People first became exposed to the radiofrequency radiation that radar equipment emits in the 20th century. Radar was primarily used by the military at first, but in peace-time, radar emissions have been mainly from airports and seaports, with some Ministry of Defence establishments adding to local environmental exposure.
Radar emissions travel some considerable distance in order to communicate with their intended recipients (aeroplanes, ships, control towers, etc). The power is high at transmission to carry such distances, and in fact only fall to levels of 1 V/m at the following distances (all approximate, and assuming free-space radiation):
|1.0 kW DME on aircraft and at airfields
|25 kW marine radars (both fixed and ship-borne)
|100 MW ship harbour radars
|1 GW air traffic control and weather radars
|10 GW some military radars
There are other, more localised, uses for radar such as for traffic control measures, when it is used by police to track traffic speed. Exposure of police personnel using the equipment (in a US study, Fink 1999) resulted in RF radiation at seated ocular and testicular positions of up to 12 V/m; below the legal guidelines, but significantly higher than the levels found to have health effects in situations of RF exposure. Police radar operators have been the subjects of various studies, and there have been associations made between this type of exposure and an increased risk of getting certain cancers, see below.
All of the studies looking at potential health effects as a result of exposure to radar have been occupational studies, where the RF fields can be significantly higher, rather than studies looking at the potential effects suffered by people as a result of living near to the transmitting equipment.
Concern about the potential health effects of working with radar produced a study by Daily (1943), who reported a statistically significant increase in immature red blood cells among workers exposed to radar. Goldoni (1990) found that radar-exposed workers had significantly lower levels of leukocytes and red cells than workers further away from the microwave source.
An increased incidence of testicular cancer (Davis & Mostofi 1993) and in testicular and melanoma skin cancer (Finkelstein 1998), was found in police officers working with traffic radar. Several different forms of cancer, melanoma of the eye, testicular, nasopharyngioma, non-Hodgkin's lymphoma, breast cancer, were reported in radar technicians with prolonged exposure to high levels of RF/MW radiation (Richter 2000). The latency periods between exposure and diagnosis were brief, suggesting an aggressive form. An investigation took place into a cancer cluster in a Canadian police detachment. A possible link was suggested between the different cancers (including testicular, cervical, colon, skin, melanoma, leukaemia and lymphoma) and the use of police traffic radar (van Netten 2003).
Tikhonova (2003) found that personnel of the civil aircraft radar-tracking system exposed to EMFs had a higher prevalence of cardiovascular disease, and that this occurred at a younger age, in the 30-39 year age group.
Laboratory studies using animal cells (Garaj-Vhrovac 1990, 1991) and subsequently human cells (Garaj-Vhrovac 1992, d'Ambrosio 1995) found DNA changes to be a result of RF radiation exposure.
Personnel repairing aircraft traffic control radar suffered chromosomal aberrations, when accidentally exposed to high level fields (Garaj-Vhrovac 1993), though there were only 6 workers so exposed.
Almost three times the amount of DNA damage has been found in radar-facility workers, compared with other workers (Garaj-Vrhovac 2009). There was quite a lot of variation between individuals, and whether the person smoked or not made a difference.
Weyandt (1996) found lower sperm counts and sperm/ejaculate in personnel exposed to radar, but Schrader (1998), a member of the original team, in a follow up study did not find the effect, suggesting that the difference may have been due to the type of radar investigated originally.
Liu (2003) concluded, after investigating various parameters to do with sperm DNA, that "Radar radiation inflicts damage to male reproduction system." Ding (2004) found significant changes to sperm quality, but stated that "it did not affect the male reproductive function".
Ye (2007) found that radar radiation damaged sperm quality, as shown in the reduction of sperm motility and the amount of sperm abnormality in seamen. Yan (2007) found that exposure to microwave radiation from radar produced sexual dysfunction and reduced fertility in operators. Møllerløkken (2008) also found that navy personnel working with radar and/or sonar were more than twice as likely to have reduced fertility. Ye suggested that when the exposure stopped, the sperm quality would return to normal.
Effect on birds
In a personal communication, we were told that in 1956, when a new radar system was being tested that used a fast rise time and very short duration pulse (similar to that used in modern digital communications systems), a large flock of thousands of migrating birds (mainly swifts and house martins) were found dead, or dying, over a wide area of the South Downs.
Daily LE 1943 - A clinical study of the results of exposure of laboratory personnel to radar and high frequency radio U.S. Naval Medical Bulletin 41:1052-1056
D'Ambrosio G et al 1995 - Genotoxic effects of amplitude-modulated microwaves on human lymphocytes exposed in vitro under controlled conditions Electro Magnetobiol 14:157-164
Davis RL & FK Mostofi 1993 - Cluster of testicular cancer in police officers exposed to hand-held radar
Ding XP et al 2004 - A cross-sectional study on nonionizing radiation to male fertility Zhonghua Liu Xing Bing Xue Za Zhi 25(1):40-3
Fink JM et al 1999 - Microwave emissions from police radar Am Ind Hyg Assoc J 60(6):770-6
Finkelstein MM 1998 - Cancer incidence among Ontario police officers Am J Ind Med 34(2):157-62
Garaj-Vrhovac V et al 1990 - The effect of microwave radiation on the cell genome Mutat Res 243:87-93
Garaj-Vrhovac V et al 1991 - The relation between colony-forming ability, chromosome aberrations, and incidence of micronuclei in V79 Chinese hamster cells exposed to microwave radiation Mutat Res 263:143-149
Garaj-Vrhovac V et al 1992 - The correlation between the frequency of micronuclei and specific chromosome aberrations in human lymphocytes exposed to microwaves Mutat Res 281:181-186
Garaj-Vrhovac V et al 1993 - The rate of elimination of chromosomal aberrations after accidental exposure to microwaves Bioelectrochem Bioenerg 30:319-325
Garaj-Vrhovac V & V Orescanin 2009 - Assessment of DNA sensitivity in peripheral blood leukocytes after occupational exposure to microwave radiation: the alkaline comet assay and chromatid breakage assay Cell Biol Toxicol 25(1):33-43
Goldoni J 1990 - Hematological changes in peripheral blood of workers occupationally exposed to microwave radiation Health Phys 58:205-7
Liu X et al 2003 - Evaluation of radiation damage to the sperm DNA of radar operators Zhonghua Nan Ke Xue 9(7):494-6,500
Mollerlokken OJ & BE Moen 2008 - Is fertility reduced among men exposed to radiofrequency fields in the Norwegian Navy? Bioelectromagnetics 29(5):345-52
Richter E et al 2000 - Cancer in radar technicians exposed to radiofrequency/microwave radiation: sentinel episodes Int J Occup Environ Health 6(3):187-93
Schrader SM et al 1998 - Reproductive function in relation to duty assignments among military personnel Reprod Toxicol 12(4):465-8
Tikhonova GI 2003 - Epidemiological risk assessment of pathology development in occupational exposure to radiofrequency electromagnetic fields Radiats Biol Radioecol 43(5):559-64
Van Netten C et al 2003 - Cancer cluster among police detachment personnel Environ Int 28(7):567-72
Weyandt TB et al 1996 - Semen analysis of military personnel associated with military duty assignments Reprod Toxicol 10(6):521-8
Yan SW et al 2007 - Long-term exposure to low intensity microwave radiation affects male reproductivity Zhonghua Nan Ke Xue 13(4):306-8
Ye LL et al 2007 - Radar radiation damages sperm quality Zhonghua Nan Ke Xue 13(9):801-3