Assessment of indirect inhalation exposure to formaldehyde evaporated from water.

Volatilization volumes and health risks associated with indirect inhalation exposure to formaldehyde evaporated from water have not been investigated quantitatively. We experimentally investigated formaldehyde volatility, compared with chloroform volatility, predicted formaldehyde inhalation exposure concentrations in Japanese bathrooms, and then re-evaluated drinking water quality standards. Although the Henry's law constant of formaldehyde is 1/10 that of chloroform, with a 30-min exposure period, the formaldehyde non-equilibrium partition coefficient (K') was 1/500th the chloroform value because of formaldehyde's faster volatilization rate.