Abstract: Objective  To study the changes of peripheral blood cells of the employees who accept a long-term extremely low frequency electromagnetic radiation,
and to investigate the effects of the extremely low frequency electromagnetic radiation on the peripheral blood cells.
Methods The employees accept extremely low frequency electromagnetic radiation were chosed as exposure groups,the worker
s who exposed to the low level of electromagnetic radiation were used as  low exposure group (n=123),and those who exposed to the high level radiation a
s  high exposure group(n=229),another workers who did not contact with extremely low frequency electromagnetic radiation were chosed as control group (n=212).The electromagnetic field intensity was detected by EFA-300 Field Analyzer,the workshop noise intensity was detected by AWA5610D integrating sound level meter,and the number of peripheral blood cells was tested by automated hematology analyzer.
Results Compared with control group,the mean corpuscular volume (MCV) and the number of  white blood cells (WBC) in low exposure group were significantly increased (P<0.05);the  MCV,WBC,hematocrit (Hct),and lymphocyte (LC) in high exposure group were markedly
increased (P<0.05),but the mean platelet volume (MPV) in high exposure group was decreased(P<0.05).Conclusion Extremely low frequency electromagnetic radiation might affect the peripheral blood cells of employees,even cause the changes of blood system. 

Key words: electromagnetic radiation, blood cells, employees