Environment & Health HKFP Voices

Breath of suspicion: why is Hong Kong’s air cleaner by local measures… and dirtier according to outsiders?

On the morning of Feb. 6, the second day of our New Year holiday, I opened my curtains and looked out my window to see the distant mountains shrouded in fog. Wondering whether this fog was just mist, or something more sinister, I checked three websites that provide metrics on air quality.

The night before, I noted the air quality forecast from the government’s Environmental Protection Department (EPD) website for the next day, which gave the pollution health risk as “low.” I made special note of this forecast because the quality of our local air had been poor lately, and the weather forecast for the next day was for light winds.

Therefore, my own amateur forecast was for high levels of pollution for the following day, although this seemed to contradict the official forecast.

low Air Quality Health Index

Air Quality Health Index website by the Environmental Protection Department. Photo: Screenshot.

Anyway, after opening my curtains and seeing the fog, I went to three websites to check the air quality metrics. As expected, the government site gave a low overall rating, with most of its stations around town showing the number “3” (on a scale of one to ten) with a green background — presumably to lend a clean image.

Another site, the Hedley Index, run by the University of Hong Kong, rated our air as a red-coloured “6” (out of 12), which is on the high side of “moderate”, with several of the individual monitoring stations around town showing a dark brown, “9”, just below a “very high” rating.

Hedley Environmental Index

Hedley Environmental Index. Photo: Screenshot.

The third site I checked was the World Air Quality Index, which provides metrics for cities around the world. It showed Hong Kong’s 2.5pm (tiny particulate matter that can penetrate deep into the lungs) was an orange “146,” or “unhealthy,” with some stations around the city already exceeding a red 150.

In sum, our government’s EPD forecast, and their real-time rating of our air quality was conspicuously lower than the two other official sites.

World Air Quality Index

World Air Quality Index. Photo: Screenshot.

If this were an isolated incident, the EPD’s forecast and rating could be forgiven. After all, air quality is enormously complex, influenced by many factors such as the presence of 2.5pm, ozone, NO2 and the like, in addition to sunlight and wind. However, over the past few years, I have noticed the EPD site frequently rates our air quality better than the other two sites, sometimes remarkably so.

Noting this discrepancy, on two occasions I wrote to the EPD asking for an explanation for their consistently lower rating of the health risks due to local air pollution. On both occasions, the EPD kindly replied with lengthy explanations detailing the challenges that come with measuring the quality of our air.

However, while there are surely difficulties in combining all of the factors that affect the quality of our air into one number, or word, such as “low” or “unhealthy,” it is puzzling why our own government’s site frequently appears to be out of step with other sites from reputable sources.

air pollution Hong Kong

Air pollution in Hong Kong. File Photo: GovHK.

I am imagining parents with young children, who are particularly vulnerable to air pollution, planning their outdoor activities based on the EPD’s forecast and perhaps being blissfully unaware of the potential damage they are doing to their children’s lungs by spending a day at the beach, or worse, at a sporting event where their kids are taking deep breaths of air.

I can come to only two conclusions based on my observations. Either the two other websites that consistently report higher levels of pollution are exaggerating the dangers that our air poses to our health, or the EPD employs standards that are much more relaxed and understate the dangers.

Unfortunately, it is the latter that appears to make more sense perhaps because by understating the dangers, the government receives less pressure to tighten standards from the public. However, isn’t the main job of the EPD to protect the public from environmental dangers?

Roadside air quality monitoring station Central

Roadside air quality monitoring station in Central. Photo: GovHK.

When an amateur forecaster like me can simply open the curtains each morning and obtain a more accurate reading of air quality than a government website, it appears time is ripe for an overhaul.

Breath of suspicion: why is Hong Kong's air cleaner by local measures... and dirtier according to outsiders?