This month Hong Kong had another bout of air pollution, with two official warnings just five days apart. Here is what everyone should know about pollution in Hong Kong.
What are the main health effects of air pollution?
There is ample evidence that air pollution leads to a variety of health problems, including:
- aggravated asthma
- respiratory issues like irritation of the airways, coughing or difficulty breathing
- premature death in people with heart or lung disease
- nonfatal heart attacks
- decreased lung function
Children, older adults and people with heart or lung diseases are the most likely to be affected by particle pollution exposure.
How is pollution measured? What is PM and PM2.5?
PM stands for particulate matter (also called particle pollution): it’s a mix of solid and liquid particles floating in the air, which come in various sizes:
- PM10 with a diameter of less than 10 micrometers (for instance, dust).
- PM2.5 with a diameter of less than 2.5 micrometer. These come from combustion such as motor vehicles or power plants.
PM2.5 are tiny particles that are so small and light that they tend to stay longer in the air. They penetrate deeper into the lungs and cause a range of health effects.
How is pollution measured in the world?
The World Health Organization (WHO) daily PM2.5 limit is 25 micrograms per cubic meter. In the US, PM2.5 standards are about the same: 15 / 35 micrograms per cubic meter (annual/daily). In Hong Kong, PM2.5 levels have reached over 200 on several occasions in the past years, including this month.
How is pollution measured in Hong Kong?
Hong Kong uses its own measure called the Air Quality Health Index (AQHI). The AQHI doesn’t specifically reflect the PM2.5 levels. This has led various voices to request an adoption of a PM2.5 based measure. The AQHI ranges from 1 (lowest) to 10+ (highest). Levels 8 to 10 mean a “very high risk” for health while 10+ brings a serious risk. Last week’s pollution was “serious” in three districts: Yuen Long, Tuen Mun and Tung Chung. PM2.5 levels in Hong Kong can be checked here.
How is air pollution in Hong Kong compared to the rest of the world?
According to the last update of the WHO, over 80% of urban areas monitored for air pollution exceed the WHO air quality limits. The WHO database of nearly 3000 monitored cities has ranked Hong Kong in the top 20% most polluted cities.
Actually, more than 50% of these 3000 cities are located in developed European cities where regulatory bodies actively try to reduce air pollution. Cities in some developing economies may not be included in this list due to the absence of measuring stations. Although far from ideal, the situation Hong Kong is not the worst.
Does staying indoors protect you from pollution?
It is important to note that while recommendations on highly polluted days involve staying indoor, PM2.5 levels inside may actually be just as high, if not higher as indoor air quality can be impacted by cooking, the type of gas used, poor ventilation or dirty air filters.
Does wearing a face mask protect you against pollution?
Unfortunately, many masks do not fully protect against breathing in polluted air. Only face masks with an airtight seal around your nose and mouth will effectively filter polluted air.
Read more on a new face mask that protects against air pollution: