New York: The widespread belief that radiations from X-rays and CT scans can cause cancer has flaws and is based on an unproven theoretical model, suggests a study.
To estimate cancer risk from low-dose radiation, scientists used a model known as linear no-threshold (LNT) in the study published in the American Journal of Clinical Oncology.
But risk estimates based on this model “are only theoretical and, as yet, have never been conclusively demonstrated by empirical evidence”, wrote researcher James Welsh from the Loyola University in Chicago.
The use of the LNT model drives unfounded fears and “excessive expenditures on putative but unneeded and wasteful safety measures”, Welsh noted.
In the LNT model, the well-established cancer-causing effects of high doses of radiation are extended downward in a straight line to very low doses.
The model dissuades many physicians from using appropriate imaging techniques and “discourages many in the public from getting proper and needed imaging, all in the name of avoiding any radiation exposure”, the researcher explained.
This model assumes there is no safe dose of radiation, no matter how small.
However, the human body has evolved the ability to repair damage from low-dose radiation that naturally occurs in the environment.
Studies of atomic bomb survivors and other epidemiological studies of human populations have never conclusively demonstrated that low-dose radiation exposure can cause cancer, according to the study.
Any claim that low-dose radiation from medical imaging procedures is known to cause cancer “should be vigorously challenged, because it serves to alarm and perhaps harm, rather than educate”, the scientists suggested.
The LNT model “should finally and decisively be abandoned”, the authors concluded. (IANS)(Photo: www.continentalhospitals.com)
Cigarettes are not the only tobacco products which can cause death
Other tobacco products like cigars and pipes are just harmful
All these tobacco products can cause cancer
Cigarettes are not the only type of tobacco products that can lead to premature death or fatalities from smoking-related cancers, a U.S. study confirms.
While people who exclusively smoke cigarettes have twice the risk of premature death from all causes compared to people who avoid tobacco altogether, exclusive cigar smokers have a 20 percent higher risk of early death, researchers report in JAMA Internal Medicine.
When it comes to fatalities from specific cancers that have been tied to tobacco use, cigarette smokers have four times the risk of people who never used tobacco, but cigar smokers are 61 percent more likely to die of these cancers and pipe users have 58 percent higher odds.
“We knew exclusive users of cigars and pipes were at greater risk of disease than people who do not use tobacco,” said lead study author Carol Christensen of the U.S. Food and Drug Administration’s Center for Tobacco Products. “However, this study provides information that reflects today’s patterns of tobacco use.”
These data “underscore the importance of complete quitting,” Christensen said by email.
For the study, researchers examined nationally representative survey data, collected starting in 1985, from 357,420 participants who were followed through 2011.
Overall, 203,071 people, or about 57 percent, never used tobacco at all. Another 57,251 participants were current daily cigarette smokers, while 9,414 said they had a less frequent habit and 77,773 were former cigarette smokers.
In addition, 531 people were current daily cigar smokers, while 608 individuals used cigars less frequently and 2,398 had quit.
For pipes, 1,099 participants had a current daily habit, while 78 people used pipes less often and 5,237 had quit.
During the study period, 51,150 people died of all causes.
With a daily cigarette, cigar or pipe habit, people had an elevated risk of death from tobacco-related cancers including malignancies of the bladder, oesophagus, larynx, lung, mouth and throat, and pancreas.
Even with a nondaily cigarette habit, people were more than six times more likely to die of lung cancer than individuals who never used tobacco. They also had more than seven times the risk of dying from a chronic obstructive pulmonary disease, more than four times the odds of death from oral cancers, and 43 percent higher odds of death from a circulatory system disorder.
Current cigar smokers had more than three times the odds of dying of lung cancer, and for current pipe smokers, the risk was 51 percent higher, compared with never-smokers.
The results were limited, however, by the relatively small numbers of cigar and pipe smokers in the sample, the authors noted.
Another limitation was that survey questions about tobacco use changed over time and didn’t determine how often nondaily smokers might have used cigarettes, cigars or pipes.
Even so, the results suggest that doctors may need to broaden how they discuss smoking with patients to make sure people understand they’re at risk even when they don’t have a daily habit, said Dr. Michael Ong of the University of California-Los Angeles and VA Greater Los Angeles Healthcare System.
“Patients often do not associate the occasional use of cigar or pipes with health risks, but this study shows that current, particularly daily, cigar use is associated with increased overall risk of death,” Ong, who wasn’t involved in the study, said by email.
Doctors also need to broaden their message about smoking and cigarettes to include other tobacco products that are becoming more popular, said Judith Prochaska, a researcher at Stanford University in California who wasn’t involved in the study.
Traditionally, doctors have asked just whether people smoked cigarettes, but they should instead be questioning patients more broadly about tobacco use, Prochaska said by email.
“The tobacco landscape has been changing dramatically,” Prochaska added. “While cigarettes remain the primary tobacco product used, cigars, smokeless tobacco, e-cigarettes, hookah, and even pipe tobacco have seen gains in use, while cigarette use in the U.S. has been declining.” VOA