(Photo: Peter Rad)

When I was pregnant, I was always smelling weird things and calling my husband at work in a panic. The odors were rarely detected by anyone other than me—I never received the validation of the mayor or the New York Times. Then one winter day something really happened: There was an oil spill in our basement. We were living on the second floor of a brownstone in Park Slope. I went out for a morning walk, and while I was away the fuel truck came and added heating oil to a tank that was already full. The oil overflowed onto the basement floor, and the odor wafted up into our apartment. I was pretty sure that I was inhaling something other than “the normal house smell,” as my husband reassured me in an e-mail, but my impulse to flee was counteracted by my periodic resolution not to give in to my paranoia. So I opened the window and plugged in the space heater and did some work. Late in the afternoon the housekeeper working downstairs got sick from the fumes. Our neighbor called the fire department, and soon their trucks were parked in a line outside, closing off our block, and I cried on our stoop. We moved out for a month and found a company called Microecologies to test the environmental health of our apartment.

On the day of the test, two guys showed up, and to start, one of them pulled out a pen and took down a “history.” It was not unlike our first appointment with the OB/GYN, where we’d been deferential, double-checking dates, answering with the extra I don’t know if this matters, but … While an assistant attached collection tubes and air pumps to the moldings around several doors, the company’s founder, Bill Sothern, sat with me and my husband in the living room. He had lots of advice. He asked us how far we kept the windows open, and when I indicated a gap of about three inches, he seemed to approve. (In his line of work, fresh air is more important than saving energy.) He also said that he didn’t like to drink water sold in soft plastic bottles, because he believed the chemicals in the plastic could leach. Instead he drank out of glass. He left the pumps to collect our air overnight. By the morning the tubes were filmy, but the lab test showed that our apartment was fit for habitation. I came to think of it as “the purity test.”

Up to that point, this was a kind of purity I hadn’t thought too much about. I was already mindful of the purity of my food. But while I was busy shopping at the Greenmarket, other New Yorkers were discovering untreated cotton mattresses and odorless paint. Pure food? Check. Pure—everything? That’s what comes next.

This kind of purity attracts the chemically suspicious. Its adherents distrust anything “unnatural.” They fear air freshener, fire retardants, and fabric softener. They know which substances have already been banned in European countries. Their inner peace is achieved by the studious avoidance of all hazards. But their quest itself—and here I speak from experience—is characterized by bursts of panic. There’s a lot of uncertainty: What does it mean if something is classified as a “likely” carcinogen? Is our children’s low-level, daily exposure to any number of chemicals perfectly fine, or causing subtle neurological damage? And if these things aren’t good for us, what are they doing to our overtaxed planet? Like many paths to serenity, this one involves renunciation: in this case, of household items like nonstick cookware, waxed dental floss, and water bottles.

Whenever I told the story of the purity test, I always included the example of how Sothern was even more neurotic than me: He won’t drink water out of plastic bottles. But, as a lot of my neighbors could have made clear, Sothern isn’t so unusual. The e-mail list “Park Slope Parents” has about 6,000 members, including some from surrounding neighborhoods like Ditmas Park and Prospect Heights. The philosophical orientation of the list falls somewhere between UrbanBaby and MotheringDotCommune. Preschool admissions are discussed, but not household income; co-sleeping, but not sewing your own menstrual pads. A few months ago, during a lively online discussion about the ethics of buying bottled water, a mom named Cary Walker casually mentioned a reusable, kid-friendly bottle—“a good alternative to plastic if you are concerned about its safety”—from a company called Sigg. What are Sigg bottles? I thought. While I Googled, other people e-mailed Walker directly, and hours later she posted again. Sigg bottles were aluminum, with a liner so they couldn’t leach, and they were available at 3r Living, a green-household store down on the Slope’s Fifth Avenue. After Walker’s post, sales of Sigg bottles at 3r Living increased 100 percent.