Apparently, no one told the folks at Forbes not to mess with Philadelphia.

In an article published Monday, the mag ranked Philly No. 1 on its "America's 10 Most Toxic Cities" list, and even nicknamed us the "capital of toxicity."

Pretty harsh words, especially when their sources are as thin as a slice of prosciutto.

Forbes staffers based the list on five measurements, three drawn from Sperling's Best Places - a website that compiles data on U.S. cities but warns users not to "assume that the provided content is error-free."

Philadelphia's water-quality rating on Sperling's was what pushed the city into the No. 1 spot.

The alleged contamination of Philly water was news to the Water Department, considering that its three treatment plants received an award from the Partnership for Safe Water in 2008.

"The Philadelphia Water Department consistently produces high-quality drinking water, substantially better than the drinking-water-quality standards set by state and federal regulations," said John DiGiulio, a department spokesman.

Sperling also knocked the Philly area for its proximity to a high number of contaminated Superfund sites. The remaining factors were two air-quality measurements and a toxic-release inventory - a list of potentially dangerous chemicals released, recycled, treated or managed in the area.

Philly scored fairly well on air quality but low on the inventory, though Forbes noted that it doesn't necessarily mean that residents are exposed to chemicals.

"These kind of slap-and-dash reports that compare cities or regions based on arbitrary data are not very meaningful," said Mark McDonald, a spokesman for Mayor Nutter's office. "Philadelphia is not toxic at all."

He cited the mayor's mission to make Philly the nation's greenest city. "We are a vibrant city and region, and we're getting greener all the time."

Data in the survey reflect a vast area that also includes cities in New Jersey, Delaware and Maryland, said Morgan Brennan, the Forbes scribe who wrote the story. She urged Philly residents not to take the "toxic" title personally. "This list is not to trash these cities," Brennan said. "It is a compilation of data that was available."