DNA integrity invitro study of human peripheral blood leukocytes exposed to extremely-low-frequency electromagnetic fields using comet assay

摘要

Exposure to extremely-low-frequency (ELF) electromagnetic fields (EMFs) of various intensities is ubiquitous in both domestic and occupational environments. There is a concern over the possibilities that exposure to EMFs might affect the process of carcinogenesis. Controversial information is available on the effect of EMFs on DNA integrity. Hence, the present study was carried out to investigate the invitro effects of ELF-EMFs of varying flux densities (0.2, 0.4, 0.6, 0.8 and 1 mT at 50 Hz) on DNA integrity in human peripheral blood leukocytes using comet assay. All exposures were given at 37°C (i.e., human body temperature). The experimental setup to produce the EMF consisted of an assembly of a dimmerstat, transformer, ammeter and air-cored coils to provide the desired field intensity at the seat of the blood samples. One set of coils was shielded against external, stray electromagnetic fields by housing the set of coils in a mu-metal (extremely-high-relative permeability magnetic material) box. Four types of exposures were studied simultanesouly: (1) EMF exposure, samples shielded inside mu-metal box, placed in an incubator; (2) EMF exposure, samples not shielded, arranged inside the same incubator; (3) no EMF exposure, samples not shielded, but placed in dummy coils inside another incubator, and (4) no EMF exposure, no shielding, no dummy coils, but samples placed in a thermos containing water maintained at 37°C. In addition, one set of samples was processed immediately after collection without any treatment. Heparin zed peripheral blood samples were collected from 6 adult males in the age group of 20-24 years. The subjects were non-smokers and non-drinkers of alcohol. Their leukocytes were processed by comet assay in the above mentioned treatments and controls. 100 cells per treatment were scored for comet tail-length which is an estimate of DNA damage. DNA damage increased with exposure dose. The results are similar to our earlier studies. Moreover, DNA damage had the following trend according to the types of exposures mentioned above: non-shielded exposed inside incubator>shielded exposed inside incubator>non-shielded non-exposed inside incubator>non-shielded nonexposed inside thermos>control.