Hong Kong's Air Pollution: Causes And Concerns

Air pollution in Hong Kong is a serious problem, with the city ranking 63rd out of 138 in the world for air pollution in 2024. The main sources of air pollution in Hong Kong are motor vehicles, marine vessels, and power plants. The city has one of the highest vehicle densities in the world, with 275 vehicles per kilometre, and diesel vehicles, particularly trucks, buses, and light buses, are the main source of street-level pollution. In addition to vehicular emissions, air pollution in Hong Kong is also caused by the extensive use of plastics in the construction and renovation industry, emissions from power plants, and regional pollution from neighbouring manufacturing hubs in China, such as the Pearl River Delta.

Motor vehicles, especially diesel vehicles

Motor vehicles are a significant contributor to Hong Kong's air pollution. The city has one of the highest vehicle densities in the world, with 275 vehicles per kilometre. Diesel vehicles, in particular, are a major concern as they produce a large number of particulates and nitrogen oxides (NOx). Trucks, buses, and light buses with diesel engines emit toxic pollutants, including CO, NOx, HC, particulate matter, and CO2. The Hong Kong government has acknowledged this issue and implemented measures to address it. In March 2021, they announced the "Hong Kong Roadmap on the Popularisation of Electric Vehicles," aiming to promote the adoption of electric vehicles and improve air quality.

The impact of diesel vehicle emissions on air quality and public health is significant. Diesel exhaust contains a complex mixture of pollutants, including particulate matter, nitrogen oxides (NOx), carbon monoxide (CO), and volatile organic compounds (VOCs). These pollutants can have both short-term and long-term effects on human health. Short-term exposure to diesel exhaust can cause respiratory irritation, aggravate asthma and other lung diseases, and increase the risk of cardiovascular problems.

Long-term exposure to diesel emissions has been linked to more severe health issues. Numerous studies have associated it with increased risks of lung cancer, cardiovascular disease, and respiratory problems, particularly in children and the elderly. Diesel particulate matter is a complex mixture of solid and liquid particles, which are mostly in the fine and ultrafine range. These fine and ultrafine particles can penetrate deep into the respiratory system, reaching the alveoli in the lungs, and even enter the bloodstream. Once inhaled, they can cause oxidative stress, inflammation, and DNA damage, leading to various adverse health effects.

To combat the harmful effects of diesel vehicle emissions, the Hong Kong government has implemented several measures. They introduced the Clean Air Plan for Hong Kong in 2013, which outlined strategies to tackle air pollution from power plants, land and sea transport, and non-road mobile machinery. This included the implementation of a comprehensive vehicle emission control programme, which has shown significant improvements in air quality. As of 2020, roadside levels of nitrogen dioxide, respirable suspended particulates, fine suspended particulates, and sulphur dioxide have decreased by up to 50% compared to 2010 levels.

In addition to government initiatives, individuals can also play a role in reducing the impact of diesel vehicle emissions. For example, people can opt for more sustainable modes of transportation, such as walking, cycling, or using public transportation. When purchasing a vehicle, individuals can consider choosing electric or hybrid options, which produce fewer emissions. Proper maintenance of vehicles is also essential, as well-maintained engines tend to emit fewer pollutants. Furthermore, public awareness and education about the health risks associated with air pollution can empower individuals to take precautionary measures, such as limiting outdoor physical exertion on high-pollution days.

Construction and renovation work

The extensive use of plastics in the construction and renovation industry also contributes to the problem. Plastics can generate airborne microplastic dust during renovation, building, bridge, and road reconstruction projects, further adding to the air pollution levels. The deterioration of building materials over time can also release microplastics into the air, posing long-term environmental challenges.

To address the impact of construction and renovation work on air quality, Hong Kong has implemented regulations and initiatives. The Air Pollution Control Ordinance regulates emissions and aims to improve air quality and protect public health. However, the complete replacement of older, high-polluting construction equipment with more environmentally friendly alternatives will take time due to their long service lives.

In addition to regulatory measures, Hong Kong has also focused on public awareness and protection. The Environmental Protection Department (EPD) plays a crucial role in monitoring local air quality and communicating health risks to residents through the Air Quality Health Index (AQHI). The AQHI provides a scale and health risk categories to help people understand the potential dangers and take necessary precautions, especially on days with high pollution levels.

Furthermore, the Hong Kong government has recognised the need for a long-term strategy to enhance air quality. The Clean Air Plan for Hong Kong 2035 outlines future goals and strategies to tackle air pollution from various sources, including construction and renovation work, power plants, and land and sea transport. By implementing comprehensive plans and collaborating with regional partners, Hong Kong aims to mitigate the adverse effects of construction and renovation work on air quality and create a healthier environment for its residents.

Fireworks

In 2007, there were concerns about the environmental impact of nightly fireworks at Hong Kong Disneyland on nearby residents. William Fitzgerald, a representative of a homeowners group, stated that high concentrations of chlorate were leaking into the ground and contaminating underground water. In response, Disney switched to compressed air technology in its California theme park in 2004, reducing smoke and noise. However, Disney has not adopted this technology for low-level fireworks at its Hong Kong park, claiming that it is not suitable.

Hong Kong's Environmental Committee has examined the pollution generated by the nightly fireworks and its potential impact on residents of nearby areas. While Disney asserted that its fireworks met government standards, a professor of chemical and biomolecular engineering at Clarkson University disagreed, stating that the fireworks could cause issues for asthma sufferers and those with other breathing problems.

Ronald Lo and Roy Chan, MSc students of Environmental Science and Management at the Hong Kong University of Science and Technology, analysed the Environmental Protection Department's air pollutant concentration data during firework displays in 2023 and 2024. They found no significant increase in sulphur dioxide (SO2) concentrations, and while there were fluctuations in nitrogen dioxide (NO2) levels, the increases were not attributed to the firework displays. However, they did observe spikes in particulate matter (PM2.5 and PM10) levels during the New Year and Chinese New Year fireworks, with levels up to four times higher than pre-event levels. These effects were transient, as particulate matter levels returned to normal within three hours.

The Hong Kong government has proposed holding monthly firework displays to attract tourists, and studies suggest that these events can contribute to short-term air pollution while still meeting Air Quality Objectives (AQO) standards. The students who conducted the study recommended on-site measurements to further examine the dispersion characteristics of fireworks and their impact on air quality.

Power plants

The Hong Kong government has recognised the problem and taken steps to address it. In 2013, they released the first Clean Air Plan, which outlined measures to tackle air pollution from power plants, including reducing emissions and strengthening collaboration with neighbouring regions. The government has also set Air Quality Objectives (AQOs) and is committed to reviewing them regularly to improve air quality and protect public health. The current AQOs came into effect on January 1, 2022, and a new review round is underway to further tighten standards.

The Environmental Protection Department (EPD) plays a crucial role in monitoring local air quality and informing the public about health risks through the Air Quality Health Index (AQHI). This index is reported on a scale of 1 to 10+ and categorised into five risk levels: Low, Moderate, High, Very High, and Serious. The EPD provides health advice and suggested precautions based on these categories.

In addition to government efforts, Hong Kong has seen a shift towards electric vehicles, with the government announcing a roadmap for the popularisation of electric vehicles in 2021. This transition is expected to positively impact air quality, as vehicle emissions, particularly from diesel engines, are a significant contributor to local street-level pollution.

While progress is being made, power plants continue to be a key factor in Hong Kong's air pollution, and further efforts are needed to mitigate their environmental impact.

Pollution from factories in the Pearl River Delta

Hong Kong's air pollution is caused by a combination of local and regional factors. The Pearl River Delta, a densely populated and urbanised region in Southern China, is one of the main contributors to regional smog in Hong Kong.

The Pearl River Delta, a network of cities in the province of Guangdong, has been a manufacturing hub for Hong Kong-based companies since the 1980s. In 2001, nearly 5% of the world's goods were produced in the Greater Pearl River Delta, with over 70,000 Hong Kong companies operating factories in the region. The industrial output of the Pearl River Delta was dominated by state-owned enterprises, but private enterprises and joint ventures have increased their share of output over time.

The economic reforms in Mainland China during the 1980s provided favourable conditions for Hong Kong industrialists to relocate their factories there. The Pearl River Delta offered lower land rents, cheaper labour costs, and less stringent pollution controls than Hong Kong. By the 1990s, over 80% of factories had been relocated to Mainland China, with most moving to the Pearl River Delta region.

The pollution from these factories contributes significantly to the air pollution in Hong Kong. The governments of Hong Kong, Guangdong Province, and Macau have been working together to address this regional issue. They have established the Guangdong-Hong Kong-Macao PRD Regional Air Quality Monitoring Network, which provides real-time air quality data and assists in formulating control measures.

The air pollution in Hong Kong and the Pearl River Delta is influenced by local meteorological factors, such as inversions and sea-breeze convergences, which can cause temporal differences in pollution peaks between the two regions. Tropical storms and monsoon patterns can also impact pollution levels, with certain storm positions resulting in higher pollution episodes in both Hong Kong and the Pearl River Delta cities.

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