Epidemiologic radon studies have found trends to increased lung cancer risk from radon with a no evidence of a threshold, and evidence against a threshold above high as 150 Bq/m3 (almost exactly the EPA's action level of 4 pCi/L).[1] Another study similarly found that there is no evidence of a threshold but lacked the statistical power to clearly identify the threshold at this low level.[75] Notably, the latter deviance from zero at low level convinced the World Health Organization that, "The dose-response relation seems to be linear without evidence of a threshold, meaning that the lung cancer risk increases proportionally with increasing radon exposure."[76]