Gray skies and breathing difficulties are a daily issue for Mexico City residents. 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 low winds favor the concentration of pollutants that are ozone precursors.
This Thursday, the Megalopolis Environment Commission, which brings together 59 municipalities and downtown mayors, decreed the first environmental emergency of 2023 due to the high ozone concentrations in the region. One of the measures taken by the environmental authorities to reduce pollution is the restriction of private traffic.
Víctor Hugo Páramo, head of the Environment Commission, announced that 30% of the vehicle fleet was grounded on Friday due to the emergency, ie around 5.7 million cars. Wind conditions improved and the measure was lifted on Friday evening to continue with the Hoy no circula regulamente programme.
However, the restriction to cars is not enough to prevent pollution in the city. “It was not a sufficient measure,” says Ricardo Torres Jardón, head of the Atmospheric Physicochemical Group at UNAM’s Institute of Atmosphere Sciences and Climate Change, in an interview. “We should apply other measures, maybe finer ones, so that the ozone season, since it is precisely the meteorological conditions that limit its spread, requires a different kind of environmental policy,” he says.
In the past three years, the citizens of the capital have seen the use of the ozone emergency program more frequently. In 2019 four were declared, one lasting two days and another nearly three shot in the southwest area of the Valley of Mexico; in 2020 only one was declared in November and lasted a day and a few hours, but three contingencies were recorded for 2021 (two in April and another in June) and six in 2022, one of which lasted 51 hours.
According to an analysis by the Atmospheric Monitoring Directorate of Mexico City’s Environment Secretariat, it’s not just vehicles that are responsible for pollutant emissions. On the one hand, most of the volatile organic compounds (VOC) are generated by residential buildings. “The main source is the LPG leaks from cylinder tanks, there are millions of tanks in the city, there are many leaks, and however there is no short-term demand for an approach to control all these types of gas leaks,” says Torres Jardón.
On the other hand, and where there is a direct contribution from cars and other modes of transport using gasoline and diesel as fuel, the emission of nitrogen oxides accounts for 86% of total emissions. Ozone is formed from two precursors, nitrogen oxides and volatile organic compounds as well as solar radiation. Of these, only the first are subject to environmental regulations and are systematically measured by the Ministry of the Environment through the Automatic Atmosphere Monitoring Network.
Sergio Zirath Hernández, director general of air quality in Mexico City, said vehicles increase their speed by about 9 kilometers per hour when environmental quotas are applied, causing less pollution from cars. “Improving the speed of transit in the city would be good because it suddenly reduces emissions, but I repeat, it’s not the only solution, cars are not enough,” says Torres Jardón.
The UNAM specialist points out that environmental risks are a reactive measure, which is why this institute proposes taking preventive measures to avoid high concentrations of ozone or other pollutants. “Our idea is that instead of reactive conditions, we take preventive measures and focus on other areas such as homes and industry,” says Torres Jardón.
It has been observed that the consumption of household products for cleaning and personal care, as well as paint and chemical products in industry, has a very important impact on the formation of ozone, 15% of this potential comes from the so-called oxygenated organic compounds. With this in mind, the Institute of Atmospheric Sciences and Climate Change is conducting a survey to find out which products are most commonly used by the people of Mexico City.
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