It's Curious City, where we take your questions about Chicago and the region, and investigate, report, explore, from WBEZ.

Regan Burke lives in the Gold Coast, so she used to walk down to Oak Street Beach every morning with her dog Usher to get some exercise

and play in the water. That is until this one day...

I was taking my dog to the beach and a lifeguard came up to me and said, get your dog out of the water.

There's E. coli. That's back when the city used to close beaches, when E. coli levels,

showing feces in the water, got too high.

In the early 2000s, they really reported that every day.

I mean, it was on the regular news, on the Chicago News, but I don't hear it at all now.

So that's left Regan with a lot of questions.

Like, why don't they close the beaches free coli anymore? Can that water really get

dog sick? But most important, just how safe are the beaches for swimming these days? We'll get to those

other questions in a minute. But with beach season finally here, that safety issue seems the most

pressing. First, it's important to measure the poop because high

levels can make swimmers sick, usually with a stomach bug. Even days after swimming, you can end up with

nausea, diarrhea, a fever, and worse. So when fecal bacteria hits a certain level, the feds say you have to warn people.

Last summer, on nine out of ten days, at least one Chicago Beach was over that mark.

And when it hits that level, at least 4% of swimmers are likely to get sick.

To check those levels here, teams of researchers head to Chicago beaches every summer morning.

They scoop up two water samples at each beach, then bring them to a lab at the University of Illinois, Chicago.

I met up with Regan at this lab to meet the scientists.

Sam Dorvitz, welcome to UIC School of Public Health.

Thanks, and this is Regan Burke, our question asker.

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