hamed akbari health research center, baqiyatallah university of medical sciences, tehran, ir iran; department of hse, science and research branch, islamic azad university, zahedan, ir iran ramazan mirzaei department of occupational health, health promotion research center, zahedan university of medical sciences, zahedan, ir iran; department of occupational health, health promotion research center, zahedan university of medical sciences, zahedan, ir iran. tel: +98-9122887587, fax: +98-2182482483 tahereh nasrabadi department of nursing, islamic azad university, zahedan branch, zahedan, ir iran mohammad gholami-fesharaki biostatistics department, faculty of medical sciences, tarbiat modares university, tehran, ir iran