Thursday, July 12, 2012

Children and Ionizing Radiation



HISTORICAL AND CONTEMPORARY DISCUSSION OF THE STUDY OF THE BIOLOGICAL EFFECTS OF IONIZING RADIATION ON CHILDREN (authored by me):
Research on the effects of ionizing radiation on children particularly mobilized public distrust of the U.S. Atomic Energy Commission (AEC). British epidemiologist Alice Steward of Oxford University raised awareness of the harmful effects of X-rays on human fetal development and childhood leukemia in her groundbreaking work published in the late 1960s and early 1960s. Children born to mothers who had X-rays during pregnancy had a forty percent increase in incidents of leukemia and other cancers.[i] Ernest J. Sternglass followed Steward’s work. In 1963 he published in the journal Science a research paper titled: "Cancer: Relation of Prenatal Radiation to Development of the Disease in Childhood" in the journal Science.[ii] In 1969, he publicized his research by arguing in Esquire Magazine that radioactive fallout from atmospheric testing had caused the death of 375,000 infants less than a year old and countless fetal deaths between 1951 and 1966.[iii] In 1972 Sternglass published Low-Level Radiation, re-titled in 1981 Secret Fallout: Low-Level Radiation from Hiroshima to Three Mile Island.
 Not surprisingly Sternglass’s argument drew controversy, although his most pointed critic, Arthur R. Tamplin, did not dispute that fallout deaths had occurred, but disagreed with Sternglass about the magnitude of them. Tamplin calculated eight thousand fetal deaths and four thousand infant mortalities.[iv] Although he was disputing Sternglass’s estimates, the AEC attempted to censor his report by asking him to withdraw his mortality calculations, fearing the public would find them alarming. Tamplin’s subsequent research on the health effects of nuclear power earned him more enmity. However, he had support at Lawerence Livermore Lab where he worked from John W. Goffman. In 1969 they argued together in a research paper that seventeen thousand additional cases of cancer annually would derive from the permissible lifetime dose of 0.17 rads per year.[v] They argued for lowering the permissible dose.
Tamplin’s and Goffman’s proposal for lowering the permissible dose drew significant criticism for presuming that all levels of ionizing radiation exposure cause effects. Their position conflicted with the “threshold” theory still promoted by the AEC that held that ionizing radiation did not cause harmful somatic or genetic effects below a specific threshold. The critics charged that Goffman and Taplin had inappropriately used known health effects for high doses of radiation to derive estimates for the effects of low doses of radiation. At issue in the debate about threshold was the idea that long-term exposure to low-doses of radiation causes the same effect as acute exposure to high levels of radiation, especially for children.
However, the public was growing increasingly alarmed about the relationship between radiation and cancer, especially after the March 28 accident at the Three Mile Island nuclear plant in Pennsylvania. Indeed, an article in The New York Times published on page 1 of the July 1, 1979 issue was titled “Public Fears Over Nuclear Hazards are Increasing: Low-Level Radiation: How High the Risk.” The article notes “From New York to Washington State, from Texas to Montana, people are edgy, if not outright angry, over radiation … over potential hazards that exist, in some cases, literally in their own backyards.” In 1980, Harvey Wasserman and Norman Solomon wrote (in consultation with Robert Alvarez and Eleanor Walters) examined some of those ubiquitous risks in Killing Our Own: The Disaster of America’s Experience with Atomic Radiation. The book examined the dangers of artificially produced radiation across a variety of contexts ranging from nuclear fallout from atmospheric testing to the “industrial underside” of bomb production in Colorado, uranium milling in Church Rock New Mexico, and Tritium from American Atomics in Tucson Arizona. This book challenged the idea that the permissible dose was safe and sensitized the public to a wide array of sources of unsafe exposure.
To this day conflict exists about the legitimacy of a permissible dose for guaranteeing public safety, especially for those populations living in close proximity to nuclear power plants. It is instructive to examine briefly some current findings on the health effects of children’s exposure to ionizing radiation across three areas of research: proximity to nuclear plants, medical imaging, and background radiation.
Recent research on nuclear plants and childhood leukemia suggest that ongoing plant releases may cause cancer in children residing in close proximity to the plant. A study by the Institut National de la Sante et de la Recherche Medicale (French Institute of Health and Medical Research, or INSERM) documented a leukemia rate twice as high among children under the age of fifteen living within a five kilometer radius of France's nineteen nuclear power plants as compared to the rate found in the child population living twenty kilometers or more away from the plant.[vi] The French study reinforced previous findings on excess risk for leukemia in young children living in close proximity to German nuclear power plants.[vii] In a commentary, “Childhood Cancer near Nuclear Power Stations,” published in Environmental Health Perspectives, Ian Fairlie observed: “Doses from environmental emissions from nuclear reactors to embryos and fetuses in pregnant women near nuclear power stations may be larger than suspected. Hematopoietic tissues appear to be considerably more radiosensitive in embryos/fetuses than in newborn babies.”[viii]
Exposure to tritium may be the primary agent culpable for cancer and leukemia. Water that cools reactor cores and spent fuel pools becomes extensively contaminated with tritium.[ix] Tritium is a radioactive isotope of hydrogen with a 12.32 half-life. Tritium emits beta particles (high speed electrons) as it decays. It is very difficult to contain and is therefore nearly continuously emitted from nuclear power plants. It binds with oxygen and ends up in precipitation and water supplies, where it can be inhaled or ingested. It can also be absorbed through the skin. Harrison and Day describe the biological effects of tritium in their article “Radiation Doses and Risks from Internal Emitters”
low energy beta emissions from tritium (3H) decay have been shown to have RBE (ratio of the absorbed dose) values of up to between 2 and 3 (compared to gammay rays), for in vitro end-points including cell killing, mutation and induction of chromosomal aberrations.[x]

Evidence of tritium contamination can be found in Clyde Stagner’s Hidden Tritium, which examines tritium emissions from spent fuel pool evaporations at the Palo Verde Nuclear power plant located near Phoenix. His calculations of evaporation rates and accumulation of tritium in precipitation, based on EPA data and analysis of evaporation rates conducted by Arizona State University, document risks posed by the beta emitter to populations throughout the Phoenix area. Stagner illustrated the risks graphically in an analysis of tritium concentrations in public swimming pools in Phoenix. Accordingly, "Swimming 2 hours a day during a six  month swimming season results in a dose of . . . 1.927 millirem. Swimming 2 hours a day annually results in a dose of 3.908 millirem."[xi] This dose exceeds the As Low as Reasonably Achievable dose of 3 millirem.[xii] In 2011 the EPA discontinued its monitoring of tritium in Phoenix despite evidence of steadily growing accumulation of the isotope in the local environment across time. Tritium has been linked to chromosomal breaks, brain tumors, ovarian tumors, decreased brain weight in offspring, and mental retardation in animal studies.[xiii]
Another area of investigation of the biological effects of radiation on children concerns medical imaging. Studies on medical imaging show children are very vulnerable to the radiation used in the imaging. A study published in The Lancet in 2012 found that CT scans cause a small but significant increased risk for leukemia and brain cancer.[xiv] Two to three scans of the head for children under three tripled the risk for brain cancer as compared to the general population while five to ten scans tripled the risk for leukemia. A study of adults found that “For every 10 mSv of low-dose ionizing radiation, there was a 3% increase in the risk of age- and sex-adjusted cancer over a mean follow-up period of five years (hazard ratio 1.003 per milliSievert, 95% confidence interval 1.002–1.004).[xv]
Finally, recent research has documented that even background levels of radiation can cause cancer in children. One study addressing background gamma radiation found a twelve percent increase in childhood leukemia for every millisievert of natural gamma-radiation does to bone marrow.[xvi] This study demonstrates that low dose gamma radiation can cause produce genetic changes significant enough to cause leukemia. One area of DNA particularly vulnerable to background radiation is mitochondrial DNA. An innovative study examined how naturally occurring high background radiation produced mitochondrial DNA mutations that were transmitted across generations:
The observation that radiation accelerates point mutations at all is unexpected, at first glance, because radiation was, until recently, thought to generate primarily DNA lesions (1). A potential explanation is provided by our additional observation that these radiation-associated point mutations are also evolutionary hot spots, indicating that the radiation indirectly increases the cell's normal (evolutionary) mutation mechanism (5).[xvii]
Mitochondrial damage transmitted across generations could eventually result in a level of inherited damage capable of compromising this vital cell function. Children are thus vulnerable not only because their DNA appears more vulnerable but also because they have inherited all the germ-line genetic damage from previous generations.
Taken together these studies demonstrate that common forms of exposure to ionizing radiation can cause cancer and leukemia and that genetic damage can be transmitted across generations. Moreover, they demonstrate that children are particularly susceptible to detrimental effects. The studies are significant because they suggest that current estimates for dose-risks may under-estimate actual risks.
The 2006 BEIR report, Health Risks from Exposure to Low Levels of Ionizing Radiation produced by the National Research Council of the National Academies predicts cancer rates at different levels and ages of exposure for males and females (see Goddard's Journal for analysis http://www.iangoddard.com/journal.htm). For instance, the report predicts that at 0.1 grays (which equals 100 millisieverts) of exposure the lifetime attributable risk (LAR) of solid cancer incidence and mortality for male children at age 10 would be an increased rate of cancer of 1330 and increased mortality rate of 640 per exposed 100,000 people. For female children at age 10 this same level of exposure would produce a 2530 increased incidence of cancer and a 1050 increased incidence of mortality.[xviii] The risk would multiply with every year of exposure subsequently. However, the report introduces uncertainty in risk calculations based on internal exposure and on the effects of protracted low-dose exposure.[xix] The report notes that ingested alpha particles are more effective than low LET radiation (e.g., gamma rays) in produce genomic instability and that “at low doses, the effectiveness per unit absorbed dose of standard X-rays may be about twice that of high-energy photons.[xx] The effectiveness of lower-energy X-rays may be even higher. How this translates into risks of late effects in man is an open question.”[xxi]
The studies reported in this section suggest that the BEIR report may under-estimate risk, especially for internally ingested radioisotopes. Two other sources of data about radiation risks also suggest that the BEIR tables under-estimate risk. First, epidemiological research on the effects of Chernobyl indicate significant somatic health effects at exposures not predicted to produce them, although the conclusions are hotly contested. Second, in vitro studies on the effects of ionizing radiation, particularly alpha particles, on cell biology and DNA mutations indicate that extremely low levels of exposure can have mutagenic effects.


[i]               Cited in Ford, The Nuclear Barons, 315.

[ii]               E.J. Sternglass. "Cancer: Relation of Prenatal Radiation to Development of the Disease in Childhood", Science, 7 June 1963: Vol. 140. no. 3571, pp. 1102 - 1104.

[iii]              Samuel Walker Permissible Dose: A History of Radiation Protection in the 20th century  p. 37

[iv]              Walker, p. 37.

[v]               Walker, p. 39.

[vi]              Claire Sermage-Faure, D. Laurier, S. Goujon-Bellec, M. Chartier, A. Guyot-Goubin, J. Rudant, D. Hemon and J. Clavel. 2012. Childhood leukemia around French nuclear power plants – the Geocap study, 2002 – 2007,” International Journal of Cancer 131, E769–E780 (2012): http://onlinelibrary.wiley.com/doi/10.1002/ijc.27425/pdf.

[vii]         Kaatsch P, Spix C, Schulze-Rath R, Schmiedel S, Blettner M. Leukaemia in young children living in the vicinity of German nuclear power plants. Int J Cancer 2008; 122: 721–6.

Kaatsch P, Spix C, Jung I, Blettner M. Childhood leukemia in the vicinity of nuclear power plants in Germany. Dtsch Arztebl Int 2008; 105: 725–32.

Spix C, Schmiedel S, Kaatsch P, Schulze-Rath R, Blettner M. Case-control study on childhood cancer in the vicinity of nuclear power plants in Germany 1980–2003. Eur J Cancer 2008; 44: 275–84.

Kinlen L. A German storm affecting Britain: childhood leukaemia and nuclear power plants. J Radiol Prot 2011;31: 279–84.

[viii]         Ian Fairlie. Commentary: Childhood Cancer near Nuclear Power Stations. Environmental Health Perspectives, 8:43 (2009), http://www.ehjournal.net/content/8/1/43.

[ix]              Helen Caldicott Nuclear Power is Not the Answer. New York: The New Press, 2006, p. 13.

[x]           Harrison, J., & Day, P. Radiation Doses and Risks from Internal Emitters. Journal of Radiological Protection, 28 (2008), 37-159. p. 144.

[xi]              Clyde Stagner personal correspondence. Stagner provided me the data and analysis he sent to the EPA expressing concerns about the excess exposure to tritium in Phoenix precipitation and bodies of water, including swimming pools.

[xii]         ALARA stands for As Low as Reasonably Achievable and is a regulatory requirement. See http://www.ncsu.edu/ehs/radiation/forms/alara.pdf for background.
  
[xiii]        Helen Caldicott, p. 57. 

[xiv]         Mark S Pearce, Jane A Salotti, Mark P Little, Kieran McHugh, Choonsik Lee, Kwang Pyo Kim, Nicola L Howe, Cecile M Ronckers, Preetha Rajaraman, Sir Alan W Craft, Louise Parker, Amy Berrington de Gonz├ílez. Radiation exposure from CT scans in childhood and subsequent risk of eukaemia and brain tumours: a retrospective cohort study. The Lancet. June 7, 2012DOI:10.1016/S0140-6736(12)60815-0, http://press.thelancet.com/ctscanrad.pdf/.

[xv]          Mark J. Eisenberg, Jonathan Afilalo, Patrick R. Lawler, Michal Abrahamowicz, Hugues Richard, and Louise Pilote. Cancer risk related to low-dose ionizing radiation from cardiac imaging in patients after acute myocardial infarction. Canadian Medial Association Journal 183.4 2011, 430-436.  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3050947/pdf/1830430.pdf

[xvi]         Natural gamma rays linked to childhood leukaemia. University of Oxford (2012, June 12) http://www.ox.ac.uk/media/news_stories/2012/120612.html.

[xvii]        Lucy Forster, Peter Forster, Sabine Lutz-Bonengel Horst Willkomm, Bernd Brinkmann Natural radioactivity and human mitochondrial DNA mutations PNAS http://www.pnas.org/content/99/21/13950.long.

[xviii]       Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation, National Research Council. Health Risks from Exposure to Low Levels of Ionizing Radiation:BEIR VII Phase 2Table 12-5 page 281 http://www.nap.edu/openbook.php?record_id=11340&page=281).


[xix]             Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation, National Research Council. Health Risks from Exposure to Low Levels of Ionizing Radiation:BEIR VII p. 276, http://www.nap.edu/openbook.php?record_id=11340&page=276

[xx]             Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation, National Research Council. Health Risks from Exposure to Low Levels of Ionizing Radiation:BEIR VII p. 70.

[xxi]             Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation, National Research Council. Health Risks from Exposure to Low Levels of Ionizing Radiation:BEIR VII . 276 http://www.nap.edu/openbook.php?record_id=11340&page=276.

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