April 30, 2011

Applying the Union of Concerned Scientist analysis of Chernobyl to Commercial Aviation

The Union of Concerned Scientists (UCS) All Things Nuclear blog has an analysis of how many deaths occurred at Chernobyl based on linear no threshold view of radiation. So 0.01 milliSieverts (1 milliRem) for each of 6 billion people in the world is calculated to add 4000 deaths from cancer. 0.3 milliSieverts (30 milliRem) for 500 million people in europe is calculated to add 9000 more deaths from cancer.

Using the same analysis (NEI Nuclear Notes) found that, 79,000 and 40,000 would be reasonable estimates of the number of excess cancers and cancer deaths attributable to the flying in the past decade. The numbers increase even more over the 25 years since Chernobyl and would be 200,000 excess cancers and 100,000 excess deaths from commercial aviation over the last 25 years.

As the US EPA (Environmental Protection Agency) explains, exposure to cosmic radiation depends on altitude, latitude, and solar activity, but the EPA estimates that "a typical cross-country flight in a commercial airplane" results in "2 to 5 millirem (mrem)" of dose from radiation.

The statistics from the US Bureau of Transportation Statistics indicate that over 7 billion airline passengers (international and domestic) flew in the US between January 2001 and January 2011. Thus, if we assume a fairly low average value of 3 millirem per passenger, then aviation has resulted in a collective dose of 210,000 passenger-Sv over the past decade.

This is quite a large number already, but Dr. Gronlund did not consider the radiation exposure within just one country. She provided an estimate for the entire world. So we should follow suit.

The US aviation market comprises somewhere between 25 to 30 percent of the entire world's airline passengers (e.g., in 2009, passengers in the US comprised roughly 28% of the airline passengers worldwide, according to IATA statistics). Thus, if we conservatively assume that US passengers comprised 30% of the passengers worldwide during the past decade, then worldwide, the collective dose due to commercial aviation is 700,000 passenger-Sv.

Using Dr. Gronlund's methodology (which was taken from the BEIR VII report), we should assume that "the expected incidence and mortality of solid cancers and leukemia are 0.1135 cancer cases and 0.057 cancer deaths per Sv." Thus, because of radiation exposure due to the airline industry, the expected number of cancer cases is 79,000, of which some 40,000 should result in death.

Note however that, because exposure only increases the probability of developing cancer, we should keep in mind that no given cancer can be attributed to flying. Moreover, because these additional cancers will be distributed among hundreds of millions of people, it is practically impossible to discern them among all the other cancer cases. (About 42% of the general population have cancer at some point in their lives, and about 20% of the population die because of cancer or complications that result from cancer.)

It is somewhat illustrative to compare these numbers to the numbers presented by Dr. Gronlund for the Chernobyl accident: 68,000 cancer cases with 34,000 deaths. Given these numbers, one can scientifically conclude that the airline industry is far more dangerous -- in terms of deaths due to low-dose exposure to radiation -- than old, Soviet-era nuclear reactors.

In light of these numbers, I expect that the UCS will be setting itself up as an "aviation watchdog" any day now.

Understanding how civil nuclear technology is the safe green solution, Oxford Physics

Oxford Physics Estimate using the study of survivors of the atomic bombs based on radiation exposure as they were tracked for many decades - 28(acute)+3(thyroid)+c.78(solid cancers)+c.3(leukaemia). Crude but unbiased estimate. Anyway less than 200 deaths.

•Radiation is like other hazards –life has defenses
•Low-dose repair time is on the scale of a day or so
•Doses below threshold (100mSv) cause no damage.
•Above threshold, permanent damage (scar tissue) results. Such scar tissue may remain benign, or later become malignant, like other scars

Examples where radiation at 2-9 millisieverts (200-900 milliRem) per year and 40 millisieverts (4 Rem) per year did not increase cancer risk

In Taiwan, there was an incident where radioactive steel rebar was used in a building and people lived with the radiation for many years.

In Taiwan, there was an incident where radioactive steel rebar was used in a building and people lived with the radiation for many years.

An extraordinary incident occurred 20 years ago in Taiwan. Recycled steel, accidentally contaminated with cobalt-60 (half-life: 5.3 y), was formed into construction steel for more than 180 buildings, which 10,000 persons occupied for 9 to 20 years. They unknowingly received radiation doses that averaged 0.4 Sv - a collective dose of 4,000 person-Sv.

Based on the observed seven cancer deaths, the cancer mortality rate for this population was assessed to be 3.5 per 100,000 person-years. Three children were born with congenital heart malformations, indicating a prevalence rate of 1.5 cases per 1,000 children under age 19.

The average spontaneous cancer death rate in the general population of Taiwan over these 20 years is 116 persons per 100,000 person-years. Based upon partial official statistics and hospital experience, the prevalence rate of congenital malformation is 23 cases per 1,000 children. Assuming the age and income distributions of these persons are the same as for the general population, it appears that significant beneficial health effects may be associated with this chronic radiation exposure.

Radiation exposure of airline crews. (100 Rems equals one Sievert)

Epidemiological studies of cancer in aircrew find no increase in cancer (other than skin cancer for those who tan too much)

There are about 250,000 pilots and flight attendants in the world. Another 450,000 pilots of other types.

Full time pilots and flight attendants can get two to four times the regular amount of radiation in a year.

2.2 mSv: airline crew member, short flights for one year
3-6 mSv: airline crew member, cross-country flights, 900 hrs/yr for one year
10 mSv: cooking with natural gas (radon) for a year
5-15 mSv: one full-body CT scan for about 20 minutes
6-18 mSv: one chest CT scan for about 10 minutes
9 mSv: airline crew member, polar flights, such as Tokyo-NYC, 900 hrs/yr for one year
13 mSv: smoking one pack of cigarettes per day for a year
20 mSv: nuclear plant worker, maximum 5-year average*+
50 mSv: nuclear plant worker, maximum total exposure in one year
50-100 mSv: changes in blood chemistry
100 mSv: lowest clearly carcinogenic level; 1 millimort

So airline crew flying long haul routes for ten years would get 30-90 mSv and for 20 year would get 60-180 mSv

Where is the increased cancer ? The peer reviewed studies do not find it.
Not for the 10,000 people in Taiwan and not for the airline crews

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