It certainly cannot be proven. No effects have been seen from such low doses in scientific studies done over 40 years. However, in Canada, both the regulator and licensees take a very conservative approach to radiation doses and assume that any exposure might carry some risk. By controlling small doses, you assuredly prevent large doses. That is why licensees have been voluntarily working under the lower limits, soon to become law, for the better part of a decade.
Safety is the top priority for Canada's nuclear industry.
The strict regulatory process works. It works for radiation workers. It works for the public.