William E. Murray

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 womens 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.

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.

A Radiation and Industrial Hygiene Survey of Video Display Terminal Operations

Radiation surveys were performed on 136 terminals of some 530 in use at three different sites. Researchers measured both ionizing and nonionizing radiation. In the industrial hygiene survey, samples of workroom air were analyzed to determine worker exposure to selected airborne chemical contaminants. The results of these tests demonstrated that the VDT operators included in this investigation were not exposed to hazardous levels of radiation or chemical agents.

The Effectiveness of a Shield in Reducing Operator Exposure to Radiofrequency Radiation from a Dielectric Heater

Abstract The objective of this study was to design and install a shield on a radiofrequency (RF) dielectric heater used in the water bed industry and to determine its effectiveness in reducing worker exposures. In work sites where industrial dielectric heating is utilized, occupational RF radiation exposures frequently exceed occupational exposure limits. A water bed manufacturer that used dielectric heaters in its production operations agreed to participate in this developmental study. The mean-squared (ms) RF electric (E 2) and magnetic (H 2) field strengths, the root-mean-squared (rms) RF-induced foot current and the heater frequency were measured for each unit. A heater utilizing a common sealing process and producing high worker exposures was selected for this study. The water bed mattress is a large, bulky product and can not be contained inside the shield. Thus, the shield required a slot or opening to allow passage of the material between the applicator plates for sealing while minimizing the leak...

Optical radiation levels produced by single-phase direct arc furnaces

Radiometric and spectroradiometric measurements of three similar 1700 kW single-phase direct arc electric furnaces revealed that optical radiation hazards could exist for furnace workers in unshielded work areas unless proper safety precautions are taken. The measurements indicate that over 95% of the optical radiation produced by such furnaces at the end of their charge cycle is infrared radiation. The optical measurement protocol is outlined and suggestions are presented to reduce potential optical radiation hazards.