4-10 October 2013 #676

Mexico City's lessons for Kathmandu

Arnico Panday

In 1993 I published an article titled Kathmandu: Another Mexico City? describing the geographical similarities of the two cities, analysing population and vehicle growth rates to establish the potential for Kathmandu’s air pollution to get as bad as Mexico City.  


Twenty years later, I finally visited Mexico City, met policy makers and scientists, and toured its air pollution monitoring network. The similarities to Kathmandu are uncanny: Mexico City is the historical capital of a remittance-dependent country sprawling out across a former lake bed that is water-starved outside of the rainy season from June to September.

Mexico City has fragile historical brick houses in an earthquake zone (a 8.1 magnitude quake in 1985 killed 10,000) and it is also surrounded by mountains that trap choking air pollution within an inversion layer that often obscures views of snow-capped peaks.

But while congestion and air pollution have steadily worsened in Kathmandu, they have improved in Mexico City.  At its worst in 1990-94, Mexico City’s ozone levels exceeded WHO standards of 90 per cent of the year. 70,000 people a year died of respiratory illnesses. There were even serious discussions about leveling a mountain and installing fans to blow the pollution out. While still polluted, Mexico City today is much more liveable, with pollution levels often below WHO standards

What can Kathmandu learn from Mexico City to improve air quality? Air pollution is reversible and disappears quickly when emissions are cut. Mexico City closed its most polluting petroleum refinery in 1991. Fuel standards were gradually improved. It switched to unleaded petrol and reduced diesel sulfur content to cut atmospheric sulfur dioxide by three quarters. Catalytic converters cut carbon monoxide by two thirds. Focusing on taxis, microbuses, and buses yielded the biggest improvements, since those vehicles spend the most time on the roads.

Mexico City’s air quality monitoring network has 29 state-of-the-art stations that transmit live data to a control centre which uses radio, Twitter, and even a children’s website to inform the public about where the days’ air quality is on a scale ranging from ‘good’ to ‘extremely bad’. Local technicians maintained the network at a fraction of what it would cost in the West.  

There were also failures. In 1989 Mexico City introduced ‘Hoy No Circula’ (no driving day), banning private vehicles one day per week based on the last digit of their number plates. Within a year people bought 275,000 used cars to drive on days when their primary cars were banned and then drove both cars on days when both were allowed. Lagos, Nigeria, tried a similar policy, but there people just ‘bought’ secondary number plates for their cars. Mexico City now has strict vehicle inspection and maintenance programs to restrict the most polluting vehicles.

Widening Kathmandu’s roads may provide temporary relief, but ultimately it just creates bigger traffic jams. A transport system that takes riders away from cars and motorcycles to bicycles and public transport is the answer. Mexico City today has attractive bicycle lanes, a subway train network, and has copied the Bus-Rapid-Transit (BRT) system from Curitiba in Brazil in which big buses run on dedicated lanes, while cutting stopping times by having passengers prepay the fare before entering boarding platforms. BRTs match the capacity of urban trains at a fraction of the cost. It is not too early for Kathmandu to think about an urban train network, but road widening should include BRTs on the Ring Road. While Mexico City still has major air pollution problem, it has come a long way: 20 years ago it was used to warn Kathmandu. Now it is turning into a role model.

Arnico Panday is Senior Atmospheric Scientist at ICIMOD in Kathmandu.

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