June 23, 2022

Report: Research on Indoor Chemistry Should Be a National Priority

A new report from the National Academies of Sciences, Engineering, and Medicine identifies research priorities for the study of indoor chemistry. Written by a committee of experts in toxicology, chemistry, engineering, indoor air quality, and environmental health, the report argues that emissions from cleaning products, building materials, pesticides, personal care products, stoves, and other sources are increasingly in need of study given that people spend approximately 80 percent of their time indoors. The authors note that indoor chemistry is a complex process that can create new chemicals of concern, and that indoor chemicals can affect IAQ in ways that result in adverse health effects.

Central to the authors’ concerns is the process of partitioning through which chemicals move from one phase to another. The report explains that partitioning can result in the distribution of chemicals from building materials, furniture, dust, and other sources throughout an indoor environment, as when phthalates emitted from plastics partition to surfaces, porous materials, and dust. Chemicals that partition to aerosols can increase human inhalation exposure while those that partition to dust and surfaces can increase exposure through ingestion.

One reason partitioning is not well understood for indoor environments is the lack of information about chemicals in building materials and consumer products. “Even when products list their contents, trace or contaminated product chemical components may not be listed,” the report states. “New composition or emission testing requirements of indoor products could help mitigate health risks.”

Other factors such as the effects of occupant activities and hazard control systems on partitioning remain to be explored. The uncertainties regarding partitioning and the complexity of chemical reactions, which can lead to the formation of new chemicals, complicate efforts to determine the relative importance of exposure pathways, the report explains. An example that demonstrates these challenges is the use of bleach to clean indoor surfaces: research is just now beginning to explore the generation of new chemicals from this application and has not yet addressed how bleach reacts with other cleaners such as hydrogen peroxide. And the development of sensors that detect chemicals at low concentrations has revealed the existence of several chemicals that were previously not known to be present in indoor air. According to the report, one recent analysis using proton-transfer-reaction mass spectrometers (PTR-MS) found that decamethylcyclopentasiloxane, an ingredient in personal care products, comprised around 30 percent of total volatile organic compound mass in a school classroom.

The report concludes with a list of 15 recommendations for additional research on chemical mixtures and transformations, indoor exposures to outdoor contaminants, the effects of products on indoor chemistry, and other topics. Also recommended is the study of indoor chemistry in buildings other than schools, the creation of “emissions inventories” for different types of buildings, and the integration of indoor chemistry into building design. “Given the challenges, complexity, knowledge gaps, and importance of indoor chemistry, federal agencies and others that fund research should make the study of indoor chemistry and its impact on indoor air quality and public health a national priority,” the report states.

The report “Why Indoor Chemistry Matters” is available as a free PDF download from the website of the National Academies Press.