Air pollution is the main environmental risk to public health in the Americas, where around 380,000 premature deaths were attributed to this cause in 2019, according to the Pan American Health Organization.
Data from the World Health Organization (WHO) showed that almost all (99%) of the world’s population is exposed to air with pollutant levels that exceed the limits established in its guidelines. Among the most dangerous for public health, the United Nations agency highlighted suspended particles smaller than 10 and 2.5 µm in diameter (particulate matter-10 [PM10] and PM2.5, respectively), ozone, nitrogen dioxide, sulfur dioxide, and carbon monoxide.
Numerous studies have documented that exposure to polluted air, especially air polluted with PM10 and PM2.5, is the main risk factor for the development of respiratory and cardiovascular disorders such as ischemia, myocardial infarction, stroke, and chronic obstructive pulmonary disease.
Regarding deaths from outdoor pollution, 80% are attributed to heart diseases and strokes, while the remaining 20% correspond to respiratory disorders and cancer.
In addition, the burden of morbidity and mortality associated with air pollution, which is classified by the WHO as the second most important risk factor for noncommunicable diseases, is exacerbated by increasing industrialization and the effects of climate change (eg, droughts, heat waves, and forest fires near large and inhabited areas), making it much more dangerous for exposed populations, especially children and the elderly.
Horacio Riojas-Rodríguez, PhD, director of environmental health at the Center for Studies in Population Health of the National Institute of Public Health, told the Medscape Spanish edition that the riskiest pollutants differ according to region. For example, he explained that in cities like Monterrey, Mexicali, and some in the Bajío region, the greatest problems are with high concentrations of PM10 particles.
For the Mexico City metropolitan area, Mexico, the main pollutants are PM2.5 and ozone, he said. In this region, the Metropolitan Index of Air Quality has been used since 1982, with its corresponding modifications, to monitor the criterion pollutants established by WHO.
Mexican Cities
“Since 2014, various Mexican institutions, including the National Institute of Public Health, have participated in updating air quality standards,” said Riojas-Rodríguez. In the 2019 update, the maximum permissible levels of pollutants were reduced, and it was established that particles should be reduced every 2 years to approach WHO criteria.
In 2019, said Riojas-Rodríguez, the federal Ministry of Environment extended pollutant measurements to all cities in the country for the first time, thus obliging local governments to issue recommendations on air quality and associated risks.
The most recent change was made in 2023 and came into effect this year, which “speaks of the effort to update regulations in this area, although it does not necessarily imply that cities already have these [desirable] air quality levels,” said Riojas-Rodríguez. Pollutant concentrations in Mexican cities are four times higher than the levels established in WHO recommendations, he added.
“Almost all Mexican cities are at levels of 20 µg/m3 of particles when WHO guidelines indicate they should not exceed 5 µg. The same goes for other pollutants. That’s the size of the gap we need to fill,” said Riojas.
The researcher and his collaborators have found that a reduction in PM10 particle levels to 20 µg/m3, as well as to 0.050 parts per million of ozone (98 µg/m3) in the air of the Mexico City metropolitan area could prevent 2300 and 440 deaths per year, respectively. According to their study, the greatest impact of these pollutants has been seen in people aged > 65 years, as well as in mortality from cardiopulmonary and cardiovascular disorders.
Negative Biologic Effects
“PM2.5 particles are more associated with deaths in people suffering from respiratory diseases, but the range of possibilities for causing damage includes cardiovascular, cerebral, reproductive, and endocrine alterations in terms of insulin resistance and diabetes,” said Octavio Gamaliel Aztatzi-Aguilar, PhD, a researcher at the Department of Toxicology of the Center for Research and Advanced Studies (CINVESTAV) of the National Polytechnic Institute in Mexico City.
Poor air quality can also be associated with different types of cancer, as several studies have documented, he said. “We must not lose sight of the fact that there are other factors in the population that can determine if someone is more susceptible to suffering, such as lifestyle or diet.”
Aztatzi-Aguilar, head of the Inhalatory and Integrative Toxicology Laboratory 26 of the Toxicology Department at CINVESTAV, noted that there is no safe level of exposure because any of the pollutants can cause negative biologic effects. Thus, when a pathogen like the tuberculosis bacillus or SARS-CoV-2 appears, exposed individuals become much more vulnerable to contagion.
“Exposure to particulate matter and other pollutants also contributes to making us more susceptible to respiratory infections, not only infections by SARS-CoV-2 but also others like influenza or tuberculosis,” Aztatzi-Aguilar added.
Most of the research on the effects of air pollutants has focused on evaluating cardiorespiratory symptoms, airway inflammation, and lung function damage. However, the inflammatory response in the airways can extend to other organs, thus causing genetic, biochemical, physiologic, and tissue alterations.
Effects of Endotoxins
PM2.5 particles, said Aztatzi-Aguilar, contain a component called endotoxin (originating from biologic decomposition, mainly from bacteria, and not regulated in environmental air quality standards), which can cause damage beyond the cardiovascular and pulmonary systems, especially affecting kidney function.
These types of effects have been clinically documented in various studies. One study, conducted by experts from the Nephrology and Hypertension Division of the Department of Medicine at Stony Brook University in Stony Brook, New York, found that high concentrations of endotoxin in the blood of critically ill patients were associated with poorer kidney function and longer hospital stays.
In animal models, Aztatzi-Aguilar and his collaborators have observed that endotoxin can induce acute and chronic changes in kidney function. “These [changes] result from the modulation of cellular responses: They start in the lung and contribute to damaging other structures and organs like the heart. Respiratory alterations indirectly lead to cardiovascular deterioration, which attempts to compensate for these modifications in the pulmonary pathway by raising blood pressure, leading to renal hemodynamic changes.”
Aztatzi-Aguilar acknowledged that modifying environmental standards to include endotoxin monitoring requires more epidemiologic evidence and multicenter studies. He warned of the need to study the speciation of particulate matter because it is a heterogeneous and complex mix of organic and inorganic molecules.
“Monitoring other components of particulate matter could help us explain the phenomena that occur in our [Mexican] population and thus implement actions to correct or mitigate the emission of these pollutants,” said Aztzazi-Aguilar. He considered it essential to raise awareness among the population and medical personnel about health problems associated with air pollution.
“This is one of the challenges we face, for example, in Mexico City with recent environmental contingencies: People will not die in the streets due to air pollution, but we must understand that this phenomenon generates acute or chronic effects and that the consequences of exposure at a liver, heart, or pancreas level can occur much later after inhaling the pollutant.”
Riojas-Rodríguez and Aztatzi-Aguilar reported no relevant financial relationships.
This story was translated from the Medscape Spanish edition using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.
Source: medscape.com
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