Air pollution in Hong Kong reaches 'very dangerous' levels

Air pollution in Sham Shui Po yesterday reached levels considered "very dangerous" by the World Health Organisation, although a later brief and extraordinary spike in readings was dismissed as the result of a technical glitch.

The Environmental Protection Department's website showed that the concentration of PM2.5 pollution - tiny particles in the air which are particularly hazardous to health - reached 91.7 micrograms per cubic metre of air in Sham Shui Po at 3pm yesterday. WHO guidelines say any reading above 25 is "dangerous", while a reading above 75 is "very dangerous".

The level of PM10 pollutants - bigger particles less likely to lodge deep inside lungs, but still hazardous - was at 115 micrograms per cubic metre of air at 3pm.

At 4pm, PM2.5 concentration surged suddenly to 653.5, while PM10 concentration also spiked, reaching 659.8.

However, in response to questions from the last night, the department said it believed the latter readings were caused by a technical fault. The figures remained unusually high until the department stopped updating PM2.5 and PM10 measurements for the area at 7pm.

While the brief scare was a false alarm, the actual levels remained hazardous. The Air Pollution Index (API) reached a "very high" level at two roadside monitoring stations yesterday - 127 in Central and 118 in Causeway Bay. The city strives to keep API below 100. At higher levels, the department's guidelines advise those with heart or respiratory illnesses to avoid exposure to heavy traffic and reduce physical exertion.