Tuesday, April 9, 2019

The Pollution We Produce in Our Homes


We have become accustomed to regular reports on outdoor pollution levels in our cities where auto traffic and industrial plants are expected to be major contributors.  And we thrilled at the improvements in air quality that technology has provided over the years.  The existence of this outdoor pollution has driven studies that can quote seemingly precise numbers of deaths that a given level of chemicals or particulates in the air will cause over time—and even how the deaths will occur.  This focus on the external conditions has allowed the study of what we encounter in our own homes to be almost totally ignored.  An article in The New Yorker by Nicola Twilley discusses attempts to rectify this situation and the troubling results that have begun to emerge.  The article was titled Home Smog in the paper magazine version, and The Hidden Air Pollution in Our Homes for the online version.

Twilley begins with this lede.

“Outdoor air has been regulated for decades, but emissions from daily domestic activities may be more dangerous than anyone imagined.”

She provides this perspective on our indoor versus our outdoor encounters with pollutants.

“Since the seventies, emissions of many harmful gases, such as carbon monoxide and sulfur dioxide, have fallen by half, and particulate counts by eighty per cent. But this victory may be less significant than we assume, because, in America, we spend, on average, ninety per cent of our lives indoors. (By way of comparison, this means that humans spend more time inside buildings than sperm whales spend fully submerged in the ocean.) The statistic, from an E.P.A.-funded study conducted in 2001, might seem implausible, but it probably understates the case. More recent data, from the U.K., show that, on average, Britons are outside for just five per cent of the day—an hour and twelve minutes.”

“Unlike outdoor air, the air inside our homes is largely unregulated and has been all but ignored by researchers. We know barely the first thing about the atmospheres in which we spend the vast majority of our time.”

It is not quite true that nothing has been researched about indoor air quality.  Back in the 1980s concerns about dangerous chemicals being introduced via construction materials led to regulation of those products.  However, any detailed study of our indoor environments waited on 9/11 and the concern over airborne terrorism attacks.  How could we detect invasion by chemical or biological threats if we didn’t know what the standard constituents of our indoor air were?  This led to the formation of a research collaboration labeled HOMEchem.

“HOMEchem—House Observations of Microbial and Environmental Chemistry—was the world’s first large-scale collaborative investigation into the chemistry of indoor air. Thoroughly dissecting the data accumulated will take a couple of years, at least, and, even when the findings are published, no one will be able to state their public-health implications with certainty; HOMEchem was designed to explore what the chemistry of indoor air is, not what it’s doing to us. But the experiment’s early results are just now emerging, and they seem to show that the combined emissions of humans and their daily activities—cooking, cleaning, metabolizing—are more interesting, and potentially more lethal, than anyone had imagined.”

Most of Twilley’s reporting describes the activities taking place in a highly diagnosed home-like structure located at a site associated with the University of Texas at Austin. The goal is to closely monitor hosehold activities such as cleaning, cooking, and personal grooming to determine the levels of small particulates and volatile organic chemicals (VOCs).  The first lesson learned from collecting researchers and sensors from the external air community was that levels of pollutants to be measured were often much higher than encountered in the open air.  A second lesson involved the complexity of the chemical reactions that could take place when cleaning and personal emissions were cooked along with foods in a high temperature environment.  The complex emissions became even more pronounced when combined with the opportunity for combustion when cooking with gas.

One of the major activities involved monitoring the air quality produced in the process of preparing a typical (meaning big and complex) Thanksgiving dinner.  The result was the discovery of chemical levels even higher than the researchers expected.

“Simply measuring concentrations of a chemical in a test house is not enough to infer potential exposure, however. John Balmes, a pulmonologist at the Human Exposure Laboratory, at the University of California, San Francisco, told me, ‘Going from chemistry to epidemiology is a big leap.’ To gauge the varying levels of each compound that the Thanksgiving cooks and their guests likely inhaled would require precise readings at various heights in various rooms, correlated with activity patterns. Still, when I told Balmes that the carbon-dioxide reading for Thanksgiving had peaked at four thousand parts per million, he was taken aback. ‘Wow,’ he said. ‘Those kinds of levels will lower your cognitive functioning, at least in the short term. Whether it has any long-term effect, we don’t know’.”

“Similarly, when I told Francesca Dominici, a biostatistician at Harvard, that the Thanksgiving levels of fine particulate matter had reached two hundred and eighty-five micrograms per cubic metre, she responded with shock. ‘Even short-term increases of just ten micrograms per cubic metre from one day to the next will increase hospital admission rates and mortality in the over sixty-fives,’ she said.”

That measurement of fine-particulate density briefly meant that pollutant exceeded that of the dirtiest city in the world.

“One of the scientists, Lea Hildebrandt Ruiz, said that conditions inside the house had briefly exceeded those of the world’s most polluted city—'and I can say that,’ she added, ‘because I have a monitoring program in New Delhi.’ According to the World Health Organization, the Indian capital's air quality is the worst of any major city. During the dirtier winter months, levels of fine particulate matter in the air there typically hover at around two hundred and twenty-five micrograms per cubic metre. That’s still significantly lower than the two hundred and eighty micrograms per cubic metre that was reached during the final, frenzied hour of cooking. Everyone had expected Thanksgiving to be bad, but no one had expected it to be that bad—a finding that was alarming but also, from a research point of view, thrilling.”

The Thanksgiving experiment was an exceptional event.  Is it likely that everyday activities will generate dangerous chemical levels?  The scientists are concerned.

“’The scariest thing in this house is probably the toaster,’ Erin Katz, another student volunteer, said. ‘I just had no idea that toasters emitted so many particles’.”

“A group of volunteers would spend the day in the house, cooking breakfast and lunch, checking their e-mail, cleaning up, making dinner, and running the dishwasher, in order to see whether, say, the emissions from frying vegetables in teriyaki sauce would react with the bleach fumes from mopping the kitchen floor afterward. Farmer told me that, based on her preliminary data, it seems as though they did, producing temporary spikes of chloramines, a class of chemicals that are known to inflame airway membranes. Another product of the marriage of bleach-based mopping and gas-burner ignition is nitryl chloride, a compound that is known to atmospheric chemists for its role in coastal smog formation. No one had expected to find it indoors.”

“Hydroxyl radicals drive much of outdoor atmospheric chemistry, and are a mixed blessing from a health point of view: they break down VOCs but also react with nitrogen oxides to produce ozone, making smog formation more likely. Stevens was surprised when his readings registered their presence, because their production requires sunlight, and a house’s walls and windows block much of the sun’s energy. Like many researchers, he’d assumed that indoor air, lacking sunlight and, thus, hydroxyl radicals, wouldn’t yield the kind of rapid photochemical reactions that atmospheric scientists like to study. But his results, supported by a colleague’s measurements of light intensity inside the house, have convinced him that afternoon sunshine filtered through a window, combined with emissions from a gas stove, is sufficient to produce chemical reactions ‘similar to what you might find outside on a smoggy urban day’.”

We humans also contribute to the chemical stew in our homes.  Our breathing sprays not only carbon dioxide into the air, but also chemicals such as “isoprene, acetone, and acetaldehyde.”  We also dose ourselves with a host of chemical compounds in the form of cosmetics and other personal-care products.

“Novoselac and another HOMEchem researcher, Richard Corsi, recently collaborated on a separate study of nearby high schools and found that the highest emission levels were always of the same two chemicals, found in exactly the same ratio at every location. After a little bit of detective work, they identified the culprit: Axe body sprays, which the teen-age boys of Texas apparently apply lavishly in classrooms between periods.”

The ability of a single home to generate copious amounts of complex molecules and particulates suggests a curious paradox.  There are about as many homes in a given area as there are cars.  Could our pollution creating dwellings become competitive with external sources such as automobiles?  We used to worry that filthy outside air could leak into our homes and harm us.  Is it possible that we should now be worrying that filthy inside air might be leaking out of our homes and polluting the outside air?  Some people are beginning to ask that question.

“…one HOMEchem researcher, Allen Goldstein, recently co-authored a paper that suggests a fascinating inversion. The dominant source of VOCs in Los Angeles is now emissions from consumer products, including toiletries and cleaning fluids. In other words, vehicle emissions have been controlled to such an extent that, even in the most car-clogged city in America, indoor air that has leaked outdoors may create more smog than transportation does.”

Stay tuned.


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