Hong Kong’s air pollution is bad. Very bad. The city’s air pollution is a poisonous cocktail of nitrogen dioxide, sulphur dioxide, particulate matters and ozone, and is three times worse than New York, two times worse than London and also ranks behind Singapore and Tokyo in terms of air quality.
Only 50 days in 2013 were registered as “clear” on a local pollution scale, the Hedley Environmental Index. More shockingly, around nine preventable deaths and more than 400 hospitalisations occur each day in the city as a devastating result of air pollution.
The “vertical city” is a victim of its design: Hong Kong festers in roadside emissions and regional smog as pollution gets trapped amongst the city’s many high-rises, particularly on days with little wind.
And it’s not getting better. While there has been some small improvement in the reduction of particulate matters that travel deep into our airways, noxious gases in the air are on the rise, says Professor Hak Kan Lai, a research assistant professor in epidemiology and biostatistics at the Hong Kong University’s School of Public Health.
“Gas pollution, such as roadside emissions including nitrogen dioxides and sulphur dioxide, is getting worse every month. The result is that Hong Kong’s air quality consistently exceeds the WHO guidelines by more than 300 per cent.”
The WHO guidelines don’t even represent “good quality air”, warns Professor Anthony Hedley, creator of the Hedley Environmental Index and Emeritus Professor at the Hong Kong University’s School of Public Health. “You could think of them as standards for ‘safer air’, but I’m not going to call them ‘safe’ as the criteria continues to change the more we discover about the ill effects of air pollution on the body,” he says.
“These events, where Hong Kong’s pollution exceeds acceptable levels, occur on a daily basis,” laments Professor Hedley. “The effect is we’re having a long-term, continuous, high-level exposure to pollutant levels commonly known to be predictably injurious to the body.”
In summary, Professor Hedley says Hong Kong’s air “is not fit to breathe”.
And for children, the picture is even more worrisome. Exposure to chronically high levels of air pollution early in a child’s development has a lasting, irreversible impact on several biological systems such as the brain, the lungs and the immune system – meaning even just a few years in the city can impact your child’s health.
Is the pollution in Hong Kong worse for kids?
Children are still growing. Their bodily systems are immature in comparison to adults: they have less efficient detoxification systems, developing lungs that are more permeable by pollutants, and weaker immune systems that render them less able to handle toxic air pollutants.
“Given the fact they’re in a very rapid growth phase, this means that the growing cells, tissues and organs are more readily influenced by certain types of pollution,” explains Professor Hedley.
Adjusting for body mass index, children have a higher respiratory minute volume – the volume of gas inhaled and exhaled from our lungs per minute – than adults: 400 ml/min/kg compared with 150 ml/min/kg.
As children are also prone to mouth breathing due to enlarged adenoids, they lose the benefit of nasal filtering, with the result that more air pollutants end up in the lower airways. Add a child’s increased activity rate, where they take in more breaths per minute, and the resultant exposure of the lungs to air pollutants is even greater.
When children are exposed to air pollution, the lungs and cardiovascular system are the first to take a hit. “Every lungful of air laden with pollutants has the potential to cause damage to the tissues, which manifests itself by causing inflammation,” explains Professor Hedley.
A child affected by exposure to air pollution may have increased phlegm, appear wheezy and begin coughing. In more severe cases, it can trigger asthma, result in infections and even bring about a bronchitic reaction. But in some children, the effects may be silent, and not appear until many years later.
Each pollutant affects the body in different ways. “Polluted air is actually a mixture of pollutants that may have common or specific effects,” explains Professor Ignatius Yu, head of occupational and environmental health at the Chinese University of Hong Kong.
Ozone, for example, which is soluble in the fluids that line the respiratory tract, has the ability to penetrate deeply into the area of the lungs responsible for vital gas exchange with the blood, resulting in breathing problems and possibly triggering asthma.
Carbon dioxide, when inhaled, reacts rapidly with haemoglobin in the blood, preventing the uptake and transport of vital oxygen. Worse still, it hangs around in the blood for hours after exposure.
Nitrogen dioxide and sulphur dioxide suppress the immune system and place a child at an increased risk of respiratory infections.
Some children, of course, are more susceptible to the harmful effects of air pollution than others. Those with underlying chronic lung disease, particularly asthma, are potentially at greater risk than those who don’t have such conditions.
Overall, Professor Yu cautions that the long-term effect of air pollution on children is suffocating. “Inflammation reduces lung function,growth and a child’s cardio-pulmonary fitness. It reduces the volume of oxygen the lungs can take in and breathe.”
To play, or not to play?
It’s a terrible dilemma: we know children should exercise, but exercise speeds their breathing and increases the throughput of air through their airways.
“If children exercise in polluted air, they’re dumping more of this rather dangerous cocktail of particles and gasses into their body system at a higher level than if they were leading a more sedentary lifestyle,” explains Professor Hedley.
Even Professor Lai struggles to find a solution of ensuring his children, aged nine and five, get enough exercise. “I am also worried… There are obviously beneficial effects to exercise, but there are harmful effects for exposure to air pollution.”
Playing in urban parks makes little difference. “The residential locations in Hong Kong are densely packed, so the positive impact of the country parks are not felt,” explains Professor Lai. “There is a lot of overseas literature that finds proximity or distance from highways and traffic is very important… the closer you are the more exposure.”
Moving children’s activities from high-traffic areas to the trails of the country parks may help, but it’s not enough, says Professor Hedley. “The point is, people need to understand that they’re making a compromise… the ambient levels of air pollution are extremely high across the whole territory.”
As a compromise, Professor Lai takes his children to play indoor sports, like badminton and table tennis.
Yet, he admits: “Honestly? It’s better for children to grow up in areas where the pollution is not so bad and move to Hong Kong when they’re older.” As that’s not possible for many, Professor Yu suggests regular holidays to places with better quality air may give a child’s lungs a break.
But for those who don’t have the luxury of escaping the city, the message is clear: reduce a child’s exposure to high-risk levels of air pollution, particularly when playing.
Hong Kong issues the Air Quality Health Index (AQHI) to indicate the state of the city’s air. The index is based on the cumulative health risk attributable to the three-hour moving average concentrations of high-risk air pollutants.
According to a letter issued by the Education Bureau to all schools in late 2013, children should reduce their level of activity when the AQHI measures 7 (“serious”) and above. By AQHI 8, activities should be reduced to a minimum; in AQHI 10+, children should be kept indoors.
However, Sum Yin Kwong, CEO of Hong Kong’s Clean Air Network (CAN), suggests parents should also keep an eye on the WHO standards, and make their own decisions. “Hong Kong citizens have no way of knowing how serious their level of exposure is every day – the Government’s data is not easily accessible and Hong Kong’s air quality standards, called Air Quality Objectives (AQOs), are over 25 years old and are severely lax and outdated.” CAN issued an air quality-mapping app, “HKCAN”, last year, which compares the city’s air pollution to the WHO standards and provides a better overall picture than just the AQHI.
Keeping your child healthy and nourishing them with a good diet will help to equip them with a strong immunity to battle the effects that some air pollutants have on the body – and life in general. “We can’t say definitely that there is a connection with stronger immunity and [the ability to cope better with] exposure to air pollution – pollution is pollution – but it may help, of course, if your child is healthy and strong,” says Professor Yu.
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