Objective To evaluate the radiation prevention of X-ray baggage inspection system and possible exposure doses received by the public and the security officers in Shanghai subway stations, in order to provide basic data for radiological health protection and management.
Methods Nineteen X-ray baggage inspection systems were randomly selected from 6 subway stations in Shanghai to detect the air kerma at 0.05 m from the external surface and at various distances and angles from the inlets and outlets of the inspection system (including spots where passengers and the staff could stand).
Results The monitoring results at the staff position, the passenger channels, the X-ray machine upper covers, and the X-ray machine covers facing passenger flow showed no statistical difference with the local environmental background level (P > 0.05). At all the 5 sampling spots of the systems inlets and outlets, the air kerma rates at the lower positions were recorded the highest value, with 3 out of 19 systems above the national protection standard; and the middle position showed the second highest, with 2 systems above the standard. The average air kerma rates at the surface of inlets and outlets were 1.585 μGy/h and 0.248 μGy/h, both of which were significantly higher than the local environmental background level (P < 0.001), but still within the limit of 5 μGy/h. With the distance and angle increasing, the air kerma rates were gradually reduced. When the distance was 5 m and the angle was 90& #176; from the center of the sampling doors, the radiation intensity was close to the local environmental background level.
Conclusion The possible level of radiation leakage of X-ray baggage inspection system is low and poses minor health hazard to the public and the security officers, but the current inspection protocol doesn't meet the radiation exemption requirements, and therefore need to strengthen the X-ray inspection management.
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