Is there any limit to the amount of radiation a passenger can be exposed to ?
The unit for measuring radiation dose is milli-Sievert (abbreviated "mSv"). The International Commission for Radiological Protection (ICRP) recommends the following limits for radiation exposure. For the general public, i.e. those people who do not have frequent contact with radiation as part of their work, the recommended limit is 1 mSv per year. For those whose work requires frequent contact with radiation, the limit is 20 mSv per year. The above limits do not include any background radiation.
As an example, according to calculations by computer program, a flight from Hong Kong to Vancouver will result a radiation dose of about 0.04 mSv, and about 0.005 mSv for a flight from Hong Kong to Bangkok. Thus the radiation received by pleasure travelers in general is not high. For frequent business travelers, their employers are obliged to evaluate their radiation exposure to ensure safety.