CITY COUNCIL President Darrell Clarke wants to raise millions of dollars by selling advertising on some of the city's properties. Last week, Council overwhelming passed his bill that would allow the city to do just that.

Clarke's office prepared a brochure designed to argue the case by showing how other cities, like Chicago, Boston, and Austin, are raking in money through sponsorships, naming rights and ad space on city property.

And while Clarke is to be commended for thinking creatively to find ways to generate cash for the city, that very brochure underscores the fact that we should proceed with caution and a good deal of thought before we start charging McDonalds to allow William Penn to hold a Happy Meal from atop his perch on City Hall.

Case in point: The cover of Clarke's municipal-marketing brochure is a photograph of a basketball backboard that serves as an ad for Glaceau Vitaminwater.

What could be healthier or more innocuous than water? Surely, it wouldn't belong on the list of products from whom the city shouldn't accept advertising, like booze and cigarettes, right? Except that Vitaminwater's maker, Coca-Cola, has been sued by the Center for Science in the Public Interest for misleading claims. And the water, sold as a healthy drink, has 33 grams of sugar, only slightly less than an equal serving of Coke or other sugary beverages.

In other words, what seems at cursory glance to be a healthy, safe product isn't what it seems. Which, of course, is part of the job of advertising: to get you to buy, instead of ask questions.

In a city with the obesity rate being what it is, do we contradict our concern about health by selling ad space to the companies that make products that can promote obesity? That would lengthen the discussions about such ads, and shorten the list of potential advertisers considerably.

That's why the rush to sell space on our municipal buildings and properties isn't the easy money that Clarke is making out.

We know that Clarke is anxious for something to happen here, and says that the Nutter administration has been dragging its heels on making it happen. The fact is, 10 years ago, the Street administration was touting the same idea. The point is, this isn't a slam dunk - nor should it be.

There are other considerations, as well: Public property - and public space - is not the same as private property. It is space that belongs to all of us, a benefit of citizenship. Selling ads on public spaces turns citizens into consumers, and that's a line that should forever remain unblurred.

Clarke says that a design-review committee could oversee the content of the ads. But we'd like more: more discussion about what the limits and pitfalls are, which buildings might be exempt and who gets to weigh in.

We are not naive, nor purists; we know we live in a world where gas stations and cabs install TV sets just to serve us more ads. Ads will encroach wherever they are allowed to.

That doesn't mean that the city should aid and abet that.

We should hold our government, our city - and ourselves - to higher standards, and proceed with caution.