The most recent cases are those of Santiago de Chile and Mexico City. But the case of Medellín, for example, is also still on the minds of many people. And cities such as Bogotá, Lima, Sao Paulo, Buenos Aires and La Paz have been classified by the World Health Organization (WHO), according to its latest report last year, which measured 3,000 cities in 103 countries, as some of the cities where you can breathe the most polluted air in the region.
Why is this happening and what can citizens and businesses do to help improve the quality of the air they breathe?
The Chilean capital entered the first environmental pre-emergency of 2017 on Monday, due to poor ventilation conditions, as it told CNN Chile.
Among the measures decreed by the mayor of Santiago de Chile Claudio Orrego there is a vehicle restriction from 7:30 in the morning to 9 at night this Monday, several exclusive environmental axes were established for public transport vehicles and the use of heaters was prohibited of firewood and other derivatives of wood. Chile is about to enter winter.
Although the authorities did not prohibit outdoor physical activity classes, they did recommend not taking them for the next few days. The decision must be made by each school.
According to Orrego, "the restrictions have to do with the health of the population, especially the weakest, the elderly and children."
In Mexico City, for its part, the Megalopolis Environmental Commission (CAMe) suspended this Sunday the so-called atmospheric environmental contingency due to ozone, five days after it was implemented.
Since May 16, the city authorities restricted the circulation of private vehicles and carried out inspections in 106 companies, most of them corresponding to the industrial sector. According to the Secretariat of the Environment of Mexico City (Sedema), all complied with the restrictions imposed during Phase I of the environmental contingency.
And on March 22, the authorities of Medellín, the second largest city in Colombia, decreed the red alert, also due to the poor quality of the air that its inhabitants breathed. The measure was active for five days.
Why do we breathe dirty air?
The WHO measures two types of particulate materials (PM) and establishes certain values that, if exceeded, determine that the air that is breathed in a city is of poor quality and, therefore, dangerous for health.
Particulate materials are known as PM10 and PM2.5 and differ in the size of the polluting particle "that can penetrate and lodge inside the lungs." According to the WHO Air Quality Guidelines, safe values for health are between 10 and 25 micrograms per cubic meter of air for PM2.5 (annual average and 24-hour average, respectively). and between 20 and 50 micrograms per cubic meter of air for PM10 (annual average and 24-hour average, respectively).
During the environmental red alert decreed in Medellín in March, for example, a maximum level of 63 micrograms per cubic meter of air was reached for PM2.5.
In Lima, according to the most recent WHO report, up to 88 micrograms per cubic meter of air have been measured in pollutant particles lower than PM10.
Pollutant particles can be black carbon and methane, for example, but they are not caused only by outdoor pollution, such as that produced by large industries or by vehicular traffic, but by indoor pollution, since still millions of homes in the region it continues to cook over wood.
"Indoor smoke represents a serious health risk for some 3 billion people who cook and heat their homes with biomass and coal fuels," says WHO.
In 2014, says the WHO, 92% of the world's population lived in places where the Air Quality Guidelines are not respected.
What to do?
The WHO divides into five categories the recommendations to avoid declarations of emergencies or environmental contingencies and, therefore, avoid that the inhabitants of cities suffer from health problems that can even lead to death.
1. Industry: must increasingly make the switch to clean technologies "that reduce emissions from industrial smokestacks" and make "improved management of urban and agricultural waste".
2. Transportation: it should adopt “clean electricity generation methods, prioritize rapid urban transport, pedestrian and bicycle paths in cities, and inter-urban transport of cargo and passengers by rail”, in addition to promoting the “use of vehicles cleaner diesel engines and vehicles and low emission fuels, especially low sulfur fuels ”.
3. Urban planning: the idea is that city authorities improve "the energy efficiency of buildings" and also consider the issue of concentration of cities to achieve greater efficiency in the use of energy.
4. Electricity generation: it is recommended to “increase the use of low-emission fuels and renewable energy sources without combustion (solar, wind or hydroelectric), the joint generation of heat and electricity, and the distributed generation of energy (for example , electricity generation through small networks and solar panels) ”.
5. Waste management: are necessary, says WHO, the “strategies of reduction, separation, recycling and reuse or reprocessing of waste, as well as improved methods of biological waste management such as anaerobic digestion to produce biogas, by means of viable methods and economic alternatives to substitute solid waste incineration ”. When incineration is unavoidable, "combustion technologies with rigorous emission controls" must be used.