Despite what some say, evidence of genetic effects from exposure to radiation is mounting, writes Tami Thatcher.
By Tami Thatcher
The perennial debate about the “linear no-threshold” model of radiation health effects at low doses is about whether or not there is a “safe” level of radiation that the nuclear industry can ignore. This is the thrust behind Steven Piet’s recommended article by Maurice Tubiana and others (guest column, May 10).
The Tubiana article discusses well-known problems in the linear no-threshold model and the well-known fact that damaged cells can often repair themselves. The problem is the article’s conclusions require tossing out any human evidence not supporting their effort to keep hope alive for existence of a meaningful threshold limit. For all the bluster, the article boils down to animal cell studies where they conclude that “the concept of a practical threshold for carcinogenesis is plausible.”
Many of the flaws in the Tubiana article’s optimistic charade are described in detail in the same journal volume by authors Mark P. Little and Richard Wakeford, who conclude that existing human evidence does not support a threshold above 100 mrem. They recognize that Alice Stewart’s Oxford study from the 1950s cannot be thrown out and that it showed “strong evidence that low dose irradiation of the fetus in utero … causes an increased risk of cancer in childhood.” Also, nuclear workers exposed in daily increments yet receiving doses far under the protection limits also have elevated cancer risk.
Both articles focus on external radiation from “low linear energy transfer” or “low LET” radiation from gamma, X-ray and beta rays. The passing mention of “high LET” radiation from alpha emitters is limited to studies of radium dial painters and medical exposures to thorotrast which, like the atomic bomb Japanese survivor studies, also rely on guesstimates of dose and ignore the unusually high number of premature deaths within five years of the exposure, thus underestimating the cancer death risk.
Neither article addresses the underestimation of health risks from internal radiation from inhalation or ingestion of radionuclides. And neither article adequately addresses genetic effects of radiation. Human evidence of genetic effects from radiation is mounting - from Chernobyl fallout and from exposure to depleted uranium.
The attention given to the linear no-threshold model overlooks the large uncertainties in estimating the dose received by the public in the first place. It ignores the large uncertainty in the cancer death coefficients derived from studies of atomic bomb survivors carefully honed to reduce the stated risks while ignoring a multitude of other serious health impacts. It does not address the variation in radiosensitivity among people, with the developing unborn child being the most vulnerable of all, even vulnerable to radiation exposure of either parent prior to conception.
I don’t mind that Piet is not worried about radiation exposure. But I do find propaganda masquerading as science in order to fool the public to be very troubling.