The WHO sets as dangerous levels of air pollution considered safe until now

The World Health Organization (WHO) has tightened air quality indicators for the main air pollutants, which implies setting stricter safety thresholds for four harmful substances, most of them linked to the burning of biomass and fossil fuels —Oil, gas and coal. The previous guidelines were established in 2005 and more than 15 years later the WHO decides to give one more turn of the screw and put pressure on the governments of the world to fight against a scourge that each year causes around seven million premature deaths and serious problems. health, as recalled by this organization linked to the United Nations. The step taken by this agency puts combustion engine vehicles in the spotlight.

Based on the scientific knowledge achieved in recent decades, the WHO has established new safe exposure limits for humans for six types of pollutants: suspended particles less than 2.5 microns in diameter (PM₂, ₅), particles less than 10 microns (PM₁₀), ozone (O₃), nitrogen dioxide (NO₂), sulfur dioxide (SO₂) and carbon monoxide (CO).

The greatest reduction is made in the case of nitrogen dioxide: until now it was considered that the safety threshold was at an annual exposure of 40 micrograms per cubic meter.

The new guidelines lower it to 10 micrograms per cubic meter.

This pollutant causes problems in the respiratory system and is closely linked in cities to diesel and gasoline vehicles, which is why the step taken by the WHO places cars with combustion engines in an even more complicated situation.

The advancement of electric vehicles and environmental awareness is also joined by the health problems generated by these combustion engines.

More information

• Why does air pollution kill us?

• The European Commission sets the end of the sale of combustion cars for 2035

In the case of particles - which are capable of entering the lungs and even reaching the bloodstream causing cardiovascular and respiratory diseases - the WHO also tightens the safety limits. Particulates are now the air pollutant with the widest health effects in the world and, although they are also linked to traffic, their sources of origin are more varied. For PM₂, ₅ the WHO has decided to halve the maximum recommended annual exposure: it goes from a value of 10 micrograms per cubic meter to five. For the largest particles, PM₁₀, the annual limit goes from 20 micrograms per cubic meter to 15.

To design the new guidelines, the WHO explains that it has been based "on the abundant scientific evidence currently available" on the effects of pollutants on human health.

“We have more and more evidence,” explains Dr. María Neira, director of the WHO Department of Public Health and Environment to EL PAÍS.

Widespread non-compliance

The safety thresholds established by the WHO are not legally mandated.

Each country decides if it places limits on each pollutant and if it establishes the same limits as this organization.

In fact, as this agency explains, more than 90% of the world's population lived in 2019 “in areas where concentration levels exceeded those indicated in the 2005 WHO air quality guidelines for prolonged exposures to PM₂, ₅ ”.

With the current tightening, that percentage will increase further.

Illuminated panels on the M30 in Madrid indicate the activation of the anti-pollution protocol in phase 1. VICTOR SAINZ

"The new limits mean that you have to multiply the level of ambition to reduce pollution," says Neira. Miguel Ángel Ceballos, an expert in air quality and mobility at Ecologistas en Acción, believes that these changes imply "an ethical obligation for the rulers." The European Union, which is increasingly setting stricter air quality limits, plans to review the directive that will set the maximum exposure thresholds to the main pollutants. And, as the Commission has advanced, the new guidelines will be taken as a reference to set the objectives for the end of this decade, explains Ceballos.

But the WHO admits that there is an evident double speed on the planet. In developed countries, “air quality has gradually improved”, which does not mean that certain pollutants, such as fine particles, continue to exceed safety thresholds. In contrast, in most low- and middle-income countries, “air quality has deteriorated due to large-scale urbanization and economic development that has been largely based on the inefficient combustion of fossil fuels, such as coal, in addition to industry and the inefficient use of residential fuels ”. Neira explains that while in developed countries the main sources of pollution are linked to traffic, industry and power generation in general,In the less wealthy nations, the burning of biomass, the use of solid fuels and kerosene in heating stoves and kitchens without ventilation are also very influential.

The WHO hopes that its new thresholds can reduce the premature deaths caused by pollution on the planet. For example, “around 80% of deaths attributed to exposure to PM₂, ₅ worldwide” could be prevented if the exposure levels contemplated in the new guidelines are reached.

Beyond the deaths, the WHO recalled this Wednesday that science has well identified the effects of pollution on children, who may suffer for this reason "a reduction in growth and lung functions, respiratory infections and exacerbation of asthma" .

In adults, "ischemic heart disease and strokes are the most common causes of premature death attributable to outdoor air pollution, and evidence of other effects such as diabetes and neurodegenerative diseases is also emerging."

Therefore, the morbidity attributable to air pollution is "on the same level as other major health risks worldwide, such as unhealthy diet and smoking."

Unloading coal in the city of Ahmedabad, India.Amit Dave / Reuters

Other pollutants

The WHO has decided to leave the maximum exposure to ozone - in this case measured in micrograms per cubic meter for a period of eight hours - at the same level as established by the 2005 guidelines. And in the case of carbon monoxide, it is set by the first time a threshold for exposure in 24 hours: four milligrams per cubic meter. Only in the case of sulfur dioxide has the WHO decided, after analyzing the scientific literature, to approve more lax guidelines. In 2005 it was established that the safe exposure for a period of 24 hours was below 20 micrograms per cubic meter; the limit is now at 40.

More than 40 medical societies around the world have issued a joint statement on Wednesday supporting the guidelines and urging governments to combat pollution.

These entities have recalled that the new limits reflect well "the broad scientific consensus" on the impact of air pollution on health.

Mark Nieuwenhuijsen, president of the International Society for Environmental Epidemiology and researcher at ISGlobal, has defended through a statement that "the guidelines are a wake-up call for policy makers" and has been hopeful that "they will influence the policies of air quality around the world ”even though they do not have legal force.

Impact in Spain

Spain, like the rest of the European Union countries, has set limits for exposure to air pollutants that are based in part on the 2005 WHO recommendations. In the case of nitrogen dioxide, the limit is set. established by European directives hitherto coincided with that of the World Health Organization. And only two population centers in the country, Madrid and Barcelona, ​​surpass them, which has led to a complaint against Spain in the European Court of Justice. But if the EU decides to assume the new limits for this pollutant that the WHO has set now, all the large and medium-sized cities in the country would be in breach of these guidelines, explains Miguel Ángel Ceballos, from Ecologists in Action. Or what is the same: "the population affected by NO₂ goes from seven to 33 million",about 70% of the country's inhabitants.

In the case of particles, European legislation is more lax than what the European directives indicate.

If only the 2005 WHO recommendations are taken, 23 million of the country's inhabitants reside in areas of the country where the PM₁₀ thresholds are exceeded.

With the new limits, 39 million are reached, 84% of the national population, according to Ceballos' calculations.

In the case of PM₂, ₅, it goes from 29 to 43 million people affected, 92% of the inhabitants of Spain.

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