5 Myths you should bust about the air pollution in Hong Kong


The post is addressing common misconceptions about the air pollution on Hong Kong. Some sources have been widely quoted in the document:

Misconception #1 : “The air quality in Hong Kong is much better than Shanghai or Beijing so my children are fine in HK with no air filter” : WRONGMisconception #2 : “The pollution comes from cars and mostly China” : WRONGMisconception #3 : “Locations such as Stanley or Sai Kung are not very polluted” : WRONGMisconception #4 : “My child is fine, he is not coughing or showing any sign of illness so the air quality must be fine” : WRONGMisconception #5 ” I don’t want to put my child in a air-filtered class, breathing bad air will make my child stronger”. WRONG


1. The air pollution level in HK is very serious, way above the WHO recommendations

PM 2.5 : PM2.5 are tiny particles in the air that reduce visibility and cause the air to appear hazy when levels are elevated. The widths of the larger particles in the PM2.5 size range would be about thirty times smaller than that of a human hair.Particles in the PM2.5 size range are able to travel deeply into the respiratory tract, reaching the lungs. The Environmental protection Department www.edp.gov.hk published that the average annual concentration of PM 2.5 levels in Central or Causewaybay were respectively about 29 and 38 μg/m3 in 2014 or much worse than Madurai in India or the same as Shenzen (the factory of the world).In contrast, WHO recommends an upper limit of 10 ug / m3 per year for the PM 2.5

NO2 or nitrogene dioxide is a toxic gas– The EDP measured that annual concentration of NO2 in Central and Causewaybay at 103 and 104 ug/m3In contrast, WHO recommends an upper limit about 40ug / m3 per year for the No2

O3 or Ozone, is is a serious pollutant. It’s produced when sunlight combines and reacts with chemicals produced by cars, power plants, and factories.From January to June 2014, average annual concentrations of the pollutant was 43 ug/m3, nearly double WHO’s annual recommended concentration level of 23.5 ug/m3 per cubic metre. The ozone pollution in Hong Kong is at worst level in a decade. The figure has been rising since its lowest recorded level in 2005, at 35mcg per cubic metre.

SO2 or Sulfur dioxide has a nasty, sharp smell. It reacts easily with other substances to form harmful compounds, such as sulfuric acid, sulfurous acid and sulfate particles. About 99% of the sulfur dioxide in air comes from human sources.

VOC or volatile organic compound is one of a number of chemicals, including benzene and acetone, that evaporate or vaporize readily.

Hong Kong polluted air in winter source wikipedia


2. What are the sources of air pollution in Hong Kong ?

The diagram below shows the emission inventory for 2012 under different emission source categories :– Navigation– Public electricity generation– Road transport(FSP= PM 2.5 and PM10)


Navigation : Ships


As per a study from the EDP the RSP respirable particulate matter (PM 2.5 and PM10) as well as the SO2, NO2 and VOC are mostly produced by the 480 000 boats coming to HK every year. This represents an average of 1 ships every 65 seconds coming close to HK. People who have been doing some trekking on Po Toi Island can confirm this by simply observing this very high frequency of boats coming to the delta river. Being surrounded by water on three sides, Hong Kong is greatly impacted by pollution that is generated from ships traveling to ports on either side of the city, not to mention ships that travel directly to Hong Kong’s port.

The island of Tap Pun is a good example: there is no factory and no cars but its average levels of air pollutants from March 2014 to February 2015 were alarming and at least twice the WHO standards:– PM10 : 43 (WHO 20)– PM 2.5 : 28 (WHO : 10)The island just happens to be alongside the direct ships routes into Yantian port and winds in HK are N / N easterlies are passing through here for 11 months of the year.Mainland Chinese factoriesHeavy metal concentrations in the air in Hong Kong, can be found in air coming from mainland china. Several teams of scientists have studied smog in Hong Kong and at least two detected heavy concentrations of trace metals. Excessive amounts of zinc and chromium are toxic and can lead to a wide range of problems, from premature ageing to cancer and exspecially with children. The Hong Kong overall PM2.5 levels are lower than in most urban centres on the mainland, but it has a higher concentration of health-threatening trace metals, the scientists say. Nearly 20 per cent of PM2.5 particle samples collected in the city carried metals such as zinc, a hazardous element that can permanently damage DNA. Which means that these heavy concentration will impact negatively our children’s children as well.

Other factorsThe air pollution problem is influenced by multiple factors in which weather conditions may accentuate oralleviate the problem such as the wind direction and rain. Southern marine monsoon helps clean the air whilenorthern winds transport pollutants from Pearl River Delta region to Hong Kong.

What about Stanley’s or Sai Kung’s air pollution ?

The governement has not installed pollution sensors in locations such as Stanley or in some areas in Sai Kung.

The car traffic is lower than central Hong Kong so people say that the pollution levels are low and the air is good in these locations but whether citizens live in Stanley, Kennedy town or Shenzen they are impacted in almost same manner by the pollution of PM 2.5, PM 10, SO2, NOx, RSP coming from the boats and the public electricity generation. The impact of road transport may be felt more in dense areas such as Central or Causeway Bay but is getting less and less important due to recent measures implemented by the government to encourage cleaner euro 5 cars and buses on the road.

As conclusion, the air pollution is a problem across Hong Kong which impacts every part of the territory in more or less the same way including Stanley and other remote places.


1. Increase health risks, allergies, asthma and mortality especially with children

Researchers found significant associations between hospital admissions for asthma to 15 major hospitals in Hong Kong and the levels of NO2, O3 , PM10 and PM 2.5 from January 2000 to December 2005. For every 10 g/m3 increase in NO2, O3, PM10 and PM2.5, there were 2.8%, 3.4%, 1.9% and 2.1% increases in the rates of asthma hospitalizations respectively.

– Nox and No2 are toxic gas which causes significant inflammation of the airways and form an important fraction of PM2.5 and, in the presence of ultraviolet light, of ozone. NO2 causes detrimental effects to the bronchial system which leads to allergies, asthma etc.

– So2 is present in the boat fuel. This low cost fuel is rich in sulphur, with a percentage ranging form 2.7 to 4.5 %, to be compared with road vehicles using now Ultra Low Sulfur Diesel (ULSD) with a sulphur content of 0.001% in Europe, making ship fuel 4,500 times more polluting and harmful. Sulfur dioxide irritates the nose, throat, and airways to cause coughing, wheezing, shortness of breath, or a tight feeling around the chest. The effects of sulfur dioxide are felt very quickly and most people would feel the worst symptoms in 10 or 15 minutes after breathing it in.– On the top of the know air pollutants, heavy metal concentrations in the air in Hong Kong, can also be found in air coming from mainland china. These metal particulate matter penetrate the lungs deeply and impact our DNA.Some genetic damage will be passed down to the next generations.

the poinson in the air we breathe. Courtesy SCMP


Sources : http://www.cleartheair.org.hk/marine-pollution.phphttp://usceh.blogspot.hk/2014/11/hong-kong-simon-ng.htmlhttp://www.scmp.com/news/hong-kong/article/1522257/hazardous-level-trace-metals-chinas-air-warn-scientists?page=all

2. Greater impact for young children especialy in indoor polluted spaces

Air pollution impact on childrenA slight increase of the concentration of air pollution matter increases the risks of asthma, allergies and other illness with young children whose respiratory system is under development.When outdoor levels of PM2.5 are elevated, going indoors may be seen as reducing the exposure, but some outdoor particles will come indoors and levels inside may not be lower than outside.


It is proven that air filters indoors and in the classroom have a positive impact on the children’s health

An exploratory study was performed to evaluate a combination of the two systems in a primary school. Measurements of PM-10 and PM-2.5 were performed by filter sampling and aerosol spectrometry. Other indoor air quality parameters included black smoke (BS), volatile organic compounds (VOC), nitrogen dioxide (NO2) and formaldehyde. Both interventions were introduced in one classroom during one week, using another classroom as a reference. In a second week the interventions were moved to the other classroom, using the first as a reference (cross-over design). In three remaining weeks the classrooms were compared without interventions. Indoor air quality parameters were compared to the corresponding outdoor parameters using the indoor/outdoor (I/O) ratio. When the classrooms were occupied (teaching hours) interventions resulted in 27–43% reductions of PM-10, PM-2.5 and BS values. During the weekends the systems reduced these levels by 51–87%. Evaluations using the change in I/O ratios gave comparable results.Source : http://pubs.rsc.org/en/content/articlelanding/2015/em/c4em00506f#!divAbstract

Nicolas Giraudon