I Smell Bad Data: Mexico City Ranked 5th Dirtiest City

The “Mercer Human Resource Consulting’s 2007 Health and Sanitation Rankings” put Mexico City 5th on their list of the world’s dirtiest cities.

This might be a fair ranking among giant mega-cities (as in the world’s top 20 most populated cities). But as I flipped through the slideshow on Forbes.com, and read the facts/figures of the other cities, I’ve grown extremely skeptical of this ranking, and suspect that if I traveled to any of the other cities on this list, I’d see conditions far worse than here in Mexico City.

Take Luanda, Angola: A “portion of the population lives in settlements called musseques built on hardened waste.”

Or Niamey, Niger: “Niamey is a cesspool of pollution and waste. In a country with a total population just under 14 million, the healthy life expectancy at birth is 35 for males and 36 for females, thanks in part to poor sanitation and drinkable water. About one in four children raised here will die before age 5, the World Health Organization says.”

And Baghdad, Iraq: “Fatal outbreaks of cholera struck several provinces of the country, including Baghdad from August 2007 to December 2007.”

About Mexico City, Forbes says: “Mexico City, Mexico, ranks No. 5 on this year’s list. Residents can thank industrial and automobile emissions for air quality so bad that city ozone levels fail to meet World Health Organization standards an estimated 300 days of the year. But things could be worse.

“Mexico City has actually seen great improvement recently in terms of air pollution,” says Dave Calkins, founder of the Sierra Nevada Air Quality Group and former chief of the Air Planning Branch of the U.S. Environmental Protection Agency in San Francisco. “So much so that the government actually has to campaign to let everyone know that pollution is still a problem.”

I agree. The blue skies here are deceiving since they don’t scream ozone alert, but when I moved here, I expected far worse air. In New York, I was already acquainted with layers of black soot on my windowsills — and in my lungs. You’d think if things were so god-awful as to be the 5th dirtiest city in the word we’d all be keeling over before middle-age. But no: The life expectancy in New York is 77, in Mexico City it’s 70. By comparison, in “cesspool” Niamey, it’s 35.5.

But what is Niamey’s ranking? 21!

One thought on “I Smell Bad Data: Mexico City Ranked 5th Dirtiest City

  1. Guy Courchesne says:

    Forbes is definitely incorrect in placing Mexico City 5th, and in the stat that there were 300 days in 2007 (or 2006 for that matter) that Mexico City failed WHO standards. Their data must be coming from the late 90’s.

    One can see the actual data, current and historical at http://www.sma.df.gob.mx/simat/

    I’ve been living in Mexico City since 2000. When I arrived, I noticed the bad air quality. But, the city has put in many programs to reduce 6 categories of pollution and has largely succeeded in most of the categories. Ozone and PM10 can still be a problem, but it doesn’t rise above WHO ‘bad’ standards more than 2 or 3 days a year, usually in winter when thermal inversion can provoke the problem. 2 or 3 days is hardly 300!

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