Update
For two topics treated in this monograph, there are important recent articles or reports that could not be included in the body of the monograph, primarily because of their recency. The editors take this opportunity to mention some of them here, with apologies for selection bias.
The problem posed by the incomplete and possibly inaccurate assessment of the radiation exposure of liquidators is treated by Shantyr and his colleagues, from St. Petersburg (1). By analyzing the data of 36,700 such occupationally exposed workers, they rank the importance of items of history, and from data already available on exposure, they derive exposure estimates where data were missing. Goldsmith et al. (2), studying a much smaller number of liquidators who emigrated to Israel, derive a scoring system and illustrate its relevance in relation to various laboratory findings. Bigbee et al. (3,4) used glycophorin A mutation to study the relationship of physical doses and biodosimetry in 782 workers from Estonia, Latvia, and Lithuania. Their controls had median values of 6 per million erythrocytes with loss of the glycophorin allele; median values for the liquidator groups ranged from 6.5 to 7. Their pooled results, with average increased frequency in liquidators of approximately 1 to 2 per million, corresponded to radiation doses of approximately 4 to 8 cGy. Follow-up studies with fluorescence in situ hybridization (FISH) translocation analyses and analysis of the incidence of leukemia and thyroid cancer are ongoing. Granath et al. (5) report retrospective dose estimates using FISH in Estonian liquidators. The subjects they studied were exposed during the months immediately after the accident in 1986. The exposure estimates were based on the Lucas calibration curve. The number of subjects was small, but the estimated mean doses were as follows: for 5 workers engaged in constructing sarcophagus, 0.07 Gy; for 5 workers on the roof or vicinity (4-7 months), 0.31 Gy; for 5 workers on the roof or vicinity (0-3 months) 0.27 Gy; and for 11 workers outside the 30-km zone, 0.15 Gy. Inskip et al. (6) studied thyroid nodularity in relation to dose estimates and glycophorin tests among 1984 Estonian liquidators. They also compared results of palpation and of ultrasound. Of 139 nodules detected by palpation, 44 were also detected by ultrasound. Overall, ultrasound detected 201 nodules (10.2%). Seventy-seven workers had biopsies; two had papillary carcinoma and three had follicular neoplasm. There was no relationship to estimated doses, type of work, or glycophorin test. There was a borderline significant increase (p=0.09) in translation frequency for FISH analyses when nodules were present (0.66%), compared to the absence of nodules (0.54%). Rahu et al. (7) found no increase in all cancers (25 observed/26.5 expected) in a follow-up study of 4742 Estonian male liquidators. Non-Hodgkin's lymphoma and lung cancer were observed slightly more often than expected. With 144 deaths the standard mortality ratio was 0.98. No cases of leukemia occurred in the cohort. There was a 50% increase in deaths due to suicide. Lazutka et al. (8) studied cytogenic changes in peripheral blood lymphocytes for 509 Latvian clean-up workers and 50 controls. They also evaluated a number of possible confounders such as alcohol use, smoking, recent febrile illness, and diagnostic X-ray exposures. Chromosomal patterns in 328 clean-up workers were comparable to controls; 180 workers had significantly increased frequencies of abnormal findings, with a dose-dependent relationship. When transformed data were analyzed by analysis of variance, alcohol abuse made a significant contribution to total aberrations, chromatid breaks, and chromatid exchanges. Smoking was associated with frequency of chromatid exchanges. Exposure to Chernobyl radiation was associated with total numbers of aberrations, chromatid exchanges, and chromosome breaks. Diagnostic X-rays were associated with total aberrations and frequency of chromosome breaks. Age was significantly associated with rates of chromatid exchanges and chromosome exchanges, and history of recent viral infection was associated with increased frequency of chromosome exchange rates.
Conclusion
The new findings illustrate a number of methods for dealing with the gaps and uncertainties in dosage of liquidators. The lack of better exposure data is therefore becoming less critical. Virtually all studies recognize the greater exposure and effects on workers who were on-site during the early months after the disaster, as well as the importance of radiation exposure symptoms. The various biological indicators, if applied to a general sample of liquidators may give rather nondescript findings; however, if they are applied to those with evidence of greater exposure, they are likely to show stronger associations. In any event the stage is set for the follow-up of this unique population of occupationally exposed workers. This is important, as it provides a valuable way of trying to understand the biological meaning of persistant mutation activity in radiation-exposed populations.
Hocking et al. (9) studied cancer incidence and mortality at two distances from three clustered transmission towers in North Sydney, Australia. The towers were broadcasting video at 100 kW and FM at 10 kW, on a carrier frequency of 63 to 215 MHz. Cancer data were obtained from a population-based cancer registry. Significant increases in leukemia incidence were noted when all age groups were included. For children, significant increases in leukemia incidence and mortality were reported. Dolk et al. (10) initiated a study after a press report of a high rate of leukemia within 2 km of a broadcast tower at Sutton Coldfield in the United Kingdom. They also used cancer registry data and found that adult leukemia was 83% above expected incidence, based on sex, age, year, and socioeconomic group. Incidence of leukemia decreased significantly with distance from the tower (p=0.001). A significant decline with distance was also found in adult skin and bladder cancer. A nonsignificant excess for leukemia was noted in children. A set of similar studies was conducted in other populations living within 10 km of 20 other U.K. broadcast facilities (11). Adult leukemia was 3% more than expected, but because of the large population base this excess was statistically significant. A significant gradient with distance from the towers was also found.
Repacholi et al. (12) reported a doubling of lymphomas in transgenic mice exposed up to 18 months to pulsed 900 MHz electromagnetic fields resembling the midfield exposure associated with cell phone use. Hayes et al. (13) reported on a multicenter prospective study of possible interference with cardiac pacemakers by cellular telephones. In 5533 tests, some type of interference was found in 20%; the symptom incidence was 7.2%. No clinically significant interference was found if the phone was placed over the ear, but was noted in 1.7% of the tests when the phone was held over the pacemaker.
Lagorio et al. (14) studied 481 female plasticware workers using radiofrequency heat sealers. In a cohort followed from 1962 to 1992, the all-cancer standard mortality ratio was higher in the women exposed in the sealing department. Excess mortality from leukemia was found for the whole population (two cases where 0.3 were expected). The authors could not exclude a possible role for vinyl chloride monomer and solvents.
Conclusion
There is a tendency for a series of studies of radiofrequency carcinogenicity to point to a positive relationship, even though taken one-by-one, the results are not always clear. From these findings there may even emerge some dose-effect relationships that will need to be digested and possibly explored with new confirmatory research. A continual search for and follow-up of occupationally exposed populations seems a useful strategy. At the same time there is now an animal model for cell phone carcinogencicity. Additional work will be required to determine how valid and how useful it may be. Prudent avoidance of inappropriate cell phone exposure for persons with cardiac pacemakers has been suggested. However, if the phone is placed over the ear in the normal position, no clinical problems should be expected.
John R. Goldsmith
Michael R. Quastel
1. Shantyr II, Nikiforov AM, Romanovich IK, Schwartz VA, Makarova NV, Deryapa LN, Saygina EB. Estimation of radiation exposures of "liquidators" of the Chernobyl nuclear power station: identification of risk groups. Int J Occup Environ Health 3:45-50 (1997).
2. Goldsmith JR, Merkin L, Quastel MR, Poljak S, Kordysh EA, Wishkerman V, Emerit I. Evaluation of the radiation exposures of Chernobyl "liquidators": exploratory studies of a sample of immigrants to Israel. Int J Occup Environ Health 3:51-59 (1997).
3. Bigbee WL, Jensen RH, Veidebaum T, Tekkel M, Rahu M, Stengrevics A, Kesminiene A, Kurtinaitis J, Auvinen A, Hakulinen T, et al. Glycophorin A biodosimetry in Chernobyl cleanup workers from the Baltic countries. Br Med J 312:1078-1079 (1996).
4. Bigbee WL, Jensen RH, Veidebaum T, Tekkel M, Rahu M, Stengrevics AJ, Auvinen A, Hakulinen T, Servomaa K, Rytomaa T, et al. Biodosimetry of Chernobyl cleanup workers from Estonia and Latvia using the glycophorin A in vivo somatic cell mutation assay. Radiat Res 147:215-224 (1997).
5. Granath F, Darroudi F, Auvinen A, Ehrenberg L, Hakulinen T, Natarajan AT, Rahu M, Rytooma T, Tekkel M, Veidebaum T. Retrospective dose estimates in Estonian Chernobyl clean-up workers by means of FISH. Mutat Res 369:7-12 (1996).
6. Inskip PD, Hartshorne MF, Tekkel M, Rahu M, Veidebaum T, Auvinen A, Crooks LA, Littlefield LG, McFee AF, Salomaa S, et al. Thyroid nodularity and cancer among Chernobyl cleanup workers from Estonia. Radiat Res 147:225-235 (1997).
7. Rahu M, Tekkel M, Veidebaum T, Pukkala E, Hakulinen T, Auvinen A, Rytomaa T, Inskip PD, Boice JD Jr. The Estonian study of Chernobyl cleanup workers. II: Incidence of cancer and mortality. Radiat Res 147:653-657 (1997).
8. Lazutka JR, Mierauskiene J, Slapsyte G, Dedonyte V, Kesminiene A, Riomdeika G. Cytogenetic study in peripheral blood lymphocytes of Chernobyl clean-up workers. Acta Med Lituanica 2:62-67 (1997).
9. Hocking B, Gordon IR, Grain HL, Hatfield GE. Cancer incidence and mortality and proximity to TV towers. Med J Australia 165:601-605 (1996).
10. Dolk H, Shaddick G, Walls P, Grundy C, Thakrar B, Kleinschmidt I, Elliott P. Cancer incidence near radio and television transmitters in Great Britain. I: Sutton Coldfield transmitter. Am J Epidemiol 145:1-9 (1997).
11. Dolk H, Elliott P. Shaddick G, Walls P, Thakrar B. Cancer incidence near radio and television transmitters in Great Britain: all high power transmitters. Am J Epidemiol 145:10-17 (1997).
12. Repacholi MH, Basten A, Gebski V, Noonan D, Finnie J, Harris AW. Lymphomas in E µ Pim1 transgenic mice exposed to pulsed 900 MHz electromagnetic fields. Radiat Res 147:631-640 (1997).
13. Hayes DL, Wang PJ, Reynolds DW, Estes NAM III, Griffith JL, Steffens RA, Carlo GL, Findlay GK, Johnson CM. Interference with cardiac pacemakers by cellular telephones. N Engl J Med 336:1473-1479 (1997).
14. Lagorio S, Rossi S, Vecchia P, De Santis M, Bastianini L, Fusilli M, Ferrucci A, Desideri E, Comba P. Mortality of plasticware workers exposed to radiofrequencies. Bioelectromagnetics 18:418-421 (1997).
Last Update: February 19, 1998