From Mike Avison
Hugh Robertson is of course right to work for safer environments for his union members
(8 April, p 64).
However, there are a couple of errors in his
letter. The average annual dose limit for workers in the European Union is 20
times the public limit, not 50. It is 20 millisieverts (mSv) per year, and this
was enacted in Britain by the Ionising Radiations Regulations 1999.
It is not strictly true to say there is no safe level. No effects have been
proved at the 20 mSv per year level. The risk factors are derived by
extrapolation from much higher doses. So it is only true to say that there is no
known safe level.
Bradford
