Wildfires, heatwaves endanger air quality, health: UN

Wildfires and heatwaves, which generate microscopic airborne pollutants, risk undermining international efforts to improve air quality, protect human health and safeguard nature, the World Meteorological Organization (WMO) said today (7 September).

The United Nations' weather and climate agency underlined the links between air pollution and climate change, which scientists say are leading to more frequent and intense heatwaves and wildfires.

"Extreme wildfires are increasing, leading to significant health consequences because of the high toxicity of smoke," the WMO said in a statement accompanying its latest annual Air Quality and Climate Bulletin.

"Whilst regulations in Europe and North America have reduced industrial and transport PM2.5 emissions, exposure to fire-related PM2.5 has increased."

Particulate matter PM2.5 is composed of microscopic particles and droplets less than 2.5 micrometres in diameter. It is a health hazard because it can penetrate deep into the lungs and bloodstream.

It is emitted by fossil fuel-driven industrial activities, farming, domestic heating and transport, as well as by wildfires and dust storms.

The report said the world needs to better monitor air pollutants such as aerosols, including black carbon and microplastics, fine particles and ground-level ozone.

These pollutants "are not sufficiently monitored even though they are widespread and are potentially harmful to ecosystems", the WMO said.

"(We need) complementary and coordinated policies on air quality and climate because they cannot be dealt with in isolation."

Toxic wildfire smoke

"Air quality and climate change can't be dealt with separately. If one worsens, the other does too," Lorenzo Labrador, from the WMO's Global Atmosphere Watch network of scientists, told AFP.

"In places where there are relatively powerful forest fires, we find a lot of fine particle pollution," he said.

Microparticles generated by burning vegetation are "much more toxic" than those emitted by other sources, even car exhaust, he stressed.

They damage the health of people and wildlife living far from the fire itself because they are carried by the wind, but their poisonous effects are not sufficiently taken into account in air quality assessments, Labrador said.

"Conventional risk models based on total PM2.5 concentrations may underestimate wildfire-attributable mortality by up to 93 percent," the WMO said.

One study cited in the WMO Bulletin says extreme fire-smoke events have tripled globally since the 1990s, contributing to nearly 100,000 additional deaths per year between 2010 and 2018, although this may be an underestimate.

Ozone, microplastics

Another source of air pollution that carries major health risks is ground-level ozone, which accumulates when temperatures rise, atmospheric conditions stagnate, and solar radiation is intense, as seen during recent heatwaves in China, Europe and the southeastern United States.

"This increased exposure to ozone pollution has the potential to lead to tens of thousands of additional premature deaths," particularly due to respiratory diseases, the WMO warned.

Another growing concern is aerosol particles, which can also travel to oceans and continents far from their source.

They can alter the way the atmosphere reflects sunlight, change the chemical properties of land and water, and pollute otherwise clean environments.

"One example is the deposition of black carbon, or soot, on snow and ice, which reduces the amount of sunlight reflected by these surfaces and, in turn, can hasten the melting process," the WMO explained.

Another example is microplastics, formed when plastics break down because of sunlight or other factors. They are found virtually everywhere, including in the air, soil, and oceans.

One simulation in the WMO Bulletin estimates there are "51 million tonnes for land and 22 million tonnes for the ocean, which are in turn a source of microplastics for the atmosphere".

"As plastic production and, critically, mismanaged plastic waste continue to increase," monitoring the airborne paths that carry microplastics from their sources and deposit them in remote environments will be "crucial", the report said.