Christopher Busby - Second Event Theory and Photoelectric Effect Controversy

Second Event Theory and Photoelectric Effect Controversy

From 1987 onwards Busby has worked in particular on the health effects of ionizing radiation, developing the 'Second Event Theory' and 'Photoelectric Effect Theory' which distinguishes between hazards from external radiation and internal irradiation from ingested radioisotopes, upon which he claims the widely accepted linear no-threshold (LNT) model substantially underestimates the risk of low level radiation (the LNT model is largely constructed from the 1958 to 2001 'Life Span Study' of the 120,321 Japanese Atomic Bomb Survivors (hibakusha (被爆者?)) who were exposed to a powerful external burst of neutron and gamma radiation). Busby claims that in the low dose regime, radiation moderately above background causes more cancer than much higher levels of radiation i.e. a biphasic (bimodal) curve; a claim based on the work of Elena Burlakova.

Busby initially proposed the Second Event Theory (SET) in 1995, in his self-published book 'Wings of Death: Nuclear Pollution and Human Health' claiming that isotopes which decay sequentially, emitting two or more particles in a short decay chain, have far greater genotoxic effects than predicted by the LNT model. In particular, Busby's SET predicts that the 90Sr-90Y decay chain might be some ~30 times more carcinogenic than predicted by LNT, because primary exposure to a beta particle alters a cell to the G₂ Phase, in which it is highly radio-sensitive, and a second particle "hit" within a few hours is more likely to cause carcinogenesis.

SET was criticized by Cox & Edwards (2000) who stated that if Busby's "biologically implausible" theory was correct and all irradiated cells undergo transformation to the G₂ Phase, it would cause an increased risk factor of just 1.3 times and predict, on the contrary, substantial risk reduction at low doses for single emitting radioisotopes. Furthermore, it was established in 1906 (The Law of Bergonié and Tribondeau) that cells in the G₂ Phase are more resistant to radiation than cells in the M Phase (Radiosensitivity and Cell cycle). The Committee Examining Radiation Risks of Internal Emitters (CERRIE) report, on which Busby was one of twelve members, exhaustively examined the biological plausibility of SET and commissioned an independent consultant to conduct a literature review. In 2004 CERRIE rejected the SET by a 10 to 2 majority consensus (Busby and non-scientist Richard Bramhall, dissented). The rejection was made for following reasons:

• The lack of biological plausibility for the basic preconditions of the SET
• The paucity of supporting evidence in the proponents’ reviews of the SET
• The weakness of studies cited in support of the SET
• The absence of supporting evidence found by the independent review commissioned by the Committee

CERRIE also considered and rejected by 10 to 2 consensus the biphasic (bimodal) curve of Burlakova et al. (1999), due to the study's "substantial shortcomings"; tables were so ambiguous that the risk-dose response could be interpreted as linear, biphasic or even promoting health (radiation hormesis).

Busby responded by selling for £25 a 3 person minority report on his website, which claims that internal low-level radiation is 300 times more dangerous than predicted, the currently accepted LNT model is meaningless, and in Sweden and Belarus cancer rates have risen by 40% since Chernobyl.

Later work by Busby focused on the health effects of ingested Depleted Uranium particles. In particular he proposes that ingested Uranium particles cause photoelectric enhancement that increases the genotoxic effect of natural background gamma radiation by 500 to 1000 times (he claims natural gamma rays strike Uranium and generate via the photoelectric effect secondary electrons that damage cells). Recent work by Busby (2008) focusing on the photoelectric enhancement as a mechanism of cells damaged by ingested Uranium particles has been covered by New Scientist magazine, with most of the scientists quoted in response expressing interest but also some skepticism that the effect could be as large as claimed. Additionally, according to Busby, photoelectric enhancement is not limited to radioactive isotopes but involves all heavy atoms (high-Z) e.g. stable platinum particles from catalytic converters are similarly theoretically capable of enhancing the effects of natural gamma radiation if ingested.

However, subsequent computer simulations by Pattison, Hugtenburg & Green (2010) indicate a radiation enhancement factor of only 1 to 10 fold for uranium particles, considerably lower than Busby's preliminary estimate. Indeed, a large body of research has accumulated into the efficacy of gold nanoparticle-aided radiation therapy (GNRT), where the effects of radiotherapeutic intense gamma ray and x-ray sources are modestly enhanced via the photoelectric effect by 0.3 to 1.16 fold, a lower range than estimated for uranium particles.