Exposure to Formaldehyde in Indoor Air

Trends in formaldehyde concentrations to which residents are exposed are reviewed, as are the means for assessing these exposures. Concentrations as high as a few ppm encountered in manufactured housing during the 1970s were eliminated after the Housing and Urban Development (HUD) 1984 ruling came into effect. The pressed‐wood product industry, and its trade organizations, have made concerted efforts to comply with the ruling. Moreover, they have imposed additional voluntary product standards upon themselves intended to be applicable to a range of pressed‐wood products wider than that defined in the HUD standard. Quarterly product testing on arbitrarily selected products shows a general lowering of emission rates with only a few percent of products now being above the HUD level. Measurement of ambient indoor levels of formaldehyde has been largely replaced by testing to assure conformance to product standards. The loweremitting products on the market, if used in mobile home construction and furnishing, will expectantly produce formaldehyde levels not exceeding 0.1 ppm, except under conditions of unusually high temperature and humidity. Recent studies implicate household dust as a significant carrier of bound formaldehyde. In a few instances, old urea‐formaldehyde cavity wall insulation has become friable and particles have blown into living areas. Future health assessments might need to consider this additional pathway of potential exposure.