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How Risky are CT Scans?

February 13, 2014 by Michael Greger M.D. in News with 26 Comments

Cancer Risk from CT Scan Radiation

The greatest radiation exposure risk comes not from the Fukushima fallout or the polonium naturally found in all seafood (see my last video, Fukushima and Radioactivity in Seafood), but from doctors.

This was the study that originally shook things up: “Estimated Risks of Radiation-Induced Fatal Cancer from Pediatric CAT scans.” Researchers concluded that the best available risk estimates suggest that pediatric CAT scans (also known as CT scans) will result in significantly increased lifetime radiation risk. How increased? In the United States, of the approximately 600,000 abdominal and head CT scans annually performed in children under the age of fifteen, 500 of these individuals might ultimately not just get cancer but die from cancer attributable to the CAT scan radiation. In response to this revelation, the editor-in-chief of the leading radiology journal admitted that radiologists have not been watching out for children.

The cancer estimates were based on data from Japanese atomic bomb survivors, in terms of how many deaths one can expect from what kind of radiation dose. However, there’s never been a study able to actually document the excess cancers—until now. It turns out that the X-rays released by CAT scanners may be twice as carcinogenic as the higher energy gamma rays released from atomic bombs. Just a few CT scans may triple the risk of brain tumors and leukemia in children.

Other studies are being performed around the world to quantify the risk and should be out in the next few years. Until then, what can we do? First of all, we should get X-rays only when absolutely necessary. Good evidence suggests that between a fifth and a half of CAT scans aren’t necessary at all—they could be replaced with another type of imaging or not performed at all. That’s a lot of added cancer risk for no added benefit.

If you check out my 4-min video Cancer Risk From CT Scan Radiation, you can see the risk of developing cancer for different groups after getting one CT scan. The risk of developing cancer after a single CT scan may be as high as 1 in a 100 for a baby girl. It can take years for cancer to develop, though, which is why the risk is lower in the elderly since they have fewer years left to live. The diagnostic medical radiation dealt out in one year is estimated to cause 2,800 breast cancers among women in the United States, and 25,000 other cancers. That’s doctors causing a lot of cancer.

One chest CT scan is like getting 400 chest X-rays, and a stress test heart scan can be like getting over a thousand X-rays. Doctors need to communicate the risks of these procedures, using relatable analogies. For example, the risk of a chest CT is like the risk of having a car crash during 2500 miles of highway driving or of smoking 700 cigarettes. You pick up a pack of cigarettes and there’s a warning label, but then you go in for thallium heart scan, and no one minds telling you that the risk corresponds to smoking 1400 cigarettes. One in every 270 middle-aged women that get an angiogram may get cancer because of that one test.

The risk associated with the thallium heart scans shocked me. By eating healthy, we may not only eliminate the death and disability associated with heart disease and its treatment (such as open heart surgery), but the risks associated with heart disease diagnosis as well. See these videos for my advice on preventing heart disease:

As I explain in my full-length live presentation on preventing, arresting, and reversing the 15 top killers (Uprooting the Leading Causes of Death), adverse drug reactions from prescription drugs are estimated to cause more than 100,000 deaths in the United States every year, making doctors the sixth leading cause of death. And that’s not counting other “iatrogenic” (physician-caused) harm, such as these radiation risks or medication errors or infections acquired in hospitals. My profession needs to do a better job of offering fully informed consent, clearly and comprehensively explaining the risks and benefits of each alternate course of action.

What about getting X-rays at the dentist? I’ve got a video about that too: Do Dental X-Rays Cause Brain Tumors?. And cell phone radiation? See my video Do Cell Phones Cause Cancer?

-Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death and More Than an Apple a Day.

Image credit: thesmokingsection / Flickr

Fukushima Radiation and Seafood

February 11, 2014 by Michael Greger M.D. in News with 25 Comments

Fukushima and Radioactivity in Seafood

With prevailing westerly winds over Japan, radioactive fallout from the Fukushima nuclear power plant tragedy was detected throughout North America at levels comparable to those seen 25 years earlier from Chernobyl, the only other category 7 nuclear event in history.

The highest levels of radioactive iodine in rain water were found in Boise, Idaho, and the highest levels in milk were found in San Francisco at levels ten times higher than the federal maximum allowed in drinking water. This is below that which would be expected to pose a direct threat to U.S. public health, but a controversial paper in the International Journal of Health Sciences suggested the radioactive plume from the nuclear meltdowns in Fukushima may be responsible for the subsequent bump in U.S. mortality — similar to what we saw after Chernobyl (see my 4-min video Fukushima and Radioactivity in Seafood for details). However, the authors themselves underscore that their research shows merely a correlation, and potential evidence of a causal link. They stress that more research is necessary.

Of all the radiation released, only a tiny fraction of the fallout reached U.S. shores—most was absorbed by the Pacific Ocean. What does that mean for seafood safety?

Researchers report unequivocal evidence that Pacific Bluefin tuna have transported Fukushima-derived radioactive fallout across the entire North Pacific Ocean. Tuna migrate from Japan to California and appear to have taken some radioactivity with them.

Unfortunately, more than just radiation from nuclear disasters enters our oceans. Our oceans have become humanity’s sewers; everything eventually flows down into the sea. This has implications for other aspects of seafood safety:

Even though there was a 10-fold spike in radioactive cesium levels in tuna, the researchers put it in context by noting that there were baseline levels of radioactivity in fish even before Fukushima, due to everything from thermonuclear weapons tests and sunken nuclear submarines to the radioactive elements found naturally in the earth’s crust.

The levels in seawater of radioactive polonium (the element used in the horrific assassination of Russian dissident Litvinenko) are miniscule, but it strongly bioaccumulates up the food chain into fish. Polonium is a by-product of uranium decay and is frequently cited as one of the reasons that tobacco is so carcinogenic. That was something the tobacco industry was well aware of and could have easily removed, but the process that could have removed the polonium affected the absorbability of nicotine. The loss of the nicotine “kick” sensation was found unacceptable by industry executives. So they kept the polonium in.

Cigarette manufacturers’ protection of stockholders over the public is not unique to that sector. More industry hijinks in:

The radioactive polonium in cigarettes has been speculatively blamed for the link between smoking and male infertility, but most of human exposure comes from diet—mainly fish and shellfish. And this was before Fukushima.

So what happens if we eat seafood? Researchers measured the increase in radioactive polonium levels in semen after a single seafood meal. It caused a 300 percent spike in radioactivity levels. Probably not enough to cause infertility—but that was just one meal. Whether the kind of dose you can get from eating seafood is high enough to damage sperm cells still needs to be established. Researchers calculate that may have to eat as much as a pound of seafood a month before we might realize the harmful effects of the radiation.

More on infertility in:

Interestingly, there’s 8 times more polonium in cooked shrimp than in raw. Researchers think it’s because most of the polonium is in the shrimps’ internal organs, which is released in to the boiling water and contaminates the muscle. Gutting crustaceans before cooking may therefore decrease radiation exposure.

The greatest radiation exposure risk, however, comes not from Fukushima fallout or the polonium naturally found in seafood, but from doctors. See my video, Cancer Risk from CT Scan Radiation. This was touched on in a recent New York Times op ed.

-Michael Greger, M.D.

PS: If you haven’t yet, you can watch my live year-in-review presentations Uprooting the Leading Causes of Death and More Than an Apple a Day or sign up for my free daily, weekly, or monthly video updates.

Image credit: Photl

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