EPA issues revised Blue Book of Radiogenic Cancer Risk Models and Projections for the US
2011 EPA Exposure Factors Handbook released.
Introduction - The Big "IF"
Whether radiation or radioactivity at the levels most TENORM wastes contain is dangerous is the big unknown. The premise that any exposure to radiation, no matter how small, carries some element of risk is the current basis for radiation protection. The "Linear No Threshold Hypothesis" has been integral to radiation protection laws for over 40 years.
This section will review the different arguments for and against LNT, and try to provide resources for further review. Estimating risk is a complicated task, and discussing it objectively is not easy either. There are numerous factors that go into estimating risk, and there have been arguments about the metric involved - cancer deaths, instead of estimating risks for non-fatal insults - like blood disease or osteoperosis. Others are concerned that the "standard man"
The victims of the Hiroshima and Nagasaki bombings have been tracked since 1950 for impacts from the bombings. The dosimetry used from those studies (along with the radium dial painters and uranium miners) are the basis for corellating exposure to risk of cancer. The type of radiation from the bombs - mostly gamma and neutron, are used to estimate both external exposure and internal exposure. This dosimetry is being questioned as to whether correct risk factors have been assigned to neutrons. There may be evidence showing that neutrons are more responsible for the damage to the survivors as previously thought.
Changing the relationship between exposure and risk changes the basis for all our radiation protection regulations. Extrapolating risk down to very low exposures to chronic background-levels of radiation is tricky, because we cannot distinguish cell damage from radiation from normal cell damage from natural processes like oxidation.
There are raging debates in the scientific community about the validity of the LNT. Epidemiology can't prove one way or the other whether there are harmful or beneficial effects of low level radiation exposure. Some studies show a positive benefit from low levels of radon exposure based on county by county statistics. Others show a linear response, as predicted by the LNT based on data from uranium miner studies. Biologists are working towards identifying markers that would distinguish cell damage from radiation from other types of insults. Other scientists are discovering that a single alpha particle traversing both strands of DNA can damage the DNA enough to overcome normal cell repair process and mutate, potentially causing cancer.
This section under construction - more to come as time allows!