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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