Health Protection Agency howler
Uranium toxicity calculations defeat the best brains at Britain's statutory radiation risk agency
The Radiation Protection Department of the UK Health Protection Agency (HPA-RPD) has released a "technical response" to questions from the Low Level Radiation Campaign (LLRC). It contains an elementary error in labeling a graph and raises serious doubts about the HPA's competence to advise British authorities on radiation risk, which is the statutory function of its Radiation Protection Department (it used to be the National Radiological Protection Board).
The error concerns evidence for the so-called Secondary Photoelectron Effect (SPE) submitted to HPA by us during a recent consultation on Solid Radioactive Waste Disposal. The Secondary Photoelectron Effect has the potential to explain why releases of some kinds of material from nuclear processes are associated with increased rates of disease.
Elements of high atomic number are known to have a very large ability to block and absorb photons of background radiation. The energy of incident gamma photons is transferred to electrons in the electron cloud of the element's atoms; the absorbed energy causes electrons to be ejected into each atom's immediate vicinity.
This is of particular concern for Uranium, which has a high affinity for the phosphate in the DNA molecule. At quite low ambient levels, DNA becomes saturated with Uranium. This means that DNA begins to act as an antenna, as the Uranium intercepts photons from background gamma fields and re-emits their energy precisely where it will do the most damage. Actual particles of Uranium from nuclear bombs and reactors or from the use of Uranium weaponry will behave in a similar way.
These concerns have been published:
Detailed calculations by researchers show that genetic damage caused by secondary photoelectrons from Uranium would be 1500 times greater than from the inherent radioactivity of the Uranium itself.
On 9th December LLRC received a detailed response, reportedly prepared by John Harrison, Head of the HPA's Dose Assessments Department. In two ways it attempts to diminish the importance of the Uranium photoelectron effect.
· First, it ignores the binding of Uranium to DNA, and presents calculations of average energy absorbed in a hypothetical block of tissue into which Uranium has (unrealistically) been uniformly dispersed. This results in a slight enhancement of average absorbed dose to the tissue.
· Second, it displays graphs purporting to show that the increased absorption by Uranium relative to uncontaminated muscle tissue is a modest 200-fold. To achieve this it compares, on the same axis, the mass energy absorption coefficient ratio for the two different substances with both different absorption coefficients and different densities. This is a mathematical impossibility; the axis label cannot exist as a physical unit. A short paper outlining the HPA's error and recalculating the comparison using correct data from the US National Institute of Science and Technology is at http://www.llrc.org/wobblyscience/subtopic/uraniumhowler.htm. It shows that the result is 20 times greater than HPA calculated, because the HPA forgot that Uranium is about 20 times more dense than living tissue.
The HPA paper acknowledges that little is known about sub-cellular distribution of Uranium in vivo, but as far as we know has no plans to fill the knowledge gap.
HPA also ignores the impact of Uranium particles such as those from Depleted Uranium weapons; the Photoelectron Effect is particularly important for such particles.
In February Dr. Harrison is due to make a presentation to the 5th International Conference on the Effects of Low Dose Radiation (3rd - 5th February 2009, Millennium Point, Birmingham: http://www.ldr09.com/ibis/ldr09/home).
His topic is Internal Dosimetry Recent Developments.
Readers might be interested to know that at the 3rd International Conference in Stratford on Avon, England in May 1997, the Low Level Radiation Campaign conducted a Non-Violent Direct Action; the figure of Death chained himself to the podium while Sir Richard Doll gave his keynote address and activists gave a copy of Chris Busby's Wings of Death to every delegate. At the 4th Conference in Oxford in 2002 Chris Busby was an invited speaker on the health effects of low doses of radiation.