What’s in the Subway Water That Drips on Your Head?

A semi-scientific inquiry.

Photo-Illustration: Curbed; Photos: Getty
Photo-Illustration: Curbed; Photos: Getty

Benjamin Bostick is standing on the Fulton Street 4 platform at 3:30 p.m. on an overcast Tuesday in early May, arm outstretched, tiny plastic bottle in hand. It’s a testament to the average commuter that no one even stops to ask what he’s doing, standing perfectly still like that, brow furrowed in quiet concentration. Every few seconds, he manages to catch a drop of water from the station ceiling. Sometimes he misses. “It splatters your face!” Bostick says cheerfully as another drop ricochets off the rim of the collection tube and mists his cheek. This is actually why we’re there. Bostick is a research professor at Columbia University’s Lamont-Doherty Earth Observatory, and together (though it’s mostly Bostick), we are trying to find out what’s in the gross subway water that drips — and occasionally rains — onto your face.

Bostick and I are at Fulton because when we took an informal survey of other commuters, it was one of the stations I got the most drip complaints about. It was also convenient for both of us to get to, which was another important consideration. The collection process takes time, obviously. The drips are small, and catching them is kind of hard. As I wait for Bostick to successfully collect drips, I stand to the side, out of the way of commuters, and we make small talk about riding the subway. Maybe 15 minutes later, Bostick says we have enough to test — about ten to 15 milliliters. The water looks clear, but he tells me that it “doesn’t mean that there’s nothing in it.” He takes an immediate read of the pH level. It’s a seven — neutral — on the pH scale. The lower the number, the more likely that it has interacted extensively with something acidic like rusting metal (a process that would take time and mean the water was less fresh); the higher it is, the more likely it has interacted with concrete. Since it’s neutral, Bostick says, it might be “close to normal things” (think rainwater, not battery acid).

Bostick collecting drips from the subway ceiling. Photo: Clio Chang

Then we’re on to the next station: We walk to the Chambers Street J, which people also seem to think leaks a lot. We quickly find a rusty spot on the ceiling of the station where water is falling fast. Already, Bostick has adopted a new drip-catching technique: To increase the capture surface area, he holds up the bottle and its cap next to each other at the same time, which for some reason we start calling the “double-bottle catching method.” I begin to realize that Bostick, who I originally thought might not reply to my request because it was kind of stupid, is now just as invested in this project as I am. We are united in our fervor to collect samples. The people around us move awkwardly to dodge the stinky subway water. We can no longer relate to them, the people we once were; we contort ourselves to stand directly in the line of fire. When Bostick misses a drop, he looks almost pained: “I missed a big one!”

Next, we move downstairs to the platform. Bostick tells me that the deeper you are, the nastier the water may be, since it has more time to pick up gross stuff as it travels through the bowels of the subway infrastructure. Here, we find a puddle on the ground. We decide to take a sample, even though it wasn’t technically part of our inquiry, and Bostick sucks it up with a syringe. We agree that this stale floor liquid, with its unsettlingly yellow hue, is much nastier than the drips. “Don’t drink this,” Bostick says, as if the thought had remotely crossed my mind. Satisfied with what we’ve got, we’re ready to leave the station — and Manhattan — behind. During our commute to the Hoyt Street 2/3 platform, I learn Bostick is a Gemini (not a water sign) and that the white streaks on the subway walls are salt residue left behind from evaporated water. At Hoyt, we suck up another yellow-tinged floor sample and wait patiently as we collect a few more ceiling drips before calling it a day. Science is tiring.

Bostick collecting yellow water from a puddle on the ground. Photo: Clio Chang

Months pass. I’m beginning to think that Bostick has abandoned our project, since, in fact, it has nothing to do with his actual job. But in July, he contacts me to say the results are in. It happens to be on my birthday (I am a water sign). “It’s more interesting than I thought it would be,” Bostick says when we finally get on the phone. The result is startling: The water dropping on us is actually not that gross. “It’s pretty clean — it’s very fresh water that is clearly moving through whatever is above the subway pretty quickly,” Bostick explains.

First, the drips: They contain elements like sulfate, calcium, zinc, lead, and other trace metals. But while getting dripped on in the subway can feel like a medical emergency — an Am I going to die? moment — Bostick tells me they consist of “pretty much pristine water.” It’s not drinking-water quality, and “there’s some stuff in it,” he says, “but not a whole lot.” The drips are essentially similar to fresh precipitation, albeit precipitation that has traveled through concrete. Bostick didn’t test for microbial contamination — a more complicated analysis that would require more time, instantaneous measurements, and larger water samples — but he says those issues are more likely when there’s a clear source, like raw sewage. Bostick says the presence of this type of contamination would have made the water saltier than it was. “I don’t think you’re going to find super-significant bacteria contamination in the subway.” Even more good news.

Then, the puddles. Overall, they had higher concentrations of trace metals than the drips — likely because they had been sitting there longer. I had assumed the yellow was urine. (Isn’t it always?) But it was possibly from iron, Bostick tells me. There are other metals, like arsenic, which could come from old rat poison. He wasn’t surprised, or alarmed, by anything he found. While they did reflect potential contaminants found in the subway environment, he says that as long as you’re not “slurping up water from the subway floor,” there’s no real reason to worry about a run-in.

Underwhelming, but true: According to our incredibly small, somewhat arbitrary sample, most of what was dripping on us in these stations was basically just rain. As a commuter, I felt more settled; as a woman newly in STEM, I felt a sense of accomplishment at our team’s work. I asked Bostick if our findings (his findings) had made him feel any better about getting dripped on. “Yeah, I could say that,” he tells me. “I’ll still dodge the drops though.”

What’s in the Subway Water That Drips on Your Head?