PM2.5 pollution on Hong Hong Kong Island rose to it's highest level in more than two years on Friday, as winds disappeared, allowing locally generated pollution to build up to toxic levels.
Hong Kong's lax marine/vehicle regulations - including operation of coal-fired power stations right next to population centers - leads to substantial local pollution generation. Despite this, the city benefits from its geography and for much of the year, offshore winds from the south and east help mask the problem, bringing fresh(er) air in from the sea. When those winds are reduced or absent however, the consequences of Hong Kong's lack-luster emissions regulation quickly becomes apparent.
PM2.5 levels rose to 500% of the WHO limit
This is the scenario that was seen on Thursday night, when average hourly wind speed fell to 1 km/hr at times, and PM2.5 levels rose to a peak of 126 µg/m³ on Hong Kong Island and 124 µg/m³ in Tuen Mun, 500% of the threshold at which air quality is deemed Poor by the EU.
Coal-fired power stations don't belong next to urban population centers
The animation below covers this period and reveals the just how rapidly PM2.5 particulate levels can rise during still conditions. The steep rise is first apparent at the Tuen Mun environmental sensor station, which is unsurprising given its proximity to the 38-year old Castle Peak Power Station, Hong Kong's largest coal-fired power station, and emitter of 22 million tonnes of CO2 each year.
As of the time of writing (15:00 on the 24th of January), the PM2.5 concentration in Central/Western HK is yet to fall below the WHO upper limit of 25 (equivalent to the EU "Poor" air quality threshold).
As of Midnight on the 28th of January, Central/Western PM2.5 levels have only been below the EU Poor air quality threshold for 13 hours over the past six days.
Air pollution kills an estimated 6300 people annually in Hong Kong
Fine particulate pollution is particularly damaging to health, with strong evidence linking levels regularly experienced in Hong Kong to heart disease, cancer, strokes, and COPD.
Despite the health burden and estimated HK$39 billion annual costs in lost productivity, in 2020, the Hong Kong government allocated less than HK$2 billion to the Environmental Protection Department's air quality program, a reduction from the prior year. By comparison, the government spent close to HK$200 billion on anti-epidemic measures in 2020.
Embee recommends monitoring the US AQI for Hong Kong
It can be challenging to know when pollution levels are dangerously high, as pollutants that have the biggest visual impact are typically not those that are most damaging to health. The Hong Kong Air Quality Health Index (AQHI) is inadequate for this task, showing "Low" readings when pollution levels are well above thresholds that will impact health.
The US AQI is more appropriate, being based on clearer, evidence based levels. Embee calculates the US AQI hourly for every pollution monitoring station and school in Hong Kong. The readings can be viewed at the link below:
The Embee Team.