MAY 31 — At the Foreign Correspondents’ Club of Japan (FCCJ) on May 30, 2019, Tun Dr Mahathir made perhaps unscripted remarks about ‘spreading out’ the radioactive solid wastes from Lynas’ rare earths refinery at Gebeng, presumably to re-dilute its radioactive content closer down to baseline (background) radioactivity levels.

From the epidemiological (population health) perspective, this is not advisable, and here’s the reason why.

The 2006 US National Academy of Sciences Biologic Effects of Ionizing Radiation (BEIR) VII report is an authoritative source which endorses the linear no-threshold (LNT) model of a linear and causal relationship between ionizing radiation and human cancer risk.  The LNT model accepts that radiation at all levels confer proportionate risk of cancer and explicitly excludes a threshold below which radiogenic cancer risk disappears.  In simple language, cancer risk doesn’t vanish to zero, even at very low (close to zero) doses of radiation.

The way epidemiologists and radiation safety specialists calculate the expected number of radiation-caused cancers of, say leukemia, is to multiply the dose by the expected number of leukemia cases per unit dose in the dose-response relationship of the LNT model.

The BEIR VII report has done that for the US population.

The current allowable radiation exposure endorsed by International Commission on Radiological Protection (ICRP) is 1 mSv per year above natural background levels, for the general public.  (The average dose worldwide from natural background radiation is approximately 2.4 mSv per year https://nuclearsafety.gc.ca/eng/resources/fact-sheets/natural-background-radiation.cfm)

The BEIR VII report estimates that a lifetime cumulative dose of 100mSv would cause an additional 100 leukemia cases from a population of 100,000 males.  In the absence of radiation exposure, the lifetime tally of leukemia cases (from other causes) would be 830. In other words, the lifetime risk of leukemia is increased by about 12 percent as a result of lifetime radiation doses accumulated from exposures at levels close to the current allowable limits.  The corresponding figures for females are 70/590, i.e. a similar 12 percent increase in risk of leukemia  http://dels.nas.edu/resources/static-assets/materials-based-on-reports/reports-in-brief/beir_vii_final.pdf

For this reason, it is little comfort to know that if Lynas’ radioactive solid wastes are recycled as ingredients for road base, cement and other construction materials, fertilizers, Condisoil, etc and ‘spread out’, communities nationwide will be incrementally exposed to low-level radiation at doses comparable to background exposures.

Western Australia's Mines, Petroleum, Energy and Industrial Relations Minister Bill Johnston in effect conceded as much when he said: "Generally speaking, the best place for contaminated material is where it comes from, which in this case would be in the mine void [i.e. sequestered away from possibility of human exposures], but we are not going to take mine waste back from overseas”.

We urgently need Tun Dr Mahathir’s recalcitrant streak.

*Prof Dr Chan Chee Khoon is a consultant and health policy analyst at the Department of Social & Preventive Medicine, Faculty of Medicine, University of Malaya.

** This is the personal opinion of the writer and does not necessarily represent the views of Malay Mail.