Radiation within a safe range has no effects to our physical health. In our daily lives, natural radiation exposure per person is 2.4 mSv/year(milisievert) which equals to 2,400 µSv (microsievert,1mSv=1,000µSv, we'll use µSv for short) one year. This is caused by radioactive material from the Universe like the sun or something around us.
The Japanese Government is monitoring and publishing the radioactive level of nearly one hundred places in Japan every day.
Radiation level in the air of Tokyo & Yokohama Areas is between 0.09-0.11 µSv/h which is in accordance with world standard.
We measured current radiation amount in air in Tokyo & Yokohama Areas recently, and the result is between 0.09-0.11 µSv/h.
Radiation inside and around car is between 0.07-0.20 µSv/h which is also far lower than the world standard.
If needed, Nikkyo can issue the notice of environment radioactivity level.(Sample)
The relationship between radioactive level and physical health is shown in the diagram above.
Even assume one would be in the car for 24 hours everyday, the radioactive amount is between 0.07*24*365=0.6132mSv/year and 0.20*24*365=1.752mSv/year. The radioactive level inside & around the car is between one stomach X-ray exam and 1/4 of one chest X-ray CT scan.