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Basics of air pollution

What is air pollution?

Air Pollution is a complex mixture of gases and particles that are formed from burning fuels and other materials or photochemical reactions in the atmosphere.

Pollutants that are emitted directly into the air are called primary pollutants and they come from different sources:

Mobile sources like cars, trucks, boats and planes

Stationary sources like homes, power plants and factories which used polluting fuels and outdated technology

Natural sources like wildfires and volcanoes

Secondary pollutants are a bit more complex than primary pollutants and are formed as a result of primary pollutants reacting with the molecules in the atmosphere such as molecular oxygen, water and hydrocarbons. Both primary and secondary pollutants can be transported to great distances from their original source by daily and seasonal wind patterns.

Types of air pollutants

Some of the major air pollutants that are harmful to our health are shown below

Nitrogen dioxide (NO2)

Nitrogen dioxide is a gas and is a major component of urban air pollution episodes. Man-made sources of nitrogen oxides, including nitrogen dioxide, are vehicles, power stations. Diesel vehicles are major contributors in urban areas. Roadside levels are highest where traffic is busiest.

Carbon Monoxide (CO)

Carbon monoxide is a colourless, odourless, and very poisonous gas. It is formed as a by-product of incomplete combustion processes involving carbon based energy sources, such as the burning of petrol, coal or wood. The biggest sources of carbon monoxide comes from vehicles, especially when they are moving slowly or when the engine is idle.

Volatile Organic Compounds (VOCs)

Volatile Organic Compounds is the name for a group of chemicals that start as liquids or solids, but disperse into the air very easily. You can often tell when things contain a lot of these chemicals because they can have a very strong smell after you have used them, like lots of paints and varnishes. They also come from products like air fresheners, hair sprays and cleaning products.

Mould

Mould tends to grow in damp places. The damp might be because of leaking pipes or roofs, but is often because of condensation. Condensation often forms in bathrooms from the use of showers or baths with inadequate ventillation, in kitchens from washing up and from cooking, and also from drying clothes indoors.

Ozone (O3)

Ozone is made by a chemical reaction between the sun’s rays and organic gases and oxides of nitrogen emitted by cars, power plants, chemical plants and other sources. Ozone is usually highest in the spring and summer and lowest in the winter. Ozone levels are highest during the afternoon and are often higher in the country than in towns. Ozone is a major component of summer air pollution episodes.

Particulate Matter (PM)

Particulate matter is a mix of solids and liquids, including carbon, complex organic chemicals, sulphates, nitrates, mineral dust, and water suspended in the air. Man-made particulate matter mainly comes from industry, building work, diesel and petrol engines, friction from brakes and tyres, and dust from road surfaces. Diesel engines tend to produce much more than equivalent petrol engines. Natural sources of particulate matter include volcanoes, sea spray, pollen and soil. It is also formed in the atmosphere when gases such as nitrogen dioxide and sulphur dioxide are changed in the air by chemical reactions.

Sulfur dioxide So2

Sulphur dioxide is a colorless gas, with a pungent, suffocating smell. It’s produced by burning sulphur-containing fuels such as coal and oil, like vehicles, power generation.

CO2

CO2 is a colorless, odorless gas which is caused by fossil fuels. CO2 emitted by human respiration can have negative effects on the efficiency and productivity of employees, and on their health if the air renewal of the room is bad.

Hong Kong's air

How bad is Hong Kong's air?

Air pollution in Hong Kong is considered a serious matter. Haze is often seen hanging over the city and can last for many days depending on the direction of the wind. As of the year 2020 the PM2.5 levels of Hong Kong was almost double than that of WHO safe levels but due to more stringent WHO levels as of 2021 Hong Kong’s air quality is far behind.The World Health Organization,(WHO) recommends PM2.5 levels to be no higher than 5 µg/m3 as per WHO’s new air quality guidelines. ‘

Despite the significant improvement in air quality, at both ambient and roadside levels, between 2013 and 2017 as the Hong Kong Government implemented vigorous emission control schemes, Hong Kong’s air quality is still far from satisfactory.

Hong Kong is falling behind major international cities, like London, Singapore, New York, Tokyo, in terms of annual average of particulate matters (PM2.5) level. The nitrogen dioxide levels at roadside are still doubling the safe level recommended by World Health Organisation. Global studies show that these air pollutants are causing cancer, respiratory diseases and circulatory diseases, which consequently, jeopardising the well-being of Hong Kong citizens.

What causes air pollution in Hong Kong?

Hong Kong has been facing two air pollution issues, namely local street-level pollution and regional smog problem.Commercial vehicles are the main source of street-level pollution. Let us look into some of the sources in more details.

Motor vehicles

Motor vehicles largely contribute to local street-level pollution which typically impacts the largest groups of people. Diesel vehicles such as trucks and buses are the biggest culprits as they are the main source of vehicular emissions. An increase in vehicles on the road over the past two decades has also been attributed to a sharp increase in air pollution in Hong Kong. It is considered by many to be difficult to clean up local street-level pollution because of the pollutants trapping themselves beside tall skyscrapers that surround streets.

Marine emissions

Hong Kong has an efficient and well-run system of ferries. However, this efficiency comes at an expense. Many of these ferries are still motorized and require fossil fuels to operate. Emissions from these ferries are usually very visible with its trademarked black smog. Although a switch to electric ferries might help reduce some emissions in the ferry, overstressing a power grid to charge these ferries could be counterproductive.

Power plants

Like in many other places, the use of power plants and combustion of fossil fuels has filled the air with a variety of pollutants. One of the more iconic sights in Hong Kong is the Lamma Power Station located on Lamma Island. That power station alone feeds tens of thousands of tonnes of air pollutants to Hong Kong’s air. Much of Hong Kong’s power still relies on harmful sources and with clean, alternative energy still being relatively niche and costly, a drastic change in the near future does not seem imminent.

Regional Smog from Mainland China

It is often believed that Pearl River Delta (PRD) region is a major contributor of the smog that lingers around Hong Kong, especially in the winter months. Smog is caused by a combination of pollutants from motor vehicles, marine vessels, industry and power plants both in Hong Kong and in the PRD region.

How will air pollution affect Hong Kong?

Health

The Hedley Environmental Index from the School of Public Health of the University of Hong Kong estimated polluted air has caused an additional 98,000 hospital bed days, 1.69 million doctor visits and 1,300 premature deaths, in one single year of 2021. Latest research also shows that air pollution is a risk factor for increasing hospitalizations of preschool wheeze in Hong Kong.

Economy

In 2021, as per the Hedley Environmental Index, the recorded negative impact of air pollution to the economy was HK $20 billion. These costs can be categorized as direct costs of healthcare, indirect costs due to lost productivity and intangible costs attributable to pain and suffering (defined as “loss of healthy life value”). It is estimated that 1,300 premature deaths can be avoided in 2021 if air quality of Hong Kong was improved.

Society

Social deprivation and air pollution have many correlations with one another. In a research conducted by HKU, it found that people categorized with lower income, lower educational attainment or the unemployed saw a much higher death rate when it came to premature deaths linked to air pollution. Many minority groups in Hong Kong also have experienced some degree of poverty along with a distinct lack of healthcare which in turn, amplifies the impact of air pollution within society.

How can we improve Hong Kong air quality?

What you can do at home?

Improve the energy consumption:

Reduce energy consumption at home. By switching off fans, air-conditioners and lights when you don’t need them and keeping the air-conditioned temperature at 25.5 degree Celsius in summer, you will save energy and money, and reduce air pollution from power stations.
Choose energy efficient appliances and look for the Energy Label when purchasing these products.
Use of fans instead of Air Conditioner.

Improve the Indoor Air Quality (IAQ):

We spend more than 70% of our time at homes, offices and other indoor environment. Below are some easy tips to follow to improve IAQ.
Maintain adequate air ventilation by opening windows.
Clean the filters of air conditioners at regular intervals.
Dispose of perishable food properly to avoid odours.
Remove and clean visible moulds once they are found.

What you can do while commuting?

Greener Transportation:

Planning your route ahead of time will help you find easier ways around traffic congestion – you will save time during your journey and reduce fuel/electricity consumption.
Use public transportation as often as possible – the wide availability of trains, buses, minibuses and ferries in Hong Kong means that most areas can be reached without much expense.

What you can do in school?

Apart from home, you can still do much in school to solve air pollution in Hong Kong.

Clean Air School Action Plan

Interesting facts of Hong Kong’s air

The topic of air pollution in Hong Kong is very interesting. Here are some quick paraphrased versions of various other subtopics:

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