The change could cost Sweden billions, according to the Swedish National Board of Health and Welfare (Socialstyrelsen).
The WHO recommended on Monday that limits on the radioactive element radon in residential buildings should be cut from a current 1,000 to 100 becquerel per cubic metre (Bq/m3).
In Sweden the limit for when anti-radon measures should be enacted is already lower than existing WHO recommendations - 200 Bq/m3.
But the new WHO proposal means that the Swedish limit could need to be revised, according to Michael Ressner at the welfare board.
"The WHO study shows that radon is much more dangerous to health than we have previously known. This is serious," he said to the Svenska Dagbladet newspaper.
The Swedish Radiation Safety Authority (Strålsäkerhetsmyndigheten) changed its recommendation immediately after the WHO alarm to below 100 Bq/m3.
The problem is that the change would cost the Swedish society more than 25 billion kronor ($3.6 billion) to decontaminate all of the residential property in Sweden which have a radon reading in excess of the new recommendation, according to Michael Ressner.
"Today's goal of decontaminating 450,000 homes with radon levels of over 200 Bq/m3 is incredibly difficult to achieve," said Lars Mijönäs at the Radiation Safety Authority to Svenska Dagbladet.