by KATHERINE LAGRAVE

February 26, 2016

Warning: Grab some Purell before you read this.

Chances are high that if you live in a city—or are even just visiting one—you'll take some form of public transportation. The systems are typically convenient, cost-effective, and you can feel good about reducing your carbon footprint. But given the sheer number of users, these systems can also be dirty. But just how dirty?

Travelmath, a travel logistics website, sent a team to gather bacteria samples from the handrails on public transit systems in five major cities: New York City, Washington, D.C., Chicago, Boston, and San Francisco. In their study, Travelmath reports that while "surprisingly few germs" lurked on these surfaces, there was one major exception: the New York City subways. The underground trains in the Big Apple, which transport more than three times as many travelers as the city's other four transit systems combined, was found to have an average of two million colony-forming units (CFU) per square inch. To put that in perspective, that's 900x dirtier than an airplane tray table, which has 2,155 CFU/sq. in. Touching a handrail, then, is like shaking hands with 10,000 people.

The study is quick to point out, however, that not all bacteria is bad. Some types are harmless, and others can even prove beneficial by removing toxins from the environment, or outcompeting disease-causing pathogens that otherwise lurk on surfaces. And while that may be true, it's still not much consolation for the more than four million daily riders on New York's subway system, facing germs at every turn.

(http://www.autoadmit.com/thread.php?thread_id=3986047&forum_id=2#36123556)