Presentation on theme: "Uranium & Health: radiation and mining"— Presentation transcript:
1 Uranium & Health: radiation and mining Public Health Association Australia (NT Branch) 2009
2 Uranium & Health What is Uranium? What is Radiation? Health effects of radiation.Uranium mining.Uranium mining, radiation and health.What about safety standards?
3 What is UraniumUranium 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.Other radioactive minerals include: Thorium, Rare Earth Elements.Uranium is one of the least plentiful element, only two parts per million of the earths crust.U-235 easily fissionable- therefore most useful isotope for nuclear energy.Half life time it takes to lose half its radiation.U238 the most common form of uranium half life 4.5 billion years. U238 can be used in production of fissionable material, Alpha emitter. Yields primary fissionable material plutonium 239.
4 These are known as the daughter or progeny elements Uranium 235ThoriumThese are known as the daughter or progeny elementsRadium 223Radon 219As elements decay they form new elements called daughter or progeny elements, these have varying half lives from extremely short measurable in hours to extremely long- millions of years. These are called decay chains, and they are different for each different isotope.Natural uranium has both U238 and U235, U235 is for bombs/reactors, but U238 is most important in radiation exposure since it is 99.3% of natural uranium and therefore the dominant source of exposure.Sources:http://en.wikipedia.org/wiki/Image:Decay_scheme_U235.pngBismuthLead
5 Uranium has 92 protons in the nucleus. That is it’s atomic number. U92 The atomic weight or mass is the number of protons plus the number of neutrons.Uranium- 235: 92 protons plus 143 neutrons.235U92U-235i.e. U-235 has 3 less neutrons than U-238The atom is the smallest unit of matter that retains the chemical properties of an element.An atom has an electron cloud consisting of negatively charged electrons surrounding a dense nucleus. The nucleus contains positively charged protons and electrically neutral neutrons.An atom is classified according to its number of protons and neutrons: the number of protons determines the chemical element and the number of neutrons determines the isotope of that element. The combined weight of the protons and neutrons is called the atomic weight.When the number of protons and neutrons are balanced then the element is stable. When the they unbalanced they are termed unstable and they tend towards stability by emitting energy –radiation. In doing so they change the ratio of protons and neutrons.Source(s): WISE and Goldstick, M ‘Nuclear Words and terms’ WISE Amsterdam.
6 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 asparticles (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.Radiation is the mechanism that unstable elements tend towards stability by giving off energy from the nucleus, i.e. an element that has an imbalance of neutrons and protons- to tend towards stability and gives off energy - radioactive decay.This energy is released in the form of gamma rays or fast moving alpha or beta particles.This radioactive decay is called ionising radiation because electronically charged particles called ‘ions’ are produced in the materials it strikes.Source(s): WISE and Goldstick, M ‘Nuclear Words and terms’ WISE Amsterdam.
7 Types of ionising radiation Alpha, beta particles and gamma rays.Alpha particles are positively charged particles (made up of two neutrons and 2 protons) which are emitted from the nucleus to reduce its mass. It is the largest atomic particle emitted by radioactive material. These particles are essentially a helium atom without electrons. So when an alpha particle is emitted the element changes (its lost 2 protons). It is relatively very light, so it can travel very fast. It cannot easily penetrate clothing or skin, but is highly dangerous if inhaled or digested. By itself it only travels about a centimetre in air from its source, but may attach to another particle and be transported. Alpha radiation is the most harmful form of radiation to living cells (when inhaled or ingested).Beta particles occur when a neutron expels a negatively charged part of itself (essentially an electron), and then turns from being a neutron into a proton. This changes the element, because it has gained a proton. These are smaller and lighter than alpha particles- also travel very fast, and up to about ½ a metre in air from source. Penetrates paper and several millimetres of skin, Can not go through thin steel or wood above 5 centimetres thick.An unstable nucleus while emitting alpha or beta particles will also often rid itself of excess energy through Gamma radiation a short intense burst of electromagnetic energy. Which travels at the speed of light over long distances, easily penetrating the human body, it can be stopped by a very dense substance in a thick enough layer, such as lead or concrete.X-rays are not usually produced by decaying elements, but rather are present in cosmic radiation, but more usually produced by X-ray machines.In nuclear fission reactors neutrons are ejected from the nucleus to collide with other atoms, causing a fissionable nuclear chain reaction and releasing massive energy, used to heat the water around the reactor to produce steam to drive turbines and generate electric power. I.e. boiling the kettle.Atom image from U.S. Nuclear Regulatory Commission (NRC) <http://www.nrc.gov/reading-rm/basic-ref/glossary/full-text.html>
8 Ionising radiation- health effects High speed particles (alpha & beta) and gamma rays damage living tissue:Damaging cells-sometime repairableDamaging cells and causing cell multiplications- worst from cancers- stochastic-randomKilling cells- deterministic effect.Radiation consists of high speed particles and electromagnetic waves which damage living tissue (DNA).This can occur in humans in a number of ways:as damaging cells- sometimes repairable; usually single strand DNA damagedamaging cells- chromosome damage and causing cell multiplications- in its worst form causing cancers; double strand DNA damageor by killing cells, organ (especially bone marrow or gut) damage and death.Source(s): WISE and FOE 1998 Uranium Mining: how it affects you, Collingwood; Women’s Health Resource Collective/FOE 1992 Women, Mining & radiation exposure Carlton/Fitzroy.
9 Ionising radiation- health effects Depending on the dose this could occur immediately, or over many years, or generations.High doses- nuclear accident-bombsFrom immediate death to damage to central nervous system, cancers, reproductive damage, infertility, bleeding, ulceration, nausea, vomiting.Low doses- mine workers, nearby populationsCancers, -brain, lymphatic system, oesophagus, breast tissue, lungs, spleen kidney, liver and on skin.Reproductive effects-prenatal developmental, reproductive cells.Depending on the dose this could occur immediately, or over many years, or generations.In high doses of radiation like what occurs during a nuclear reactor accident, there are immediate and long term effects ranging from immediate death usually caused by damage to the central nervous system, to Cancers such as leukaemia, Damage to bone marrow- retarding growth, infections etc, Reproductive damage, miscarriages, birth defects, genetic damage, infertility, Internal bleeding, Bleeding of gums, mouth ulcers, Eye cataracts and Nausea and vomiting. And burnt skin due to heat.In low levels of radiation exposure, as occur to mine workers and at which we put local populations at increased risk by placing them near the industry i.e. next to a mine, the effects include:* From Cancers in: the Brain, Lymphatic system, Oesophagus, Breast tissue, Lungs, Spleen, Kidney, Liver, Muscle –sarcoma) and on the skin.* Reproductive effects, either in utero (prenatal) or damaging DNA in reproductive cells (egg or sperm) , leading to birth defects or inter-generational cancers.Source(s): WISE and FOE 1998 Uranium Mining: how it affects you, Collingwood; Women’s Health Resource Collective/FOE 1992 Women, Mining & radiation exposure Carlton/Fitzroy.
10 How is radiation exposure measured? Radiation exposure is based on how much ionising radiation enters into our body’s 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, andthen 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.Equivalent dose measures not only the absorbed dose (energy absorbed per unit mass (kilojoule per kilogram measured in units called a gray) but also type (and energy) of the radiation. This is done by weighting the absorbed dose by a factor related to the type of radiation (i.e. photons weighting factor 1, electrons (1), neutrons (5-20), proton (5), alpha particle a weighting factor of 20etc)and then this is factored by the nature of the tissue being exposed to derive the effective dose. The cellular response in the body will depend how directly the radiation has reached the tissue, i.e. internal exposure from ingested / inhaled has direct access to organs so delivers higher doses than thru skin. Secondarily the more rapidly a organ metabolises and changes the more susceptible it is to radiation damage. Thus bone marrow, gut, gonads are more susceptible than muscle.Source: Radiation protection Series 1. 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 r-2/4And
11 Uranium miningOn 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.After mining, on site treatment mills the uranium ore (crushes ore into fine sand like talc- chemical treatment leaches out about 90% Uranium) and concentrates the amount of U235 into Uranium Oxide U308 or yellow cake for export, all slurry and other material is left behind as highly radioactive waste- retaining up to 85% of the total ore body radioactivity. Yellowcake is later refined into Uranium hexafluoride (UF6), which later again is enriched to concentrate the U235 into ‘enriched Uranium” to remove any residue U238 which is in turn called ‘depleted Uranium’.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.
12 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.The mining of uranium is different from any other from of mining because of the radioactive nature of the mineral and the release of radon gas and its progeny usually associated with the extraction of the mineral.Whilst we live with background levels of radiation in the form of cosmic radiation from the Sun and if you live near a deposit of uranium or some other radioactive mineral sand you will also have some heightened exposure, as a species we have evolved over generations and thousands of years to live under these conditions, although our understandings of the impacts of these background levels is also imperfect. Current background levels are estimated at internationally 2mSv per year- in Australia around 0.7mSv per year.What we do know is that increased radiation exposure causes increased risk of cell damage.Mine workers are exposed to radiation from the ore itself. And most importantly the inhalation of radon gas.For the local population, potential increased levels of exposure occur during the transport of ore through the town, due to accident whether by train or trucks. The release of radioactive dust from mine sites can also be blown across the town and inhaled or swallowed by children after settling on toys or other outside materials, we all know how kids like to explore their world with their mouths!The resultant waste ore and tailings remain an on-site highly radioactive legacy.
13 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 is a gas, so it can be breathed into the body, it is the only gas in the uranium decay series.It releases the most harmful type of radiation-alpha particles. Has fairly short life 3.8 days.1st four decay daughters solid radioactive elements have a total half life less than 1 hour, 2 are alpha emitters & 2 beta and all are gamma emitters.The next progeny lead-210 decays over 20 years.The progeny are highly reactive elements that can connect to air born particles, such as aerosols and then lodge in lung tissue.Exposes sensitive lung tissue to radiation- hence lung cancer prevalence in mine workers.
14 Radon mine fluxesMany uranium deposits don’t 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.
15 Gamma radiation at mine sites. Gamma radiation signatures vary from deposit to deposit-Some have major signatures- Ranger, Yeelirrie, Mary KathleenOthers have none- Olympic dam, Beverley.After most projects commence gamma radiation signatures appear to have increased.
16 Health risks -miners 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.In addition to the increased risk of cancers, a study of Namibian mine workers showed that there was a significant reduction in testosterone levels, increases in chromosome aberrations in addition to higher prevalence’s of cancer. These issues pose threats not only to mine workers, but also when they father children, increasing the risks of genetic abnormalities and leukaemia in their offspring.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.A recent study in the USA of drinking water with uranium below USA EPA water standard, caused estrogenic responses in mice- including a range of cell abnormalities in fertility and the reproductive system, leading the authors to concluded that uranium is an endocrine disrupting chemical and that populations with long term exposure to environmental uranium should be monitored.Other adverse health effects – (such as strokes and heart diseases) are associated with high doses and further research is needed to assess the effects of low doses of radiation on such non-cancer effects.Source(s): WISE and FOE 1998 Uranium Mining: how it affects you, Collingwood; Women’s Health Resource Collective/FOE 1992 Women, Mining & radiation exposure Carlton/Fitzroy. Raymond-Wishs, Mayer, L. O’Neil T, et al Drinking Water with uranium below the US EPA Water standard causes Estrogen receptor- Dependent responses in female Mice. Environmental Health Perspectives Vol115(12) December 2007 pp
17 Risk of radiation Open cut Underground In situ leach Radiation from ore/ on site millingMiners – highLocals- n/aMiners –very highRadioactive dust- source mining activity(Includes radon gas)Locals- mediumMiners – very highLocals- possibleMiners – n/aRadioactive dust- tailings (& radon gas)Miners – lowWater table- due to fracturing of faults and membranes during mining and exploration.Miners – possibleLocals - highWater table- leakage from tailing damTransportation accidentIt is a health hazard not only for those who work with it, but also for those who live near it and are left with its radioactive legacy, a legacy that in the form of waste lasts for hundreds of thousands of years. Think about how successfully we manage our environment over a matter of centuries- climate change, species extinction, river system management and water usage. Then think of how we can guarantee the management of uranium industry radioactive waste that lasts for thousands of years.More detailed discussion of worker exposure risks can be found at <http://www.wise-uranium.org/ruxfw.html>
18 Indicative example of radiation from tailings dam Source WISEIn addition if tailing dams are not well fenced wandering (wildlife eg kangaroos and emus) can be contaminated and later killed and consumed.
19 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.WorkersPublicyearPer year1925520mSvNo limit setUntil 19561934 ICRP360mSv1950150mSv195650mSv1956 ICRP1mSv199020mSv1987No, there is no known safe levels of exposure to ionising radiation to avoid health risks.Since the inception of ionising radiation exposure standards the level of acceptable exposure has been consistently and dramatically lowered for both workers and the public.For example if my father had worked in the uranium industry in the year before my birth the acceptable level of exposure for him as a worker would have cut by 2/3rds from 150mSv to 50mSv per year. If he had started working in the industry in 1934 he could have commenced at 360mSv per year. The current maximum a worker can now receive in Australia in one year is still 50mSv per year, but cannot exceed 100mSv over a five year period, i.e. an average of 20mSv per year. An English study found that male workers who received doses of 10mSv in the six months prior to a child’s conception, had a seven to eight times higher risk of fathering a leukemic child than normal.The European Committee on Radiation Risk (set up by the European Parliament) recommended in 2003 that the maximum dose for a nuclear worker should be 5mSv and for a member of the public 0.1mSv per year from all man-made sources.A major joint study by the US National Academy of Science, the Academy of Engineering, the Institute of Medicine and the National Research Council, in their 7th Biologic Effects of Ionising radiation Report, the BEIR report #VII found that “A comprehensive review of available biological and biophysical data supports a ‘linear-no-threshold’ risk model- that risk of cancer proceeds in a linear fashion at lower doses without a threshold and that the smallest does has the potential to cause a small increase in risk to humans” In other words there is no lowest level at which the risk of cancer disappears it just becomes smaller as the dosage becomes smaller.Sources: Beir VII Health risks from exposure to low levels of Ionising radiation European Committee on Radiation Risk <http://www.euradcom.org/2003/execsumm.htm> and Women’s Health Resource Collective/FOE 1992 Women, Mining & radiation exposure Carlton/Fitzroy
20 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 industry’s product and therefore to make a profit.The current standards do not therefore set a safe standard of radiation exposure.Acceptable exposure risk levels- those I quoted earlier are set by the International Commission on Radiological Protection (ICRP) which is comprised of either users of ionizing radiation in their employment, or are government regulators, primarily from countries with nuclear weapon programs.Problems with ICRP definition:“The recognized biological endpoints deemed to be of concern for regulatory purposes are limited to: radiation induced fatal cancers and serious genetic diseases in live born offspring other issues such as developmental disorders, mental and other physical health matters are not considered Most of the other endpoints are dismissed as transient, not consequential, not damaging of the gene pool, or not fatal. This is an administrative, not a scientific decision, with which we may well wish to disagree. Even with respect to fatal cancers, those which were promoted or accelerated by the radiation exposure are not counted, because they are not considered to be "radiation induced". Rosalie Bertell 1998In terms of its own claims, ICRP does not offer recommendations of exposure limits based on worker and public health criteria. Rather, it offers its own risk/benefit trade-off suggestion, containing value judgements with respect to the "acceptability" of risk estimates, and decisions as to what is "acceptable" to the individual and to society, for what it sees as the "benefits" of the activities.Source: Bertell, R Limitations of the ICRP Recommendations for Worker and Public Protection from Ionizing Radiation for Presentation at the STOA Workshop Survey and Evaluation of Criticism of Basic Safety Standards for the Protection of Workers and the Public against Ionizing Radiation European Parliament, Brussels, accessed at
21 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.Despite exposure monitoring, there is no long term study of the actual rates of cancers in workers from the Ranger, Nabarlek or Olympic Dam (Roxby) mines.In addition it is known that accidents and spills on site do occur and that miners, as in the case of a yellow cake spillage in December 2008 at ERA’s Ranger mine in Kakadu, don’t always have dosimeters on them when dealing with these accidents. It is therefore not possible to get a accurate radiation exposure figure for those workers, this has implications for both immediate health treatment and long term health monitoring.
22 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
23 Key References:BEIR VII Health risks from exposure to low levels of Ionising radiationEuropean Committee on Radiation Risk <http://www.euradcom.org/2003/execsumm.htm>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 2007.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.auWISEZaire, 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.Beir VII Health risks from exposure to low levels of Ionising radiationBertell, R Limitations of the ICRP Recommendations for Worker and Public Protection from Ionizing Radiation for Presentation at the STOA Workshop Survey and Evaluation of Criticism of Basic Safety Standards for the Protection of Workers and the Public against Ionizing Radiation European Parliament, Brussels, accessed atEuropean Committee on Radiation Risk <http://www.euradcom.org/2003/execsumm.htm>FOE 1998 Uranium Mining: how it affects you, Collingwood;Goldstick, M ‘Nuclear Words and terms’ WISE Amsterdam.Mudd, G 2004 A Compendium of Radon data for the rehabilitation of Australian Uranium projects. Proc. 11th international Conference on tailings and Mine Waste ’04. Taylor & Francis Group ppMudd, G 2007 Radon releases from Australian uranium mining and milling projects: assessing the UNSCEAR approach. Jrl. Enviro Radioactivity 3 October 2007.Mudd, G 2008 Radon sources and impacts: a review of mining and non-mining issues. Review paper Rev Environmental Sci Biotechnology 7: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 2002Raymond-Wishs, Mayer, L. O’Neil T, et al Drinking Water with uranium below the US EPA Water standard causes Estrogen receptor- Dependent responses in female Mice. Environmental Health Perspectives Vol115(12) December 2007 ppWilliams, B 2008 Radiation & Health fact sheet 12 energyscience.org.auWISEWomen’s Health Resource Collective/FOE 1992 Women, Mining & radiation exposure Carlton/Fitzroy.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.
24 Websites Public Health Association of Australia <http://www.phaa.net.au>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 sheetsWorld Information Service on Energy
25 AcknowledgementsFor 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.