The World Health Organisation (WHO) is significantly tightening its air quality guidelines, explaining that air pollution can be harmful at lower levels than it previously believed.

The higher air-quality bar is the first update to its air quality guidelines in 15 years, and will be challenging for many countries to meet. As of 2022, just six countries – Australia, Estonia, Finland, Grenada, Iceland, and New Zealand – currently meet the new air quality guidelines. 

The guidelines are not legally binding, being intended as a reference for policymakers, advocacy groups and academics.

However, some countries are planning to legislate in order to protect air quality. The UK – which sees between 28,000-36,000 deaths a year related to human-caused air pollution – is currently working on a so-called Ella's Law. This is named after Ella Adoo-Kissi-Debrah, a nine-year-old girl who died in 2013 and is the first person in the UK to have air pollution cited as a cause of death.

WHO: air pollution 'kills 7 million a year'

WHO estimates that air pollution kills 7 million people annually, and that 99% of the world's population breathes air that exceeds WHO air-quality limits. 

Air pollution is a complex mixture of solid particles, liquid droplets and gases. These come from multiple sources, including traffic exhausts, power generation, fuel burning, industrial chimneys and waste burning.

WHO is now calling for lower levels of six pollutants known to have impacts on health: two types of fine-particulates pollution (PM 2.5 and PM 10), as well as ozone, nitrogen dioxide, sulphur dioxide and carbon monoxide.

Inger Andersen, Executive Director of the UN Environment Programme says: “We need to trigger environmental actions and provide necessary safeguards to people worldwide. 

“It will help people stand up for their right to breathe clean air, access safe and sufficient water, healthy food, and healthy ecosystems.

WHO redefines 'air-borne' as it relates to diseases 

In related WHO news, the organisation and around 500 experts have agreed for the first time what it means for a disease to spread through the air.

This was in a bid to avoid the confusion seen early in the COVID-19 pandemic that some scientists said cost lives.

Among the health experts who contributed to the new definition were physicists, public health professionals and engineers, many of whom clashed over the topic during the pandemic.

WHO said its technical document on air-borne diseases is a first step towards better preventing the transmission of existing diseases such as measles, as well as future pandemic threats.

The document concludes that the descriptor “through the air” can be used for infectious diseases where the main type of transmission involves the pathogen travelling through the air or being suspended in the air. This is in line with other terms such as “waterborne” diseases, which are understood across disciplines and by the public.

WHO: Air-borne definition 'significant'

The definition is significant because health agencies have historically required high levels of proof before calling diseases airborne, which required stringent containment measures.

The new definition says the risk of exposure and severity of disease should also be considered.

Past disagreements also centred around whether infectious particles were ‘droplets’ or ‘aerosols’ based on size, which the new definition moves away from.

During the early days of COVID in 2020, around 200 aerosol scientists publicly complained that WHO failed to warn people of the risk the virus could spread through the air. This led to an overemphasis on measures like handwashing to stop the virus, rather than focusing on ventilation, they said.