Archive

Posts Tagged ‘radiation’

Do Cell Phones Cause Cancer? See What a Real Expert Says

November 24, 2010 6 comments

I’ve written about the issue of cell phones and Wi-Fi and the supposed health risks associated with their use. The resounding scientific evidence shows they are perfectly safe, but the media continues to stoke fear in the public with unbalanced coverage.

When reading a news story about this sort of thing, I always wonder why they don’t ask an actual expert. The answer is that an expert would say how implausible the story is, and that they are silly for reporting it.

That doesn’t sell newspapers.

Instead, they find the one person on the fringe who maintains that there is a magical mechanism by which non-ionizing radiation can harm us. But thankfully, Phil Plait posted on his blog today something I have been looking for a long time.

I’m not a researcher (anymore). I don’t have a Ph.D, so I can tell you what I think, and I can tell you I know what I’m talking about, but I will never have as much credibility as a real university professor in physics or electrical engineering.

Enter this talk by Professor Christopher Davis from the University of Maryland’s Department of Electrical and Computer Engineering. It was given at a National Capitol Area Skeptics meeting, and posted on YouTube. It’s in 5 parts and each part is about 13 minutes long.

It is a fascinating talk and not too technical, so you don’t need a science background to understand the main points. He even touches on backscatter x-ray scanners which have been in the news quite a bit lately. Enjoy!

Ontario Says “No” to Cell Phone Warning Labels

November 5, 2010 1 comment

And it’s the right call. For two reasons:

  1. There is no conclusive scientific data to support any adverse health risks associated with short, moderate, or long-term cell phone use.
  2. A warning label would serve no purpose, other than to instill fear into the users.

The bill proposed to put a sticker on all cell phones indicating that there could be an increased risk of cancer from using a cell phone. Not only is this unnecessary, but it’s also wrong.

The scientific data overwhelmingly shows that there is no increased risk of cancer associated with cell phone use.

And what purpose would a warning sticker on a cell phone serve anyway? Would any of us stop using our cell phones? Would we hold it further from our head while we talk on it?

Of course not. Eventually we would get over our initial shock and fear of the warning sticker, read all the buzz-word containing media-frenzy stories about the evils of technology, and then settle back into our normal routine. All in all, this was a bad idea to begin with.

But my oh my, look who turned up to give her opinion on this issue. Our old friend Prof. Magda Havas from Trent University. She turns up in just about every story that involves cell phones, wireless internet, power lines, dirty electricity, and many other stories trying to convince us that technology is bad.

So I want to get something straight about why she keeps showing up. Is it because she is an expert? I would argue not. Her Ph.D. is in botany (the study of plants) so I don’t see how this qualifies her to study electromagnetic fields and their interaction with the human body. The list of publications on her website has very few peer-reviewed articles. Instead, it’s littered with “Letters to the Editor” and other opinion based writing. Not a lot of scientific credibility there.

No, she shows up because media outlets try to get both “sides” of the story, even if one side is way off base. Enter Magda Havas, who is one of very few people in the world who believes in electrosensitivity and kids getting sick from wireless internet. There are so few people who think this way, that they keep going to one person on the fringe to get her opinion. It is sloppy reporting, and not indicative of the evidence.

On CSI, Grissom (who was the best character but left, and now I am sad) always tells us to “follow the evidence” because the evidence will lead us to the truth. If we follow the evidence about cell phones, we see overwhelming evidence that cell phones are safe. Why then, do we continue to read about how evil they are?

William Peterson as Gil Grissom. From Wikipedia

Be Afraid of Your Wi-Fi! Be Very Afraid!

September 1, 2010 Leave a comment

Wow. I cannot believe this is still in the news.

Its one of those things you hope only happens once and you never hear about it again. Like the Star Wars Holiday Special.

But unfortunately, the Wi-Fi hysteria remains in the news. This time with a couple of new foot soldiers. They include a drama teacher from Brock University, and a self-proclaimed specialist named Barrie Trower.

And perhaps I shouldn’t be surprised, but the reporting of this story in the CBC is really starting to irk me. Lets explore shall we?

I wrote previously about the parents in Simcoe county in Northern Ontario were claiming that Wi-Fi was making their children sick. The supposed dangers of Wi-Fi has been dismissed by teachers, the World Health Organization, Health Canada and scientists worldwide; as it should be.

But proponents of the evils of technology continue to drag the story out and spread fear throughout the community. With a little help from their friends, the news media.

Take, for example, this audio clip of an interview on CBC with Barrie Trower.

Barrie Trower on CBC Metro News

Trower claims to have worked for the British military in the 1960s on experiments dealing with low-level microwave radiation. He claims that they caused adverse health effects; everything from affecting the blood brain barrier to the immune system. He is quite vague and never explains what frequencies or power levels of microwaves he studied.

A couple of my favourite quotes from the audio file are these:

I have a document here…it lists all of the illnesses that  children and adults can get from very low-level microwave radiation. And it specifically says on the top…this must be kept secret…the ordinary general population must not be told because it will affect industrial profit.

What is this document? Who wrote it? There are no specifics given about the origin of this mysterious document. Trower claims he gets it from the freedom of information act, but if that were true he should have given us the specifics so we could look up the document for ourselves. I am skeptical…

When I saw Wi-Fis being put in schools at the same powers and the same levels that were used in the 1960s for experiments, I knew straight away that there were hidden dangers to the young children.

You knew straight away, did you Mr. Trower? What about when Wi-Fi was being put into offices, Universities, laboratories, airports, and coffee shops? Did you not think there was a danger then? It seems interesting to me that only when the story about the Simcoe area parents came out, did Mr. Trower decided that he should reveal to everyone about the secret 50 year old experiments that he did with microwaves.

Nor has Mr. Trower provided and clear arguments or evidence (at least, to the news outlets) that Wi-Fi poses any sort of threat to anyone.

And what about the other British scientists that performed these experiments? I find it odd that they all wouldn’t want to come out and save chidren’s lives if they thought that Wi-Fi was dangerous.
While the interviewer sounds slightly skeptical, he fails to ask the right questions to point out the weaknesses in what this man is saying, so thats YOUR fault CBC.

Now lets move on to the drama teacher from Brock University, one David Fancy. Said Fancy,

It’s not necessarily up to me to say that they cause harm. I think there’s a lot of evidence to suggest that they do. But we certainly can’t say with any conclusive level that they’re safe.

Actually David, yes we can. There is a large body of literature which has studied and reported the effects of exposure to microwave radiation. The conclusion is that at the frequencies and powers associated with cellular phones, cell phone towers and Wi-Fi, the exposure level does not pose any danger.

In fact, 1 years worth of exposure to a wireless signal is roughly the same exposure as you would get in a 20 minute cell phone call. And in a recent large scale study, the long term effects of cellular phone use has not shown any mal-effects over the past 10 years.

Now, just to be fair, there is a small smattering of studies which suggest a health effect from low level microwave exposure, which these fear-mongerers can spout of the top of their heads. However, one has to take into account the entire volume of literature, not just a few isolated studies (most of which have had their conclusions contested).

You see, when a subject is studied as much as RF radiation, there is bound to be some random noise in the results of individual studes; particularly if the studies involve small sample sizes. This is completely expected. What is important is what the overall picture of the studies is, and that picture is that Wi-Fi is safe.

You can all relax now.

This all would be clear in the news stories, if the news outlets bothered to get an actual expert opinion. Why haven’t the CBC gone and interviewed physics Professors or doctors or biologists or RF engineers? Doesn’t this seem like an obvious thing to do?

Apparently not, and its having an effect. On a CBC poll about 1/3 of parents are concerned about Wi-Fi and its health effects. Kudos CBC on causing fear in these parents minds.

Sadly, talking to Physicists doesn’t boost ratings (unless maybe its Phil Plait) so we won’t get those opinions in the news. You have to go and search them out yourselves.

The Physics Of X-Ray Imaging

August 31, 2010 3 comments

So here is Part One of my series of the “Physics Of” medical imaging. First up is the most recognizable: X-ray Radiography.

Radiography (which uses x-rays, but the images are generally called “X-Rays”) are the most common form of medical imaging, and are incredibly useful. Thousands of images are performed everyday and medicine was revolutionized when this non-invasive means to study the body was discovered.

But how exactly do we get x-rays and use them for imaging?

Lets start with a bit of history. The first X-ray image was created by a guy named Wilhelm Rontgen in 1895.

Wilhelm Rontgen

Rontgen called them “X” rays because they were an “unknown” type of radiation, and the name kind of stuck.

The first image was of Rontgen’s wife’s hand, and is pretty cool because you can actually make out her wedding ring.

First image using X-rays of Wilhelm Rontgen's wife's hand

I actually find this a bit funny. I just picture a crazy looking physicist saying “Honey! C’mere! Stick your hand in front of this radiation for a second!”

Luckily for Mrs. Rontgen, x-rays, in small doses, are not very dangerous. So what exactly are x-rays?

X-rays are electromagnetic waves just like visible light, radio waves and microwaves. They have a wavelength range of roughly 0.01 to 10 nanometers (1 nanometer = 1 billionth of a meter).

When talking about x-ray imaging, however, its easier to think of x-rays in terms of photons. Photons are like tiny wave “packets” and electromagnetic waves can be described as a big collection of photons.

X-rays are generated in an x-ray tube (unsurprisingly). Basically, a bunch of electrons are shot at a piece of metal (usually tungsten, the same metal used in old school incandescent light bulbs). Now what happens next is a little complicated, but really cool…

So the electron travels at a certain speed toward the piece of tungsten; it has kinetic energy, which is the energy of motion. But as it gets close to the Tungsten it will run into an electric field produced by the metal, and will actually slow down.

X-ray Tube

Now, in physics there is principle called the conservation of energy. Basically this just says that energy can never be created or destroyed, it can only change form. So when the kinetic energy (energy of movement) of the electron drops (when it slows down) that lost energy has to go somewhere. Where it goes, in fact, is in the generation of an x-ray. The electron will actually emit an x-ray when it gets slowed down by the tungsten. Pretty sweet eh?

Schematic of X-ray tube. Electrons come in from the bottom, strike the tungsten target (the anode) and emits x-rays

This is actually a type of radiation called Bremsstrahlung, which is German for “braking radiation”.

Schematic Diagram of Bremsstrahlung

Ok, so now we got x-rays, how do we make an image?

Well, if we fire x-rays at, oh lets say, YOU! the x-rays will interact with your body. How you ask?

Well when an x-ray passes through the body, it may get absorbed or scattered by the body. An x-ray gets absorbed when the x-ray hits an electron in our body, and the electron “jumps” out of the atom. This is called the photoelectric effect.

The Photoelectric Effect

The x-ray may also get scattered. This just means that the x-ray will get close to the nucleus of an atom and get kind of turned in another direction due to the electric field of the nucleus. This is known as Compton Scattering.

Compton Scattering Effect

In spots of our body that very dense like bones, the x-rays have a much higher chance of getting absorbed or scattered than if they pass through muscle or fat, which are less dense. So if we were to stick a piece of film which is sensitive to x-rays behind someone getting a radiograph, you would get lots of x-rays hitting the film when they pass through muscle or fat, but very few pass through bones (or metal, if you’re really unlucky).

So on the radiograph muscles and fat show up dark, and bones show up white. BAM! Radiograph!

Chest Radiograph

See, now that wasn’t so bad was it? Pretty interesting if you ask me.

The next installment of my “Physics Of” medical stuff  series will be something that takes x-rays to the next level: Computed Axial Tomography, commonly called “CAT” scans.