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There’s an invisible air quality threat lurking inside our homes

The increased hours many of us spend inside have consequences — from sources of pollution I didn’t expect.

A photo illustration of smoke coming from a gas stove.Images from Adobe Stock/Photo illustration by Sam Steenstrup

The morning after I moved into my new condo in Cambridge, I panicked. I’d looked at the place during the cold early spring. Windows had been shut. But when summer rolled around, the roaring, spewing traffic at the busy Massachusetts Avenue intersection seemed to aim a thousand tailpipes directly at my lungs and those of my children. I filed the issue away in the “can’t do anything about it” region of my brain, a place of dark fears that only lights up when I’m trying to sleep.

Finally, I summoned the nerve to look into the science. What I found shocked me — but not in the way I expected.


Determined to drill down into how bad the traffic pollution was for us inside our house, I bought two alarm-clock-sized air quality monitors. I placed one in the open front windows, and the other by the kitchen window in back, further from traffic. These measured ozone, volatile organics, coarse particles, and fine particles. My plan was to compare my readings to the data from dozens of IQAir stations monitoring Cambridge and neighboring towns.

Of most interest were fine particles, 2.5 microns or less in diameter, associated with vehicle emissions. According to the American Lung Association, these cause (take a deep breath) asthma, chronic obstructive pulmonary disease, heart attacks, strokes, and premature deaths among infants and the elderly. They may also contribute to cognitive decline. And though the air in Boston and New England has been trending healthier for decades, partly thanks to the Clean Air Act, living by busy highways makes everything worse. A long-term Tufts study in Somerville and Boston that looked at roadway particles even smaller than 2.5 microns showed that people nearest to highways had highly elevated levels of a protein associated with strokes, diabetes, and hypertension.


In the course of my experiment I learned the value of doing the science. I had guessed — no, I had tortured myself — about the effects of traffic. It was true, throughout the region air quality got worse during rush hours, deteriorating during the day and improving at night. But at no point did the readings at my house diverge significantly from the regional pollution levels. Our proximity to Mass Ave. didn’t seem to add additional risk.

So far, so reassuring, right? But then something else turned up in the data. Spikes of pollution appeared at unpredictable times of day, sometimes so bad that the air quality monitors flashed red. The garbage trucks! I thought — the contractor vans trailing their plumes of smog like Pigpen promenading through a Charlie Brown comic. But nothing made sense until I realized: It was me. Cooking food.

Our natural gas stove and oven were generating off-the-charts levels of particulate pollution. This shouldn’t have been a surprise, perhaps. Fossil fuel combustion is at the heart of both car engines and gas stoves, and a hot stir-fry throws off the smoke of burning oil. (This is not even to get into the issue of the too-hot stir-fry on nonstick pans, which can be hazardous in entirely different ways.) A bit of research showed that even the act of cleaning the kitchen afterward stirs up particles and, depending on the products used, adds to volatile organic compounds in the air.


Overall, air pollutants indoors have been found to be present at rates “2 to 5 times higher than typical outdoor concentrations,” the Environmental Protection Agency website notes. I’d been in denial that my everyday lifestyle, the cleaning products I used, the food I prepared, could really be that bad. But as it turned out, alongside worrying about the traffic and the summer season, I should have been tracking those long winters when it was too cold to open windows for weeks at a time.

The more hours we’re home, the more time we spend cooking (think of all that pandemic baking) and cleaning — and those routines have air quality consequences. Consider this a warning or reminder, then, as we shelter in our sealed-up spaces. Take advantage of any warmer days and ventilate. Consider upgrading the filter for your home heating system to MERV-13 or higher. Not only will a good filter reduce some of the cardiovascular consequences of pollution within hours, it will also help protect against those other fine particles we don’t want circulating in our houses — airborne viruses like COVID.

You can also transition away from fossil fuel use in your house. Massachusetts hasn’t gone as far as New York City, which is banning natural gas infrastructure in most new buildings, but through the Mass Save program the state will partially subsidize a switch to electric heat. Electric stoves cut fine particle pollution in half and reduce exposure to combustion gases — especially when paired with a properly sized range hood that vents outside the house. They’re not subsidized yet but really should be: low-income households tend to suffer most from poor indoor air quality, with more people sharing worse-ventilated housing units.


As for my family, we’re still living happily in the condo. I made a few changes beyond cracking open the windows. We now have a HEPA-filtered vacuum cleaner, more indoor plants, and, of course, air quality monitors we check on occasion.

Most importantly, a portable filter cleans the air behind me as I write these words. It does double duty, in fact: the purr muffles the noise from the engines outside. Let’s just say, the electric revolution can’t come soon enough.

Greg Harris is a writer in Cambridge. Send comments to