A novel bottom-up approach to bounding low-dose human cancer risks from chemical exposures

► The new bottom-up approach does not rely on high-dose cancer data to estimate low-dose risk. ► It utilizes background human cancer risk and background exposures from endogenous sources. ► It is low-dose linear and consistent with the “additivity to background” risk concept. ► It provides an independent “reality check” on top-down estimates derived from high-dose animal or human cancer data. ► For formaldehyde, the bottom-up risk estimates are markedly lower than recent USEPA top-down estimates.