Controversy over Radiation Fetal Dose Limits
One of the problems with knowing who to trust is that everyone has a dog in the fight that is publishing information on the issue. For instance, the medical field has a reason to want to minimize the risk of radiation, they sell a product, CT scans, X rays and other radiological procedures and they also want to manage their risk of being sued by performing tests. So they profit in two ways.
Here is a link on the risks of radiation to fetuses.
In the first paragraph, they outline the risks quite well, but then the rest ofthe article says not to worry. The most troubling portion was this:
“At the level of most diagnostic procedures ( fetal dose < 10 rem), little data in humans is available. However, some qualitative observations regarding fetal risk can be made.”
Were it my wife and baby, I would care little about “some qualitative observations”, I want to know in plain language if they really know if there is a risk or not. No disclaimer, straight up yes or no, is there a risk or not?
First Trimester of pregnancy
“The incidence of fetal wastage consequential to radiation exposure at this stage of gestation is not known, since (a) many women were never aware they were pregnant at the time of the exposure or miscarriage, and (b) the “background” rate of miscarriage is believed to be high (25 – 50 percent of conceptions). ”
Okay, fine, you don’t know…. and if there were a study of this, the results would be hidden in the normal rate of miscarriage.
“It is believed that radiation injury during early gestation is an “all-or-nothing” effect. ”
It would seem, taken in context, that they are saying that a significant radiation exposure will simply kill the fetus in the very beginning, or cause the womans body to miscarry. Reason enough for our warning to never, never, allow a pregnant woman around a granite countertop unless it has been tested and found to be safe.
Second Trimester of pregnancy
” During this period, the overall growth rate of the fetus has slowed. However, the major organ systems are beginning to differentiate. From a standpoint of future development, the fetus is in its most sensitive stage. The incidence of gross congenital malformations and mental retardation are dose-related and appear to have thresholds; i.e. doses below which the incidence above “background” is not elevated.”
The opperative word is “appear”. Again, I don’t want to know that it may “appear” or is “most likely” to have a threshold, I want to know that there is a threshold and exactly what that threshold is. And I see that “gross” problems are covered, but how about smaller defects? Is the baby safe from radiation or not? What levels are unsafe? Are the “background” levels of miscarraige also hiding any surprises?
Third Trimester
” Irradiation during this period may deplete cell populations at very high doses (over 50 rem), but will not result in gross organ malformations.”
Okay, 50 rem won’t be encountered in a medical procedure or a granite countertop, so why is it mentioned. Wouldn’t it be best to use medium dose or low dose data? And again, how about minor damage or malformations? Will you tell me straight up, is there any risk from low level radiation in the third trimester or not?
“For some prenatal irradiation effects, there is epidemiological basis for the existence of threshold doses. For others, such as childhood cancer induction, the existence of a threshold is not clear-cut. Despite these uncertainties in the dose-effect relationship, some broad generalizations based on fetal dose ranges may be made.”
Great, there is some data on some prenatal effects but childhood cancer induction is unknown. Since there is uncertainties, tell me why one woud make a broad generalization on this issue?
“Fetal Dose Less Than 1,000 millirem — There is no evidence supporting the increased incidence of any deleterious developmental effects on the fetus at diagnostic doses within this range.”
Okay, but have there been studies on this? If so, come out and make a definitive statement on the risk.
“Fetal Dose between 1,000 millirem and 10,000 millirem — The additional risk of gross congenital malformations, mental retardation, intrauterine growth retardation and childhood cancer is believed to be low compared to to the baseline risk. However, the lower limits (in terms of statistical confidence intervals around the mean) for threshold doses for some studies, especially those related to cancer induction, fall within this range.”
1,000 millirem (1,000 mR or 1 Rem) can be obtained from a granite countertop hot spot. Take our example of the Four Seasons slab, 3.2 mR per hour exposure. That is 312 hours of use of that granite countertop, 156 days at 2 hours per day. Less than the 270 day pregnacny period. Keeping in mind that some experts are predicting that our meters are from 2 to 6 times low, the 1 Rem level could be easily reached. And I could care less that it is low compared to the baseline risk, if we are the couple that gets the 1 out of 100 problem, it is a huge risk to us.
“Fetal Dose Exceeding Than 10,000 millirem — The lower limits (in terms of statistical confidence intervals) for threshold doses for effects such as mental retardation and diminished IQ and school performance fall within this range. Overall, exposure at levels exceeding 10 rem could be expected to result in a dose-related increased risk for deleterious effects. For example, the lower limit (95% confidence interval) for the threshold for mental retardation is about 15 rem, which an expectation value of about 30 rem.”
Okay, even I would admit that a 10 Rem dose would be difficult to obtain from a granite countertop in a home.. On the other hand, would a pregnant woman working in a granite showroom be likely to reach that exposure? Many granite showrooms use granite for desks, were a hot spot such as the Four Seasons slab to be in a work desk, 270 days (nine months) exposure would be 4.6 Rem for the desk alone. No doubt the lady would not spend a full 40 hours at that desk, but there will be plenty of other granite radiation sources nearby, all adding to the exposure. Let’s hope she doesn’t have a granite top at home with a hot spot.
4.6 rem is too close to 10 rem for comfort. Most safety rules have rigourous amounts of excess built in. Take as an example the strength of a rope or chain used for lifting, factors of ten are common, or ten times less than the chain will usually hold. Only prudent to have safety factors.
The same should be done with radiation risks for non essential uses of radioactive products like granite. Especially since low level granite can be found with a little care and trouble.
2 Responses to 'Controversy over Radiation Fetal Dose Limits'
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on August 15th, 2008 at 10:25 pm
The NRC sets a limit of 500 millirem for the 9 months of pregnancy of 500 millirem. Female nuclear workers trying to start a family are generally limited to 50 millirem a month, so that this limit will not be exceeded before the pregnancy is detected. Remember time, distance and shielding. As you step away from the counter, the dose rate decreases. The mother’s body and amniotic fluid provide shielding for the baby, and reducing time near the counter reduces dose. So do the dishes for your wife and take her out to dinner more! It seems that the industry is going to look at monitoring blocks before cutting slabs, and monitoring slabs before polishing. I think that is a great idea and should be implemented ASAP. Ludlum instruments makes a laundry monitor for the nuclear industry, that could be modified to monitor slabs.(they would have to beef up the conveyor belt a lot, or mount the detectors on equipment at the granite facility. The controversy seems to be driven by Silestone and Cambria funding CleanBuild, but if more becomes known about the origins of low and high level granite, and monitoring becomes common, some good may come of it.
But to give you some peace of mind in the meantime, check out this study,
in the Journal of American Physicians and Surgeons:
http://www.jpands.org/vol9no1/chen.pdf
20 years from now, the question may be: Are we getting enough radiation?
on August 15th, 2008 at 10:46 pm
Hi Gary,
great comments. You seem to be fixated on the idea that competitors brought up the issues first. However, that is usually the case in these things. Not much profit in the stone industry pointing out that some of their products carry a health risk. Most of the govt officials we have spoken with were clueless and are now playing catch up with the facts. Not blaming them, it wasn’t on anyones radar.
I think that the major difference between a nuclear worker and a homeowner is that the worker is accepting the risks, is trained to prevent as much exposure as possible, has a team of specialists monitoring her exposure, and most importanly, is taking a known risk in exchange for a paycheck. Also there is some sort of public gain for the exposure, nuclear weapons maintained, power generated, or medical knowledge gained.
For an unaware homeowner, well, she has a pretty countertop. No experts telling her to limit exposure, heck she doesn’t even know she is exposed to the risk. We are finding granite slabs with 3 mR/hr Gamma, and the experts with larger lab scintillators reporting far higher results on the same samples. If we take thet 3 mR/hr, that gives only 16 hours of using that countertop, about a half hour per day…..
As to stepping away from the counter, we have tests complete with data logs, proving that some granite types have radiation that will reach six feet and futher. Sure it is lower, but plenty of radiation is still there.
We are looking at block testing, but the majority of the stone industry is not very willing to go to the expense. Some are have already started crude testing, some are claiming to test and slapping stickers on their slabs that say “Radon Free”.
As for Hormesis, BEIR VII studied that issue to death, then specifically rejected it as unproven. I understand the Health Phyicists Society types will take issue, but they aren’t exactly known for objectivity, more known for supporting the nuclear industry.
The most important thing is this, will a woman willingly take even a small chance with the health and development of her baby? Absolute insanity to even consider spending time around a hot granite countertop. It is just not worth the risks.