Semen quality and hormone levels among radiofrequency heater operators.

Approximately 9,000,000 US workers are occupationally exposed to radiofrequency (RF) radiation; over 250,000 operate RF dielectric heaters. Our purpose was to determine whether male RF heater operators experience increased adverse reproductive effects reflected in reduced semen quality or altered hormone levels. We measured incident RF heater radiation exposures and RF-induced foot currents at four companies. For 12 male heater operators and a comparison group of 34 RF-unexposed men, we measured 33 parameters of semen quality and four serum hormones. Despite wide variation in individual exposure levels, near field strengths and induced foot currents did not exceed current standard levels and guidelines. We observed minor semen quality and hormonal differences between the groups, including a slightly higher mean follicle-stimulating hormone level for exposed operators (7.6 vs 5.8 mIU/mL). Further occupational studies of RF-exposed men may be warranted.

Work with video display terminals and the risk of reduced birthweight and preterm birth.

To determine whether the use of video display terminals (VDTs) is associated with an increased risk of reduced birthweight (RBW) and preterm birth, a cohort of telephone operators who used VDTs at work was compared to a cohort of non-VDT-users. Among 2,430 women interviewed, 713 eligible singleton live births were reported. Exposure was estimated from company records and a representative sample of electromagnetic fields was measured at the VDT workstations. For RBW (< or = 2,800 g), we found no excess risk associated with any VDT use during pregnancy (odds ratio [OR] = 0.9; 95% confidence interval [CI] = 0.5-1.7). For preterm birth (< or = 37 weeks), we similarly found no excess risk (OR = 0.7; 95% CI = 0.4-1.1). The risks estimated did not change substantially when hours working with VDTs were used as exposure variables. By contrast, increased risks were found for several known risk factors for LBW and preterm birth. We conclude that occupational VDT use does not increase the risk of RBW and preterm birth.

Foot currents and ankle SARs induced by dielectric heaters.

Data are presented on ankle-specific SARs and foot currents as a function of strengths of radio-frequency electromagnetic fields encountered by operators of dielectric heaters. The determination of foot currents was based on near-field exposures in which reactive coupling dominates, and which can result in substantial SARs in exposed workers. The operators were located less than one wavelength from--usually within one meter of--the dielectric heaters, which generated fields at frequencies from 6.5 to 65 MHz. At distances normally assumed by workers, maximal strengths of electric fields ranged from 10(4) to 2.4 x 10(6) V2/m2; maximal strengths of magnetic fields ranged from 5.0 x 10(-3) to 33.3 A2/m2. Currents through both feet to ground were measured while operators stood where they normally worked. Maximal currents ranged from 3 to 617 mA, rms. Nearly 27 percent of the dielectric heaters induced foot currents that exceeded the 200-mA limit that has been proposed for a new ANSI C95.1 standard. Twenty percent of the heaters induced foot currents that exceeded 350 mA. SARs in ankles were calculated from foot currents, and they approximated 5 W/kg at 100 mA, 29 W/kg at 250 mA, and 57 W/kg at 350 mA. The maximal SAR in the ankle was approximately 176 W/kg at 617 mA.

Video display terminals and the risk of spontaneous abortion.

BACKGROUND: The relation between spontaneous abortion and the use of video display terminals (VDTs) is of great public health concern. Previous investigators of this issue have reported inconsistent findings. METHODS: To determine whether electromagnetic fields emitted by VDTs are associated with an increased risk of spontaneous abortion, a cohort of female telephone operators who used VDTs at work was compared with a cohort of operators who did not use VDTs. To obtain reliable estimates of exposure, we determined the number of hours of VDT use per week from company records and measured electromagnetic fields at VDT workstations and, for purposes of comparison, at workstations without VDTs. Operators who used VDTs had higher abdominal exposure to very-low-frequency (15 kHz) electromagnetic fields (workstations without VDTs did not emit very-low-frequency energy). Abdominal exposure to extremely-low-frequency fields (45 to 60 Hz) was similar for both operators who used VDTs and those who did not. Among 2430 women interviewed, there were 882 pregnancies that met our criteria for inclusion in the study. RESULTS: We found no excess risk of spontaneous abortion among women who used VDTs during the first trimester of pregnancy (odds ratio = 0.93; 95 percent confidence interval, 0.63 to 1.38), and no dose-response relation was apparent when we examined the women's hours of VDT use per week (odds ratio for 1 to 25 hours per week = 1.04; 95 percent confidence interval, 0.61 to 1.79; odds ratio for greater than 25 hours per week = 1.00; 95 percent confidence interval, 0.61 to 1.64). There continued to be no risk associated with the use of VDTs when we accounted for multiple pregnancies, conducted separate analyses of early abortion, late abortion, and all fetal losses, or limited our analyses to spontaneous abortions for which a physician was consulted. CONCLUSIONS: The use of VDTs and exposure to the accompanying electromagnetic fields were not associated with an increased risk of spontaneous abortion in this study.

Controlled release infusion kinetics of tobramycin.

Ten healthy male volunteers received two doses of tobramycin (2 mg/kg) in a crossover fashion, first by intravenous piggyback (IVPB), then by the CRIS infusion system after a washout period. Serum samples were drawn both during and after the infusions. Twenty-four-hour urine collections were assayed for tobramycin. Residual fluid from the lines of both delivery systems was measured and assayed for tobramycin concentration. All samples were run in duplicate, using an enzyme-multiplied immunoassay technique assay. The results indicate that there was a statistically higher amount of drug delivered via the CRIS system (98.3 +/- 0.3% versus 90.4 +/- 2.3%). No significant difference was found in urinary recovery between the two groups. Peak serum levels were significantly higher with the CRIS system, with 8/10 subjects having at least one serum level greater than 10 micrograms/ml, as compared to 0/10 when given by IVPB. Peak serum levels occurred at 30 min in all subjects given tobramycin through the CRIS system, compared to 50-60 min when delivered by IVPB. This difference in peak serum levels is primarily related to the rate of drug delivery and to the difference in the dose delivered to each subject. The significance of the serum concentration profiles is discussed.

Case-control study of lung cancer in civilian employees at the Portsmouth Naval Shipyard, Kittery, Maine.

Case-control analysis of deaths due to lung cancer (International Classification of Diseases, Eighth Revision, code 162) among persons who worked at the Portsmouth Naval Shipyard, Kittery, Maine, between 1952 and 1977 found elevated odds ratios for exposures to ionizing radiation, asbestos, and welding byproducts. The radiation-related excess was statistically significant in persons with cumulative lifetime exposures of 1.0-4.999 rem. When asbestos and welding histories were combined into a single risk factor, odds ratios for the combined exposure were significantly elevated for two of three duration-of-exposure categories examined. Further analysis of data on radiation exposure, controlling for exposures to asbestos and welding, found reductions in initial estimates of radiation risk at all levels of radiation exposure. This reduction suggests that radiation workers were more heavily exposed to asbestos and/or welding fumes than were other workers and that those exposures confounded the observed association between radiation and lung cancer. Analysis of mortality by time since first exposure to radiation revealed no pattern of progressive increase as latency increased. By contrast, odds ratios for asbestos/welding increased with latency. Data on cigarette smoking and socioeconomic status were not available. The results of this study do not preclude a possible association between radiation exposure at the Portsmouth Naval Shipyard and excess mortality from lung cancer. However, they provide no evidence in support of such a relation.

A case-control study of leukemia at a naval nuclear shipyard.

A matched case-control study was conducted of 53 leukemia deaths and of 212 controls within a previously studied cohort of 24,545 on-shore workers employed between January 1, 1952 and August 15, 1977 at the Portsmouth (New Hampshire) Naval Shipyard. The study sought to ascertain a priori whether there was an association between leukemia deaths and occupational exposure to either ionizing radiation or organic solvents. To obtain information on individual exposures, radiation dose histories and detailed work histories by job and shop were evaluated for each subject. No statistically significant associations were found either between ionizing radiation or presumed solvent exposure and myelogenous or lymphatic leukemia. However, when specific job categories and shops were examined without benefit of a priori hypotheses, two occupations, electrician and welder, were found to be associated with leukemia. For electricians, the Mantel-Haenszel odds ratio (ORMH) was significantly elevated for all leukemias (ORMH = 3.00, 95% confidence interval (CI) = 1.29-6.98), particularly for lymphatic leukemia (ORMH = 6.00, 95% CI = 1.47-24.45). For welders, the odds ratio was not significantly elevated for all leukemias (ORMH = 2.25, 95% CI = 0.92-5.53), but was significantly elevated for myeloid leukemia (ORMH = 3.83, 95% CI = 1.28-11.46). These findings persisted when potential confounders were adjusted by means of a conditional logistic regression model.

Magnetic field measurements near RF induction heaters.

We discuss initial magnetic field strength measurements made around radiofrequency (RF) induction heaters. These measurements were made with a monitor developed for the National Institute for Occupational Safety and Health (NIOSH) by the National Bureau of Standards (NBS). The monitor has a dynamic range of .01 to 10,000 A2/m2, a frequency range of 300 kHz to 100 MHz, an isotropic response (+/- .3 dB) with three mutally orthogonal loop antennas that have the ability to measure and display each of three orthogonal magnetic field components, a high probe burnout protection level of 20,000 A2/m2, and an accuracy of +/- 1.0 dB at 13 calibration frequencies. The portable survey monitor was used to measure the magnetic field strengths in the vicinity of 16 RF induction heaters. Typically these induction heaters are operated continuously for several hours. The maximum field strengths (without duty factor correction) ranged from 15 to 4,500 A2/m2 and were measured 5 to 51 cm from the loop applicators of the induction heaters. At locations commonly occupied by workers (ie, approximately 30 to 76 cm from heaters), the fields ranged from .01 to 300 A2/m2 (without duty factor correction).

Occupational exposures to radiofrequency radiation (18-31 MHz) from F dielectric heat sealers.

The National Institute for Occupational Safety and Health (NIOSH) has initiated an epidemiologic study to evaluate whether or not radiofrequency (RF) radiation in the 10--100 MHz range has any effects on the reproductive functions of exposed workers. Initial investigations indicated that a suitable population for this study might exist in industries utilizing RF dielectric heat sealers. To estimate exposure levels of RF heat sealer operators, NIOSH made exposure measurements for 82 operators in 13 facilities with a Narda Broadband Isotropic Radiation Monitor, Model 25540 with an electric (E) field probe. Model 8644 and a magnetic (H) field probe, Model 8635. The geometric mean of the maximum measured exposures was at least 200 V/m for the E-field and 0.094 A/m for the H-field. The Occupational Safety and Health Administration (OSHA) exposure standard for RF radiation in the range of 10--100,000 MHz is 10 mW/cm2 as averaged over any 0.1-hour period. This value corresponds to an exposure of 200 V/m for the E-field and 0.5 A/m for the H-field. NIOSH found that 55% of the heat sealer operators were exposed to levels for the E-field above 200 V/m; for the H-field, 21% of the operators were exposed to levels above 0.5 A/m. For the heat sealers evaluated, the frequencies ranged from 18 to 31 MHz. On the basis of these environmental data, RF heat sealer operators experience a wide range of exposures both above and below the OSHA standard. The exposure range is sufficiently broad to make these operators adequate candidates for epidemiologic study.

Cancer mortality at a Naval Nuclear Shipyard.

To evaluate a reported five-fold increase in leukaemia mortality among workers exposed to ionising radiation at Portsmouth (New Hampshire) Naval Shipyard (PNS), a retrospective cohort mortality study of all PNS civilian workers employed from 1952 to 1977 was done. Three subcohorts were identified: 7615 workers with radiation exposure of 0.001 to 91.414 rem (mean 2.779 rem, median 0.545 rem), 15 585 non-radiation workers, and 1345 workers selected for radiation work who received no measurable exposures. Vital status on 96% of the workers was ascertained and observed mortality due to all causes, all malignant neoplasms, and malignant neoplasms of the lymphatic and haematopoietic tissues, including leukaemia, was compared with that expected from mortality-rates for United States White males. Leukaemia mortality in radiation and non-radiation workers at PNS was also compared. Although the study had a power of greater than 99% to detect statistically a five-fold increase in leukaemia mortality among the radiation workers, and a power of 67% to detect a two-fold increase, there was no excess due to leukaemia or any other cause. The standardised mortality ratio for leukaemia among radiation workers was 84 (95% confidence interval, 34--174). There was no dose-response relation with radiation or any increased mortality in radiation over non-radiation workers. The study was, however, limited by short latency (time since first radiation); only 53% of the workers had less than 15 years' latency.