Radiation
Authors
The information in this chapter was prepared by the following individuals:
Descriptions of Exposure to Electromagnetic Fields and to Ionizing Radiation
o Mark Coombs, Ph.D., Radiation Protection Facility, Arizona State University.
Descriptions of Exposure to Ultraviolet Radiation
o Tim Flood, M.D., Medical Director, Chronic Disease Epidemiology Section, Arizona Department of Health
Exposure to Electromagnetic Fields
Introduction
The public is exposed to electromagnetic energy through a variety of media, including microwaves, radio-waves, and low frequency fields from transmission and electric power use.
Until very recently exposure to these fields was not associated with life-threatening or debilitating injury and illness. Tissue heating was the only cause for injury taken seriously, and compliance with regulatory limits established to prevent tissue heating made incidents of thermal injury rare.
A 1979 study reports a possible link between electromagnetic fields from household uses of electric power and childhood leukemia. This report was followed by a number of additional epidemiological studies, some of which reported similar links between low-frequency electromagnetic fields and cancer. Others, however, found no association.
The positive studies have, of course, generated a lot of public concern about exposures near transmission lines and in homes where the wiring configuration and use of household appliances result in elevated electromagnetic fields.
In addition to epidemiology, a number of laboratory studies have been conducted which have reported various biological effects. Interpretation of these results is complicated, however, since effects seen are often dependent in unusual ways on windows in frequency, wave form, and field strength. Investigators have not been able to supply convincing causes for the results reported, and it is usually difficult to link the reported effect with a potential human health risk.
The reported links between low frequency electromagnetic fields and cancer remain extremely controversial. Results of epidemiological studies have been inconsistent and positive studies have been criticized for inadequate description of fields to which individual were exposed, and for possible confounding factors.
Relative risk factors reported have been less than three, with large confidence intervals.
Two important reviews have been conducted recently on the health effects of low frequency electromagnetic field exposure. One was sponsored by the U.S. Government, the other by the United Kingdom.
In the U.S., the Oak Ridge Associated Universities was tasked by the Committee on Interagency Radiation Research and Policy Coordination to evaluate reported health effects from exposures to low frequency electromagnetic fields. The Oak Ridge Associated Universities panel concluded that there is no convincing evidence to support the contention that exposure to these fields is a demonstrable health hazard, and felt that research in this area should not receive a high priority.
Similar conclusions were reached in a review conducted by the United Kingdom's National Radiological Protection Board.
Conclusion
As a result of the uncertainty and controversy surrounding potential health effects of exposure to electromagnetic fields, it seems premature to conduct a comprehensive risk assessment at this time.
Review of recent research has revealed one study which might be used to make an assessment for childhood leukemia: Feychting and Ahlbom's 1993 study.
The report appeared after completion of the Oak Ridge Associated Universities and National Radiology Protection Board reviews, and has attempted to respond to many of the criticisms leveled at prior studies. The authors conducted a case-controlled study of cancers in children living near high tension power lines in Sweden, and found a link for childhood leukemia. No association was found for other childhood cancers.
In the study, children living within 50 meters of high tension power lines were found to have 2.9 times the risk for childhood leukemia. According to the study, of the 80 or so childhood leukemia cases diagnosed in Sweden each year, power lines may be responsible for one.
Results of the Feychting and Ahlbom study could be used to estimate the number of childhood leukemia cases each year in Arizona caused by living near high tension power lines. The number of childhood leukemia cases in Arizona each year, and the number of people in Arizona living within 50 meters of high tension power lines would be needed. It is important to recognize that such an assessment would have a high degree of uncertainty associated with it.
In addition, the assessment would not rule out the possibility that electromagnetic field sources other than high tension power lines may be important, or that cancers other than childhood leukemia may be promoted by electromagnetic field exposure.
Exposure to Ultraviolet Radiation (UVR)
Introduction
Ultraviolet Radiation (UVR) is a known cause of all types of skin cancer. Additional effects of UVR exposure include premature aging and wrinkling of the skin and the appearance of benign skin lesions called actinic keratoses.
Exposure to UVR takes place most frequently through contact with direct sunlight, but may also occur in settings such as tanning parlors and arc welding sites.
UVR consists of three wavelengths: UVA, UVB, and UVC.
UVB is the wavelength primarily responsible for tanning and burning. It initiates cell damage and alters immune function. Sunscreens are effective in blocking this wavelength. However, the use of sunscreens has increased the amount of time people spend in the sun, thereby increasing the population's exposure to UVA.
UVA wavelengths are not blocked by sunscreen. These wavelengths do less visible damage to the skin but are 10 to 100 times more common than UVB and penetrate the skin more deeply, causing chronic damage (Fraser et al., 1991).
UVC rays in sunlight do not reach the earth's surface. The effects of UVC from artificial lamps are unclear.
Arizona receives abundant sunlight compared to other states in the U.S., making exposure to ultraviolet rays particularly high among Arizona residents.
Skin Cancer
Skin cancer is classified into three cell types:
o Basal cell carcinoma (BCC)
o Squamous cell carcinoma (SCC)
o Cutaneous malignant melanoma (CMM)
BCC and SCC are also known as nonmelanoma skin cancer (NMSC). The number of NMSC cases is very large, accounting for one-third of all cancers in the U.S. It is the most frequent cancer diagnosed among whites, while it is uncommon in African- Americans, Asians and Hispanics.
Of particular concern is the rise in incidence rate of all types of skin cancer over the past two decades in the U.S.
An accurate count of skin cancer cases throughout Arizona is not available. However, data collected by the Arizona Cancer Center shows that residents of the southeastern part of the state are developing BCC at a rate 1.5 to 3.9 times the national average, and SCC at a rate 2.5 to 7.6 times the national average.
Melanoma
Among the various types of skin cancer, melanoma receives the most attention because it is the most likely to metastasize. Between 1973 to 1991, the national incidence rate of CMM increased by 94%. This rate of increase was surpassed only by prostate cancer in males, and lung cancer in females.
The Arizona Cancer Center reported that the incidence of CMM in southeastern Arizona increased at a rate twice the national average during the 1970s.
Arizona's statewide melanoma mortality rate of 2.4 is similar to the rate for the entire U.S. (2.2), but 16th highest among the 50 states. Between 1991 and 1993, Arizona death certificates indicate that 118 females and 196 males died from CMM.
Many scientists now believe that the risk for melanoma is mostly related to sunburns and sun exposure during childhood among fair-skinned, sun-sensitive individuals. Persons with many skin moles (nevi) are at increased risk of having a melanoma arise from one or more of the moles. The excess risk for CMM appears to be low for individuals whose skin is sun-tolerant.
A recent study from Sweden has linked melanoma with prior use of tanning parlors.
Unlike BCC and SCC, melanoma in Arizona is often found on body parts not usually exposed to the sun.
Data Sources & Risk Assessment
BCC and SCC occur so frequently in Arizona that it is impractical to report these cases to the central cancer registry. In order to estimate the number of cases in Arizona, the Committee has multiplied the rates published for southern Arizona times the Arizona white population.
In contrast to BCC and SCC, CMM is relatively uncommonly. It is reportable to the Arizona Cancer Center. However, since melanoma is often treated in a doctor's office, it is likely that a substantial number of cases go unreported.
In this report, the Committee presents both national data and cancer registry data.
It is difficult to ascribe a particular cause to individual cases of cancer. Therefore, the Committee has relied upon published articles that describe various risk factors and the proportion of skin cancer cases thought to be attributable to UVR (see references).
The Committee's estimates for Arizona's population are shown in Table 14.1.
Table 14.1 Estimate of the Number of Skin Cancer Cases Attributable to UVR (Sunlight) Exposure, 1992
--------------------------------------------------------------------------------------------------------------------------------------------------------------- | Type of | Incidence Rate | Population | Number of Incident | Proportion Attributed to | Number Attributed to | Low - High Range of the | | | | at Risk | | | | | | Skin Cancer | per 100,000 | | Cases (All Causes) | UVR Exposure (%) | UVR Exposure | Attributable Estimate | =============================================================================================================================================================== | Basal Cell | 317 | wh 3,115,738 | 10,118 | 90 | 9,106 | -- | --------------------------------------------------------------------------------------------------------------------------------------------------------------- | Squamous Cell | 104 | wh 3,115,738 | 3,319 | 90 | 2,988 | -- | --------------------------------------------------------------------------------------------------------------------------------------------------------------- | Melanoma, | at least | wh 3,115,738 | 466 | 50 | 233 | 116.5 | | Malignant SEER | 7.43 | | | | | to | | - Whites | | | | | | 745.6 | --------------------------------------------------------------------------------------------------------------------------------------------------------------- | ACR - All Races | at | 3,858,850 | 309+ | 50 | 154+ | 116.5 | | | least | | | | | to | | | 7.43 | | | | | 745.6 | ---------------------------------------------------------------------------------------------------------------------------------------------------------------
The CMM rate for African-Americans is 0.9 per 105. This is only 1/14th the rate for whites. Thus, African-Americans are at much lower risk compared to whites.
There is no comparable data for Native Americans at this time.
Mortality data is available from the ADHS Office of Vital Records. Table 14.2 shows the number of CMM and skin cancer deaths in 1991-93.
Table 14.2 Deaths from Skin Cancer
----------------------------------------------------------------------------- | Type | Number of | Proportion | Number | | | Deaths 1991-93 | Attributed to | Attributed to | | | (Annualized ) | UVR Exposure | UVR Exposure | | | | | | | | | (%) | | ============================================================================= | Melanoma | 103 | 50 | 52 | ----------------------------------------------------------------------------- | Other skin cancer | 39 | 90 | 35 | -----------------------------------------------------------------------------
Uncertainty
Non-melanoma Skin Cancers
The public health impact of NMSC should not be underestimated. According to a study in Rhode Island, the mortality from NMSC equals about one-fourth the mortality from melanoma (Weinstein et al., 1991).
There is much agreement that BCC and SCC are linked to UVR exposure. Ninety percent agreement is often quoted in the dermatology literature.
Melanoma
Data is from the following two sources suggest that Arizona's melanoma rate is two to three times the national rate:
o ACR
o Southern Arizona Skin Cancer Registry
Although the ACR received reports of only 309 melanoma cases in 1992, this number is almost certainly incomplete. The real number is likely to be at least two times as great.
The proportion of CMM cases attributable to UVR has not been reported in the medical literature. This is clearly a controversial subject. While most scientists would agree that sunlight plays some role in the development of CMM, the quantitative nature of this risk is much harder to define.
The evidence supporting UVR as a cause of melanoma includes:
o Rates of CMM are higher in southern states than northern states.
o In several comparisons of cases and controls, short periods of intense sun exposure in early life have been moderately linked to CMM.
o The national incidence and mortality of CMM are 2.1 and 1.5 times higher than they were 20 years ago. This increase parallels the social acceptability of sunbathing, suntanning and outdoor leisure activities.
o There is an apparent link between the number of nevi and sun exposure. A large number of nevi is a risk factor for CMM.
Evidence that factors other than UVR are involved in melanoma include:
o CMM affects a greater relative percentage of urbanites who work indoors.
o The incidence of CMM does not correlate well with latitude in Australia and Central Europe.
o The anatomic distribution of CMM does not correlate well with body areas that receive the most sun exposure.
o There is little evidence of chronic sun damage to areas around a CMM lesion.
One expert has estimated that 70-80% of CMM are attributable to sun exposure, especially among sun-intolerant individuals.
Alternatively, if there is some other factor in our society accounting for the increase over the past 20 years, then the role of UVR has been over-estimated. So far, however, no environmental factor has been shown to be as hazardous as UVR.
The last column of Table 14.1 shows a range for the number of CMM cases attributable to UVR exposure. The low figure represents the number of cases estimated by SEER times a UVR attribution factor of 25%; the high figure is two times the number of SEER cases divided by an attribution factor of 80%.
The figures of 25% and 80% reflect the author's personal opinion based on review of the literature, knowledge of cases, and conversation with other cancer professionals.
The Ozone Hole
Ozone (O3) occurs naturally in the earth's stratosphere about 30 miles above the earth's surface.
The ozone layer blocks much of the UVR that originates from the sun. Many are concerned that man-made chlorofluorocarbons (used mainly as refrigerants) attack and destroy this protective layer of ozone. For every 1% decrease in the ozone layer there may be a 2% increase in the amount of UVB radiation reaching the earth's surface.
Such an increase is predicted to result in a 1-3% increase in NMSC per year. So far, increased amounts of UVB have been measured at Antarctica, but a change has not been measured over the U.S..
This issue deserves our attention because it has the potential to impact the life-style and health of millions of fair-skinned people throughout the world for decades to come.
Many of the world's consumers have agreed to phase out their use of chlorofluorocarbons over the next decade, but the economic and social consequences of this phase out also will be substantial.
Conclusion
Arizona receives a high amount of sunlight (UVR) compared to other states.
The Committee estimates that exposure to UVR is associated with about 12,000 skin cancers that occur each year in Arizona. At least 200 of these skin cancers are melanomas.
About 87 Arizonans die each year from skin cancer related to the UVR exposure.
We have a moderately high degree of certainty about the risk associated with exposure to UVR.
Preventive Measures
The following actions can be taken to reduce the risk associated with UVR:
o Avoid sunlight during the peak hours of 10 a.m. to 2 p.m. in the winter, and at all times during the summer
o Wear a hat that shields the face, neck, and ears
o Wear sensible clothing
o Reduce sun exposure in childhood and adolescence (especially for individuals who tan poorly)
o Educate children and their parents about the skin types which burn easily
o Use sunscreen
o Avoid tanning parlors
The EPA has published information about this topic, including an index that informs the public about the amount of sun that will cause a sunburn.
Natural Ionizing Radiation
Introduction
Ionizing radiation occurs when atoms or molecules lose or gain electrons, which makes them radioactive.
The principal detrimental effect from exposure to ionizing radiation is cancer. For this report, the Committee has used the risk factor from the International Commission on Radiological Protection (ICRP, 1991a). This is 5x10-2 fatal cancers per sievert (Sv).
In addition to cancer, it is also assumed that radiation exposure may result in genetic effects. These inheritable effects result from gene mutations and chromosomal aberrations in germ cells transmitted to the progeny of exposed individuals. The risk factor proposed by the ICRP (1991a) is 1x10-2 serious genetic effects per Sv. The dose of importance is the dose to the gonads, or the genetically significant dose.
Because of the following considerations, only risk estimates for cancer fatality have been presented in this assessment.
o The risk factor for serious genetic effects is l/5 of that for fatal cancer.
o The genetic risk is based on the genetically-significant dose which, for the average Arizonan, is approximately l/3 of the effective dose used for cancer risk assessment (NCRP, 1987b).
o Genetic effects have not been observed in human populations. Risk factors for genetic effects are based on animal studies relying on a number of assumptions.
The risk factor presented is very uncertain and admittedly conservative (ICRP, 1991b).
Table 14.3 summarizes the collective doses and projected fatal cancer risks presented for various sources of ionizing radiation to which the Arizona public are potentially exposed.
Table 14.3 Projection of Fatal Cancers in Arizona from Public Exposure to Ionizing Radiation
----------------------------------------------------------------------------------- | Source | Annual | Annual | Fatal | | | Average | Collective | Cancers | | | Effective | Effective | Each Year | | | Dose (uSv) | Dose | | | | | (person-Sv) | | =================================================================================== | Natural Background Excluding Radon | 950 | 3470 | 170 | ----------------------------------------------------------------------------------- | Residential Radon | 250 | 914 | 243 | ----------------------------------------------------------------------------------- | Diagnostic Medical Procedures | - | 14 | 46 | ----------------------------------------------------------------------------------- | Occupationally Exposed Workers | - | 5.3 | 0.7 | ----------------------------------------------------------------------------------- | Inactive Uranium Mines | - | 1.2 | 0.3 | ----------------------------------------------------------------------------------- | Inactive Uranium Mills | - | 0.005 | 0 | ----------------------------------------------------------------------------------- | Palo Verde Nuclear Generator Station | 70 | 255 | 0 | ----------------------------------------------------------------------------------- | Consumer Products | 10 | 36 | 13 | ----------------------------------------------------------------------------------- | Fallout | - | 2.2 | 1.8 | ----------------------------------------------------------------------------------- | Transportation and Radioactive Waste | - | 0.056 | 0.1 | ----------------------------------------------------------------------------------- | Miscellaneous Sources | - | - | 0 | -----------------------------------------------------------------------------------
Uncertainties
Dose estimates used in this assessment are subject to a number of errors in measurements and assumptions used in models of human exposure.
Uncertainties in the estimation of the risk factors derived by the ICRP and others are usually larger than the errors in dose estimates. Uncertainties exist in dosimetry for Japanese bomb survivors upon which risk factors depend. Similar uncertainties exist in risk projection models used.
A more controversial uncertainty is in the extrapolation of high dose risks observed in Japanese bomb survivors and other groups exposed to high doses to low doses.
Some observers have called into question the use of the non-threshold linear model for this extrapolation (Abelson, 1994). However, the ICRP (1991b) and the National Research Council Committee on the Biological Effects of Ionizing Radiation (1990) have stated that the linear non-threshold model for fatal cancer risk is not contradicted by current data.
While it is unlikely that the risks are larger than projected, the possibility of fewer fatalities must be considered.
An excellent discussion of uncertainties in radiation risk assessment has been provided in the Biological Effects of Ionizing Radiation report (1990).
Natural Background Radiation
Exposure of the public to ionizing radiation from natural sources, so called "background radiation," can be conveniently discussed in three categories: cosmic radiation, external radiation from terrestrial radioactive materials, and internal radiation exposure from radioactive material in the body.
Cosmic Radiation
Cosmic radiation includes solar radiation but is dominated by galactic sources.
This radiation is attenuated by the earth's atmosphere. As a result, the magnitude of individual exposure depends on the altitude. Approximate annual dose equivalents for major Arizona population centers are shown in Table 14.4. The data have been adjusted to take into account shielding from homes and structural materials.
Table 14.4 Annual Dose Equivalent Received by the Population in Arizona Cities
---------------------------------------------------- | City | Altitude | Annual Effective Dose | | | | | | | (Feet) | (uSv) | ==================================================== | Yuma | 160 | 230 | ---------------------------------------------------- | Phoenix | 1090 | 260 | ---------------------------------------------------- | Tucson | 2389 | 300 | ---------------------------------------------------- | Flagstaff | 6910 | 600 | ----------------------------------------------------
The estimated national average is 260 uSv per year (NCRP 1987a). It has also been estimated that the average American receives an additional 10 uSv each year from exposure during travel on commercial airlines (NCRP 1987b).
External Exposure from Terrestrial Radioactive Material
External exposure from terrestrial radioactive material is dominated by radiation from uranium, thorium and their radioactive decay products. Additional doses result from exposure to radiation from other long-lived primordial radionuclides such as 40K and 87Rb, and from the fission products of uranium, thorium, and protactinium (NCRP, 1987a).
The magnitude of the external terrestrial exposure depends on the concentration of radionuclides in the local geology. There is, however, inadequate information to provide an accurate estimate of the magnitude of this exposure to the population of Arizona. An estimate of the national average, 280 uSv per year, has been used in this report (NCRP, 1987b).
Internal Radiation Exposure
Internal radiation exposure results when naturally-occurring radioactive materials are ingested or inhaled. Some of these are long-lived primordial radionuclides such as potassium-40, uranium, thorium or their radioactive decay products.
Other nuclides, including tritium and carbon-14, are generated by nuclear interactions of cosmic radiation with atmospheric molecules. The dose from many nuclides including uranium, thorium and their decay products varies locally depending on concentration in food, water, and air.
Since radioactive 40K and 14C are physiologically controlled by the body, doses from these nuclides will not vary. Over one-half of our internal radiation exposure is contributed by these two nuclides. The average effective dose from internal radiation exposure is 400 uSv each year (NCRP, 1987b).
Summary
A summary of the effective dose equivalent from natural sources of ionizing radiation are shown in Table 14.5.
Table 14.5 Summary of Effective Dose Equivalent from Natural Sources of Ionizing Radiation Excluding Radon
------------------------------------------ | Source | Annual Effective Dose | | | | | | (uSv) | ========================================== | Cosmic | 270 | ------------------------------------------ | Terrestrial | 280 | ------------------------------------------ | Internal | 400 | ------------------------------------------ | Total | 950 | ------------------------------------------
Exposure to Ionizing Radiation from Medical Sources
This summary evaluates the public exposure to ionizing radiation from x-ray and nuclear medical procedures for diagnostic purposes.
Exposure to patients from therapy has not been included, since this category of exposure involves individuals with critical illnesses justifying large doses of radiation.
The average annual effective dose in the U.S. population from diagnostic x-ray and nuclear medical procedures is estimated to be 390 uSv (NCRP, 1987b; NCRP, 1987c). However, the age distribution of those receiving diagnostic procedures involving exposure to radiation is skewed; over 25% of the procedures are for patients older than 64, even though this age group represents only 11% of the population (NCRP, 1989). When a correction is made for age distribution of those exposed, the annual average effective dose in the U.S. is 250 uSv.
Exposure from Occupational Radiation
The National Council on Radiation Protection and Measurements has recently evaluated ionizing radiation doses received by radiation workers in the U.S. (NCRP, 1989b). Reliable data does not exist specifically for Arizona radiation workers, so estimates of the NCRP have been used in this report except for the following categories:
o DOE facilities (none in Arizona)
o Uranium mines and mills (non-active in Arizona)
o Nuclear Power (specific data for the Palo Verde Nuclear Generating Station has been used)
Since the Arizona population represents 1.4% of the population of the U.S., the number of exposed workers has been estimated by assuming that 1.4% of all U.S. radiation workers for each category live in Arizona.
Table 14.6 summarizes the occupational exposure of Arizona radiation workers.
Table 14.6 Occupational Exposure of Arizona Radiation Workers
------------------------------------------------------------------------------- | Category | Number of | Average Annual | Annual Collective | | | Workers | Effective Dose | Effective Dose | | | | | | | | | (uSv) | (person-Sv) | =============================================================================== | Industrial | 98 | 1560 | 0.15 | ------------------------------------------------------------------------------- | Nuclear Power | 2422 | 270 | 0.65 | ------------------------------------------------------------------------------- | Well Logging | 123 | 3500 | 0.4 | ------------------------------------------------------------------------------- | USPHS | 65 | 70 | 0.004 | ------------------------------------------------------------------------------- | Flight Crews | 1334 | 1700 | 2.3 | ------------------------------------------------------------------------------- | Medical | 8274 | 700 | 5.7 | ------------------------------------------------------------------------------- | Government | 2890 | 600 | 1.7 | ------------------------------------------------------------------------------- | Education/Transport | 1077 | 700 | 0.75 | ------------------------------------------------------------------------------- | Other | 1629 | 1700 | 2.8 | -------------------------------------------------------------------------------
Uranium Mining
While there are no active uranium mines in Arizona at this time, approximately 350 inactive and abandoned mines exist at remote sites in Arizona. The principal route for public exposure to ionizing radiation from these mines is from radionuclide releases to air and water.
Data available for estimating population doses from these releases have been inadequate and uncertain (NCRP, 1987c), especially for Arizona mines.
Annual collective doses for regional populations near active mines is estimated to be 0.31 person-Sv (NCRP, 1987b).
Releases from inactive mines are less by a factor of 20 (NCRP, 1987c). A rough conservative estimate for an inactive mine would be 0.015 person-Sv. Under the assumptions for Arizona's 350 or so inactive mines, the annual collective dose would be 5.25 person-Sv.
Uranium Mills
There are no active uranium mills in Arizona at this time; however, two inactive mill sites are located in Arizona on the Navajo reservation.
An assessment published by the EPA in 1982 estimated that the risk of death for these sites would be on the order of ten deaths in 100 years for both sites.
It has been estimated elsewhere that the annual collective dose to regional populations near a typical active mill is 0.62 person-Sv (NCRP, 1987b). Since 1980, both Arizona sites have undergone remediation under the Uranium Mill Tailings Remedial Action Act passed by Congress in 1978.
Since remediation radiological characterization of the sites have not been found. This report will use the conservative NCRP estimates.
Palo Verde Nuclear Generating Station
The three nuclear reactors of the Palo Verde site came on line in 1986 and 1987, and are among the newest in the country.
Public exposure from newer reactors has been very small. Public exposure from nuclear power generation is dominated by older reactors located in other parts of the country (NCRP, 1987c).
The regional population near (50 miles) the reactors is 1.3 million. The annual collective dose to the public in 1989 was 4.9x10-3 person-Sv (Baker, 1993).
Consumer Products
A number of common products emit small amounts of ionizing radiation or contain radioactive material. Examples include airport luggage inspection systems, radioluminous products, static eliminators, and smoke detectors (NCRP, 1987d).
The annual average effective dose to members of the U.S. population has been estimated to be approximately 68 uSv (NCRP, 1987b).
Tobacco
The use of tobacco products contributes an estimated annual effective dose of 13 mSv (1.3 rem) to the average smoker (NCRP, 1987d).
The dose is due to 210Pb and 210Po naturally present in tobacco. This is a significant dose. The risk associated with the radiation dose is included in assessments from epidemiological studies of tobacco smokers, however, and is not treated in this report.
Miscellaneous Environmental Sources
There is no published information on the Arizona public exposure to radiation from use of radioactive materials by DOE, NRC, and state licensed facilities, or from release of radioactive material during aluminum, copper, lead and zinc smelting.
Nationwide, the annual collective effective dose from these sources has been estimated at four person-Sv (NCRP, 1987b).
Population-based adjustment of this figure results in an annual collective effective dose of 0.056 person-Sv.
Fallout
There is still some radioactive material present in the environment which was released during nuclear weapons testing in the 1950s and 1960s. The amount remaining is small, however.
The average annual effective dose for the U.S. population is less than 10 uSv (NCRP, 1987b).
Transportation and Radioactive Waste
There are no active radioactive waste sites in Arizona. Doses from radioactive waste are from storage sites at individual licensed users of radioactive material and nuclear power generation.
There are no accurate assessments of public exposure to radiation from low-level radioactive waste. It has been estimated that low-level radioactive waste storage for the nuclear power industry results in an annual average effective dose for the public of less than 10 uSv (NCRP, 1987b).
Transportation of radiopharmeceuticals and other sources, including those for nuclear power operation, results in an estimated annual collective effective dose of approximately 160 person-Sv (NCRP, 1987b).