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Cellphones, brain cancer, and other cheery thoughts

9 Jan 2010. As you may have heard, the state of Maine is considering "legislation requiring cellphone makers to affix labels on their devices warning consumers of possible brain cancer risks due to electromagnetic radiation."* [update: The bill failed to pass; the vote was 83-62.]

Below are some facts and well-supported opinions relevant to the issue of cellphones causing brain cancer:

logic and methodology

Correlation is a necessary but not a sufficient condition for causality. Without correlation, there is no causation. Correlation does not establish causation, however.

No scientific study on this issue is or can be a randomized control study on humans because of the ethical issues. Besides, if there is an effect, it might take 20 or 30 years to manifest, not to mention how hard it would be to find an adequate control group and keep watch on them. Studies on animals, such as rats, exposed to various amounts of electromagnetic radiation to specific parts of the brain are possible, but mimicking human cellphone use, while possible, might not reveal anything significant unless the rats could live and be studied for, say, 15 or 20 years. In any case, the studies usually cited by those warning that cellphones cause brain tumors are prospective and retrospective studies involving humans. All such studies suffer from a major, but not fatal, methodological flaw: they must rely on the recall of participants as to when they began using a cellphone, how often they use it, the percentage of time they use it on the right side or the left side, etc. A study that has to rely on data stored in human memories of people with brain tumors is troubled from the start, since memory isn't always reliable, brain tumors can affect memory, and some participants might misremember to fit their belief that the cellphone caused their tumor. Small, but statistically significant differences between groups of cellphone users and non-users might be due to faulty memory rather than electromagnetic radiation.

Prospective studies examine a population in which the potential cause is known to be present: in this case, they survey cellphone users. There are various ways to do this. You could get a large random sample of American adults and divide them into those who do and those who don't use cellphones, and look for a significant difference in the rate of brain tumors between the two groups. If you have a large enough sample and if the rate of brain tumors is much larger in the cellphone group, you would be justified in concluding that this is not likely due to chance and that it is highly probably that something causal is going on. You could not be sure that it is the cellphone that is causing the excessive brain tumors, however. There might be something else that cellphone users have in common, for example, that causes the tumors. Or, it's possible, though not likely, that you just have a statistical fluke. Even small differences in brain tumor rate between the two groups might be statistically significant, but that doesn't necessarily mean that there is a causal relationship between cellphone use, or some other factor, and brain tumors.

An alternative prospective study might analyze the data without dividing the population into users and non-users of cellphones. Instead, one might try to find a correlation between such things as years of use, or average number of hours used per day, which ear is commonly placed next to the phone, etc., and brain tumors. If you found that the more years one used a cellphone, the greater the brain tumor rate, you would have a correlation between the two, but you still couldn't confidently say that you have proof of causality. Something else might account for the correlation. For example, age might be the reason for the correlation. As people get older, the brain tumor rate increases.

Correlation doesn't prove causality, and all prospective studies on cellphone use and brain cancer attempt to find a correlation between the two. Those researchers or journalists who reason that because a correlation has been found a causal connection has been established are wrong. If there are many large, well-designed studies and all of them find a correlation between cellphone use and brain tumors, then one can be confident that there is most probably a causal connection. The correlations, however, will give you no clue as to what that causal mechanism might be.

The weakness of prospective studies is that there is no control group. The purpose of a control group is to reduce the chances that some unknown factor is the cause of the effect you are measuring. If sample sizes are very large, however, one expects any differences between cellphone users and non-users to be randomly distributed in more or less equal fashion between the two groups. Thus, one expects that any unknown factor that might be causally related to brain tumors to be distributed more or less evenly between users and non-users. In general, the smaller your sample, the greater the probability that an unknown factor might be at work and the lower the probability that any correlation you find will be due to the cause you are trying to isolate.

In a retrospective study, one surveys a population whose members demonstrate an effect: in this case, one surveys people with brain tumors. You can then do several things. You could find out how many of those with brain tumors use cellphones, how often they use them and for how many years, etc. You would then look to see if there are significantly more people with brain tumors who use cellphones. Or, you could do a case-control study and try to find a comparable group (in relevant factors such as age, sex, general health, etc.) without brain tumors. You then compare cellphone use in the two groups. The chance that some unknown factor is responsible for any significant difference you find between the two groups is much greater in retrospective studies than in prospective studies. Generally, the groups are smaller, reducing the chances that an unknown factor would be evenly distributed in the two groups. The qualities one selects by which to match the two groups are subject to bias, conscious or unconscious. The least reliable retrospective study would simply look for correlations like years of use or average number of hours per day using the cellphone among the sample of people with brain tumors. The chance that you are just measuring some obvious feature like an effect of aging increases if you don't have anything to compare your sample group to.

Anecdotes aren't usually sufficient to establish causal relationships, but if the first ten people who used a cellphone developed brain cancer within hours of using the phones, you'd have a strong case for claiming something in the phones caused the cancers. Thousands of anecdotes of people who use cellphones and develop brain cancers some time after they began using the phones would be of no more interest to the scientist than thousands of anecdotes of iPod users or baseball-hat wearers developing brain cancer after they began wearing ear buds or baseball caps. If anecdotes generate enough fear and fear generates enough funding, then some scientists might find the anecdotes compelling enough to do a scientific study.


"Unless one is willing to discard the concept of photons, Planck's law, and the interaction between photons and atoms—and thus the entire body of quantum physics—it is simply not possible for the photons associated with either a power line or a cellphone to cause cancer." (S. T. Lakshmikumar,  "Power Line Panic and Mobile Mania." Skeptical Inquirer. September/October. 2009.)

"The photon energy of a cellphone EMF [electromagnetic field] is more than 10 million times weaker than the lowest energy ionizing radiation." (Lorne Trottier, "EMF and health: A Growing Hysteria. Skeptical Inquirer. September/October. 2009.)

The energy emitted by cellphones, cordless phones, and baby monitors (10 milliwatts) is pretty weak. There is more EMF exposure from radio and TV, and the wiring in our homes and the electrical appliances we use, than from our cellphones or Wi-Fi. No one can avoid electromagnetic radiation. It is everywhere. We are constantly exposed to it from light, commercial radio and television transmissions, police 2-way transmissions, walkie-talkies, etc.

Photons of visible light carry more energy than microwaves and bombard us much more frequently than microwaves from such things as cellphones or wireless networks.

All known cancer-inducing agents — including radiation, certain chemicals and a few viruses — act by breaking chemical bonds, producing mutant strands of DNA. Not until the ultraviolet region of the electromagnetic spectrum is reached, beyond visible light, beyond infrared and far, far beyond microwaves, do photons have sufficient energy to break chemical bonds. Microwave photons heat tissue, but they do not come close to the energy needed to break chemical bonds, no matter how intense the radiation. --(Dr. Robert L. Park of the American Physical Society, New York Times, Oct. 1, 2002.)

the studies

The preponderance of the evidence as of winter 2010 is that there is no great danger to humans from using cellphones, Wi-Fi, or living near power lines.

Some studies have collected data suggestive of possible harmful effects from cellphone microwave exposure, but they are too small to have ruled out chance or other causal agents (2006) or they have not been tested on in vivo cells (2004; 2006a; 2006b).

A report published in the Journal of the American Medical Association on a study of 891 adults who used their cellphones between 1994 and 1998 found that there was no increased risk of brain cancer associated with cellphone use. (Joshua E. Muscat et al. "Handheld Cellular Telephone Use and Risk of Brain Cancer," JAMA. volume:284. December 20, 2000.)

In 2006, in the Journal of the National Cancer Institute, Danish researchers published the results of a study of more than 420,000 mobile phone users. They looked at data on people who had been using mobile phones from as far back as 1982. They found no evidence of an increased risk of tumors in the head or neck. They found no evidence to suggest users had a higher risk of leukemia or of tumors in the brain, eye, or salivary glands.*

Last month [December 2009], the results of the latest study on the subject were published. Researchers identified 59,984 cases of brain tumor diagnosed between 1974 and 2003 out of a population of 16 million from four Scandinavian countries. Cellphones were first introduced in these countries in the 1980s, but use did not become widespread until the 1990s. No difference in brain cancer rates was found after cellphone use became common.

The Interphone study, sponsored by the World Health Organization involves a compilation of studies from 13 nations and has been going on for a decade. Different countries have found conflicting results. The latest results from the Interphone studies were published on 8 Oct 2008. None of the findings show a robust correlation between cellphone usage and brain tumors or other diseases. Where positive correlations were found, the authors used cautious language, e.g., "possibly reflecting participation bias or other methodological limitations," "finding could either be causal or artifactual, related to differential recall between cases and controls," "based on few subjects (7 cases and 4 controls) needs to be investigated further," and "additional investigations of this association...are needed to confirm these findings."

update: 16 May 2010. The largest study to date looking for links between mobile phone use and brain cancer has proved inconclusive, according to researchers. The 10-year study of 13,000 people didn't find any increased risks of brain cancer among cell phone users, but "we can't conclude that there is no risk because there are enough findings that suggest a possible risk," said the study's chief author, Elisabeth Cardis. The study was conducted by the World Health Organization, which said further research was needed for more conclusive answers. In other words, we'll keep on looking until we find something, but if we don't find anything that doesn't mean there isn't a risk. I think we knew that before any studies were conducted. In any case, another study has been initiated in the UK to study the health effects of mobile phone use. This one will involve 250,000 participants over 20-30 years. Check back in 2040 to find out if they found out anything or need to keep searching.

update: 9/11/2010. More results from the Interphone study have been published. The latest data can be found in the International Journal of Epidemiology. "CONCLUSIONS: Overall, no increase in risk of glioma [malignant brain tumor] or meningioma [benign brain tumor] was observed with use of mobile phones. There were suggestions of an increased risk of glioma at the highest exposure levels, but biases and error prevent a causal interpretation. The possible effects of long-term heavy use of mobile phones require further investigation."

the history

The arousal of public fear over electromagnetic radiation did not originate with scientists but with a journalist. In 1989, New Yorker magazine ran a series of scare stories by staff writer Paul Brodeur.

The public fear that cellphones might be causing brain tumors was first aroused not by scientists but by a talk show host. On January 23, 1993, Larry King's guest was David Reynard, who announced that he and his wife Susan had sued NEC and GTE on the grounds that the cellphone David gave Susan caused his wife's brain tumor.1,2,3,4 There was nothing but junk science to back up her claim, plus the fact that the tumor appeared near where she held the phone to her ear. She was diagnosed seven months after receiving her phone and died a few months after filing the suit. The suit was dismissed in 1995. A dozen similar lawsuits followed; all were dismissed.

The public fear that cellphones might be causing brain tumors was enhanced in October 1999 by ABC's "20/20" in a story that focused on the claims of Dr. George Carlo, who contradicted the conclusions of most other researchers in the field and maintained that "we now have some direct evidence of possible harm from cellular phones (italics added)." Carlo also claimed there is a causal connection between Wi-Fi and autism.

For those who think scientists and industries don't take anecdotes seriously, consider this: soon after Susan's lawsuit was dismissed the cellphone industry committed $25 million for safety studies. Many studies have been conducted over the past fifteen years and so far no evidence of a causal link between cellphones and brain cancer has been found.

the manufactroversy

Despite the fact that the preponderance of evidence over the past fifteen years indicates there is no correlation, much less a causal connection, between cellphone use and brain tumors, the "controversy" continues. Lobbying groups and the media continue to publish stories that convey the message that the verdict is still out on the dangers of cellphones.

21 Dec 2009. St. Petersburg Times: cellphone-cancer link remains unclear, but some scientists urge caution by Stephen Nohlgren. In this article, the author notes: "Just this month, two sources of popular health wisdom — Prevention magazine and Dr. Mehmet Oz on his new TV show — warned against cellphones and other devices that emit electromagnetic radiation." Nohlgren also notes that the next report from "The Interphone study, a World Health Organization compilation of studies from 13 nations, is due out any day. Different countries found conflicting results, so authors struggled to craft a joint conclusion. But many observers predict that — at the very least — the report will include cautionary language about phones."

26 Aug 2009. CNET News ran a story with the headline Once again: Do cellphones cause brain tumors?: "A collaborative of international electromagnetic radiation (EMR) watchdogs, including Powerwatch and the EMR Policy Institute, sent a paper to government leaders and media Tuesday detailing several design flaws in a major but oft-delayed telecom-funded Interphone study."

In a follow-up article, CNET's Don Reisinger reports that "electromagnetic radiation watchdogs," including Powerwatch and the EMR Policy Institute, released the findings of a study that claimed there is a "significant risk of brain tumors from cellphone use."

"Science has shown increased risk of brain tumors from use of cellphones, as well as increased risk of eye cancer, salivary gland tumors, testicular cancer, non-Hodgkin's lymphoma and leukemia," the report read. "The public must be informed."

But, as Reisinger notes: "The only problem is that several well-known organizations disagree with those watchdogs. Both the World Health Organization and the National Cancer Institute say that there's no conclusive evidence that mobile phones can cause cancer."

Which brings me to the point of this little piece: the headline of Reisinger's article reads: Maine to consider cancer warnings on cellphones. State Rep. Andrea Boland, a Democrat, believes that "numerous studies point to the cancer risk." So, she has proposed that a law be passed in Maine that would require cellphone manufacturers to put warnings on packaging, like those on cigarettes. [As noted above, her proposal failed to pass.] According to the New York Times:

Ms. Boland said she was convinced from what she had read that the radiation from cellphones increased the risk of brain cancer when held at the ear, especially in children under 18. She said she was swayed by a 2006 study by the Swedish National Institute for Working Life that showed a correlation between brain tumors and heavy cellphone use, and by a recent report by a retired engineer and consumer advocate, Lloyd Morgan, that compiled research showing that cellphones can lead to an increased risk of brain tumors.

The Swedish study is a retrospective study. It looked at the mobile phone use of 905 people between the ages of 20 and 80 who had been diagnosed with a malignant brain tumor. Eighty-five, or 9%, of the 905 were heavy cellphone users (at least 2,000 hours of usage). Kjell Mild, who led the study, said heavy users had a 240 percent increased risk for a malignant tumor on the side of the head the phone is used. "Side of the head" covers 50% of the brain. How close to the ear these tumors were would seem to be a more relevant area to examine. In any case, Kjell doesn't know if there is any risk, much less a 240% risk; his data showed a correlation from which he inferred a causal connection. Worse, he has nothing to compare his data to. What percentage of heavy users doesn't have brain tumors on the side of the head where they might be expected to have them were they to use a cellphone? Furthermore, the absolute numbers are so small that a 240% difference might be a fluke. The fact that this study conflicts with studies involving significantly larger samples with much better controls leads me to question its significance.

Lloyd Morgan is a retired electronic engineer and one of the main forces behind Powerwatch, the source of the claims mentioned above that science has shown increased risk of brain tumors from use of cellphones, as well as increased risk of eye cancer, salivary gland tumors, testicular cancer, non-Hodgkin's lymphoma, and leukemia. Morgan is not lying, as far as I can tell, but he is selective in the studies he cites. Contrary to his claim about science having shown an increased risk from cellphone use of "salivary gland tumors, testicular cancer, non-Hodgkin's lymphoma," Kjell Mild has published (2006) the results of six case-control studies that concluded: "No consistent pattern of an increased risk was found for salivary gland tumours, NHL [non-Hodgkin lymphoma] or testicular cancer." Kjell did find evidence for an increased risk for brain tumors, mainly acoustic neuroma and malignant brain tumors. Larger prospective studies have not replicated Kjell's work and do not support his findings regarding brain cancer. The last report from the Interphone study, for example, has this to say:

For meningioma and acoustic neurinoma, most national studies provided little evidence of an increased risk. The numbers of long-term and heavy users in individual studies were even smaller than for glioma, however, and prevent any definitive conclusion about a possible association between mobile telephone use and the risk of these tumours.

Morgan is a one-man propaganda machine for the belief that EMFs are causing all kinds of health problems. Others may find it interesting that the Interphone studies he declares flawed are those that disagree with his contentions. The ones he cites to support his beliefs are viewed quite differently by those who are actually doing the studies and reporting the data. Protocols for the Interphone studies are published here.

Boland's position, in effect, rests on the claims of two men, both of whom are outliers in the scientific community on this issue. She ignores the studies done by dozens of others that have found no correlation between cellphone use and brain tumors. Nevertheless, her bill was put on the fast track and labeled as an emergency because there are over 900,000 cellphones in the state, “and if there’s a need to put these warning labels on them, doing it sooner rather than later is probably better.” This is the precautionary principle in action, generated by a manufactroversy.

It gets murkier. According to the New York Times:

In San Francisco, Mayor Gavin Newsom plans to introduce an amendment this year requiring that cellphone packages in the city display the amount of radiation a phone emits.

“The mayor believes that cellphone safety is the next frontier,” said Brian Purchia, a spokesman for Mr. Newsom, a Democrat.

Newsom once had thoughts of running for governor of California. To win, I think he'll need to come up with something scarier than "beware of cellphone radiation."

Meanwhile, the Times declares: "The debate over the safety of cellphone radiation has been brewing for years, and there is a great divide on the issue." Not really. The scientific community isn't divided on the issue, but the contrarians and practitioners of pseudosymmetry continue to raise doubts and create uncertainty, leading to pointless legislation and inane declarations from politicians. The general public, however, doesn't seem to be trembling.

Cellphone sales continue to move briskly. According to the CTIA wireless association, more than 276 million Americans are now subscribers to some sort of cellphone plan. I don't know where they got that number, but considering that the US population is currently somewhere around 308 million, I'd say the number might be misleading. That's almost 90 percent of the U.S. population.

Wait....this just in from Reuters: "A study in mice suggests using cellphones may help prevent some of the brain-wasting effects of Alzheimer's disease, U.S. researchers said on Wednesday." Yes, it's true! "After long-term exposure to electromagnetic waves such as those used in cellphones, mice genetically altered to develop Alzheimer's performed as well on memory and thinking skill tests as healthy mice, the researchers wrote in the Journal of Alzheimer's Disease." Read all about it here.

That sound you hear may be Boland and Newsom rewriting their proposed warning labels. After all, fairness does require that they tell both sides of the story.

update: 19 Feb 2010. California state Sen. Mark Leno, D-San Francisco, has authored a bill that would require manufacturers of cell phones to print radiation information on packaging and instruction manuals and retailers to display that information on the sales floor. Leno said that cell phones "emit radio frequency radiation that does have human health effects." So does the Sun, but Leno is apparently not pursuing legislation to require anyone to post radiation information about it.

Leno pointed to studies from around the world that found people who have used cell phones for more than a decade had an increased risk of brain tumors, both malignant and benign, and benign tumors in the salivary glands. Leno didn't point out that those studies did not claim to provide robust evidence of a causal connection, but rather cautioned against drawing strong conclusions from studies with small samples, methodological flaws, and needed to be investigated further before any action would be justified.

further update on San Francisco law: The law passed in June 2010. The law is under fire from CTIA, the wireless industry group. CTIA filed a lawsuit to block enforcement of the ordinance.

update: 3 Mar 2010. Maine lawmakers heard testimony from several people claiming cell phones are hazardous to our health. "We can do nothing and wait for the body count. That's what happened with smoking" before warnings on cigarette packs were mandated, David Carpenter, director of the Institute for Health and Environment at the University of Albany, told Maine lawmakers.

Olle Johansson, a scientist at Karolinska Institute in Sweden, submitted testimony saying that "very serious biological changes" that include cancer risks have been noticed for years from exposure to low-frequency magnetic fields like those emitted from cell phones.

Supporters also included a brain cancer patient and relatives of victims who said the disease was triggered by cell phone use.

"When you put that phone to your head, you are unknowingly playing Russian roulette," said Alan Marks of the San Francisco Bay area, who's been diagnosed with a brain tumor.

I can understand the political value of acting like a TV talk show and parading forth self-proclaimed victims, especially when the scientific evidence is stacked against you. The legislators are playing to the gallery with some high drama, even if there isn't any proof that anyone's brain cancer was triggered by cell phone use. Even so, the lawmakers should be ashamed for displaying cancer victims to bolster their flimsy case.

The use of a director of something called "the Institute for Health and Environment" at a university seems reasonable. I don't know anything about Mr. Carpenter or his institute, so I can't comment on his dire warning except to say that it conflicts with the preponderance of the evidence.

Johansson, on the other hand, has been around for quite a long time and has frequently called attention to himself by his fearmongering regarding EMFs. Johansson is a Swedish neuroscientist who was awarded the not-so-prestigious Misleader of the Year award in 2004 by the Swedish Sceptics (Vetenskap och Folkbildning, VoF). He was given his title "Following many years of public assertions and cocksure, blatant warnings of numerous negative health effects allegedly caused by electromagnetic fields."

Olle Johansson receives the award as one of the most prominent representatives of the far too many scientists who, to draw attention to themselves and funding for their own activities, disseminate worry among the public in mass media by presenting unsubstantiated hypotheses as established facts.

VoF described Johansson's research pertaining to electromagnetic fields as being of "low quality." Why? What makes his work "low quality"?

In controversial risk issues, nine criteria are often used (A. B. Hill, Proc R Soc Med 58, pp. 295-300, 1965) as the basis for claiming, for instance, that a specific environmental factor indeed causes a disease. The components of Olle Johansson's activities which concern electromagnetic fields, mobile phones and radiofrequency waves do not fulfill these criteria. This conclusion is also shared by the Swedish Research Council in the report "Research on health effects due to electromagnetic fields" (November 1, 2004, in Swedish), where it is emphasized that the research by Olle Johansson has a weak basis both theoretically and methodologically. In addition the Nordic radiation protection authorities have in a consensus communication noted that scientific evidence for dangers from mobile phones is lacking.

A number of rigorous studies have been done on the health dangers of EMFs and Johansson wasn't involved in any of them.

Johansson is not a physicist, but a neuroscientist, yet he makes claims as if he were an expert in physics:

....when Johansson talks about microwaves, he indicates that they are comparable with X-rays and gamma radiation, in spite of the fact that these different sorts of electromagnetic waves relate to entirely different physical phenomena. The important variables relating to electromagnetic fields are frequency and intensity. Unless these are given, deliberations about dangers are meaningless.

In addition, Olle Johansson's discussions of DNA strand breaks manifest grave lack of basic knowledge. As an example, Johansson recently (Stockholms Fria Tidning, December 24, 2004, in Swedish) gave an underestimate of the natural occurrence of such DNA breaks by a factor of 100,000. If one wants to be taken seriously a minimum requirement is to be correct at least with regard to orders of magnitude.

Finally, it has been noted that Olle Johansson insinuates that a large number of diseases such as cancer, blood pressure problems, asthma, allergies and sleep disorders, may be caused by electromagnetic fields. He has also come to the conclusion that malignant melanomas may be caused by TV- and FM-transmissions. A few years ago Johansson received particular attention after he claimed that brain damage, and specifically mad cow disease could be caused by the use of mobile phones (Aftonbladet, March 12, 2001).

In short, the legislators in Maine might have found a better source than Johansson — if they were interested in truth rather than scaring people and getting their pointless bill passed. It is true that Johansson is affiliated with a venerable institution, the Karolinska Institute. However, his main claim to fame is outside his field of expertise and consists in large part of a number of correlations that he has been repeating for years to instill fears — with use of digital PCs and decline in general health, with use of microwave PCs and days of sick leave taken, sales of antidepressant drugs, and death from Alzheimer's.

Johansson has also posited that adverse reactions to cell-phone radiation may develop only after long periods of exposure, as the immune system fails, much in the way that allergies develop." Just as correlation doesn't prove causality, so positing doesn't prove it's so, especially when the positing involves making a claim about the development of allergies as due to immune system failure, which is nonsense. (See Immune System Quackery.)

further reading

The Skeptic's Dictionary entry on electromagnetic radiation, electrosensitives, and Warning: Your Magazine May Be Hazardous to Your Health and WHO Says Cell Phones May Not Cause Cancer by R. T. Carroll.

Cell Phones and Cancer Risk -  The National Cancer Institute Factsheet

Do Cell Phones Cause Cancer? by Bernard Leikind, Skeptic, June 2010. "A cell phone emits about 1 Watt of electromagnetic radiation. Most of that zooms away to find a cell phone tower....while I jog on my local gym’s treadmill for half an hour, I produce 1100 or 1200 Watts....If the cell phone’s less than 1 Watt causes cancers, then why doesn’t my exercise session’s more than 1000 Watts cause cancer?"

John Renish comments: I don’t believe what he says about his energy expenditure on a treadmill. 1100-1200 Watt is well over one horsepower, and trained bicycle racers cannot exceed about 600 Watt in sustained (and much more efficient) effort. IIRC the bicycle racer who flew “Daedalus” (http://en.wikipedia.org/wiki/Human-powered_aircraft) averaged about 300 W for nearly four hours. Also see “300 W” at http://en.wikipedia.org/wiki/Bicycle_performance.

Bob Carroll comments: Phil Stewart, a fitness guru in New Zealand writes on his blog: "One of the best measures of athletic performance is power output. Measured in watts, it’s exactly equivalent to the power that lights a bulb or moves a car. Tour de France cyclists run at about 500 watts for hours on end, and can hit output of 1500 watts in short bursts." So, professional cyclists produce about 500 times the wattage of a cell phone, but do you think they're worried about self-induced tumors from the radiation or the heat?

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