The “health benefits” of radon are still touted today; see http://www.radonmine.com/The penetrating power of radiation is of particular concernDifferent forms of radiation have different penetrating powerNatural background varies greatly, according to local geology and altitudeThe U.S. Atomic Energy Commission was particularly interested in determining the biological effects of low-levels of exposureOn the one hand, radiation in low & controlled doses has therapeutic effects & diagnostic usesOn the other hand, sustained exposure to low doses poses serious problems, especially ion in the case of ingestion & inhalatioSustained damage to cells may result, and can trigger cancers after a long latency period1The Atomic War at Home2In the 1500s, pitchblende miners in the Erz Mountains complained of a chest disease called “mountain sickness”—later identified as lung cancer3Following the discovery of X-rays, many scientists tested radiation on themselves, eventually resulting in a number of early deaths. The mechanisms of illness were not understood.4In the 19thand early 20th centuries, X-rays were touted for medical treatment & healing5Radium beguiled consumers during the early 20thcentury67Radium was also used in a number of consumer and industrial products—with sometimes deadly results8Casual uses of radiation continued until well after WW II: Kids could get their feet X-rayed for shoe fitting“I remember the foot X-ray machine. I'm 62 now. Back about 1950 we lived in Miami Florida. Mom use to take my sister and me to the neighborhood "Stride-Rite" shoe store on Flagler Boulevard about twice a year. After we had our feet measured and picked out a pair of shoes we'd march right over to the X-Ray machine followed by mom and the shoe salesman. I'd step up on the platform, stick my feet in the recessed area and peer through the scope. The shoe salesman and mom would look through their own scopes while he pointed out the growth area in the toe. I got a real thrill looking at the bones in my feet. I doesn't seem to have done me or my sister any harm.” http://www.spitting-image.net/archives/000497.html9The “health benefits” of radon are still touted today; see http://www.radonmine.com/10Eventually, the deleterious health effects of radiation came to be widely recognized11The penetrating power of radiation is of particular concern12Different forms of radiation have different penetrating power13The effects of high doses are relatively well-known and understood14Low-level effects are much less certain: How much radiation are people exposed to & what are its sources?1516What are the physiological effects of low doses of radiation?Is it good for you?Is it bad for you?What do the data say?There is still controversy17Natural background varies greatly, according to local geology and altitude18Average annual exposure from “background” is about 360 milliRem—which may contribute to some level of illness19The U.S. Atomic Energy Commission was particularly interested indetermining the biological effects of low-levels of exposure• Determine “safe” levels of exposure to atomic workers• Assess exposure of public to test fallout for public health purposes• Reassure public that exposures were not harmful• Support nuclear power industrtyAEC’s safety standard for the general public of 100 “sunshine units,” the AEC-named unit for one picocurie of radioactivity from Sr-90 per gram of calcium (as, for example, in the body), determined by Edward Lewis.20On the one hand, radiation in low & controlled doses has therapeutic effects & diagnostic uses21On the other hand, sustained exposure to low doses poses serious problems, especially ion in the case of ingestion & inhalation of small quantities of radioactive materials22Sustained damage to cells may result, and can trigger cancers after a long latency periodDiagram of the leukemia frequency among atomic bomb survivors by age at exposure, latent period, and city (Hiroshima, black; Nagasaki, hatched). ATB, at time of bomb.23There are a number of sources of data, but great uncertainty in measurements“Radium Girls”Navajo minersHuman subjectsAtomic bomb survivorsand other nuclear “events” (e.g., Chernobyl)Downwinders24Epidemiology is probabilistic and depends on large N data sets25And there are multiple steps in estimating exposure and risk26Total external and internal radiation dose (mGy) to the thyroid of adults in the United States from all tests at the Nevada test site (background is about 3.6mGy/yr.)Exposure data are inferred from monitoring of fallout patterns, estimates of time spent in places, location relative to detonation: all of this is very uncertain2728The radium watch dial painters who ingested high amounts of Ra-228 tended to contract cancer; others did not29The incidence of “excess cancers” is highest among the youngest Hiroshima survivors (in excess of background rate)30Uranium miners show elevated levels of cancers and mortality due to radon exposure—but effects depend on length of employment underground31The vulnerability of young children to Iodine 131 is clearly visible in this graphSome other malignancies have shown higher-than-expected rates, but the exposure data are very unreliable321997 Nat’l Cancer Institute summary suggests that from 25,000 to 50,000 additional cases of thyroid disease and 2,500 deaths would be likely in fallout areas as diverse as New Mexico, New York, Massachusetts, Iowa, Oklahoma and Wisconsin.33OrganNRC Limit(mrem/year)University investigation level (mrem)CommentsWhole Body 5000 100Includes dose from both internal and external sources. The Whole Body limit applies to exposure of the torso and head when the radiation is penetrating enough to irradiate tissues at a depth of 1 cm where the deeper blood-forming tissues are located.Lens of the Eye15,000 300The Lens of the Eye limit applies to exposure of the eye to radiation penetrating enough to irradiate the lens, at a depth of 0.3 cm.Extremities 50,000 1000The extremities include the arm or leg below the elbow or knee. The Extremities limit applies to exposure of the extremities when the radiation is penetrating enough to irradiate tissues at a depth of 1 cm.Skin 50,000 1000The Skin limit applies to dose deposited in the skin when the radiation is penetrating enough to irradiate tissues at a depth of 0.007 cm.Embryo/Fetus500 (for the entire pregnancy)50Applies only when a Declaration of Pregnancy has been