Photo: John Springer Collection/Corbis via Getty Images

I’m moving next month, and although I’m looking forward to the relative airiness of life on the fourth floor (up from the ground floor), I’m having some regrets now that I know my current, lower apartment’s microbes are likely friendlier.

This is one of the many things I learned in this recent and riveting episode of Fresh Air, in which Terry Gross talks with ecology professor Rob Dunn about the various bugs, viruses, and parasites that live on and among us, as well as about his new book, Never Home Alone: From Microbes to Millipedes, Camel Crickets, and Honeybees, the Natural History of Where We Live. Here’s Dunn on why it’s harder for good bacteria and fungi to get up to, say, a 20th-floor apartment:

Terry Gross: Can you talk about the difference between one- and two-story buildings and high-rises?

Rob Dunn: Yeah. In general, the more removed from the outside world that an apartment-home gets, the more it’s filled almost exclusively with the microbes that fall off human bodies and food. If you look at an apartment in a high-rise, the windows don’t open very often. These apartments tend to be filled with skin microbes, fecal microbes, oral microbes, vaginal microbes, and here and there some food things. And nothing else.

[Whereas] the first floor of a home that opens its windows pretty often will have soil microbes, plant microbes, and maybe some things that fell off a bird. It’s a much more diverse and interesting set of species.

Reduced exposure to earthy plant and soil microbes is part of what’s causing the rising rates of autoimmune conditions, Dunn says, including allergies and asthma, as well as Crohn’s disease and inflammatory bowel disease — “all of which seem to be associated in one way or another with losing exposure to the microbes we used to encounter every day.” Children’s day cares, too, are especially sealed off: the microbes found there, he says, are “typically 50–60 percent [human] body microbes, and there’s no connection with the outside world anymore.”

Well, a fourth-floor apartment is a lot lower than a 20th-floor one, and maybe it helps to keep the windows open. (A friend of mine who once lived in Germany told me that every day there, no matter how cold it got, they’d all open their windows for at least a half-hour to rotate the air. According to one Canadian newspaper, we should all be doing this year-round, and even “15 to 20 minutes is enough to make a difference.”) I emailed Dunn for his thoughts on this, and I’ll update the post if he responds — although according to his auto-response it sounds as if he’s been inundated with colorful questions since the episode aired. (The response includes links to research about face mites and sourdough starters, as well as a general disclaimer that he’s not a doctor and can’t answer medical questions, plus a cute picture of a tardigrade.)

Update: I spoke with Dunn about the benefit of opening the windows to improve a higher-up home’s microbial profile. “All things being equal,” Dunn said, “in general it does seem beneficial to open the windows whenever you can” – especially if your home is near green spaces with tree- and soil-related microbes that might “drift in.” These microbes go up pretty high, too, so even if you’re on the 21st floor, you’d stand to benefit.