After over 16 years, the World Health Organization (WHO) updated its air quality guidelines, including its recommended limits for one of the world’s biggest killers, PM2.5 air pollution. The WHO lowered their annual PM2.5 limit by half, from 10 micrograms to 5 micrograms. So are these new guidelines safe air quality levels for yourhome?
The update is welcome news, given evidence that the WHO PM2.5 guidelines are unsafe. Research has found that PM2.5 harms human health even below 10 micrograms.
Why the WHO Updated Its Safe Air Quality Guidelines
First, let’s look at what was wrong with the previous WHO recommended safe air pollution levels. The WHO air pollution guidelines were last updated in 2005. Since 2005, there have been many major new findings on the effects of air pollution on our health. These findings include strong links of higher mortality and cardiovascular rates at pollution levels below the recommended limits. We have also learned much more about how pollution affects infertility, new born’s health, and brain health.
From 1987 to 2005, there were approximately 130,000 studies on the effects of air pollution on our health. During that time period, the WHO made two revisions to their guidelines.
Since the WHO’s last update of their air quality guidelines in 2005, there have been 177,000 new studies.
That new research has given clarity about the harms of even “low” levels of air pollution.
What is New in the Updated WHO Air Quality Recommendations?
The WHO also updated the 24-hour PM2.5 limit from 25 to 15 micrograms.
Despite the stricter limits, the limits for one pollutant (sulfur dioxide) actually increased two-fold.
Since 99% of the world’s population lives in places where the WHO safe air guidelines are not met and many countries are far from reaching these goals, the WHO created interim targets. These interim targets are more achievable for countries that are far above the levels, yet reductions to these levels would still result in a significant reduction in disease. The new guidelines also offer additional recommendation levels, such as for peak season O₃ and 24-hour NO₂ and CO.
|Pollutant||Time||2005 AQGs||2021 AQGs|
|PM2.5 μg/m3||24 hr||25||15|
|PM10 μg/m3||24 hr||50||45|
|O3 μg/m3||Peak Season#||–||60|
|O3 μg/m3||8 hr||100||100|
|NO2 μg/m3||24 hr||–||25|
|SO2 μg/m3||24 hr||20||40|
|CO, mg/m3||24 hr||–||4|
|# Average of daily maximum 8-hour mean O3 concentration in the six consecutive months with the highest six-month running- average O3 concentration. Note: Annual and peak season is long-term exposure, while 24 hour and 8 hour is a short-term exposure|
Are the New Updated WHO Recommended Safe Air Quality Limit Actually Safe For Your Home?
It is good to see the WHO updating their air quality guidelines. However, the limits can give people the idea that the limit is the “safe” level. Yet the WHO is careful not to use the word “safe.” The research suggests there is actually no “safe level” of air pollution. Even small amounts of particulate pollution increase our risk of health effects such as raised blood pressure.
Surprisingly, a meta-analysis found that low levels of air pollution cause more harm than higher levels of air pollution.
The PM2.5 guidelines may end up following the history of lead guidelines. After lowering “safe” lead limits for decades, the US EPA declared “there is no known safe level of lead.” Yet some research (see chart above) shows fatality from air pollution increases significantly at around 5 micrograms. Therefore, you should at least aim to have your indoor air under 5 micrograms of PM2.5.