TABLE 9: RFR AND CONGENITAL ANOMALIES
| Authors | Effects Sought or Examined | Exposure Modality | Effects Reported | Notes & Comments
| Sigler et al. (1965)
| Down's syndrome in children of mothers nonoccupationally exposed to ionizing radiation, and those with occupational fluoroscopic exposure in medical practice.
| Exposure of mothers to ionizing radiation and radar exposure of fathers.
| The percentage of case mothers who had received fluoroscopy before childbirth was significantly higher than control mothers, but the percentage of case fathers who reported close association with radars was also significantly higher than control fathers.
| See Cohen et al. (1977) below.
| Cohen et al. (1977)
| Down's syndrome. See Sigler et al. (1965).
| Radar exposure of fathers.
| This study of the larger data base found no association of Down's syndrome with radar exposure of fathers.
| These authors augmented the number of matched case-control pairs in Sigler et al. (1965).
| Peacock et al. (1971)
| Birth defects. The authors examined Alabama-wide birth records by county over a period of 17 months.
| Proximity to military bases.
| The authors found a higher percentage of newborns with anomalies for the military personnel in the 6 counties surrounding Fort Rucker than for the civilians.
| See Burdeshaw and Schaffer (1977) below.
| Peacock et al. (1973)
| Birth defects. The authors used more accurate data spanning 4 years, and used better statistical treatment.
| Proximity to military bases. The authors compared data for military hospitals at Fort Rucker and Eglin AFB with non-radar bases.
| Abnormally high anomaly rates were found at Lyster Hospital (within Fort Rucker) and the military hospital at Eglin AFB; the authors associated this finding with radar exposure.
| See Burdeshaw and Schaffer (1977) below.
| Burdeshaw and Schaffer (1977)
| Birth defects. These authors reexamined the original Alabama birth records but compared the data for the 2 counties encompassing Fort Rucker with the other 65 Alabama counties on a score and rank basis rather than by statewide averages.
| Proximity to military bases.
| The overall anomaly rate was found to be within expectations for hospitals like Lyster; no significant clustering of anomalies was found in the vicinity of the presumed radar sites.
| The reported higher incidence of congenital anomalies at Lyster Hospital was found to be attributable to a higher than normal reporting rate of one physician who apparently included "birth defects" not characterized as such by other physicians.
| Källén et al. (1982)
| Perinatal mortality and birth defects in infants of female physiotherapists in Sweden.
| Occupational exposure of physiotherapists to various treatment modalities.
| For the total cohort, the expectation values for all of the endpoints were statistically better or comparable to those for the general population, a finding the authors hypothesized as a "healthy worker" effect. In a case-control study within the cohort, the authors matched two normal infants with each dead or malformed infant, and estimated the exposures of the mothers to various occupational modalities from their responses to a questionnaire. The only possible association with RFR-exposure was authors' report that the use of shortwave equipment was higher by mothers of a dead or malformed infant.
| The shortwave-equipment finding was of borderline statistical significance. However, use of responses to a questionnaire is questionable because of self-selection by the respondents. Thus, the finding above is of doubtful validity.
| Taskinen et al. (1990)
| Spontaneous abortions or birth defects in infants of Finnish physiotherapists.
| Patient treatments with ultrasound (0.5-3 MHz); "deep-heat therapy" (including "shortwaves" [27.12 MHz] and "microwaves" [not characterized]; electric-current modalities; and physical exertion.
| Significant increases of spontaneous-abortion risk were found for: ultrasound use more than 20 hours a week, electric-current therapies more than 5 hours a week, and heavy lifting or frequent transfers of patients. No significant risk increase of spontaneous abortion was found for deep-heat therapies (shortwaves or microwaves). Regarding congenital malformations, a significant risk increase was reported for deep-heat therapies for 1-4 hours per week but not for 5 or more hours a week, results likely due to selective recall bias.
| Statistical treatment of the response data was reasonably extensive, but absent were any data on exposure levels to the various treatment modalities and their variations with time and patient-treatment site. Thus, at least with regard to RFR, little if any credence can be given to either the positive or negative findings of this study.
| Larsen et al. (1991)
| Possible reproductive hazards among female physiotherapists in the Union of Danish Physiotherapists from RFR-exposure.
| Exposures to short-wave diathermy (and to ultrasound and the performance of other duties) during the first pregnancy month were assessed, and an a priori diathermy-exposure index was formed.
| Data for 1978-1985 on spontaneous abortions, gestation durations, low birth weights, premature births, stillbirths, gender, and deaths within 1 year were analyzed. Twins and induced abortions were excluded from the study. The odds ratios for "subfecundity" (waiting time to pregnancy more than six months), spontaneous abortion, still-birth or death within 1 year, premature birth, and low birth weight did not differ significantly from 1.0. The sole positive finding was a low ratio of boys to girls for those presumed exposed to RFR from diathermy.
| As with other epidemiologic studies, lack of measurements of the RFR-exposure levels and vague estimates of exposure durations diminish the credibility of the single positive finding, as well as of the negative findings. Moreover, as noted by the authors, the results are based on sparse data and must be interpreted with caution.
| Ouellet-Hellstrom and Stewart (1993)
| Possible reproductive hazards among female physiotherapists listed in 1989 by the American Physical Therapy Association from occupational use of microwave or shortwave diathermy.
| Exposures from treating patients with microwave or shortwave diathermy of frequencies not stated and from use of other modalities and chemicals, just before or during the first trimester of pregnancy.
| Tabulated were the odds ratios (ORs) and 95% confidence intervals (CIs) for an association of miscarriage risk and exposure to microwave and shortwave diathermy. For microwaves, 209 of 1,759 (11.9%) case pregnancies and 167 of 1,759 (9.5%) control pregnancies had any exposure. Those data were shown in terms of <5, 5-20, and >20 exposures a month. The respective ORs and CIs were 1.07 (0.77-1.43), 1.41 (1.04-2.17), and 1.55 (0.99-2.55), for overall values of 1.28 (1.02-1.59). The authors stated that by the chiČ test, the trend in OR increase with exposure was significant (p<0.005). However, the CI for the most exposure durations (more than 20 hours a month) encompassed 1.00, rendering that OR value nonsignificant. Similar results were displayed for 167/1102 cases and 151/1258 controls who had no prior fetal losses.
| For shortwaves, all of the CIs spanned 1.00, with no significant trend with increasing exposure. Thus, the authors concluded that women were at higher miscarriage risk from administering microwave diathermy during their first trimester of pregnancy, but not from shortwave diathermy. Of 6,684 respondents to mailed questionnaires, 1,753 case pregnancies were selected from those who had first-trimester miscarriages. Those cases were matched with 1,753 control pregnancies selected from all pregnancies irrespective of outcome. Some of the women selected had reported only 1 case pregnancy and others only 1 control pregnancy, but still others contributed 1 each case and control pregnancy, 2 case pregnancies, 2 control pregnancies, 3 or more case pregnancies, or 3 or more control pregnancies.
| The positive findings of this study are dubious, because the percentages of exposed cases and controls were too small yield much statistical power. Second, the authors gave no estimations on RFR-exposure levels for either of the diathermy modalities. Third, as the authors stated, the use of other modalities could not be stratified adequately. This conclusion applies as well to any of the negative findings in this study. |
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