A controversial epidemiological study, unexpectedly showing decreased cancer risk vs. radon domestic exposure (5 pCi/L ≈ 200 Bq/m3).[70] This study lacks individual level controls for smoking and radon exposure, and therefore lacks statistical power to draw definitive conclusions. Because of this, the error bars (which simply reflect the raw data variability) are probably too small.[71] Among other expert panels, the WHO's International Agency for Research on Cancer concluded that these analyses "can be rejected."[72]