Gray skies and respiratory discomfort are a daily issue for the inhabitants of Mexico City. Every year, in mid-February, the ozone season begins in the Metropolitan Area of the Valley of Mexico, where atmospheric conditions, high solar radiation and little wind favor the concentration of pollutants that are ozone precursors.
This Thursday, the Megalopolis Environmental Commission, which brings together 59 municipalities and mayors in the downtown area, decreed the first environmental contingency of 2023 due to the high concentrations of ozone in the area. One of the measures taken by the environmental authorities to reduce pollution levels is to restrict the circulation of private cars.
Victor Hugo Paramo, head of the Environmental Commission, announced that 30% of the vehicle fleet stopped circulating on Friday due to the contingency, that is, some 5.7 million cars. The wind conditions improved and the measure was lifted on Friday night to continue with the Hoy no circula regulamente program.
In the last three years, the citizens of the capital have more frequently experienced the application of the ozone contingency program. In 2019, four were declared, one of which lasted two days and another almost three, which were shot in the southwestern area of the Valley of Mexico; in 2020, only one was declared in the month of November and it lasted a day and a few hours, but for 2021 three contingencies were registered (two in April and another in June), and in 2022, six, one of which lasted for 51 hours.
According to an analysis by the Atmospheric Monitoring Directorate of the Mexico City Environment Secretariat, vehicles are not the only ones responsible for polluting emissions. On the one hand, volatile organic compounds (VOCs) are generated for the most part by dwelling houses. “The most important source is the LP gas leaks, from the cylinder tanks, there are millions of tanks in the city, there are many leaks and, however, there is no request in the short term for an approach to control all these kinds of leaks”, says Torres Jardon.
On the other hand, and where there is a direct participation of automobiles and other types of transportation that use gasoline and diesel as propellants, is in the emission of nitrogen oxides, with 86% of total emissions. Ozone is formed from two precursors, nitrogen oxides and volatile organic compounds, plus solar radiation. Of these, only the first are under environmental regulations and are systematically measured by the Ministry of the Environment through the Automatic Atmospheric Monitoring Network.
Sergio Zirath Hernandez, general director of Air Quality for Mexico City, specified that when environmental contingencies are applied, vehicles increase their speed by approximately 9 kilometers per hour, which generates less pollution from cars. “Improving the speed of transit in the city would be good because it suddenly reduces emissions, but I reiterate, it is not the only solution, cars are not enough,” says Torres Jardon.
It has been observed that the consumption of household products for cleaning and personal hygiene, as well as paints and chemical products in the industry, have a very important impact on the formation of ozone, 15% of this potential comes from the so-called oxygenated organic compounds. In this sense, the Institute of Atmosphere Sciences and Climate Change is conducting a survey to find out the products most used by the population of Mexico City.