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http://www.sciencedaily.com/releases/2011/09/
110928142450.htm
Big Tobacco Knew Radioactive Particles in Cigarettes Posed Cancer Risk but Kept
Quiet, Study Suggests
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Tobacco companies knew that cigarette smoke contained radioactive alpha
particles for more than four decades and developed "deep and intimate"
knowledge of these particles' cancer-causing potential, but they deliberately
kept their findings from the public, according to a new study by UCLA
researchers. (Credit: © Aimee / Fotolia)
ScienceDaily (Sep. 28, 2011) Tobacco companies knew that cigarette smoke
contained radioactive alpha particles for more than four decades and developed
"deep and intimate" knowledge of these particles' cancer-causing potential, but
they deliberately kept their findings from the public, according to a new study
by UCLA researchers.
The analysis of dozens of previously unexamined internal tobacco industry
documents, made available in 1998 as the result of a legal settlement, reveals
that the industry was aware of cigarette radioactivity some five years earlier
than previously thought and that tobacco companies, concerned about the
potential lung cancer risk, began in-depth investigations into the possible
effects of radioactivity on smokers as early as the 1960s.
"The documents show that the industry was well aware of the presence of a
radioactive substance in tobacco as early as 1959," the authors write.
"Furthermore, the industry was not only cognizant of the potential 'cancerous
growth' in the lungs of regular smokers, but also did quantitative
radiobiological calculations to estimate the long-term lung radiation
absorption dose of ionizing alpha particles emitted from cigarette smoke." The
study, published online Sept. 27 in Nicotine & Tobacco Research, the
peer-reviewed journal of the Society for Research on Nicotine and Tobacco, adds
to a growing body of research detailing the industry's knowledge of cigarette
smoke radioactivity and its efforts to suppress that information.
"They knew that the cigarette smoke was radioactive way back then and that it
could potentially result in cancer, and they deliberately kept that information
under wraps," said the study's first author, Hrayr S. Karagueuzian, a professor
of cardiology who conducts research at UCLA's Cardiovascular Research
Laboratory, part of the David Geffen School of Medicine at UCLA. "Specifically,
we show here that the industry used misleading statements to obfuscate the
hazard of ionizing alpha particles to the lungs of smokers and, more
importantly, banned any and all publication on tobacco smoke radioactivity."
The radioactive substance -- which the UCLA study shows was first brought to
the attention of the tobacco industry in 1959 -- was identified in 1964 as the
isotope polonium-210, which emits carcinogenic alpha radiation. Polonium-210
can be found in all commercially available domestic and foreign cigarette
brands, Karagueuzian said, and is absorbed by tobacco leaves through naturally
occurring radon gas in the atmosphere and through high-phosphate chemical
fertilizers used by tobacco growers. The substance is eventually inhaled by
smokers into the lungs.
The study outlines the industry's growing concerns about the cancer risk posed
by polonium-210 inhalation and the research that industry scientists conducted
over the decades to assess the radioactive isotope's potential effect on
smokers -- including one study that quantitatively measured the potential lung
burden from radiation exposure in a two-pack-a-day smoker over a two-decade
period.
Karagueuzian and his colleagues made independent calculations using industry
and academic data and arrived at results that very closely mirrored those of
that industry study, which was conducted nearly a quarter-century ago. They
then compared those results to rates used by the Environmental Protection
Agency to estimate lung cancer risk among individuals exposed to similar
amounts of alpha particle-emitting radon gas in their homes.
"The gathered data from the documents on the relevant radiobiological
parameters of the alpha particles -- such as dose, distribution and retention
time -- permitted us to duplicate the industry's secretly estimated radiation
absorbed dose by regular smokers over a 20- or 25-year period, which equaled 40
to 50 rads," he said. "These levels of rads, according to the EPA's estimate of
lung cancer risk in residents exposed to radon gas, equal 120 to 138 deaths per
1,000 regular smokers over a 25-year period."
Despite the potential risk of lung cancer, tobacco companies declined to adopt
a technique discovered in 1959 and then another developed in 1980 that could
have helped eliminate polonium-210 from tobacco, the researchers said. The 1980
technique, known as an acid-wash, was found to be highly effective in removing
the radioisotope from tobacco plants, where it forms a water-insoluble complex
with the sticky, hair-like structures called trichomes that cover the leaves.
And while the industry frequently cited concerns over the cost and the possible
environmental impact as rationales for not using the acid wash, UCLA
researchers uncovered documents that they say indicate the real reason may have
been far different.
"The industry was concerned that the acid media would ionize the nicotine,
making it more difficult to be absorbed into the brains of smokers and
depriving them of that instant nicotine rush that fuels their addiction,"
Karagueuzian said. "The industry also were well aware that the curing of the
tobacco leaves for more than a one-year period also would not eliminate the
polonium-210, which has a half-life of 135 days, from the tobacco leaves
because it was derived from its parent, lead-210, which has a half-life of 22
years."
Karagueuzian said the insoluble alpha particles bind with resins in the
cigarette smoke and get stuck and accumulate at the bronchial bifurcations of
the lungs, forming "hot spots," instead of dispersing throughout the lungs. In
fact, previous research on lung autopsies in smokers who died of lung cancer
showed that malignant growths were primarily located at the same bronchial
bifurcations where these hot spots reside.
"We used to think that only the chemicals in the cigarettes were causing lung
cancer," Karagueuzian said. "But the case of the these hot spots, acknowledged
by the industry and academia alike, makes a strong case for an increased
probability of long-term development of malignancies caused by the alpha
particles. If we're lucky, the alpha particle-irradiated cell dies. If it
doesn't, it could mutate and become cancerous."
Karagueuzian said the findings are very timely in light of the June 2009
passage of the Family Smoking Prevention and Tobacco Control Act, which grants
the U.S. Food and Drug Administration broad authority to regulate and remove
harmful substances -- with the exception of nicotine -- from tobacco products.
The UCLA research, he said, makes a strong case that the FDA ought to consider
making the removal of alpha particles from tobacco products a top priority.
"Such a move could have a considerable public health impact, due to the
public's graphic perception of radiation hazards," he said.
To uncover the information, Karagueuzian and his team combed through the
internal tobacco industry documents made available online as part of the
landmark 1998 Tobacco Master Settlement Agreement. Documents from Philip
Morris, R.J. Reynolds, Lorillard, Brown I Williamson, the American Tobacco
Company, the Tobacco Institutes and the Council for Tobacco Research, as well
as the Bliley documents, were examined, Karagueuzian said.
The team searched for key terms such as "polonium-210," "atmospheric fallout,"
"bronchial epithelium," "hot particle" and "lung cancer," among others.
Karagueuzian said the earliest causal link between alpha particles and cancer
was made in around 1920, when alpha particle-emitting radium paint was used to
paint luminescent numbers on watch dials. The painting was done by hand, and
the workers commonly used their lips to produce a point on the tip of the paint
brush. Many workers accumulated significant burdens of alpha particles through
ingestion and absorption of radium-226 into the bones and subsequently
developed jaw and mouth cancers. The practice was eventually discontinued.
Another example involves liver cancer in patients exposed to chronic low-dose
internal alpha particles emitted from the poorly soluble deposits of thorium
dioxide after receiving the contrast agent Thorotrast. It has been suggested
that the liver cancers resulted from point mutations of the tumor suppressor
gene p53 by the accumulated alpha particles present in the contrast media. The
use of Thorotrast as contrast agent was stopped in the 1950s.
In addition to Karagueuzian, authors of the study include the late Amos Norman,
professor emeritus in the departments of radiation oncology and radiological
sciences at UCLA; James Sayre, of the departments of biostatistics and
radiological sciences at UCLA; and Celia White, who served from 1999 to 2002 as
director of content and services at the Legacy Tobacco Documents Library, which
contains more than 13 million documents created by major tobacco companies
related to their advertising, manufacturing, marketing, sales and scientific
research activities.
The study was funded by the University of California Tobacco-Related Disease
Research Program, established by the passage of California's SB1613 in 1989 to
fund a comprehensive University of California grant program to support research
into the prevention, causes and treatment of tobacco-related diseases.
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Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily
staff) from materials provided by University of California - Los Angeles Health
Sciences, via EurekAlert!, a service of AAAS.
Journal Reference:
Hrayr S. Karagueuzian, Celia White, James Sayre, and Amos Norman. Cigarette
Smoke Radioactivity and Lung Cancer Risk. Nicotine & Tobacco Research,
September 27, 2011 DOI: 10.1093/ntr/ntr145
Need to cite this story in your essay, paper, or report? Use one of the
following formats:
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MLA
University of California - Los Angeles Health Sciences (2011, September 28).
Big Tobacco knew radioactive particles in cigarettes posed cancer risk but kept
quiet, study suggests. ScienceDaily. Retrieved September 30, 2011, from
http://www.sciencedaily.com /releases/2011/09/110928142450.htm
Note: If no author is given, the source is cited instead.
Disclaimer: This article is not intended to provide medical advice, diagnosis
or treatment. Views expressed here do not necessarily reflect those of
ScienceDaily or its staff.
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