In the United States alone roughly 24 million people, including 6 million children, have
asthma, and air pollution is a known trigger for asthma attacks.
That’s because microscopic particles, called particulate matter, float around in the air,
get breathed in and irritate the airways.
The most obvious air pollution, like city smog or wildfire smoke, is outdoors, and being
exposed to higher levels of outdoor particulate matter is known to cause higher levels of
asthma.
That said, on average, Americans are spending over 80% of their day indoors.
So indoor air pollution is important to consider as well.
The most obvious cause of indoor air pollution is second-hand smoke from cigarettes—which
is a major risk factor for asthma—but it can also come from dust, mold, pet dander,
air conditioners, and cooking.
Now, cooking habits differ from one region to another.
For example, cooking over open fires indoors is common in some parts of the world, and
improving ventilation in those situations can improve asthma.
But what about cooking over modern stovetops?
Well, it turns out that cooking over a stovetop definitely produces airborne particles—just
consider what it’s like to clean grease off the stovetop after cooking bacon.
But is it enough particulate matter to trigger asthma?
Well, a study was done that looked at household behaviors, particulate matter levels, and
asthma severity.
The study included 35 low-income households in the San Francisco Bay Area that had children,
between the ages of 6 and 10 years old, with asthma, but no other major illness.
To measure particulate matter levels, particle sensors were placed in the main living area
of each home and they measured the air every five minutes over the course of a month.
A temperature sensor was placed next to the stove, to know when the stove was on, so that
air quality in the living area could be compared to stove use.
Asthma severity was measured using standardized interviews and by doing a medical chart review,
also with spirometry which measures how well your lungs work.
The study also asked each household other questions like whether or not they turned
on the range hood when using the stove.
So what did they find out?
Well, of the 35 households, 29 said that they used the ventilation hood at least some of
the time when cooking over the stove.
The other six did not.
There were a lot of ways that the data was looked at, but there were two observations
that stuck out.
First, for all homes there was a modest increase in concentration of particulate matter in
the air of about 1 𝝻g/m3 when someone was cooking on the stove.
Remember the particulate matter was being measured in the living area, which was likely
separate from the kitchen, so the particulate matter in the kitchen was likely quite a bit
higher.
Second, households that used the range hoods only spend about 1% of the time during the
month with more than 35 𝝻g/m3 of particulate matter in the air.
This is considered a high concentration of particulate matter by the Environment Protection
Agency’s ambient air quality standards and could be problematic for people with asthma.
This is compared to households that did not use range hoods that spent 9% of the time
with more than 35 𝝻g/m3 of particulate matter in the air.
That was a significant difference.
However, when the researchers looked to see if asthma severity was linked to increases
in particulate matter inside the home, there was a promising trend, but there wasn’t
enough data to show statistical significance.
So what does this study tell us?
Well, one thing that’s striking about this study is that it only included 35 households
and it’s often hard to show significant differences in small samples like that.
But even with this small sample, it’s clear that range hoods over the stovetop appear
to decrease the concentration of particulate matter significantly.
Now, although this study didn’t show a link between cooking, using the range hood and
asthma severity, it’s well known that increased exposure to particulate matter in other environments,
like smog in the outdoors or open-fire cooking indoors, do lead to worse asthma symptoms.
Also, using a range hood is essentially risk free, so it may be a simple and underappreciated
way to decrease particulate matter in the home.