Adverse health effects of occupational exposure to radiofrequency radiation in airport surveillance radar operators

Abstract

Introduction:

Radar workers are exposed to pulsed high frequency electromagnetic fields. In this study, health effects of these radiations in personnel who routinely work with radar systems are investigated.

Materials and Methods:

The 28-item General Health Questionnaire was used as a self-administered tool for assessment of general mental health and mental distress. One hundred workers occupationally exposed to radar radiations (14-18 GHz) participated in the study. Visual reaction time was recorded with a simple blind computer-assisted-visual reaction time test. To assess the short-term memory, Wechsler Memory Scale-III test was performed.

Results:

Twenty to 39% of the radar workers reported different problems such as needing a good tonic, feeling run down and out of sorts, headache, tightness or pressure in the head, insomnia, getting edgy and bad-tempered. Furthermore, 47% of the radar workers reported feeling under strain. In response to this question that if they have been able to enjoy their normal day-to-day activities, 31% responded less than usual. It was also shown that work experience had significant relationships with reaction time and short-term memory indices i.e., forward digit span, reverse digit span, word recognition and paired words.

Conclusion:

To the best of our knowledge, this is the first study to show that occupational exposure to radar microwave radiation leads to changes in somatic symptoms, anxiety and insomnia, social dysfunction, and severe depression. Altogether these results indicate that occupational exposure to radar microwave radiations may be linked to some adverse health effects.

INTRODUCTION

The rapidly increasing use of microwave radiation, has raised public concern about possible detrimental effects of non-ionizing radiation sources, which work in this frequency range.[1,2,3] Radio Detection and Ranging (Radar) equipments send and transmit high-power radio frequency (RF) waves by producing a high-voltage and high frequency alternating electrical current. Radar workers are routinely exposed to pulsed high frequency electromagnetic fields (EMF), which are produced to locate and identify the presence, direction or range of airplanes, ships, control towers or other, usually moving objects. Nowadays, radar systems, which operate at RF between 300 MHz and 15 GHz, are widely used for navigation, aviation, national defense, weather forecasting, and even speed control (hand-held police radars). As radiations emitted by radar systems must travel long distances to detect objects, the power must be relatively high at transmission site. Recent studies conducted on the health effects of occupational exposure to military radar radiations indicate some detrimental effects such as induction of oxidative stress (decreased glutathione concentration vs. increased concentration of malondialdehyde),[4] reduced fertility,[5] increased level of DNA damage and chromatid breaks.[6] Furthermore, some non-EMF hazards such as radar equipment-related electrical injury are also reported.[7] There are also reported risks such as increased incidence of hemolymphatic cancers that can be caused by microwaves generated by radars or ionizing radiation produced by electronic devices producing the microwaves.[8] On the other hand, there are published reports that could not show any detrimental effect in radar workers. In a 40-year controlled longitudinal Belgian study, no increase in all-cause mortality in military personnel who were in close contact with radar equipments was found.[9] The aim of this study was to assess if occupational exposure of military radar personnel affect their general health.

MATERIALS AND METHODS

Participants

This study was conducted on apparently healthy male and female workers employed in airport surveillance radar sites with a frequency range of 14-18 GHz. In this study, health effects of these radiations in personnel who routinely work with radar systems are investigated. After obtaining informed consent, 100 workers (mean age of 33.42 ± 6.87 years, ranged 24-50 years) including 91 males and 9 females, participated in the study. Seventy one percent of these workers had university degrees (B.Sc. and M.Sc.). A previously approved questionnaire[10] including personal information, job status, possibility of exposure to other sources of EMF (Mobile phones, cathode ray tubes (CRT), etc) and adverse health symptoms (self reported) was used.

General health questionnaire

The 28-item General Health Questionnaire (GHQ) initially developed by Goldberg and Hillier to screen for somatic symptoms, anxiety, and insomnia, social dysfunction, and severe depression was used as a self-administered tool for assessment of general mental health, and mental distress. Higher scores indicate a worse general health condition. The validity and reliability of the Persian version of this questionnaire, which is understandable to almost every Iranian, was approved previously.[11]

Reaction time

A modified Bracy simple visual reaction time test[12] that was developed in the Center for Research in Radiation Sciences (CRRS), Shiraz University of Medical Sciences, was used in this study. Visual reaction time (VRT) of all participants was recorded with a simple blind computer-assisted-visual reaction time test. To evaluate participants’ sustained attention and response time, the participants were asked to respond as quickly as possible by a single right click on a computer mouse when a red square on the display was replaced by a green one. The students had to perform some preliminary tests for orientation with the test. In this stage, reaction time was not recorded. After orientation, to reduce random variation of measurements, each test was repeated 7 times in both real and sham exposure phases.

Memory test

Wechsler Memory Scale-III (WMS 1991) test was performed on all participants. The test includes four subtests including forward and backward digit span, paired words, and word recognition. To perform the WMS digit span memory test, participants were asked to repeat back a list of digits, which were spoken live-voice, by an expert member of our research team at a rate of approximately one digit per second.

RESULTS

As shown in Table 1, the mean age of the participants was 33.42 ± 6.87 (ranged 24-50) years. Forty-eight percent of the participants had worked 8 hours or less than 8 hours per day, while 48% and 2% of the participants had worked 9-10 hours per day and more than 10 hours per day, respectively. Only 1% of the participants had worked less than 5 days per week, while 84% and 15% of the participants had worked 5 days per week and 6 days per week, respectively. Moving to work experience as a cardinal factor that determines the occupational health effects, 20% of the participants had work experiences of 24 months or less while 30%, 35%, and 15% had work experiences in the range of 25-148, 49-120, and more than 121 months, respectively. On the other hand, considering the average distance of the participants from radar antennas, 33% had worked in distances of 4 meters or less, while 47% and 20% had worked in distances of 5-10 meters and more than 10 meters, respectively.

Table 1.

Demographic and occupational characteristics of the sample (n =100)

Mean (±SD) GHQ-28 scores of participants in all subsets and the scores in each subsection of somatic symptoms, anxiety/insomnia, social dysfunction, and severe depression are shown in Table 2. The mean score of GHQ in all subsets was 0.44 ± 0.52 while these scores for somatic symptoms and anxiety/insomnia were 1.03 ± 0.49 and 0.99 ± 0.58, respectively. The GHQ scores for social dysfunction and severe depression were 1.08 ± 0.34 and 0.44 ± 0.52, respectively. Thirty percent of the participants have reported that rather more than usual they had recently been feeling in need of a good tonic (Question#2). In response to this question that if they have recently been feeling run down and out of sorts (Question#3), 31% responded “rather more than usual”. In response to this question that if they have recently been getting any pain in their head (Question#5), 29% responded “rather more than usual”. Regarding feeling of tightness or pressure in their head (Question#6), 24% responded “rather more than usual”. On the other hand, in response to this question that if they had difficulty in staying asleep once you were off (Question#9), 20% responded “rather more than usual”. Regarding feeling constantly under strain (Question#10), 37% responded “rather more than usual” and 10% responded “much more than usual”. Considering been getting edgy and bad-tempered (Question#11), 32% responded “rather more than usual” and 7% responded “much more than usual”. In response to this question that if they have been able to enjoy their normal day-to-day activities (Question#21), 31% responded “less than usual”. As shown in Table 3 the number of work hours per day could not affect the GHQ-28 scores of participants. On the other hand, work experience [Table 4] and the distance [Table 5] from the antenna played no role in mean GHQ-scores of the participants.

Table 2.

Mean (±SD) GHQ-28 scores of participants in each subsection of somatic symptoms, anxiety/insomnia, social dysfunction, and severe depression

Table 3.

Mean (±SD) GHQ-28 scores of participants with different hours of work per day

Table 4.

Mean (±SD) GHQ-28 scores of participants with different work histories

Table 5.

Mean (±SD) GHQ-28 scores of participants who work in different distances from the antenna

Chi-square test showed statistically significant relationship between work experience and forward digit span (P < 0.001). On the other hand, significant relationships were found between work experience and reverse digit span (P < 0.001), word recognition (P < 0.001) and paired words (P < 0.001). There were also significant relationships between age of the participants and the majority of these short-term memory indices i.e., forward digit span (P < 0.003), reverse digit span (P < 0.011), and word recognition (P = 0.001). The relationship between age and paired words was not statistically significant (P < 0.001). After adjustment for age, forward digit span, reverse digit span, word recognition and paired words remained associated with work experience. The relationship between reaction time and the participants’ work experience is shown in Table 6. Chi-square test revealed a statistically significant relationship between work experience and reaction time (P < 0.001). Again, there was a significant relationship between participants’ age and the reaction time (P < 0.001). After adjustment for age, reaction time remained associated with work experience. Chi-square test could not show any statistically significant relationship between average distance of participants’ work place from the radar antenna and short-term memory indices; forward digit span (P = 0.590), reverse digit span (P = 0.107), word recognition (P = 0.172) and paired words (P = 0.631). This test also could not reveal any significant relationship between distance and reaction time (P = 0.200).

Table 6.

The relationship between reaction time and the participants’ work experience

The results of a linear regression analysis showed that the work experience had a significant positive correlation with reaction time (R square = 0.556, P < 0.001). Neither work experience (R square = 0.003, P = 0.602) nor distance (R square = 0.005, P = 0.479) had any significant positive correlation with total score of GHQ. On the other hand, work experience had a significant positive correlation with forward digit span (R square = 0.162, P < 0.001), reverse digit span (R square = 0.223, P < 0.001), word recognition (R square = 0.250, P < 0.001) and paired words (R square = 0.264, P < 0.001).

DISCUSSION

The findings of the GHQ-28 test indicated that at least 20-39% of the radar workers reported different problems such as needing a good tonic, feeling run down and out of sorts, headache, tightness or pressure in the head, insomnia, getting edgy, and bad-tempered. Interestingly, 47% of the radar workers reported feeling under strain (37% rather more than usual and 10% much more than usual). On the other hand, in response to this question that if they have been able to enjoy their normal day-to-day activities, 31% responded “less than usual”. It was also shown that work experience had significant relationships with reaction time and short-term memory indices such as forward digit span, reverse digit span, word recognition, and paired words.

Results obtained in this study generally confirm the findings of other investigators who have reported detrimental health effects of the occupational exposure to radar radiations such as decreased sperm motility and viability in highly exposed group compared to those of the lowly exposed and control groups.[13] increased sperm dysmorphia and alteration in quality of semen in response to changes in microwave frequency, distance, intensity, exposure time and quality of shielding,[14] increase in frequency of micronuclei.[15] On the other hand, these findings are not in generally in line with those reports that showed biological alterations without major clinical implications such as increased IgG, IgM, and IgA level and decreased count of lymphocytes and T8 cells[16] or even some beneficial bio effects such as lower all-cause mortality rate in military conscripts who served in battalions with anti-aircraft radars versus controls.[9]

Investigation of the general and more specifically mental health that is believed to be an integral and essential component of health was among the main goals of this study. The World Health Organization (WHO) constitution states: “Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity”. In this light, mental health is more than the absence of mental disorders or disabilities.[17] While exposure to radiofrequency radiation has not consistently been shown to have an effect on well-being or self-reported symptoms such as headache, fatigue, dizziness, and concentration difficulties,[18] our study showed that a considerable portion of the radar workers participated in this study suffer from problems such as needing a tonic, feeling run down and out of sorts, headache, tightness or pressure in the head, insomnia, getting edgy, and bad-tempered. Despite much dissimilarity, our findings are clearly in contrast with some recent studies that report lack of evidence for a direct association between frequency and severity of non-specific physical symptoms and higher levels of EMF exposure.[10,19,20]

CONCLUSION

Altogether the results obtained in this study indicate that occupational exposure to radar microwave radiations may be linked to some adverse health effects. In this light, attempts for reducing exposure of radar workers to radiofrequencies generated by radar systems should be considered as a critical goal.