Politically Incorrect" view of radiation protection policy. Don't take it at face value, check the science. BL Cohen's radon study (inverse correlation with radon and lung cancer) and the Nuclear Shipyard Workers Study (higher dose groups have less cancer) are a couple of examples.

// CyCrow

[Goshawk]

Your position is quite reasonable--for a woo who wants to believe something that has no physical evidence to support it. There are many people out there who believe in fairies, with an equal amount of evidence to support that.

No, wait, I'm wrong: there are people out there who say they have actually seen fairies, while there is nobody out there--at all--who says he has actually seen cataract damage from dental x-rays. So, thus, all those believers in fairies are actually one up on you, having at least a semblance of some eyewitness testimony in their corner. :rolleyes:
The only significant difference between CAT scans and dental x-rays is their intensity and duration...
Right. :rolleyes: "The only difference between a four-alarm fire and striking a match is intensity and duration..."

"The only difference between a 100,000 volt streak of lightning and getting a shock from a household outlet is intensity and duration..."

But I'm going to stop now.
This is just stupid.
So we can reasonably conclude that dental x-rays also contribute to eye damage.

Nope, we cannot reasonably conclude this. But it doesn't matter, 'cause I'm outta here. The jig's up, game's over, go play with someone else.

Your position ("dental x-rays cause cataracts") is so far out in left field, being completely non-existent on the Web, whereas, as I mentioned, there is hardly a woowoo theory, no matter how strange, that doesn't have at least one page of Google hits for it, that I have finally--belatedly--twigged to the fact that I have unfortunately let you know where my goat is tied, that you suddenly realized you could get lots of attention from me for championing this truly bizarre notion. But you've overplayed your hand here, and suddenly I "get it", and so I am not going to feed you any more.

Bye.

[Wrath of the Swarm]

The statements about matches and four-alarm-fires simply isn't true.

A better analogy would be putting out one cigarette on someone's skin versus putting out ten cigarettes on randomly chosen spots on someone's skin. Damage is done either way, although the same is more extensive in the second case.

The damage that you accept occurs during CAT scans happens one photon at a time. Why do you find it so difficult to accept that lower-intensity exposures of photons at similar energies cause similar, if lesser, harm?

[Wrath of the Swarm]

Originally posted by CyCrow
Unlike the hypothetical cancer risk from low doses of ionising radiation, radiation induced cataracts are considered a determinisic effect. Below a certain threshold (1-2 Gy) which is NOT a low dose, and many orders of magnitude above a dental X-Ray, no cataracts are observed. With higher dose, all subjects get cataracts. The question is not whether someone develops cataracts soon after exposure. The question is whether those low doses cause damage to the eyes, and the answer is yes.

Whether that damage is worth worrying about is another matter.

I've heard that claim before, and it's a very interesting one, but it's as political as the opposite claim. I don't think either position really has enough evidence to support itself for the moment.

[CyCrow]

Remember that in biological organisms, damage does not equal harm. All organisms suffer continual damage, and are continually repaired. For example, exercise causes "damage" to muscle tissues, but also stimulates muscle growth, thus improving fitness. So as long as you do not overstress the bodys repair mechanisms, no harm is caused. It's the dose that makes the poison.

// CyCrow

(edited for clarity for non-C++ programmers, "!=" means not equal)

[Wrath of the Swarm]

Yes, but there are some kinds of damage that can't be repaired easily, if at all.

Radiation damage to the retina, for example, doesn't heal. Lost cells are gone for good, which is one of the reasons why vision worsens with age.

If the damage that results in cataracts could be repaired, I think they'd heal over time, which they don't AFAIK.

In any case, I know that the eyes are considered much more vulnerable to radiation damage than, say, the hand. We're not discussing major health risks here, just pointing out that the upper part of the head is not shielded during dental x-rays.

[Marian]

Originally posted by Wrath of the Swarm
I'm not suggesting that people will suddenly go blind.

But the eyes are particularly sensitive to x-rays - this is a factor with people who undergo repeated CAT scans, for example. Also, the effects tend to be delayed. If a person's eyesight begins deteroriating faster than it would have otherwise, but twenty years after exposure, it's hard to link it to exposure.



I have had numerous CAT scans. I'd say over 20 in the last 5 years, easily. Probably more.

As far as problems with the eyes...well...why do people undergo numerous CT scans? Well, in my case it's due to increased CSF pressure in the brain (they're making sure the pressure isn't localized prior to a LP, as it would cause a gravity well, which is bad as it kills you, and they're making sure that I don't have an intercranial bleed before giving morphine at times if the pain is unusually bad.)

Heightened CSF pressure can cause blindness. I've had vision loss on 3 occassions. That's because the increased pressure puts pressure on the optic nerve, which interrupts the signal. Pressure on the optic nerves can be visible with an eye examination and is called paplidema. (That also occurs with brain tumors, as a tumor causes increased pressure within the brain.)

So problems with the eyes in those instances have absolutely nothing to do with the CT scans, but rather the reason one is having numerous CT scans in the first place.

In my situation there is absolutely nothing wrong with the structure of the eye itself, the visual problems I have are due to optic nerve problems. Fortunately when the pressure has been removed twice prior I regained all the vision I had lost. This last time I lost vision I've regained most of it, and it's still returning. (It's always a crap shoot, and each time the nerve is damaged there is a potential for degenerative problems, as well as the likelyhood that the loss is perm.) If my medical condition (PTC) went into remission (which it never and I have had it since 1999) then I am still more likely than the average person to have eye problems later in life, due to the stress my optic nerves have been under because of the pressure problems. The link would be to the increased CSF though, not the CAT scans.

Anyway, you'd have to examine why people are having numerous CT scans before you could determine whether or not any eye problems are related to the CT scans (or radiation exposure), and not to the reason that they're having the CT scans in the first place. ;)

It's also far too easy to ascribe problems to a wrong causation.
It's human nature to want to explain things, and to look at what makes the most 'sense' to us. (Which is why people still insist the flu shot can give you the flu...no matter how many times they're told otherwise.) However you can't eliminate other issues. That's why even though I personally find it redudant, they always do an additional CT scan when I have severe pain that requires morphine, because it is possible that it could be something else, and if it's an intercranial bleed, that can be fatal. Just because it's *likely* to be pain caused by the PTC doesn't mean that they don't make sure it's not something else, especially when that something else can be a fatal problem. ;)

As far as the risks of CT scans. Well here are two sites that have information:

http://cis.nci.nih.gov/fact/5_2.htm
http://www.radiologyinfo.org/content/ct%5Fof%5Fthe%5Fhead.htm

And quoting from the last site (which was sited on the National Cancer Institute's site)

CT does involve exposure to radiation in the form of x-rays, but the benefit of an accurate diagnosis far outweighs the risk. The effective radiation dose from this procedure is about 2 mSv, which is about the same as the average person receives from background radiation in eight months.

Again, head CT scans have very specific uses, someone who recieves multiple scans (as I have and will again) generally has another serious problem, and it seems more likely that those problems could relate more to problems later in life than the relatively low radiation exposure.

[Wrath of the Swarm]

The exposure from the radiation itself is harmful, whether or not there are additional correlations between the scans and eye problems. We're not discussing statistical correlation, here: radiation is known to cause eye problems of a certain type. No inference is necessary.

And, to be honest, intensity does matter a bit. Since multiple incidences of damage that occur within a short time are harder to repair than damage that is spread out over time, more intense radiation will cause more lasting harm.

Which certainly reflects well on dental scans compared to CAT.

Oh, and regarding that quote: it is accurate, but incomplete and somewhat misleading. We're not discussing risk, but a virtual certainty of harm. There will be damage; the question is whether this will lead to impairment, which is a more complex issue. Also, the harm from receiving eight months' worth of extra radiation in a few minutes is greater than receiving eight month's worth of extra radiation over a longer time.

[Marian]

Originally posted by Wrath of the Swarm
The exposure from the radiation itself is harmful, whether or not there are additional correlations between the scans and eye problems. We're not discussing statistical correlation, here: radiation is known to cause eye problems of a certain type. No inference is necessary.

What type of eye problem is only caused by radiation? Or am I misunderstanding what you're saying? (Because if there's a specific eye problem that can ONLY be caused by radiation exposure, then certainly it could be directly correlated and tracked statistically). If I'm misunderstanding you (which I think is likely since that didn't make much sense to me :)) then I would think that the question again goes back to the underlying conditions that cause the need for multiple CTs being the source (more likely) of the problem(s) and not radiation.

I won't debate "radiation isn't ideal", otherwise we would just do routine CT scans for everyone (especially since their cost has come down tremendously). It's certainly not ideal, and not without some risks. Those risks though AFAIK are largely unknown other than "radiation exposure isn't ideal and should be limited", but of course when you have a serious medical issue it completely outweighs any potential risks...whether they're likely or unlikely.

And, to be honest, intensity does matter a bit. Since multiple incidences of damage that occur within a short time are harder to repair than damage that is spread out over time, more intense radiation will cause more lasting harm.

No question there either, I'll grant you that a lifetime of radiation done all at once focused on a very specific area would be "bad". :D The real question is, how harmful are individual CT scans? The answer I've seen is "not very". What about multiple CT scans, again the answers I've seen is "not that big a deal". (Children being an exception due to a different risk factor).

If you have data on the damage that occurs with one CT scan, I'd love to see it. Or data that demonstrates the damage that occurs with say, 5 CT scans, or 10...I'd love to see it. If the data consists of "Bob has a specific type of eye cancer and also happened to have 50 CT scans" then I wouldn't personally credit the CT scans as the cause, since there could be other potential causations. (Especially if Bob had those CT scans for cancer.)

Which certainly reflects well on dental scans compared to CAT.

I'm not certain of the difference in radiation between a CT scan and a dental scan offhand, but I would assume that a dental X-ray would be considerably MUCH less radiation exposure.

Oh, and regarding that quote: it is accurate, but incomplete and somewhat misleading. We're not discussing risk, but a virtual certainty of harm. There will be damage; the question is whether this will lead to impairment, which is a more complex issue. Also, the harm from receiving eight months' worth of extra radiation in a few minutes is greater than receiving eight month's worth of extra radiation over a longer time.

And again I'd really be interested (for personal reasons as well ;)) to see any data you can offer on specifically what harm is guarenteed by exposure to specific levels of radiation (such as those levels in a CT scan), specifically what 'damage' occurs with just one scan, with 5, with 10, etc. If harm occurs, it would be demonstratable.

I'm not arguing 'risk factors', those exist, and are listed on the two sites I mentioned, but they are rather negligable risk factors given the benefits (when a CT scan is necessary, or when any X-ray is necessary). But I would be very interested in seeing evidence/data/studies of demonstratable harm/damage, especially since I've had this discussion with my neurologist and others and have been assured that there's really not a problem with the number of CT scans I unfortunately have to have. (And they also promise my head won't glow in the dark ;) hehe)

[Wrath of the Swarm]

Originally posted by Marian
What type of eye problem is only caused by radiation? Or am I misunderstanding what you're saying? Yes, you are. AFAIK, there is no eye problem that is caused exclusively by radiation.

It's certainly not ideal, and not without some risks. Those risks though AFAIK are largely unknown other than "radiation exposure isn't ideal and should be limited", but of course when you have a serious medical issue it completely outweighs any potential risks...whether they're likely or unlikely. But that's the problem: we're not dealing with merely with risks, we're also dealing with prices. There may be a risk of adverse side effects when undergoing surgery, but there is a definite cost of being cut into. The chances of that happening in a surgery are 100%.

The real question is, how harmful are individual CT scans? The answer I've seen is "not very". What about multiple CT scans, again the answers I've seen is "not that big a deal". (Children being an exception due to a different risk factor). I can't really say that I disagree, merely that my concern about a given level of damage is greater than yours. I don't fancy irradiating my brain without very good reason.

I'm not certain of the difference in radiation between a CT scan and a dental scan offhand, but I would assume that a dental X-ray would be considerably MUCH less radiation exposure. Yes. However, the radiation exposure to the torso would be much smaller, but we feel it necessary to put on the aprons anyway. If we're going to adhere to that standard, some kind of protection for the upper head would seem appropriate.

But I would be very interested in seeing evidence/data/studies of demonstratable harm/damage, especially since I've had this discussion with my neurologist and others and have been assured that there's really not a problem with the number of CT scans I unfortunately have to have. (And they also promise my head won't glow in the dark ;) hehe) How can I put this diplomatically... doctors are very good at being reassuring, and very bad at telling people unpleasant truths, particularly when they're afraid those truths will be misunderstood or misinterpreted. This does not mean that what the doctor told you is false or significantly incomplete... but it is a very plausible contingency that I think you should consider.

I can't point you to a study at the moment. Do you have access to a good online collection of journal articles? A few searches might be illuminating.

[Vitnir]

On of the perks of sitting on a University computer is to have access to electronic papers.

Too bad this medic language sounds like greek to me.

dental diagnostic radiography results in measurable radiation doses to the hypothalamus-pituitarythyroid axis and not the reproductive organs or the fetus, it provides an opportunity
to test the role of the hypothalamus-pituitary-thyroid axis in the
radiation-LBW association.

That would be the proposed mechanism for radiation causing low birth weight. However the paper doesn't state that radiation does cause low birth weight, simply that there is a association between exposure and outcome. This is a case-control study and such studies can't as far as I know prove a cause and effect.

The possible weaknesses of the study that the authors write about in the discussion are

Weaknesses of the study include potential
measurement errors of confounders
such as smoking, the lack of thyroid
function measures, the lack of
information on nondental radiation exposures,
bias in the linking process, the
possibility of a chance finding, and missing
data.

None of these factors are however concluded to have confounded the findings in a significant way. The maximum cumulated dose the women would have been exposed to is 0.4mGy or more during these years.

This study does challenge the idea that there is such a thing as a threshold where radiation is safe. However this has been challenged by findings that variations in low exposure are linked to cancer. A fellow PhD-student of mine are in the works of publishing work that describes increase in cancer from the Tjernobyl fallout in Sweden for instance.

[Marian]

Yes, I can gain access to any medical journal source available, there's some benefit to having a spouse who works for the medical board. *grin*

But that's the problem: we're not dealing with merely with risks, we're also dealing with prices. There may be a risk of adverse side effects when undergoing surgery, but there is a definite cost of being cut into. The chances of that happening in a surgery are 100%.

I absolutely agree that there's always a cost, that's actually an argument I use even with beneficial medications, there is *always* some cost. However the question isn't whether or not there is one, I'm certainly of the belief that there is, the debate is what cost...and so far that seems unclear. What I've seen leads me to believe it's very low to the point of being negligable. (And also referencing something else you said, of course no reputable doctor will recommend any type of CT scan without good cause. There's a fad lately for 'full body scans' for 'wellness checks', and they have not only dubious value, but people are exposing themselves to a full body CT scan for no medical reason.

Yes. However, the radiation exposure to the torso would be much smaller, but we feel it necessary to put on the aprons anyway. If we're going to adhere to that standard, some kind of protection for the upper head would seem appropriate.

I assume you mean with dentistry? How would any head shielding be worthwhile? The X-ray equipment is pointed at the teeth in the mouth, are we able to lead shield the interior of the mouth and the roof of the mouth to protect the brain from exposure? And primarily the abdominal lead shielding AFAIK is because of the location of reproductive organs as well as the potential for pregnancy even when people insist they're not pregnant. Again I believe (AFAIK) that the risk is unbelievably minimal (with dental x-rays or even head CT scans both when pregnant), but there's no cost in taking that safety precaution. (And it certainly helps to prevent against the inevitible lawsuits, I'd once again presume.)

I'd have to double check with on standard of care, and what (if any) studies exist on potential exposure (during a pregnancy) and what specifically the risk factors are etc. but as far as I know it's done to basically minimize any potential risks, whether or not those risks are likely or even dangerous.

[CyCrow]

Originally posted by Vitnir

(snip)

None of these factors are however concluded to have confounded the findings in a significant way. The maximum cumulated dose the women would have been exposed to is 0.4mGy or more during these years.

This study does challenge the idea that there is such a thing as a threshold where radiation is safe. However this has been challenged by findings that variations in low exposure are linked to cancer. A fellow PhD-student of mine are in the works of publishing work that describes increase in cancer from the Tjernobyl fallout in Sweden for instance.

Did the authors consider the rather obvious idea that mothers with poor dental hygiene have more x-rays?

On Chernobyl fallout in Sweden: I thought that with the doses involved, it was considered impossible to detect statistically any increase in cancer, even if LNT was true. Considering the huge variation in natural background in Sweden, how can you estimate doses? And there is no control group. From what I have read, such studies tend to produce results that are "compatible" with LNT, but also equally compatible with hormesis because the results are not statistically significant. Which of course means that politics decide the "conclusion".

// CyCrow

[yersinia29]

Originally posted by Wrath of the Swarm
The question is not whether someone develops cataracts soon after exposure. The question is whether those low doses cause damage to the eyes, and the answer is yes.

Link please.

[Vitnir]

Actually, Sweden is a great place to do epidemiological studies simply because so many things are kept records of. All cases of cancers are reported to a central registry for instance and that means you can have computer programs to pinpoint the location of each cancer case on a map. The thing that made his research possible however is that over a large part of sweden a radiation mapping project has been done where a plane has recorded the ground radiation every 200 meters in a grid and then combine this information with the cancer registry. This enabled him to estimate an elevated cancer incidence, the works is still in the process of being published though but is accepted for publication. It is a bit radical since it shows that rather small radiation doses gives an increased risk.

[Vitnir]

Did the authors consider the rather obvious idea that mothers with poor dental hygiene have more x-rays?
I don't quite understand how that could be a confounder. The number of x-rays they had taken were their exposure. They did obviously investigate a rather lengthy list of other confounders like education and alcohol consumption and smoking during pregnancy.

[CyCrow]

Originally posted by Vitnir

quote:

--------------------------------------------------------------------------------
Did the authors consider the rather obvious idea that mothers with poor dental hygiene have more x-rays?
--------------------------------------------------------------------------------

I don't quite understand how that could be a confounder. The number of x-rays they had taken were their exposure. They did obviously investigate a rather lengthy list of other confounders like education and alcohol consumption and smoking during pregnancy.

If poor dental hygiene is correlated with low birth weight (seems plausible), then you will get correlation between x-rays and low birth weight, because they have a common cause. Correlation does not equal causation. But the researchers should know that...

// CyCrow

[Pantastic]

I picked up the abstract of the paper, and it's quite revealing.

Trojan numbers strike again.

The paper reports the study was in 4500 women. Sounds impressive, certainly would provide significant results. However, of these, on 1117 had low birth weight babies. Low birth weight is defined as <2.5g. However, this includes premature babies. If you're born early, you might be normal for your age, but still fall into the definition of LBW.

Anyway, from this 1117 it turns out that 336 had dental xrays during pregnancy.

Of these, only 21 - yes 21 - had exposure over 0.4mGy. But when compared to control mothers, the results did not show a big difference (CI was close to 1).

So then, they narrowed down their search again to term LBW, that is, babies with LBW born at term, excluding babies born early who were of 'normal' size, but because of their early birth, fell into the LBW category. Term LBW is also called 'small for dates', that is, the baby is smaller than you would expect for how old it is, regardless of how early/late it was born. How many mothers were in this category?

10

This then yielded a difference when compared to control mothers. BUt a study of 10 people is hardly impressive, and the CI for this group is ridiculous.

So, an initially impressive 4,500 boils down to 10. Make what you will of that.

It's as if I survey 10,000 people and ask if they enjoy surveys and only 10 answer but of those 8 say yes they do, and me saying 'Majority of people enjoy surveys shown by recent study of 10,000 people'. No no no.

[CyCrow]

Originally posted by Vitnir
Actually, Sweden is a great place to do epidemiological studies simply because so many things are kept records of. All cases of cancers are reported to a central registry for instance and that means you can have computer programs to pinpoint the location of each cancer case on a map. The thing that made his research possible however is that over a large part of sweden a radiation mapping project has been done where a plane has recorded the ground radiation every 200 meters in a grid and then combine this information with the cancer registry. This enabled him to estimate an elevated cancer incidence, the works is still in the process of being published though but is accepted for publication. It is a bit radical since it shows that rather small radiation doses gives an increased risk.

Interesting. Is this the data?
http://www.ssi.se/kaernkraft/Bonfortjrnobyl/bonbilder/bilder/Cs-137iSverige.jpg

This only shows Cs-137 fallout from Chernobyl, not variation in natural background. I would still be surprised if it was possible to find significant correlation, and one possible result of the small variations in dose is that large spans of values for risk can fit the data. So it becomes very sensitive to random effects (publication bias anyone?) or "data selection". It will be interesting to see the what the data and conclusions are.

// CyCrow

[Vitnir]

Not really sure if that's the one CyCrow, this is a previous work that he did on this subject.

Incidence of neoplasms in ages 0-19 y in parts of Sweden with high 137Cs fallout after the Chernobyl accident. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8919079)

There is always a risk for data mining or fishing when you have a large material which everyone is aware of so it's important to do these studies with care to avoid that.

[CyCrow]

Originally posted by Vitnir
Not really sure if that's the one CyCrow, this is a previous work that he did on this subject.

Incidence of neoplasms in ages 0-19 y in parts of Sweden with high 137Cs fallout after the Chernobyl accident. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8919079)

There is always a risk for data mining or fishing when you have a large material which everyone is aware of so it's important to do these studies with care to avoid that.

Thanks, that abstract shows much the same as others I have seen, no detectable effect from fallout. Also: "A somewhat decreased relative risk of acute lymphatic leukemia appeared in areas with increased exposure." Probably not significant, but not exactly supporting LNT either ;-)

// CyCrow

[Badly Shaved Monkey]

Originally posted by Pantastic
Low birth weight is defined as <2.5g.

That really is a tough qualifying criterion. ;)

[Vitnir]

The map CyCrow linked to is that map I mentioned, a more detailed version is here (http://www.sgu.se/verksamhet/geound/geofysik/cesium.pdf). They use a gamma spectrometer to measure levels of radon from the ground and now also radioactive fallout. With this information they could link a 10-20% increase in all cancer form in the areas with the highest levels of radiation.

[Pantastic]

Originally posted by Badly Shaved Monkey


That really is a tough qualifying criterion. ;)


Ack! 2.5kg I am sorry. I would like to claim that my 'k' key occasionally does not work, but alas it was my own fault.

[Badly Shaved Monkey]

Originally posted by Pantastic



Ack! 2.5kg I am sorry. I would like to claim that my 'k' key occasionally does not work, but alas it was my own fault.

I thought maybe it was just giving birth to sperms that didn't find an egg.

Edited to add:



Yeucchhh. I just thought about that a bit more!

Sorry for that image folks.

[Goshawk]

Originally posted by Goshawk
First, I need to correct something. Researching fluorescein angiography, I discovered that x-rays are not in fact used in the procedure, so the link (http://www.cancerbacup.org.uk/Cancertype/Eye/Melanomaoftheeye) I quoted was, surprisingly, 100% wrong. I have sent their webmaster an e-mail concerning this.

Not really bumping this thread, just feel a need to put a note in the archives that I got a reply to my e-mail. (My bad for not checking my e-mail addy that I use for that sort of thing sooner.)
Dear Sir or Madam

Thank you very much for your email. It was forwarded to me by our web editor. I am the Publications Nurse Specialist.

I would like to thank you for pointing out this inaccuracy in our information.

We will amend the text on the website as soon as possible and also on our factsheets.

Many thanks once again.

Yours faithfully

Debbie Coats

-----Original Message-----
From: Lucy Ashman
Sent: 04 May 2004 09:27
To: Debbie Coats
Subject: FW: Query from website




-----Original Message-----
From:
Sent: 01 May 2004 04:27
To: Lucy Ashman
Subject: Query from website


Name:
Email:
Comments: You say that x-rays are used in fluorescein angiography, under "Ocular Melanoma". However, this is not true. Fluorescein angiography involves the use of vegetable dye that shows up under special light--x-rays are not involved at all.

Cite.
http://www.retinaeyecenter.com/fa.htm

Date: 05/01/04-27-2004 04:05

And they have in fact updated their website. It now reads:
Fluorescein angiography. A special dye, called fluorescein, is injected into a vein in the arm. In a few seconds, the dye travels to the blood vessels inside the eye. A camera with special filters that highlight the dye is used to photograph the fluorescein as it circulates though the blood vessels in the retina and choroid.