Americans spend about 90% of their time indoors, where air quality levels can decline simply because of someone’s presence, the products they use or the activities they undertake inside, according to experts on indoor air chemistry.
While more research is needed to identify airborne chemicals and to better understand their sources and health effects, recent research has illuminated the presence of harmful chemicals that can emerge and transform with different types of activities in the home, said speakers at a symposium hosted by the American Association for the Advancement of Science.
The AAAS Symposium on the Chemistry of Indoor Environments brought together an array of experts to share new research on a broad range of topics related to indoor air chemistry and the effects of exposures, from the harmful repercussions of certain building materials and consumer goods on indoor air quality to the disproportionate health effects of hazardous indoor air on vulnerable populations.
The event, held at AAAS headquarters in Washington, D.C., on Sept. 19, sought to facilitate a “new vision for what this transdisciplinary field of research has achieved and can achieve,” said Charles Dunlap, director of AAAS’ Research Competitiveness Program, which provides strategic assessment, peer review and training for governments, universities, foundations and other organizations with the goal of building research capacity in science, technology, engineering and mathematics. The Research Competitiveness Program also held an accompanying briefing on Capitol Hill on Sept. 18, where several of the indoor air chemistry experts also shared their new research and its implications with policymakers.
Indoor space “is a major location for exposure to chemicals,” said Barbara Turpin, professor of environmental sciences and engineering at the University of North Carolina, Chapel Hill, at the briefing. Already, some 75,000 different chemicals have been identified in 15,000 consumer products, said Turpin during the symposium. Of the chemicals that scientists have identified indoors, some are harmful to health, some are not, while the effects of others are still unknown.
“We expect that there are a lot more chemicals in indoor air than we know about,” Turpin added.
Although indoor air quality is also affected by outdoor pollutants that have entered homes, occupants are also a major source of chemicals in the air, experts said. Rich Corsi, dean of the Maseeh College of Engineering and Computer Science at Portland State, provided examples. “We plug in air fresheners, we change thermostats, we cook, we modify surfaces by vacuuming and dusting,” he said at the symposium.
Energy efficiency also has resulted in tightly sealed homes that harbor indoor chemicals, said Marina Eller Vance, assistant professor of mechanical engineering at the University of Colorado, Boulder. Surfaces like floors and furniture provide pollutants a place to settle and remain for long periods of time – the longer a chemical remains on a surface, the greater chance there is for a reaction to take place, creating new chemicals, according to Corsi.
“I can tell you right now, the largest source of organic chemicals in the room right now is all of you,” said Allen Goldstein, professor at University of California, Berkeley, during the congressional briefing. Goldstein offered one benign example: the airborne volatile organic compound – a type of chemical that vaporizes easily – most prevalent during the briefing was most likely D5 (methylsiloxane), he said, noting it is the dominant ingredient in deodorant and antiperspirant.
During the symposium, Vance shared results from a multidisciplinary study called House Observations of Microbial and Environmental Chemistry (HOMEChem), which, over the course of a month of cooking, cleaning and occupying a test house, gathered data about different types of chemicals in the air. The study’s results raised questions about health effects.
Scientists cooked a stir-fry, for instance, and found that more than 99% of the particulate matter observed in the air was below 100 nanometers in size. “These particles are very important from a health perspective,” said Vance. Such nanoparticles can travel deeper into the respiratory tract or enter the bloodstream, she said.
“Even with the wealth of data we’ve collected at HOMEChem, what we’re finding is it is opening up new questions, answering some but opening up many others,” Vance added.
Negative health impacts also emerge from combinations of human activities, household items, surfaces and chemical reactions. Consider someone lighting a cigarette. That activity produces secondhand smoke for anyone else in the vicinity. Yet, well after that cigarette is extinguished, thirdhand smoke remains, settling onto household surfaces like furniture and floors, said Hugo Destaillats, deputy leader of the indoor environment group at Lawrence Berkeley National Laboratory. By remaining on these surfaces, smoke then reacts with ozone in the air to generate irritating ultrafine particles.
Destaillats’ work as part of the California Consortium for Thirdhand Smoke has influenced public policies; in 2015, California’s state legislature cited the consortium’s work in enacting a smoking ban in homes that serve as day care centers.
[Associated image: A researcher measures air quality generated by a stir fry as part of the 2018 HOMEChem study. | Callie Richmond]