Environment of world’s biggest city improving

The notoriously poor air quality of Mexico City, the world’s most populated megalopolis of 20 million inhabitants, has improved, and a massive reforestation programme has seen eight million trees planted in the first seven months of this year.


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Mexico City has traditionally suffered heavily from particulate pollution, as it is situated in a basin surrounded by high mountains, as well as a heavy reliance on cars and buses, many of which are poorly maintained, and a large number of polluting industries, combined with a predominantly dry and sunny climate. All of these factors have combined to make the city one of the world’s smoggiest and most unhealthy, but this is already starting to change, says Mexico City’s environment secretary, Claudia Sheinbaum.

Sheinbaum said that a new 10-year air quality plan, by toughening standards, such as banning higher-emission vehicles from the roads on the frequent days of pollution alerts, would further lower high levels of ozone and particulates. At present, on 90% of days, international standards for ozone levels are surpassed, she said. Other key elements of the plan include retiring old lorries from the road and limiting the hours that all lorries can spend in transit, using more natural gas in public buses, giving taxi drivers incentives to buy newer cars and introducing hybrid gas-electric cars and buses.

Since earlier measures such as keeping older and more-polluting cars off the street one day a week, introducing catalytic converters and lowering sulphur levels in gasoline, have taken effect, vehicle emissions, blamed for 70% of the city’s air pollution, have decreased. Levels of smog, lead, sulphur dioxide, carbon monoxide and nitrogen dioxide, have now been brought down to less than international safety levels almost the whole year round. Under the new rules, cars registered in Mexico City will have to undergo a pollution check every six months and those that fail will be ordered off the road one day a week.

Although levels of ozone and particulate have been significantly reduced, with ozone levels not reaching extreme levels since January last year, Sheinbaum warned that they are still far too high, and said that particulate levels exceed international safety standards on 13% of days. When pollution emergencies are declared by the city’s government, high polluting cars must now stay off the road, and petrol stations and factories can be closed down for the duration of the alert.

In another development, the Mexico City government announced that eight million trees had been planted within the 4,000 square kilometres (1,500 sq miles) of the city’s limits in the first seven months of this year. The trees cover an area of 148,000 hectares, of which a third are in built up areas, with the remainder in protected zones. There are still more than four million trees waiting to be planted.

In the same week, Mexico’s environment ministry reported that nationwide only 23% of the nation’s water supplies are adequately treated, with the area surrounding the capital having the most contaminated aquifers. Some 30-50% of water is lost through leaks, and at least 30 billion pesos ($3.1 billion) must be invested to improve the situation, the ministry said.

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