Studies show how homes can pollute indoor air | Science News for Students

Studies show how homes can pollute indoor air

Teams examined emissions from cooking, cleaning, furniture and more
May 13, 2019 — 6:45 am EST
a photo of food cooking on a stovetop with a turkey in the background

Cooking for Thanksgiving or other holidays releases lots of chemicals into the air. Some are good, and some not so good.

skynesher/E+/Getty Images

WASHINGTON, D.C. — Americans spend roughly 90 percent of their time indoors, the U.S. Environmental Protection Agency notes. During that time, people cook. They clean. They chat, read, play, watch TV and do other things. People also bathe and sleep. And throughout it all, they breathe. New studies find that our activities can pollute the air we breathe indoors. And some of those compounds may harm our health.

Scientists and engineers shared some of their new findings, here, at the annual meeting for the American Association for the Advancement of Science, on February 17.

Both indoors and out, “activities can be a main driver of air quality,” observes Marina Vance. She’s an environmental engineer at the University of Colorado in Boulder. Researchers have studied outdoor air pollution for decades. Indeed, many countries have created laws to limit pollution in outdoor air. But researchers know much less about the pollutants that can be created in reactions between chemicals floating around indoors, Vance says.

a photo of the UTestHouse kitchen monitoring equipment
Electronic monitoring equipment is set up to measure air emissions inside a test kitchen at the University of Texas.
Cockrell School of Engineering, University of Texas at Austin

To learn more, she and other researchers measured how some everyday activities can affect what chemicals end up in indoor air. To do that, they went to a test house at the University of Texas at Austin. This model home is equipped to measure energy use, how much outdoor air comes in to flush out stale air, and other things related to how buildings function. Vance and her team brought in even more equipment. Then the crew got cooking — literally.

Chef scientists and engineers did all the cooking for a typical U.S. Thanksgiving celebration. They started with a hearty breakfast. Then they prepared a large holiday dinner. Team members roasted a turkey. They baked pies. They stirred up side dishes. Friends came over at dinner time to feast and visit. Then came clean-up time. All along, other team members measured chemicals present in the air.

U.S. laws don’t regulate the air inside people’s homes. But, Vance says, if the house were a little city in the United States, its indoor air “would be very unhealthy for about 5 to 7 percent of the time” on a day like Thanksgiving. That estimate is based on the U.S. Environmental Protection Agency’s Air Quality Index. It’s a gauge that describes the potential riskiness of breathing various types and levels of pollution in outdoor air.

Beyond particulates

That judgment is based only on measurements of “particulate matter,” Vance says. Particulates are teeny bits of pollution. They can harm the heart, cause breathing problems and mess with some brain functions. Indoor readings would be worse in parts of the world where people still cook indoors on wood stoves. Yet the readings from a modern gas range are still cause for concern, she says. Even the heat from an electric stove could create air currents that can spread chemicals from the food throughout a home’s air.

a photo of food being cooked on a gas stovetop
Use of a gas stovetop releases potentially toxic chemicals into the room’s air.
PeopleImages/E+/Getty Images

On other days, crew members cleaned the test house with typical household products. At the same time, other team members measured the chemicals these activities spewed into the air. Those results are being analyzed and should be published soon, Vance notes.

In real homes, people also shower or take baths and use personal-care products. Such products include deodorants, nail polish, rubbing alcohol and shampoos. Joost de Gouw is an atmospheric chemist at the University of Colorado in Boulder. Many home products use chemicals called terpenes (TUR-peens) to mimic the smell of trees or other plants. And many terpenes are volatile organic compounds, or VOCs. That means they become gases at room temperature.

Moreover, de Gouw adds, “They’re very reactive.” They easily react with other chemicals in the environment, either on surfaces or in the air. And those reactions can create new chemicals. So the mix of products used in a home, he says, is “something we care about a lot” in terms of the healthiness of indoor air.

Chemicals from personal-care products that make it into the air aren’t always the ones you can smell, he adds. A few years ago, researchers at the University of California, Berkeley, tested the air inside a college classroom. Chemicals called siloxanes (Seh-LOX-ains) were the most common organic chemicals released by the students’ bodies into the air. Those chemicals are common in deodorants, which aim to mask or block odors. The report was in Environmental Science & Technology Letters in 2015.

Furniture and flooring

Home furniture, flooring and other products also can release gases into a home’s air. And some of those can get into kids’ bodies, reports Heather Stapleton. She’s an environmental health scientist at Duke University in Durham, N.C.

In one recent study, she was part of a team that focused on chemicals released into the air by sofas. Their foam cushions had been treated with flame retardants known as PBDEs. Lab tests in animals have linked PBDEs to delays in the animals’ development, to altered hormone levels and to other health problems. New sofas no longer contain PBDEs. But many homes still have furniture that do still have them. Stapleton’s group found higher levels of these chemicals in the blood or urine of children in homes with those types of sofas, compared to kids in homes with PBDE-free furniture.

a photo of two kids lying on the living room floor playing on a tablet, with parents sitting on a sofa in the background
Some types of carpeting, flooring and furniture can pollute the air we breathe.
wavebreakmedia/iStock/Getty Images Plus

Her team also looked for evidence of a chemical in vinyl floors: benzyl butyl phthalate (BEN-zul BEU-tul THAAL-ayt). Studies have linked this chemical to breathing problems, skin irritations and other health problems. Children from homes with all vinyl floors had roughly 15 times as much of this chemical in their blood or urine as did kids in homes with no vinyl floors.

The kids may have breathed in some of those chemicals as they slowly escaped — or “off-gassed” — from products. They also probably absorbed some through skin or ingested some from hand-to-mouth contact with tainted dust. “Unfortunately, dust is a sink for many of these chemicals,” Stapleton says. By sink, she means the dust can collect and hold these chemicals.

Home products and furnishings contain many additional chemicals, Stapleton points out. Often, however, products aren’t labelled to identify them, she adds. That makes it hard for scientists to know what to look for when they do research. And it’s even harder for consumers to know what chemicals may be shed by the products they are looking to buy. Ask companies to tell you that information, she says. “Pressure from the public can raise awareness with manufacturers.”

Taking action

There still is much to learn about how chemicals in our homes interact with each other and how they might affect our health, all three researchers said. Meanwhile, they noted, young people and their families can take some steps to limit their exposures.

Environmental engineer Marina Vance, originally from Brazil, talks about why she studies indoor air pollution.
Home Performance/YouTube

“Simple things like washing your hands before you eat can reduce exposure to some of these chemicals,” Stapleton says. Washing would remove chemical-laden dust so you wouldn’t eat it with your food. Her family also chose all hardwood floors in their home, because hard surfaces collect less dust than carpets do, she says.

Vance now uses her kitchen’s exhaust fan every time she cooks. She also made sure that it works properly. Opening the windows for ventilation helps from time to time as well. However, there’s a trade-off in energy usage, she notes, if the outdoor air is very warm or very cold. Open windows also won’t help much in areas with high air pollution. Another option: Use a portable air cleaner, which filters particles from the air.

Just getting rid of chemicals probably isn’t the answer, de Gouw says. “Obviously a lot of chemical products serve important purposes.” But researchers are looking to find “greener” substitutes — ones that would be better for health and the environment. People also can choose to “use fewer chemical products,” he suggests. “If you don’t need them, don’t use them.”

Power Words

(more about Power Words)

American Association for the Advancement of Science (or AAAS)     Formed in 1848, it was the first permanent organization formed to promote the development of science and engineering at the national level and to represent the interests of all its disciplines. It is now the world’s largest such society. Despite its name, membership in it is open to anyone who believes “that science, technology, engineering, and mathematics can help solve many of the challenges the world faces today.” Its members live in 91 nations. Based in Washington, D.C., it publishes a host of peer-reviewed journals — most notably Science.

annual     Adjective for something that happens every year. (in botany) A plant that lives only one year, so it usually has a showy flower and produces many seeds.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

compound     (often used as a synonym for chemical) A compound is a substance formed when two or more chemical elements unite (bond) in fixed proportions. For example, water is a compound made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O.

consumer     (n.) Term for someone who buys something or uses something. (adj.) A person who uses goods and services that must be paid for.

development     (in biology) The growth of an organism from conception through adulthood, often undergoing changes in chemistry, size and sometimes even shape.

engineer     A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.

environment     The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).

environmental engineer     A person who uses science to study and solve problems in ecosystems — from forests to the human body.

environmental health     A research field that focuses on measuring the effects of pollutants and other factors in the environment on the health of people, wildlife or ecosystems.

Environmental Protection Agency (or EPA)     A national government agency charged with helping create a cleaner, safer and healthier environment in the United States. Created on Dec. 2, 1970, it reviews data on the possible toxicity of new chemicals (other than foods or drugs, which are regulated by other agencies) before they are approved for sale and use. Where such chemicals may be toxic, it sets limits or guidelines on how much of them may be released into (or allowed to build up in) the air, water or soil.

environmental science     The study of ecosystems to help identify environmental problems and possible solutions. Environmental science can bring together many fields including physics, chemistry, biology and oceanography to understand how ecosystems function and how humans can coexist with them in harmony. People who work in this field are known as environmental scientists.

exhaust     (in engineering) The gases and fine particles emitted — often at high speed and/or pressure — by combustion (burning) or by the heating of air. Exhaust gases are usually a form of waste.

filter     (in chemistry and environmental science) A device or system that allows some materials to pass through but not others, based on their size or some other feature.

flame retardants     Chemical coatings added to products, such as pyjamas, plastics, foam and furniture, to suppress or delay how fast they might burn in a fire.

gauge     A device to measure the size or volume of something. For instance, tide gauges track the ever-changing height of coastal water levels throughout the day. Or any system or event that can be used to estimate the size or magnitude of something else. (v. to gauge) The act of measuring or estimating the size of something.

green     (in chemistry and environmental science) An adjective to describe products and processes that will pose little or no harm to living things or the environment.

hormone     (in zoology and medicine) A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body. (in botany) A chemical that serves as a signaling compound that tells cells of a plant when and how to develop, or when to grow old and die.

literally     A term that the phrase that it modifies is precisely true. For instance, to say: "It's so cold that I'm literally dying," means that this person actually expects to soon be dead, the result of getting too cold.

organic     (in chemistry) An adjective that indicates something is carbon-containing; also a term that relates to the basic chemicals that make up living organisms. (in agriculture) Farm products grown without the use of non-natural and potentially toxic chemicals, such as pesticides.

particle     A minute amount of something.

particulate     A tiny bit of something. A term used by pollution scientists to refer to extremely tiny solid particles and liquid droplets in air that can be inhaled into the lungs. So-called coarse particulates are those with a diameter that is 10 micrometers or smaller. Fine particulates have a diameter no bigger than 2.5 micrometers (or 2,500 nanometers). Ultra-fine particulates tend to have a diameter of 0.1 micrometer (100 nanometers) or less. The smaller the particulate, the more easily it can be inhaled deeply into the lungs. Ultra-fine particulates may be small enough to pass through cell walls and into the blood, where they can then move throughout the body.

PBDEs     (short for polybrominated diphenyl ethers) These chemicals are used as flame retardants to prevent materials such as car seats, electronics or furniture from burning quickly in a fire.

phthalates     A family of chemicals used as solvents and added to plastics to increase their flexibility.

pollutant     A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.

reactive     (in chemistry) The tendency of a substance to take part in a chemical process, known as a reaction, that leads to new chemicals or changes in existing chemicals.

regulate     (n. regulation) To control with actions. Governments write rules and regulations — laws — that are enforced by police and the courts.

sink     (in biology or the environment) Some part of an ecosystem or the environment that serves as a storage depot for some chemical. For instance, trees or the soil can become a sink for the carbon released into the atmosphere.

technology     The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.

ventilation     A system that supplies a room with fresh air or processes that move air around and between different rooms.

VOCs     (short for volatile organic compounds) Certain solid and liquid chemicals that evaporate (become gases), often at room temperature or lower. Many of these chemicals can be harmful if inhaled or allowed to move through the skin. Concentrations of these chemicals tend to be higher indoors than out. Sources of VOCs include numerous household products, such as paints, varnishes, waxes, oil-dissolving solvents, cleansers, disinfecting, cosmetics, degreasers and glues. Many fuels also release VOCs.

volatile     Chemical that easily evaporates.


Meeting: J. de Gouw. Outdoor air pollution: Recognition of indoor emissions as a major contributor. American Association for the Advancement of Science Annual Meeting. Washington, D.C. February 17, 2019.

Meeting: H. Stapleton. Homes as sources of synthetic chemical exposure. American Association for the Advancement of Science Annual Meeting. Washington, D.C. February 17, 2019.

Meeting: M. Vance. HOMEChem: A collaborative indoor chemistry study. American Association for the Advancement of Science Annual Meeting. Washington, D.C. February 17, 2019.

Journal: X. Tang et al. Siloxanes are the most abundant volatile organic compound emitted from engineering students in a classroom. Environmental Science & Technology Letters. Vol. 2, September 29, 2015, p. 303. doi: 10.1021/acs.estlett.5b00256.