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Re: Some thoughts on epidemiology

At 09:59 AM 08/20/2002 -0400, RuthWeiner@AOL.COM wrote some thought-provoking comments:
Apologies in advance for a long post, but my thoughts may be of interest to RADSAFERs.

I am not an epidemiologist, but I am an observer.  Thus, I have been thinking about what troubles me about the supposed magnetic field (Fritz is right -- we were all sloppy) impacts on leukemia, miscarriages, asthma, Type-II diabetes, etc.

I am neither an epidemiologist NOT a health physicist. My interest in the effects of radiation has been as a user and designer of high-end broadcast facilities. In at least some instances, equipment may dictate E-M field limitations that are stricter than current health-based limitations.

I had my teeth cleaned with an ultrasound probe today.  I don't get exposed to that magnetic field more than a half hour every three months, but the hygeinist is exposed every day for about 6 hours.  Moreover, nowadays ultrasound pictures of fetuses are quite regularly taken.  If a group were studying the putative impact of magnetic fields on miscarriage rates, dental hygeinists and pregnant women getting ultrasounded would seem to be logical study subjects.  Why weren't they selected?

Ultrasound is sound not magnetic. Sound waves are mechanical vibrations (compressions and rarefactions of the media--such as air, flesh, water--it is transmitted through). I believe that is an entirely different series of studies.

The whole approach in the magnetic field studies contains an insidious bias.

Many good points about study design snipped to conserve bandwidth. They certainly make a point. However, the assumption early on when the power line field controversy first entered my consciousness about 20 years ago was that there were some otherwise-unexplained illnesses that might be linked to high voltage power lines in the vicinity. The hypothesis was presented and perhaps the studies are looking to confirm/refute that hypothesis.

The study cited in the recent post by Bjorn Cedervall ought to put to rest the notion that magnetic field exposure might cause leukemia, or is even correlated with it.  Actually, similar studies, with similar results, were published more than ten years ago (unfortunately I don't have citations handy).

The study that Bjorn posted about certainly makes me feel safer about cell phones (I've never been crazed about cell phones).

However, I'm not certain that I would make a jump that because electromagnetic radiation at approximately 1GHz in relatively low (but realistic) doses did not harm some mice, that 60Hz power lines carrying megawatts of power are equally safe.

I _know_ that cell phones do not interact with electronic equipment in the same way that the high-power transmission lines do. Although hospitals say "no cell phones," in broadcast facilities they're on all the time and we've seen few (if any) possibly negative effects on the equipment. Of course we're dealing with different types and levels of signals, but our microphone signals have noise floors (in passband) of lower than 775nV (yes nano volts, or 7.75E-7V) In most cases, the noise floor in microphone circuits is half or less than half of that!

Overhead transmission lines are unattractive, to say the least, but that doesn't mean that they can be correlated with an adverse health effect.  Residential and commercial development that requires new transmission lines may be unwelcome, and certainly causes irreversible changes to the landscape, the view, the natural environment, etc.

They can be fought based on zoning laws, etc.

However, the claim that magnetic fields from the associated transmission lines "cause," or are even correlated with, some adverse health effect, on the basis only of the epidemiological studies cited on the powerline webpage, is unsubstantiated.  Just because you don't like something, or it messes up the natural environment, doesn't mean that it can be correlated with health damage, or even that there is enough justification to go looking for health damage.

I believe that the people publishing the powerlinefacts.com Web page are sincere in their belief that these fields may be dangerous to them and their loved ones. I do NOT think that they are fabricating this. After all, like me, they are lay people. When a lay person reads a statement such as the following, which starts with disclaimers, but includes a perhaps unwarranted conclusion--but is published in the British Journal of Cancer-- what is one to assume? First, here is the bottom line that jumps out at the lay person:

In summary, for exposure up to 0.4 µT our data demonstrate
relative risks near the no-effect level. For the very small proportion
(0.8%) of subjects with exposure above 0.4 µT, the data show a
two-fold increase, which is unlikely to be due to random variability.

but then the study includes qualifiers that reduce the overall impact:

The explanation for the elevated risk estimate is unknown,
but selection bias may have accounted for some of the increase.
leukemia in children.

Here are the last three paragraphs of the study in their entirety, which include more disclaimers.

"The results of numerous animal experiments and laboratory
studies examining biological effects of magnetic fields have
produced no evidence to support an aetiologic role of magnetic
fields in leukaemogenesis (Portier and Wolfe, 1998). Four lifetime
exposure experiments have produced no evidence that magnetic
fields, even at exposure levels as high as 2000 µT, are involved in
the development of lymphopoietic malignancies. Several rodent
experiments designed to detect promotional effects of magnetic
fields on the incidence of leukaemia or lymphoma have also been
uniformly negative. There are no reproducible laboratory findings
demonstrating biological effects of magnetic fields below 100 µT.

"Our results have clear implications for future studies. The level
of significance that we see for the excess risk at high exposure
makes chance an unlikely explanation. Future studies will be of
use only if the operation of selection bias and confounding can be
adequately addressed, and if there are sufficient numbers with
exposure over 0.4 µT.

"In summary, for exposure up to 0.4 µT our data demonstrate
relative risks near the no-effect level. For the very small proportion
(0.8%) of subjects with exposure above 0.4 µT, the data show a
two-fold increase, which is unlikely to be due to random variability.
The explanation for the elevated risk estimate is unknown,
but selection bias may have accounted for some of the increase.
leukemia in children. "

So isn't someone supposed to avoid constant exposure to 4mG (0.4µT)? If I saw that study and was trying to organize my life, that would be a good goal. Good news is that CRT computer monitors start to wiggle at 10mG, so, once again, the equipment sets reasonably low levels.

On the other hand, the essay that Sandy Perle just posted from the New York Times "In a World of Hazards, Worries Are Often Misplaced" certainly makes a lot of sense!

I grew up spending a lot of time in my "lab" in the basement of my house which had asbestos covering over the steam heat pipes. Some of it was flaking. I have not developed lung cancer. But, like Ruth's experiences, I, too, am merely anecdotal <sigh>.

To remphasize the major points:
  (a) There was a presumed smoking gun pointing to powerlines
  (b) Anecdotal evidence proves nothing either way
  (c) Wording of at least the British Journal of Cancer leads a person
       to consider very low long-term exposure limits.
  (d) The studies are very mixed in this area.
  (e) The studies are of greatly varying quality and responsibility.
  (f)  The presumption that these fields MAY affect developing fetuses
        and children and can damage them more than adults is
        the scariest part.

As I've said, I own/use electronic equipment that is very sensitive. I'm not worried. I select location based on making that equipment happy. So far, by default, it seems that my children and I will also be happy and safe.

Cheers,

Richard