By Clare Lindsey, Fall 2020.
As a result of everyone being stuck inside during COVID-19 quarantine, air pollution outside has declined a lot—up to 60% in some countries[1]. But the flurry of activity within our homes might be doing much more damage to people’s health than expected. Things like cooking, cleaning, washing, and simply breathing can produce volatile organic compounds (VOCs), which are gases that can cause short- and long-term health effects like damage to the eyes and lungs[2], as well as particulate matter, which can cause heart disease and asthma. VOC levels are typically two to five times higher indoors than outdoors, and with many Americans working or studying at home due to the pandemic, these chemicals are unfamiliar housemates that our lungs spend a lot of time getting to know.
Recently, scientists studying the Chemistry of Indoor Environments (CIE), an emerging field of organic chemistry, have stepped up to answer growing questions about pollution inside homes. CIE is the study of chemical interactions and changes that influence the composition of indoor air[3]. Historically, indoor chemistry is not a well-documented topic, although there have been many instances in which it has made the news for one specific reason or another. One example of this is asbestos, a naturally occurring mineral that was used as an electrical insulator and heat-resistant building material for over a hundred years before discovery of its toxicity brought an end to its use. Inhaling asbestos dust causes a variety of diseases, like asbestosis, scarring of the lungs, and mesothelioma, a type of lung cancer.
Sick building syndrome, or SBS, is another common health concern that emerged in the 1970s. Residents of an improperly built or maintained building can fall ill because of their time spent inside that building, whether from poor cleaning, use of certain construction materials, or other sources. A 1984 WHO report found that up to 30% of new and remodeled buildings worldwide could have reduced air quality[4]. SBS became a prominent news topic in 2003, when an outbreak of SARS in Hong Kong was shown to have been spread by the ventilation system inside an apartment complex[5].
Despite all these instances of indoor pollution affecting health, it wasn’t until 2016 that there was a concerted effort to assemble a group of scientists committed to studying indoor chemistry. A 2017 paper stresses the need to create more mathematical models to study some of the 100,000 chemicals present in the indoor atmosphere, and the way those chemicals interact with the unique microenvironments of residential and commercial buildings[6]. Studying individual buildings or individual chemicals would not even begin to cover the dizzying amount of combinations that could result in new and perhaps dangerous interactions. The Alfred P. Sloan Foundation was one supporter of CIE that kick-started funding for the field with a 1.1 million dollar grant to study indoor chemistry in 2016. This was the beginning of what would become a community of scientists tackling the issues of CIE together, striving to shed new light on a critically understudied field.
One specific group of scientists within this community calls themselves IndoorChem.The creation of IndoorChem was brought about by the HOMEChem research project, which stands for House Observations of Microbial and Environmental Chemistry. Like a well-rehearsed theater production, student volunteers and researchers carried out a carefully planned mock Thanksgiving as the centerpiece of a month-long experiment in a specially-made house at the University of Texas at Austin[9]. Two types of experiments were performed: sequential, or the same activity performed repeatedly at regular intervals, and layered, which simulated a variety of activities occurring throughout the day. Activities included making stir-fry, cleaning the house, cooking breakfast, making coffee and toast, starting the dishwasher, and entering and exiting the house, among others[10]. Four weeks, 60 scientists, and 4.5 million dollars of equipment designed to collect and record every imaginable measurement of the air inside the HOMEChem house captured an incredible range of data, which led to a slew of papers being published in the months and years after[9]. A May 2020 paper on HOMEChem found that during cooking, indoor particulate matter levels reached a peak of 250μg m-3, a level comparable to the world’s most polluted cities[10]. Cooking, among other activities like cleaning and using personal care products, can elevate particulate matter and VOC levels above outdoor levels.
Another IndoorChem paper from May 2019 modeled the impact of clothing on ozone reactions indoors[11]. Dirty clothing absorbs human skin oils such as squalene, an alkene, fatty acids, and wax esters. All of these molecules interact with ozone (O3), a powerful oxidant that is found in the air; the combination of ozone with dirty clothing can cause reactions that create volatile and semi-volatile compounds. Researchers created a model of chemical interactions on human skin, which traces molecule transport and reactions through clothing and skin. The study recommends regularly washing clothing and bedding, and increasing ventilation to reduce carbonyls in indoor air.
In light of all these discoveries, the average reader might want to know: Should I be doing something about this? Is it time to freak out about making a stir-fry for dinner or using a couple spritzes of Windex on my window? Although indoor smog is something to be aware of, with proper ventilation, most indoor activities aren’t inherently dangerous. IndoorChem recommends using a ventilation hood while cooking, avoiding combustion activities like lighting candles and smoking indoors, and dusting frequently to avoid buildup of pollutants in household dust as well as cleaning oft-forgotten surfaces like walls and ceilings where pollutants might be stuck[8]. And, as Americans spend more and more time inside, it is more important to keep studying and researching the effects of human activities on indoor pollution to protect our lungs and keep us healthy in the long term.
[1] “COVID-19 Lockdowns Cause Global Air Pollution Declines | PNAS.” n.d. Accessed November 30, 2020. https://www.pnas.org/content/117/32/18984.
[2] US EPA, OAR. 2014. “Volatile Organic Compounds’ Impact on Indoor Air Quality.” Overviews and Factsheets. US EPA. August 18, 2014.
[3] “Asbestos.” 2020. In Wikipedia. https://en.wikipedia.org/w/index.php?title=Asbestos&oldid=989106188.https://www.epa.gov/indoor-air-quality-iaq/volatile-organic-compounds-impact-indoor-air-quality.
[4] “Sick Building Syndrome Fact Sheet.” n.d. Accessed November 30, 2020. https://www.epa.gov/sites/production/files/2014-08/documents/sick_building_factsheet.pdf.
[5] McKinney, Kelly R., Yu Yang Gong, and Thomas G. Lewis. 2006. “Environmental Transmission of SARS at Amoy Gardens.” Journal of Environmental Health 68 (9): 26–30; quiz 51–52.
[6] Morrison, G. C., N. Carslaw, and M. S. Waring. 2017. “A Modeling Enterprise for Chemistry of Indoor Environments (CIE).” Indoor Air 27 (6): 1033–38. https://doi.org/10.1111/ina.12407.
[7] “Chemistry of Indoor Environments.” n.d. Accessed November 30, 2020. https://sloan.org/programs/research/chemistry-of-indoor-environments.
[8] “About Us.” n.d. IndoorChem. Accessed November 30, 2020. https://indoorchem.org/about/.
[9] “The Hidden Air Pollution in Our Homes | The New Yorker.” n.d. Accessed November 30, 2020. https://www.newyorker.com/magazine/2019/04/08/the-hidden-air-pollution-in-our-homes.
[10] “Indoor Particulate Matter during HOMEChem: Concentrations, Size Distributions, and Exposures | Environmental Science & Technology.” n.d. Accessed November 30, 2020. https://pubs.acs.org/doi/10.1021/acs.est.0c00740.
[11] Lakey, Pascale S. J., Glenn C. Morrison, Youngbo Won, Krista M. Parry, Michael von Domaros, Douglas J. Tobias, Donghyun Rim, and Manabu Shiraiwa. 2019. “The Impact of Clothing on Ozone and Squalene Ozonolysis Products in Indoor Environments.” Communications Chemistry 2 (1): 1–8. https://doi.org/10.1038/s42004-019-0159-7.
[12] “Inside Information.” 2020. UCI News (blog). August 10, 2020. https://news.uci.edu/2020/08/10/inside-information-2/.