Flossing and Fissioning: The Importance of Evidence
- August 9, 2016
- 310 views
The US government has withdrawn its recommendation for flossing teeth, reports the Associated Press. Why? No evidence of benefit! The US is endorsing evidence-based science. Perhaps the US will also use evidence-based science to address rules for exposure to radiation from medical procedures and nuclear power plants.
Evidence everyone sees is that no member of the public was harmed from radiation from the meltdown of three nuclear power plants in Fukushima nor the one at Three Mile Island. The explosion and fire at Chernobyl did kill 26 firefighters with radiation exposures hundreds of times higher than at Fukushima, and 15 unfortunate children died from thyroid cancer from contaminated food. Though protesters hype about tens or hundreds of thousands of cancer deaths, cancer rates in the area actually went down. Evidence.
Radiation dose is measured as energy absorbed per kilogram of tissue. One Gray = 1 joule/kg = 1 watt-second/kg. A similar unit is Sievert; 1 Gy = 1 Sv for X-rays. In 1934 the NCRP (National Council on Radiation Protection) and ICRP (International Commission on Radiological Protection) recommended radiation limits be 734 mGy per year, because no one had been identifiably injured by lower doses. Evidence.
After the bombing of Hiroshima and Nagasaki, scientists sought to induce widespread fear of all radiation to discourage nuclear war. A new theory was developed called LNTH (linear no threshold hypothesis), which said even small radiation doses has a proportionate risk of cancer and death. LNTH is valid for acute exposures exceeding ~100 mGy. But today epidemiologists still analyze noisy data about low-level exposure and health, assuming LNTH is true and then solving for the parameters of the equations.
LNTH is in conflict with evidence that tissues recover quickly at lower doses. This is evidenced hundreds of times a day with fractionated cancer radiotherapy that divides an otherwise deadly radiation dose into safe daily doses over a few weeks. LNTH is in conflict with evidenced effects of 77 Brazilians in Goiania who broke open a discarded radiotherapy source, played with, and even ate some of the glowing radioactive cesium source; four died from acute radiation syndrome, but no one got cancer. LNTH is in conflict with evidence that show no secondary induced cancers in children treated for cancer with doses up to 5000 mGy.
EPA and NRC now set public radiation exposure limits to 1 mSv/year, even 0.1 mSv/year at Yucca Mountain, based on no evidence. Three petitions have been presented to the NRC, asking that public radiation limits be set to 50 mSv/year, well below any evidenced harmful rates.
The biggest obstacle to the progress of fission power plants is not the specific level of safety limit, but the public fear that even low-dose low-dose-rate radiation is harmful. Can we apply evidence-based regulation to both flossing and fission?
Photo Credit: G M via Flickr