FORBES: To determine which cities are most toxic, Forbes looked at the country’s 40 largest metropolitan statistical areas — geographic entities that the U.S. Office of Management and Budget defines and uses in collecting statistics — based on data provided by the U.S. Environmental Protection Agency. We counted the number of facilities that reported releasing toxins into the environment, the total pounds of certain toxic chemicals released into the air, water and earth, the days per year that air pollution was above healthy levels, and the total number of Superfund sites — contaminated areas that the federal government has designated for cleanup efforts — in each metro area’s principal city. MORE