Speaking at a national forum called "Answers to Climate Change: Air Quality, Mitigation and Adaptation," the Director General of the INSP Mauricio Hernandez said air pollution is a serious problem which has worsened in 11 cities with more than a million residents in Mexico.

The head of INSP, which serves as the teaching and research arm of the Health Ministry, said pollution increases the rate of cardiovascular and respiratory diseases, such as asthma.

After the city officials declared pollution emergencies on eight days, between March 14 and June 1 this year, INSP recorded an increase in hospital admissions and school absenteeism in the capital.

"We are concerned by the magnitude of the problem in the country, where air quality is unsafe several days a year," Hernandez said, adding that air pollution in Mexico incurs costs equivalent to 2 percent of the gross domestic product (GDP).

According to officials, Mexico City is home to one of the world's largest number of automobiles, estimated to be upwards of 5.4 million, which account for most of the pollutants in the air.

In other parts of the country, smoke inhalation from burning wood is a risk factor for air pollution.