HOUSTON --Houston is in the Top 10 of a rather dubious list of the dirtiest cities in America, according to a poll of readers of Travel + Leisure magazine. New Orleans is number one on the list, which is based on everything from the air quality, litter, even the taste of tap water. Philadelphia jumped two places to number two, while Los Angeles, Memphis and New York rounded out the Top 5. Houston ranked number 10 out of 35 cities. But take a look at our rankings in other areas -- Number one for hamburgers, number three and four for affordable and business hotels, and number five for barbeque.