Sampling for BTX was conducted according to the National Institute for Occupational Safety and Health (NIOSH) method 1501 [22]. Using activated charcoal sorbent tubes, (model SKC No. 226-01, SKC, Philadelphia, PA, USA) and a sampling pump (model SKC 222-mL/count, SKC), with a flow rate of 0.1e0.02 L/minute, three personal air samples at the breathing zone of the employees of each petrol station (a total of 60 samples) were collected during different shifts and hours and the average was reported as daily environmental BTX concentration for each employee of that particular petrol station