Presentation on theme: "Uranium & Health: radiation and mining Public Health Association Australia (NT Branch) 2009."— Presentation transcript:
Uranium & Health: radiation and mining Public Health Association Australia (NT Branch) 2009
Uranium & Health What is Uranium? What is Radiation? Health effects of radiation. Uranium mining. Uranium mining, radiation and health. What about safety standards?
What is Uranium Uranium is one of a number of naturally occurring elements that emit radiation. Uranium U-235 is sought in the mining process - half life of 713million years. However main form that exists is U-238 (around 99.3% of natural uranium), - half life of 4.5billion years. As uranium decays in nature, it eventually, over millions of years turns into lead.
Radon 219 Bismuth Thorium Radium 223 These are known as the daughter or progeny elements Uranium 235 Lead
Uranium has 92 protons in the nucleus. That is its atomic number. U 92 The atomic weight or mass is the number of protons plus the number of neutrons. Uranium- 235: 92 protons plus 143 neutrons. 235 U 92 U-235 i.e. U-235 has 3 less neutrons than U-238
What is radiation? Energy given off to stabilise an element (and in the process change it). Radiation comes in two forms: –Ionising radiation: travels in waves (X-rays, gamma rays) or as particles (alpha, beta) carries very high levels of energy that can alter atoms creating electrically charged particles or ions. –Non-ionising radiation: (radio waves, heat, light) carries enough energy to excite atoms but not enough to create charged ions.
Types of ionising radiation Alpha, beta particles and gamma rays.
Ionising radiation- health effects High speed particles (alpha & beta) and gamma rays damage living tissue: –Damaging cells-sometime repairable –Damaging cells and causing cell multiplications- worst from cancers- stochastic-random –Killing cells- deterministic effect.
Ionising radiation- health effects Depending on the dose this could occur immediately, or over many years, or generations. High doses- nuclear accident-bombs –From immediate death to damage to central nervous system, cancers, reproductive damage, infertility, bleeding, ulceration, nausea, vomiting. Low doses- mine workers, nearby populations –Cancers, -brain, lymphatic system, oesophagus, breast tissue, lungs, spleen kidney, liver and on skin. –Reproductive effects-prenatal developmental, reproductive cells.
How is radiation exposure measured? Radiation exposure is based on how much ionising radiation enters into our bodys cells. –This is based upon the actual energy of the source- the absorbed dose, –weighted by the nature or type of the energy- the equivalent dose, and –then factored by what part(s) of the body are exposed and how they are exposed- the effective dose- measured in milli-Sieverts, a measure of the biological effects of radiation exposure.
Uranium mining On average in Australia to produce 1tonne of Uranium oxide (U308) 848tonnes of ore are mined and 11526tonnes of combined low grade ore and waste rock are left behind to be managed at the mine site.
Uranium mining, radiation and health Exploration & mining disturb and release radioactive material. –Leading to risk of increased radiation exposure to miner workers and local populations. Mine workers primarily through inhalation of radon gas and progeny as well as radiation from the ore and other radioactive minerals and waste. Local populations from transportation of processed ore (risk of accident), dust from mine site (including tailings dam) and through contamination of the water table.
Human health and radon exposure. Radon-only gas in decay chain. Releases harmful alpha particles. 4 decay daughters solids have total half life <1hr all gamma emitters 2 alpha & 2 beta. Lead 210 half life over 20years.
Radon mine fluxes Many uranium deposits dont have a surface radon expression prior to disturbance. Some, do and its variable. Little work has been done to study or report on these sites. Some sites where there is evidence suggest lower levels after rehabilitation some increased levels.
Gamma radiation at mine sites. Gamma radiation signatures vary from deposit to deposit- –Some have major signatures- Ranger, Yeelirrie, Mary Kathleen –Others have none- Olympic dam, Beverley. After most projects commence gamma radiation signatures appear to have increased.
As well as an increased risk of cancers: a study of Namibian miners also found significant reduction in testosterone levels and increases in chromosome aberrations leading to risks to their future children of leukaemia and genetic abnormalities. Further research is needed to explore other non- cancer risks such as strokes and heart disease. Health risks -miners
Risk of radiation Open cutUndergroundIn situ leach Radiation from ore/ on site milling Miners – high Locals- n/a Miners –very high Locals- n/a Miners – high Locals- n/a Radioactive dust- source mining activity (Includes radon gas) Miners – high Locals- medium Miners – very high Locals- possible Miners – n/a Locals- n/a Radioactive dust- tailings (& radon gas) Miners – high Locals- medium Miners – high Locals- medium Miners – low Locals- n/a Water table- due to fracturing of faults and membranes during mining and exploration. Miners – possible Locals- possible Miners – possible Locals- possible Miners – high Locals - high Water table- leakage from tailing dam Miners – possible Locals- possible Miners – possible Locals- possible Miners – possible Locals- possible Transportation accident Miners – possible Locals- possible Miners – possible Locals- possible Miners – possible Locals- possible
Indicative example of radiation from tailings dam
Is there a safe level of radiation exposure? No, there is no known safe levels of exposure to ionising radiation to avoid health risks. As we learn more, levels of allowable exposure for both the public and industry workers have been lowered. yearPer year mSvNo limit setUntil ICRP360mSv mSv mSv1956 ICRP1mSv mSv19871mSv WorkersPublic
What is allowable and what is safe? Current radiation exposure levels for mine workers are based on what the nuclear industry considers is an acceptable risk to workers in order to produce the industrys product and therefore to make a profit. The current standards do not therefore set a safe standard of radiation exposure.
Australian uranium mine worker health- the evidence. No long term study of mine workers from Ranger, Nabarlek or Olympic Dam. Small scale accidents and exposures do occur.
How do you assess the risk? No practice involving exposures to radiation should be adopted unless it produces sufficient benefit to the exposed individuals or to society to offset the radiation detriment it causes. NH&MRC Recommendations for limiting exposure to ionizing radiation (1995) (Guidance note NOHSC:3022(1995)]) and National standard for limiting occupational exposure to ionizing radiation [NOHSC:1013(1995)] republished 2002
Key References: BEIR VII Health risks from exposure to low levels of Ionising radiation European Committee on Radiation Risk FOE 1998 Uranium Mining: how it affects you, Collingwood; Mudd, G 2007 Radon releases from Australian uranium mining and milling projects: assessing the UNSCEAR approach. Jrl. Enviro Radioactivity 3 October Mudd, G 2008 Radon sources and impacts: a review of mining and non-mining issues. Review paper Rev Environmental Sci Biotechnology 7: Williams, B 2008 Radiation & Health energyscience.org.au WISE Zaire, Notter et al in Worker and Community Health Impacts Related to Mining Operations Internationally A Rapid Review of the Literature Carolyn Stephens & Mike Ahern 2001 London School of Hygiene & Tropical Medicine.
Websites Public Health Association of Australia energyscience.org.au is an independent non- governmental organisation established as a collaboration of concerned scientists, engineers and policy experts to present information to people on the issue of sustainable energy. Useful fact sheets World Information Service on Energy
Acknowledgements For critical comments- Dr Gavin Mudd- Monash University, Dr Jim Green- Friends of the Earth. Local colleagues, Dr Peter Tait (PHAA) Dr Hilary Tyler (MAPW) and Dr Tom Keaney (MAPW). Dave Sweeney- Australian Conservation Foundation, Jimmy Cocking- Arid Lands Environment Centre.