Now reading The Flavor of Smog

The Flavor of Smog

Harold McGee goes behind the literal flavor of Los Angeles.


This comes from our “Los Angeles” issue, on newsstands now. For more stories like this, subscribe to the magazine.

Los Angeles has its own literal flavor, a set of airborne molecules as distinctive as any food’s.

I got my first taste of LA flavor in September of 1969, when I arrived in Pasadena to study astronomy at Caltech, the California Institute of Technology. I’d come by rail, on the Super Chief from Chicago, and while I waited for my ride in front of the train station, I took in that strange new world: the intense but diffuse light, the stucco buildings, the tall, skinny palm trees. And the air, like no air I’d breathed before.
 It wasn’t anonymous, like the suburban air I’d grown up in. It had a smell, which I eventually decoded as a mix of heady citrus blossoms, the green sweat of hot lawns and palm fronds, and raw car exhaust, with an acrid edge of ozone. LA air had substance. I could feel it as it flowed in and out of my nose and lungs, a passing brush of the airways that would eventually turn into a dull ache deep down. I could feel it etching my eyes.
 After a couple of weeks in Pasadena, I realized that I could actually see LA air. The Mount Wilson Observatory sits atop a fifty-seven-hundred-foot peak ten miles from the Caltech campus. I’d been in classes for two weeks before I caught my first glimpse of the observatory buildings or the bulk of the mountain itself. The flavor of LA was in the way.

I happened to arrive in the Los Angeles area just as smog levels were reaching their postwar peak, before pollution controls began to have an effect. Those controls were largely the work of a Dutch-born Caltech chemist, Dr. Arie Jan Haagen-Smit, who first determined what smog actually was and what caused it, and became the founding chairman of the California Air Resources Board. Dr. Haagen-Smit was in a position to make those fundamental discoveries about the noxious stuff that flavored LA air because he was a pioneer in the study of the delicious stuff that flavors food and drink. Alas, he and I never crossed paths—it wasn’t until years later that I abandoned astronomy for gastronomy, and only last year that I learned about Dr. Haagen-Smit’s interest in food.

Dr. Haagen-Smit had come to Caltech in 1937 to do research on the biochemistry of plants. Initially his focus was on plant growth hormones but, perhaps influenced by life in California, he also became interested in the psychoactive chemicals in marijuana and the flavors of pineapple and of zinfandel wine. Dr. Haagen-Smit would place the chopped fruit or wine in a vacuum chamber and draw off their aromatic vapors, then condense the vapors in sections of glass tubing progressively cooled to temperatures as low as -180 degrees Fahrenheit. From six thousand pounds of raw pineapple material, this vacuum distillation yielded more than eighty grams of aromatic concentrate, enough to perform chemical analyses and study the tiny traces of airborne chemicals that our noses detect as aromas.

One of his colleagues recalled that when Dr. Haagen-Smit performed the same extreme cooling on nothing but LA air, the cold trap yielded “a couple drops of dark brown, vile-smelling liquid.” They were a condensate of LA’s ambient airborne molecules, and like the condensates of pineapple and wine, they could be analyzed to determine their composition in detail. This was a huge advance in the field. At the time, state-of-the-art smog monitoring included the rubber-band test: tightly folded segments of rubber bands would be set outside a window and observed for the development of stress cracks at the folds. On a relatively clear day, they would appear after an hour or so; on a heavy-smog day, in four minutes.

In May of 1957, Dr. Haagen-Smit participated in a conference on food flavors organized by the Quartermaster Food and Container Institute for the Armed Forces, where the issue was how to preserve military rations indefinitely without destroying their flavor and edibility. He introduced himself by saying: Thanks to the work of Dr. Haagen-Smit and his legions of successors, the flavor of Los Angeles is now far more subtle than it was in the early 1970s, no longer as rubber-cracking and mountain-shrouding. But it’s still there and unmistakable.

Though Dr. Haagen-Smit made the connection between the flavor of a city and the flavor of foods, he doesn’t seem to have considered the possibility of flavoring foods with cities. That leap was made in 2011 in pollution-plagued Bangalore, India, by the Center for Genomic Gastronomy, an international group of artists, designers, and collaborators co-founded by Zack Denfeld and Cathrine Kramer. Denfeld was provoked, I was happy to learn, by a sentence of mine that describes egg foams and meringues as preparations that harvest the air they’re made in. Denfeld and Kramer recruited sophomores from the Srishti Institute of Art, Design and Technology to whip up meringues in different parts of Bangalore and make a collection that would map the city’s air quality. The web page for the resulting “Smog Tasting” project proposes that meringues could be tested for various pollutants, and could also be served as “Trojan horse sweets”: Take a snapshot of the air quality in any location. Serve it to politicians or business owners for a blind taste test of the air quality in their area. The tragedy of the commons never tasted so good! The Smog Tasting project soon caught the eye of Nicola Twilley, a New York–based writer, artist, podcaster, and author of the blog Edible Geography. She gave the flavor of air its inevitable name—aeroir— and began working with the Center for Genomic Gastronomy to explore the idea further. It was through Twilley that I learned about the project, the history of smog flavor, and about my missed opportunity to talk pineapples and wine with Dr. Haagen-Smit.

The aeroirists have taken the smog-meringue project high tech and global. With the help of scientists at the University of California at Riverside, they designed and built a portable smog chamber for cooking up replicas of polluted air from all over the world, whether LA or Beijing or California’s agricultural Central Valley. The recipe: Pump the raw ingredients—the major chemicals in emissions from tailpipes and smokestacks and feedlots—into the sealed chamber, turn on its bank of ultraviolet lights, and bake for hours, as the sun would.

Then, insert arms into the oven’s built-in gloves and whip up meringues with a hand mixer.

Twilley, Denfeld, and colleagues have taken their smog chamber and meringues to air-quality tastings in New York, Paris, Geneva, and Leuven, Belgium. I attended one as part of a dinner in November of 2015 at the Headlands Center for the Arts near San Francisco, where Beijing, Mexico City, and the Central Valley flavored the mignardises. Very lightly, it seemed: they must have been the equivalent of many-hour-rubber-band conditions. I wonder whether much of the pollutants get absorbed and transformed by the egg whites, or slowly diffuse out through the foam; more research is needed.

But the rest of the dinner broadened the idea of aeroir, with courses that highlighted other components of the local atmosphere. There were crackers filled with edible dust that included vegetable ash and pulverized flowers and crickets. There were sourdoughs started in three different parts of the Bay Area, soup made with condensed fog, and beef made with manzanita smoke for a hint of forest fire. A pamphlet provided brief reflections for each course, and for the general idea that air is an “overlooked element of place-based flavor.” Even when the effect wasn’t obvious, it was a thought-provoking, sense-sharpening experience.

I’m sure it primed me to be struck this year by a couple of reports that highlighted the connection between air quality and cooking. In one, toxicologists at Penn State found that modern humans have a genetic variant that probably makes us less sensitive to the mutagens and carcinogens in wood smoke than our predecessors and cousins, including the Neanderthals. And in the second report, biologists at the University of New South Wales found evidence that the lung damage early humans suffered from breathing smoke and fumes from cave fires may have been partly responsible for the emergence of tuberculosis as a significant human disease.

This makes sense: cooking flavors the air as surely as cars and smokestacks and feedlots do, and has been doing so for hundreds of thousands of years. The toxic byproducts of simple wood fires appear to have influenced our genome by wiping out anyone who was susceptible to them, and helped a deadly bacterium take hold in human lungs and kill untold numbers of us. Even today, according to the Global Alliance for Clean Cookstoves, an astounding three billion people worldwide (40 percent of the planet’s population) cook in confined spaces with wood, dung, and other smoke-generating fuels, and millions suffer premature deaths every year as a result.

What about the air in the kitchens of LA and other affluent cities, with their clean-burning gas and flameless electricity? It often carries the smells of high-temperature frying, grilling, and baking. And we enjoy these emissions—as we do the emissions from barbecues and smokers, the wok hei from flames and hot metal igniting cooking oil—as signs of cooking going well, of delicious flavors developing in the food. They’re way more pleasing than the tailpipe exhaust of an old car, but they may be just as harmful to human airways. Many of the volatile molecules and particulates generated during cooking are toxic when tested in the lab, and longtime restaurant-kitchen workers have an unusually high incidence of respiratory illnesses and lung cancer.

We know now that air quality is a problem for the entire planet. The kitchen is where it comes closest to home: food that we make flavorful and pleasing and nutritious is generally a good thing; air that we make flavorful as we prepare that food is generally not.

For cooks, a super flavor conundrum.