The 1986 Chernobyl and 2011 Fukushima nuclear power plant accidents both share the notorious distinction of attaining the highest accident rating on the International Atomic Energy Agency (IAEA) scale of nuclear accidents. No other reactor incident has ever received this Level 7 “major accident” designation in the history of nuclear power. Chernobyl and Fukushima earned it because both involved core meltdowns that released significant amounts of radioactivity to their surroundings.
Both of these accidents involved evacuation of hundreds of thousands of residents. Both still have people waiting to return to their homes. And both left a legacy of large-scale radioactive contamination of the environment that will persist for years to come, despite ongoing cleanup efforts.
So the tendency is to think of these accidents as similar events that happened in different countries, 25 years apart.
But the IAEA scale isn’t designed to measure public health impact. In terms of health ramifications, these two nuclear accidents were not even in the same league. While Fukushima involved radioactivity exposures to hundred of thousands of people, Chernobyl exposed hundreds of millions. And millions of those received substantially more exposure than the people of Fukushima.
On the occasion of the 30th anniversary of the April 26, 1986 Chernobyl accident in Ukraine, we do well to reflect on the health burden it caused – and compare it with what we expect to see from Japan’s Fukushima nuclear accident. As I report in my book “Strange Glow: The Story of Radiation,” from a public health standpoint, there’s really no comparison between the two events.
Higher doses of radiation, more health harm
Chernobyl was by far the worst reactor accident of all time. A total of 127 reactor workers, firemen and emergency personnel on site sustained radiation doses sufficient to cause radiation sickness (over 1,000 mSv); some received doses high enough to be lethal (over 5,000 mSv). Over the subsequent six months, 54 died from their radiation exposure. And it’s been estimated that 22 of the 110,645 cleanup workers may have contracted fatal leukemias over the next 25 years.
In contrast, at Fukushima, there were no radiation doses high enough to produce radiation sickness, even among the reactor core workers. Two Fukushima workers who had leaky respirators received effective doses of 590 mSv and 640 mSv. That’s above the Japanese occupational limit for conducting lifesaving rescue work (250 mSv), but still below the threshold for radiation sickness (1,000 mSv). Due to their exposure, the two workers’ lifetime cancer risks will increase about 3 percent (from the 25 percent background cancer risk rate to about 28 percent), but they are unlikely to experience other health consequences.
Beyond just the plant workers, over 572 million people among 40 different countries got at least some exposure to Chernobyl radioactivity. (Neither the United States nor Japan was among the exposed countries.) It took two decades to fully assess the cancer consequences to these people. Finally, in 2006, an international team of scientists completed a comprehensive analysis of the dose and health data and reported on the cancer deaths that could be attributed to Chernobyl radioactivity.
Their detailed analysis included countrywide estimates of individual radiation doses in all 40 exposed countries, and regionwide estimates for the most highly contaminated regions of the most highly contaminated countries (Belarus, Russian Federation and Ukraine).
Using statistical models, the scientists predicted a total of 22,800 radiation-induced cancers, excluding thyroid cancers, among this group of 572 million people. Thyroid cancer warranted separate special scrutiny, as we will discuss presently; this hormonally important gland is uniquely affected by a specific radioactive isotope, iodine-131
So that’s 22,800 non-thyroid cancers in addition to the approximately 194 million cancer cases that would normally be expected in a population of that size, even in the absence of a Chernobyl accident. The increase from 194,000,000 to 194,022,800 is a 0.01 percent rise in the overall cancer rate. That’s too small to have any measurable impact on the cancer incidence rates for any national cancer registries, so these predicted values will likely remain theoretical.
Unfortunately, at Chernobyl, the one type of cancer that could have easily been prevented was not. The population surrounding Chernobyl was not warned that iodine-131 – a radioactive fission product that can enter the food chain – had contaminated milk and other locally produced agricultural products. Consequently, people ate iodine-131-contaminated food, resulting in thyroid cancers.
Timothy J. Jorgensen, Director of the Health Physics and Radiation Protection Graduate Program and Associate Professor of Radiation Medicine, Georgetown University
This article was originally published on The Conversation. Read the original article.