air pollution

Air pollutants are responsible for 7 million premature deaths a year worldwide, says the World Health Organization (WHO). The WHO has called it “one of the greatest environmental risks to health.”

On 22 September 2021, the WHO has issued strict new standards for air pollution levels. Data suggests that the air in many regions across the U.S. contains much higher levels of dangerous matter than the standards recommend.

Every year, exposure to air pollution is estimated to cause 7 million premature deaths and result in the loss of millions more healthy years of life. In children, this could include reduced lung growth and function, respiratory infections and aggravated asthma. In adults, ischaemic heart disease and stroke are the most common causes of premature death attributable to outdoor air pollution, and evidence is also emerging of other effects such as diabetes and neurodegenerative conditions. This puts the burden of disease attributable to air pollution on a par with other major global health risks such as unhealthy diet and tobacco smoking.

The estimated 7 million premature deaths worldwide every year include 300,000 in North, Central and South America.

Australia and New Zealand

The WHO is not the only one taking action: In July, doctors in Australia and New Zealand recommended pregnant women minimize their exposure to air pollution, and in August, a study revealed high levels of exposure are linked to potential mental health issues.

In 2019, more than 90% of the global population lived in areas where concentrations exceeded the 2005 WHO air quality guideline for long term exposure to PM₂.₅. Countries with strong policy-driven improvements in air quality have often seen marked reduction in air pollution, whereas declines over the past 30 years were less noticeable in regions with already good air quality.

Almost 80% of deaths related to PM₂.₅ could be avoided in the world if the current air pollution levels were reduced to those proposed in the updated guideline, according to a rapid scenario analysis performed by WHO. At the same time, the achievement of interim targets would result in reducing the burden of disease, of which the greatest benefit would be observed in countries with high concentrations of fine particulates (PM₂.₅) and large populations.

Air pollution is one of the biggest environmental threats to human health, alongside climate change. Improving air quality can enhance climate change mitigation efforts, while reducing emissions will in turn improve air quality. By striving to achieve these guideline levels, countries will be both protecting health as well as mitigating global climate change.

The WHO announced that smaller amounts of air pollution are thought to be more damaging to human health than previously understood and updated their air quality guidelines for the first time since 2005, meaning more people worldwide live in areas with dangerous levels of contamination.

The new WHO Global Air Quality Guidelines (AQGs) provide clear evidence of the damage air pollution inflicts on human health, at even lower concentrations than previously understood. The guidelines recommend new air quality levels to protect the health of populations, by reducing levels of key air pollutants, some of which also contribute to climate change.

Since WHO’s last 2005 global update, there has been a marked increase of evidence that shows how air pollution affects different aspects of health. For that reason, and after a systematic review of the accumulated evidence, WHO has adjusted almost all the AQGs levels downwards, warning that   exceeding the new air quality guideline levels is associated with significant risks to health. At the same time, however, adhering to them could save millions of lives.

WHO’s new guidelines recommend air quality levels for 6 pollutants, where evidence has advanced the most on health effects from exposure. When action is taken on these so-called classical pollutants – particulate matter (PM), ozone (O₃), nitrogen dioxide (NO₂) sulfur dioxide (SO₂) and carbon monoxide (CO), it also has an impact on other damaging pollutants.

The health risks associated with particulate matter equal or smaller than 10 and 2.5 microns (µm) in diameter (PM₁₀ and PM₂.₅, respectively) are of particular public health relevance. Both PM₂.₅ and PM₁₀ are capable of penetrating deep into the lungs but PM₂.₅ can even enter the bloodstream, primarily resulting in cardiovascular and respiratory impacts, and also affecting other organs. PM is primarily generated by fuel combustion in different sectors, including transport, energy, households, industry, and from agriculture. In 2013, outdoor air pollution and particulate matter were classified as carcinogenic by WHO’s International Agency for Research on Cancer (IARC).

The guidelines also highlight good practices for the management of certain types of particulate matter (for example, black carbon/elemental carbon, ultrafine particles, particles originating from sand and dust storms) for which there is currently insufficient quantitative evidence to set air quality guideline levels. They are applicable to both outdoor and indoor environments globally, and cover all settings.

“Air pollution is a threat to health in all countries, but it hits people in low- and middle-income countries the hardest,” said WHO Director-General, Dr Tedros Adhanom Ghebreyesus. “WHO’s new Air Quality Guidelines are an evidence-based and practical tool for improving the quality of the air on which all life depends. I urge all countries and all those fighting to protect our environment to put them to use to reduce suffering and save lives.”

An unequal burden of disease

Disparities in air pollution exposure are increasing worldwide, particularly as low- and middle-income countries are experiencing growing levels of air pollution because of large-scale urbanization and economic development that has largely relied on the burning of fossil fuels.

“Annually, WHO estimates that millions of deaths are caused by the effects of air pollution, mainly from noncommunicable diseases. Clean air should be a fundamental human right and a necessary condition for healthy and productive societies. However, despite some improvements in air quality over the past three decades, millions of people continue to die prematurely, often affecting the most vulnerable and marginalized populations,” said WHO Regional Director for Europe, Dr Hans Henri P. Kluge. “We know the magnitude of the problem and we know how to solve it. These updated guidelines give policy-makers solid evidence and the necessary tool to tackle this long-term health burden.”

Global assessments of ambient air pollution alone suggest hundreds of millions of healthy life years of life lost, with the greatest attributable disease burden seen in low and middle-income countries. The more exposed to air pollution they are, the greater the health impact, particularly on individuals with chronic conditions (such as asthma, chronic obstructive pulmonary disease, and heart disease), as well as older people, children and pregnant women.

The road to achieving recommended air quality guideline levels

The goal of the guideline is for all countries to achieve recommended air quality levels. Conscious that this will be a difficult task for many countries and regions struggling with high air pollution levels, WHO has proposed interim targets to facilitate stepwise improvement in air quality and thus gradual, but meaningful, health benefits for the population.

Key Facts

Following the new guidelines, which lower the threshold of acceptable levels of six common and dangerous air pollutants, “could save millions of lives,” according to the WHO report.

The agency recommends decreasing amounts of ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide, and most importantly, two kinds of particulate matter, a contaminant created by fuel combustion which is capable of penetrating both the bloodstream and lungs.

The report decreased the suggested acceptable amount of PM2 to 5 micrograms per cubic meter, half of what was recommended in 2005, and the amount of PM10 from 20 to 15 micrograms per cubic meter.

The organization said that when action is taken to reduce the amount of these specific pollutants, it has a similar effect on other contaminants, and is also beneficial to the environment.

To be Noted

Whilst not legally-binding, like all WHO guidelines, AQGs are an evidence-informed tool for policy-makers to guide legislation and policies, in order to reduce levels of air pollutants and decrease the burden of disease that results from exposure to air pollution worldwide. Their development has adhered to a rigorously defined methodology, implemented by a guideline development group. It was based on evidence obtained from six systematic reviews that considered more than 500 papers. The development of these global AQGs was overseen by a steering group led by the WHO European Centre for Environment and Health.

The U.S.

An NBC News analysis of air pollution levels shows that air quality across the U.S. on average already falls short of the WHO’s guidance, updated in September for the first time in more than 15 years.

While U.S.-wide air quality is already worse than the new threshold, it is especially bad in California, Oregon, Nevada, Idaho and Washington, where levels of particulate matter are more than twice the recommended limit. The new guidance lowers the threshold for particulate matter in the air, among several other pollutants, cutting the recommended maximum amounts by half.

This form of particulate matter is a mix of microscopic solids and liquid droplets known as PM2.5, named for its size of 2.5 micrometers in diameter, or roughly one-thirtieth the width of human hair. Commonly found in wildfire smoke and vehicle exhaust, the pollutant has been connected to respiratory-related hospital admissions and increased mortality.

PM2.5 levels vary by region across the U.S., but the national average in 2020 was about 8 micrograms per cubic meter, down from 13 in 2000, according to the Environmental Protection Agency. The WHO’s new guidelines set the recommended level at 5.

In the EPA’s Western region, California and Nevada averaged 11.7 micrograms last year. The agency’s region made up of Washington, Oregon and Idaho averaged 11.9 micrograms.

The U.S. standards, last updated in 2012, are slightly less strict than the WHO’s current – and former – guidance, but the EPA said comparing the two standards is not so straightforward.

One official said the U.S. standards are based on studies that compare populations from areas with different pollution levels, and observe the likelihood of dying earlier.

The official said the WHO is relying on new types of studies that use satellite data to estimate pollutant exposure for millions and millions of people.

“What they are seeing is that there is still health effects below the current U.S. standard,” he said.

According to an analysis of EPA data, the average U.S. pollutant levels have continued to decline since at least 2000.

That number changes when looking at the regional data, which shows the western U.S. with levels barely below the EPA’s standard, while the rest of the country is in a safer range.

And while wildfires turned the sky orange in Californiathat smoke can carry over to parts of the East Coast, affecting the air quality nearly 3,000 miles away.

Despite that, the official said the air quality in the U.S. is far better than it was decades ago.

“Comparing Los Angeles in the 1970s to now, it’s just way, way better. That’s been the result of things like catalytic converters, improved vehicle technology, and controls on factories,” he said.

The official said that PM2.5 levels in the 1970s could range as high as 50 micrograms per cubic meter in California. According to the EPA, these levels haven’t become much higher than 20 micrograms in the previous 20 years.

That decline was largely attributed to the Clean Air Act of 1970, a series of laws that paved the way for air quality standards in the U.S.

“The U.S. does not adjust our standards according to the WHO guidelines. The Clean Air Act requires EPA to periodically review the science upon which U.S. standards are based and the standards themselves.”

EPA Administrator Michael Regan said last summer the agency is reconsidering a Trump administration decision to keep the existing air quality standards, but that the review process is expected to last until spring 2023.

The official said that the big and obvious sources of air quality have already been accounted for, and that the low-level improvements present challenges.

“It’s difficult to achieve low, continued improvement in the air quality without really revolutionizing the energy system.”


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