When you think about moving to a new city, you might consider its safety or night life. But do you think about its toxicity?

Men's Health magazine grades the United States' 101 largest cities on environmental toxicity in its June issue.

Only five of the cities earned A+ -- Yonkers, N.Y; Henderson, Nev; St. Petersburg, Fla.; and Irving and Plano, Texas. Seven cities got an F, with Houston coming out the most contaminated, followed closely by Portland, Ore., and Jacksonville, Fla. Other failing cities include Baltimore, Denver, Miami and Tampa, Fla.

Full List: Toxicity Grades By City

To determine the "relative toxicity" of the cities, the magazine reviewed the Environmental Protection Agency's most recent tally of facilities creating hazardous waste; the EPA's Total Environmental Release data, a.k.a. the amount of that waste being released into the air, water and land; and the number of Superfund sites -- places so dirty they qualified for federal cleanup funds.

The grades were released a day after a global treaty phasing out a dozen highly toxic chemicals took effect -- minus the United States. Still, the Bush administration is promising to abide by the accord, which has been signed by 59 nations.

The Senate has yet to ratify the treaty, and Congress hasn't passed the legislation because of disagreement over whether to add more chemicals to the ban.

The treaty aims to ban or severely restrict 12 chemicals commonly known as the "dirty dozen," including polychlorinated biphenyls (PCBs), dioxins, and several pesticides. Many have been linked to cancer and other diseases.

The World Wildlife Fund says "whales, polar bears, birds of prey and people throughout the world will benefit."

More Information: Men's Health