Hong Kong has an air pollution problem. If the territory conformed to the World Health Organisation's (WHO) standards for clean air, only 10 per cent of the days here would pass muster.
According to the WHO, air pollution is "the world's single largest environmental risk". In October last year, the WHO's International Agency for Research on Cancer (IARC) classified air pollution as a group 1 carcinogen for the first time. This puts it in the same category as smoking cigarettes, with "sufficient evidence" that exposure causes lung cancer. The IARC also classified particulate matter (PM), a major component of the air pollution in Hong Kong, as carcinogenic.
Lung cancer is only one of many negative outcomes. Air pollution both causes and exacerbates ongoing irritations such as coughs, mucous build-up and inflamed airways. It also leads to more life-threatening situations such as cardiovascular disease and heart attacks. Vulnerable groups, including children, the elderly and people with existing heart and respiratory conditions, are most at risk. Some people are genetically predisposed to be more sensitive to pollutants. Those who spend a lot of time outdoors are also more likely to succumb to health problems. The more you delve into the subject, the more our pollution-tinged skies appear ominous.
"Air pollution is certainly the most important public health risk in Hong Kong," says Dr Tian Linwei, associate professor at the School of Public Health, at the University of Hong Kong. "If you look at environmental issues of air, water and solid waste, the quality of the air stands out as being well below standard. And the air quality is worsening. Even without any pollution data, we can simply see that the visibility is getting worse. The government says it is improving, and it is in some respects, for example, the PM 10 levels. However, overall it has deteriorated."
In public-health terms, air pollution is defined as having both a chronic, long-term effect and an acute, short-term effect. The acute effect day-by-day, month-by-month, eventually merges into the chronic effect.
"There are a lot of studies in Hong Kong that demonstrate the link between air pollution and hospital admissions, in other words an acute effect," says Tian. "Data about the long-term effect of pollution on health is not readily available as a population-based study requires a lot of resources and infrastructure. Globally, there have only been about five meaningful studies, in America and Europe. They have three consistent findings. First that air pollution shortens life expectancy. Second, that a high level of the smallest particles in air pollution is related to lung cancer risk. Third, these small particles are also related to cardiovascular disease and mortality. The higher the levels of particles in the pollution, the higher the risk."
The Environmental Protection Department (EPD) monitors pollution in Hong Kong at 12 general and three roadside stations. It takes readings on the four main pollutants and then calculates the short-term health risk. This information is made available as the Air Quality Health Index (AQHI) online and via an app. It's graded into a scale from one to 10+. One indicates low risk to health and 10 a serious risk. The current health advice is to reduce activity and time outdoors when the pollution hits seven on the scale. By 10, you should be indoors.
The four main pollutants measured are sulphur dioxide (SO2), nitrogen dioxide (NO2), ozone and airborne particle matter.
SO2 and NO2 are gases caused by combustion in power plants, industrial boilers and vehicle engines on land and at sea. They lower the body's resistance to respiratory disease, aggravate existing disease and irritate and damage the respiratory system. They can cause cardiovascular disease in people with sensitive respiratory systems, including asthmatics, the elderly and the young. They also impair lung development in young children. Ozone is formed when NO2 reacts with hydrocarbons in the presence of sunlight. Ozone irritates the mucous membranes in the nose, throat and airways, which causes eye irritation, coughs, and throat and chest pain, inflames the respiratory system and decreases lung function. Airborne particle matter is made of tiny particles of solid or liquid substances suspended in the air. They are defined by size rather than substance. PM 10 particles have a diameter of less than 10 micrometers and PM 2.5 have a diameter of less than 2.5 micrometers.
The human nose does a relatively good job of filtering particles larger than PM 10. Smaller than that and it fails, allowing the particles direct access to our lungs. The very smallest, or ultrafine, particles have been found to penetrate not just the lungs but also cell membranes, which means they can get into other organs, including the brain. These particles are dangerous not just because of their size but also their chemical composition, which, in some cases, is carcinogenic.
The effect of inhaling particulate matter has been widely studied and documented, with depressing results: blocked airways, coughs, decreased lung function, aggravated asthma, lung cancer, cardiovascular disease, respiratory disease, birth defects, premature delivery and premature death.
Currently, the number of days deemed dangerous to health using Hong Kong's AQHI stands at about 30 per cent. (Hong Kong's ambient air guidelines are less stringent than those of the WHO.)
Last year, the Hong Kong government came up with a Clean Air Plan, to reduce locally produced vehicle, marine and power plant emissions. It is widely considered to be a good plan. The government is also working at a regional level with the Guangdong authorities to reduce emissions in the Pearl River Delta.
While we wait patiently for these policies to bear fruit, is there anything else that we can do to mitigate the pollution?
BEIJING, HONG KONG'S ultimate seat of power, chokes under a far thicker fug than that of the SAR. In the Chinese capital, it is common to see people wearing facemasks to filter out the smog.
Christopher Dobbing is director of Vogmask China. Vogmask is an anti-pollution facemask designed for babies, children and adults. The firm was started in California, in the United States, two years ago, producing masks developed to protect partygoers from dust at the Burning Man festival, in the Nevada Desert. The South Korean-made products are classified as removing at least 99 per cent of airborne particles and have been on sale in Beijing for 18 months, retailing at between HK$230 and HK$285.
"The average northern Chinese resident lives about five years less than a Chinese person living in the south and that's down to air pollution," says Dobbing. "Here in Beijing, doctors recommend wearing a mask at around 200 AQI, which is equivalent to level 7 in Hong Kong."
The whole mask is a filter. "If it's above 300 AQI, the mask would last 80 hours. If you're in a much less polluted environment, say, like Hong Kong, you'd expect it to last for 300 or 400 hours of use." Once that time is up, you dispose of the mask and replace it.
"The needs in Hong Kong are different from those in Beijing. If you are cycling in traffic or have a respiratory illness or sensitivity to pollen or dust, then a mask is a good non-medical solution. It will take a generation to clear the pollution up. Over that time, wearing a face mask and running an air purifier indoors is something everyone should be doing."
"There have been a lot of studies on face masks," counters Tian. "They prevent large particles. However, our noses also stop large particles. If you want to stop small particles, you need a very, very good mask, which takes a lot of pressure to breathe through. This can cause another kind of damage, which can be dangerous for the elderly and children."
AIR PURIFICATION IS big business in Hong Kong. Hospitals, businesses, schools and homeowners buy air purifiers in the hope they will render indoor air safe. IQAir manufactures air purifiers in Switzerland. It is a well-known brand, not least because of its hefty price tag. Its best-selling model, the HealthPro 250, sells for about HK$15,000.
"In the basic model, there are two filters," says Amy Yeung Mei, marketing manager for Airtek, the sole agent of IQAir in Hong Kong. "The first is the pre-filter, which tackles the large airborne particles like PM 10 and dust particles. The second filter removes smaller particles like pollen, fungi, mould spores, bacteria and allergens. It takes out up to 99.97 per cent of 0.3 micrometer."
Some manufacturers, including IQAir, claim their devices remove organic vapours, for example formaldehyde, but this is difficult to confirm scientifically.
The machines can run on a similar amount of energy as a light bulb. One machine is needed in each room of an apartment or house.
Dane Westerdahl is a research scientist at the School of Mechanical and Aerospace Engineering at Cornell University, in the US, with a consulting role at the School of Energy and Environment at City University of Hong Kong. He has undertaken many air pollution studies, in cities including Jakarta, Beijing, Milan, Barcelona and Los Angeles.