Most chemicals in commercial use have not been tested for possible health effects. Fewer than one-third of regulated, high-production chemicals, including many found indoors, have undergone even a screening level of testing for adverse effects. Health effects data are particularly critical for indoor exposure because median indoor concentrations are one to five times the median outdoor concentrations of many hazardous air pollutants. Considering that people spend approximately 90 percent of their time indoors, median indoor exposures (concentration multiplied by time) may be 10 to 50 times higher than outdoor exposures (U.S. EPA 1998).
Significant uncertainties exist in the areas of exposure assessment and control. For example, data are lacking on the rate and frequency of emissions from many sources, such as building materials and consumer products. There is also a lack of data on the identity of the chemicals emitted, as well as on the cost and performance of solutions to reduce exposures. While there are standard methods to quantify emissions from certain types of products and materials (e.g., carpets, office furniture, paints), many more are needed to facilitate widespread commercial development of new products and materials that emit significantly lower levels of indoor pollutants. Significant uncertainties still exist regarding how a change in building design, operation, and maintenance will influence the mix of indoor pollutants, as well as how to measure the concentrations of biological contaminants present indoors. Exposures in schools, residences, and most other non-occupational indoor environments still remain largely unstudied.
