Air Quality Index Definition

Air Quality Index, aqi, was developed in  1968 by  the National Air Pollution Control Administration for the purpose of  measuring and evaluating the quality of the air  by means of monitoring automatic and manual networks. In these measurements components like ozone, nitrogen oxides, carbon monoxide, sulfur oxides and particulate matter were taken into account. In order To assess the quality of air, air handling units use the AQI ( Index of Air Quality).

Air Quality Index (aqi) is based on standard air conditions.  For example “50 aqi ” means that there was a surplus of 50 units, either ppm or mg per m 3 of a particular pollutant.

For example: Carbon monoxide is normally a gas expected to be outside of the atmosphere, therefore, its concentration should ideally be zero, or close to it.

If recorded somewhere Zero  aqi of this element, means that this site is not contaminated and that the air is clean.

It has been determined for each pollutant gas that normal range starts at 0. When it is present, levels run through satisfactory, unsatisfactory, bad and very bad. As is evident, each adjective is related to the excess amount of that pollutant in the atmosphere. The levels show some differences between countries.

Each pollutant gas is evaluated according to a specific range, so that the evaluation of each is different: the air can be satisfactory in terms of carbon monoxide, but bad in terms of ozone.

Air Quality Index, aqi

Air Quality Index: Mexico

Let’s see the Mexico’s  Air Quality Index (aqi) as an example. There have been years that have been contaminated on indexes above 200 points in Mexico.

In Mexico City there are 32 automatic monitoring stations and a network of 19 stations manually.

The indices recorded by environmental stations reveal that the air quality is getting worse, and that each year more days detected Air Quality Index (aqi) readings in ranges greater than 100 points. In 1990, three days were detected over 300 Air Quality Index (aqi).

During 1993, the overall air quality was “satisfactory” only 37 days and the rest were from “unsatisfactory” to “very bad”. As a result of these high rates , the government had to implement preventive measures such as the Environmental Contingency Program. The most abundant pollutants in the city were the suspended particles and ozone.

In contrast, Monterrey has less contamination volume and toxicity. In the metropolitan area there are five monitoring stations that track emissions.

     Other states with monitoring stations are:

  • Chihuahua, with five stations in the capital
  • Coahuila Monclova five, four and five in Torreón Saltillo
  • Mexico, with five in Toluca
  • Hidalgo, with a regional network of eight stations
  • Nayarit, with three in Tepic
  • Puebla, with five in the capital
  • Querétaro, with four in the capital
  • San Luis Potosi, with four in the capital
  • Sonora, with three in Hermosillo

Data from monitoring stations reveal that the total pollutant from highest to lowest is:

Sulphur oxides : 68.8%

Oxides of nitrogen : 23.8%

Particulate Matter : 5.8%

Carbon derivatives : 0.2%

Carbon monoxide : 1.4%

The evaluation by state reveals that the highest rate corresponds to DF with 16%, with the main pollutant carbon monoxide, second Puebla with 10.5% sulfur dioxide as a pollutant, followed by the State of Mexico with 9.4% and nitrogen oxide as a dominant element and subsequently, Jalisco (6.5%), Nuevo León (5.7%), Guanajuato (4.7%), Michoacán (4.1%) and Veracruz (3.8%).

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