BOSTON -- You touch thousands of items a day, but so do many other people, and that can lead to a buildup of bacteria.

NewsCenter 5's Janet Wu asked experts how many germs are on items such as pay phones, mailbox handles and ATM screens.

What do you think has more bacteria? A clean-looking table at a food court or a gas pump handle? If you guessed the gas pump handle -- you're wrong.

Team 5 took a lesson on how to scientifically swab surfaces to test for bacteria. Then, we went out to find out just how clean some ordinary things can be. The tests showed some things we sampled were clean -- a bacteria count under 10 bacteria per square inch.

The cleanest was a park bench that's next to a garbage can. It registered less than 1 -- that's almost sterile.

"That was a little surprising. If it was out in a sunny exposed place, UVA rays from sunlight keep it reasonable sterile," said Dana Krueger, of Krueger Laboratories, Inc.

Some other items that registered as clean were a gas pump handle and a grungy, corroded water fountain spout in Boston City Hall.

"In terms of bacteria, it's probably kept fairly low because of the chlorine in the water," Krueger said.

Other items that came back clean were the keys on an ATM machine and the inside doorknob of a public restroom at a gas station.

Then there's ordinary dirty -- things that register between 10 and 100.

"One would want to wash their hands before eating after touching such a surface," Krueger said.

This includes the door going into a ladies room at a shopping mall, a crisp dollar bill from a money dispenser at a grocery store and the handle of a ladder at a city pool.

Then, the numbers jump significantly, but still fall into the category of ordinary dirty -- the shopping cart handle at a super market and the handles of a monkey bar on a playground. A mailbox handle registering 69 on the bacteria count.

Finally, there's the very dirty -- or yucky category -- things that registered over 100.

"If I had extensive contact with such a surface, probably want to wash my hands fairly soon," Krueger said.

A seemingly clean table at the food court registered 200.

"Tells me they probably had not sanitized that table in a long time, even though it may have looked clean because someone had wiped the crumbs off," Krueger said.

An elevator button at Boston City Hall registered 300. Finally, the No. 1 dirty spot tested was the pedestrian traffic light button in downtown Boston. It registered 340. Both are heavy traffic areas, probably not cleaned routinely, and are protected from any strong killer rays from the sun.

The samples were random, and Krueger said the test does not differentiate between good bacteria and bad bacteria.

"If the surface has got a high total bacteria count -- it increases the likelihood that it has pathogenic bacteria, as well," Krueger said.