Mexico city’s geographic disadvantage

Mexico city’s geographic disadvantage

Geography conspires with human activity to produce a poisonous scenario. Located in the crater of an extinct volcano, Mexico City is about 2,240 metres above sea level. The lower atmospheric oxygen levels at this altitude cause incomplete fuel combustion in engines and higher emissions of carbon monoxide and other compounds. Intense sunlight turns these into higher than normal smog levels. In turn, the smog prevents the sun from heating the atmosphere enough to penetrate the inversion layer blanketing the city.

Solving this problem has been a priority of the Metropolitan Environmental Commission. Recent efforts to curb emissions have been relatively successful. In the 1990s, for instance, the government introduced air quality improvement programs — PIICA and PROAIRE — that include a rotating one-weekday ban on private car use. On days of high pollution, the ban extends to every second day and some manufacturing activities are curtailed. In addition, car owners must have their vehicles certified every six months. But if lead, carbon monoxide, and sulphur dioxide are now under control, pollution levels of other contaminants are still far above air quality standards.

A closer look at pollution

When PROAIRE concluded in 2000, environmental authorities undertook a longer, ambitious air quality improvement program — PROAIRE 2002-2010. However, accurate measures were needed to determine how improving air quality would improve health and reduce health expenditures so that new pollution control strategies could be evaluated. A number of questions also needed to be answered about the relationship between the city’s inhabitants and air pollution: How do people perceive pollution? How does it affect them? What are they willing to do or pay for cleaner air? How can they be motivated to help solve it? [See related sidebar: What do Mexicans think? Don’t blame me!]

The Mexico City Government set out to answer these questions, with support from Canada’s International Development Research Centre (IDRC) and the Netherlands Trust Fund, through the World Bank and the Pan American Health Organization.

Examining the impact on health

The researchers focused on health hazards posed by the most serious pollutants: PM10 and ozone. PM10 comes from various sources, including road construction and dust, diesel trucks and buses, forest fires, and the open-air burning of refuse. Both pollutants can irritate eyes, cause or aggravate respiratory and cardiovascular ailments, and lead to premature death.

“It’s not air pollution that kills people but some people die sooner than they would otherwise,” says biologist Roberto Muñoz Cruz, sub-director of information and analysis at Mexico City’s atmospheric monitoring system, part of the Secretaria del Medio Ambiente. The Secretaria coordinated the project in collaboration with the National Centre for Environmental Health, the non-governmental organization GRECO, and the Women’s Institute of Mexico City.

Researchers from eight academic, governmental, donor, and non-governmental organizations in Holland, Mexico, and the US contributed to national and international health studies on ozone and PM10. Surveys also determined people’s perceptions of the pollution problem.

A population exposure model was then developed, using data from Mexico’s sophisticated air monitoring network. The study estimated that pollution levels in 2010 will be much the same as in the late 1990s when ozone levels exceeded standards on almost 90% of days and PM10 exceeded standards on 30-50% of days.

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desventaja geográfica de la ciudad de México

La geografía conspira con la actividad humana para producir un venenoso escenario. Situado en el cráter de un volcán extinto, Ciudad de México está a 2.240 metros sobre el nivel del mar. Los niveles más bajos de oxígeno

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