タバコに放射性物質が含まれているのは科学的に証明されている

このエントリーをはてなブックマークに追加

2011年04月04日(Mon) 14:47 by drharasho

タバコに放射性物質が少量ながら含まれていて、
喫煙者の肺に沈着し、内部被曝によって発がんの原因と
なるだろうことが示されています。

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Tobacco Smoke

While cigarette smoke is not an obvious source of radiation exposure, it contains
small amounts of radioactive materials which smokers bring into their lungs as
they inhale. The radioactive particles lodge in lung tissue and over time
contribute a huge radiation dose. Radioactivity may be one of the key factors in
lung cancer among smokers†.

On this page:

    * How many people are exposed to radioactivity in cigarettes?
    * How does radioactive material get into a cigarette?
    * What happens when I smoke a cigarette?+
    * Resources

How many people are exposed to radioactivity in cigarettes?

According to the American Lung Association, there are about 48 million adult
smokers in the U.S., and 4.8 million adolescent smokers. This means that the
U.S., population, directly exposed to radioactivity in cigarette smoke, is
approximately 53 million.

According to the Centers for Disease Control and Prevention, 80 percent of adult
tobacco users started smoking as teens; 35 percent had become daily smokers by
age 18.  Thirty nine percent of adult smokers smoke one pack of cigarettes per
day, and 20% smoke more than a pack a day.

Smoking is the number one cause of preventable death in the U.S., with 443,000
deaths, or 1 of every 5 deaths, in the United States each year. And, there are
 123,000 lung cancer deaths annually attributed to smoking cigarettes. Nearly 1
of every 5 deaths is related to smoking, more than alcohol, car accidents,
suicide, AIDS, homicide, and illegal drugs combined.

In addition to smokers, those exposed to secondhand or side-stream smoke have
been shown to risk disease as well. In some studies, it has been found that
side-stream or secondhand smoke is two to five times more concentrated in some
carcinogens than the mainstream smoke inhaled by a smoker. Each year,
approximately 3,400 nonsmoking adults die of lung cancer as a result of breathing
the smoke of others’ cigarettes. Environmental tobacco smoke also causes an
estimated 46,000 deaths from heart disease in people who are not current smokers.
Secondhand smoke contains over 4,000 chemical compounds, including 69 known
carcinogens such as formaldehyde, lead, arsenic, benzene, and radioactive polonium 210.

How does radioactive material get into a cigarette?

The tobacco leaves used in making cigarettes contain radioactive material,
particularly lead-210 and polonium-210. The radionuclide content of tobacco
leaves depends heavily on soil conditions and fertilizer use.

Soils that contain elevated radium lead to high radon gas emanations rising into
the growing tobacco crop. Radon rapidly decays into a series of solid, highly
radioactive metals (radon decay products). These metals cling to dust particles
which in turn are collected by the sticky tobacco leaves. The sticky compound
that seeps from the trichomes is not water soluble, so the particles do not wash
off in the rain. There they stay, through curing process, cutting, and manufacture
 into cigarettes.Lead-210 and Polonium-210 can be absorbed into tobacco leaves
directly from the soil. But more importantly, fine, sticky hairs (called trichomes)
 on both sides of tobacco leaves grab airborne radioactive particles.
For example, phosphate fertilizers, favored by the tobacco industry, contain
radium and its decay products (including lead-210 and polonium-210). When
phosphate fertilizer is spread on tobacco fields year after year,
the concentration of lead-210 and polonium-210 in the soil rises.

What happens when I smoke a cigarette?

Research indicates that lead-210 and polonium-210 are present in tobacco smoke as
 it passes into the lung. The concentration of lead-210 and polonium-210 in
tobacco leaf is relatively low, however, this low concentration can accumulate
into very high concentrations in the lungs of smokers.

As it passes into the lungs, the smoke impacts the branches of the lung passages,
 called bronchioles, where the branches split. Tar from tobacco smoke builds up
there, and traps lead-210 and polonium-210 against the sensitive tissues of the
bronchioles. Studies show filters on ordinary commercial cigarette remove only
a modest amount of radioactivity from the smoke inhaled into the lungs of smokers.
 Most of what is deposited is lead-210, but polonium-210 (whose half life is about
 138 days) quickly grows in as the lead-210 (half life = 22.3 years) decays and
becomes the dominant radionuclide. Over time, the concentration of polonium-210
directly on tissues of the bronchioles grows very high, and intense localized
radiation doses can occur at the bronchioles.


Resources

Cancer Facts & Figures 2008
August 2008 - American Cancer Society

Trends in Tobacco Use
August 2008 - American Lung Association

Source of Lead-210 and Polonium-210 in Tobacco 
August 2008

2004 Surgeon General's Report—The Health Consequences of Smoking
August 2008

The Health Consequences of Involuntary Exposure to Tobacco Smoke:
A Report of the Surgeon General
August 2008

Statement by American Cancer Society, American Lung Association,
American Heart Association and Campaign for Tobacco-Free Kids
August 2008

Radioactivity in Tobacco Leaves
August 2008


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