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Lo Hoi-ying

Hongkongers woke up to a dry and hazy Sunday with multiple districts enduring serious air pollution under the influence of a dusty airstream from the north, and conditions are expected to remain the same for the next few days.
The Observatory said the city experienced its driest April morning since the automatic weather station was set up in 1984, with relative humidity falling to as low as 21 per cent.
The Environmental Protection Department said visibility would not improve until the middle of the week when a southerly air stream was due to arrive in coastal areas of Guangdong province.
Air pollution in urban areas such as Central, Eastern and Kwun Tong districts had hit “very high” health risk levels as of 5pm, according to the department’s air quality health index.
The department warned that health risks were “very high” in Tung Chung, Tuen Mun, Sha Tin, Tai Po and North districts in the New Territories.
From Tai Mei Tuk in Tai Po, for example, the opposite shore at Ma Liu Shui and Ma On Shan, about 5km (3.1 miles) away, could not be seen at one point because of the pollution.
The index has five health risk categories, “low”, “moderate”, “high”, “very high” and “serious”, the highest level.
Other districts also experienced high levels of air pollution.
The department said suspended particulate levels in background pollutants had been higher than normal since Saturday night under the influence of a dusty airstream associated with the northeast monsoon.
“With the monsoon moderating gradually, winds in Hong Kong are expected to weaken [which is] unfavourable to pollutant dispersion in the region, leading to an increase in pollution levels,” it said.
“It is anticipated that the pollutant level will remain relatively high in the following one or two days.”
The department forecast that health risks would worsen from “high” to “serious” at dusk on Sunday.

It said dust present in the air was made up of mainly larger respirable suspended particulates (PM10).
“The increase in fine suspended particulates [PM2.5], which directly affects human health, is smaller,” the department said.
Within 12 hours, PM10 concentrations had shot up from 8 micrograms per cubic metre of air at 9pm on Saturday night to 277.4 µg/m3 by Sunday morning. The concentration of PM2.5 increased from 2.9 to 66µg/m3 in the same period.
The department said Hong Kong had been affected by dust-laden airflows in the past, with the impact lasting from several hours to several days.
As the dusty airstream had travelled a long distance, the impact of the pollutants on Hong Kong was expected to be similar to the level of air pollutant accumulation under general calm wind conditions.
Employers of outdoor workers doing strenuous work should assess the risks and take appropriate preventive measures to reduce exertion during very high levels of air pollution, the department said.
In areas with “very high” health risk levels, children, the elderly and people with existing heart or respiratory diseases should reduce outdoor physical exertion and not remain in areas with heavy traffic. When the category reaches “very high” or “serious”, the public should also reduce or avoid outdoor physical exertion.
The air quality is expected to improve by Monday morning, dropping to “low” to “moderate” risk levels.
According to the Observatory, relative humidity fell to 30 per cent or below on Sunday morning due to the northeast monsoon.
“Until 9.40am, the relative humidity recorded at the Observatory once fell to 21 per cent, the lowest recorded in April since the automatic weather station was established at the Observatory’s headquarters in 1984,” the forecaster said.
Sand and dusty weather also reduced visibility over parts of Guangdong province, it said.
Temperatures will remain between 19 and 25 degrees Celsius (66 to 77 Fahrenheit) on Sunday, with fresh northerly winds and occasional strong offshore winds.
Rain is expected in the latter half of the week, while temperatures will rise to around 27 degrees.


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Air pollution reduces the views at Hong Kong’s famed Victoria Harbour. Photo: Eugene Lee

With the monsoon moderating gradually, winds in Hong Kong are expected to weaken. Photo: Eugene Lee

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Foggy and drizzly weather over Victoria Harbour on April 5. Photo: Eugene Lee

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Expected thunderstorms across the region have resulted in a significant amount of ferry cancellations between Hong Kong and the mainland. Photo: Eugene Lee

Hazy skies expected to remain in Hong Kong for several days

Observatory says city experienced its driest April morning since 1984