2024 Annual Air Quality Review

Pollution Reduced But Still Incurred High Health and Economic Costs

Each year, CAN reviews data from the Environmental Protection Department’s air quality monitoring stations in the previous year to analyse local pollution trends. The pollutants studied are nitrogen dioxide, ozone, fine suspended particulates (PM2.5), respirable suspended particulates (PM10) and sulphur dioxide.

Overview: A Drop in Pollutant Levels Generally, But Most Still Exceeded WHO Standards by Far

The World Health Organization (‘WHO’) has established safe standards (WHO Air Quality Guidelines (‘AQGs’)) for air pollution based on its impact on human health, and Hong Kong’s air quality has not been able to meet such standards. The highest exceedance was the annual average roadside nitrogen dioxide concentration (+550%), followed by roadside PM2.5 concentration (+304%).

The School of Public Health of The University of Hong Kong estimates that air pollution led to 3,508 premature deaths and economic loss of $42 billion in Hong Kong in 2024 [1].

1. Roadside Nitrogen Dioxide Levels Most Concerning

The annual average roadside nitrogen dioxide concentration was 65µg/m3, exceeding the WHOAQGs by 550% and the air quality objective (AQO) in Hong Kong, 40µg/m3, by 63% [2] respectively.

Roadside nitrogen dioxide concentrations mostly reflect vehicle emissions. While the number of electric buses and private vehicles has increased in recent years, the green transition of the other types of commercial vehicle still lags behind. The exceedingly high level of nitrogen dioxide concentration shows that Hong Kong still has to expedite the transition to green transport for all kinds of vehicle.

2. PM2.5 Levels Exceeded WHOAQGs and Proposed AQO in Hong Kong

The annual average roadside PM2.5 concentration was 20.2µg/m3, exceeding the WHOAQGs by three times and the AQO proposed by the Environment and Ecology Bureau, 15µg/m3, by 35% [3] respectively. The annual average concentration at general stations was 15.1µg/m3, exceeding the WHOAQG by two times and slightly exceeded the proposed AQO in Hong Kong by 1%.

PM2.5 has been classified as a group one carcinogen [4], and found to increase the risk of many other conditions, including poor lung function [5], reduced birth weight [6], early birth, diabetes [7].

3. Ozone Level Remained High

The annual ozone concentration rose to a historic high in 2023 (61µg/m3), While it dropped to 54.6µg/m3 in 2024, the concentration level was still very high. The Tap Mun station reading, which is taken to reflect the concentration of regional ozone by the Environmental Protection Department [8], also remained high.

4. Kwai Chung and Sham Shui Po Suffered Most from Nitrogen Dioxide and Sulphur Dioxide Pollution, While PM2.5 and PM10 Affected Yuen Long the Most

Among the 15 general monitoring stations in Hong Kong, the Kwai Chung and Sham Shui Po stations recorded the highest annual average concentration levels of nitrogen dioxide and sulphur dioxide (see table 3).

Tap Mun station, which is away from urban emission sources, had the highest ozone concentration among the stations, reflecting that ozone pollution was mainly a regional problem.

5. Policy Recommendations

5.1 Expediting the Transition to Green Transport

Roadside air pollution remained at concerning levels, which again meant the Government should expedite the transition to green transport.

In 2024, the Environment and Ecology Bureau released the Green Transformation Roadmap of Public Buses and Taxis, which is a welcome step, and the Government should set yearly targets and ensure the roadmap is implemented without delay.

The Environment and Ecology Bureau is also implementing pilot schemes on electric public light buses and ferries.

We recommend that the Government formulate roadmaps for the green transformation of other areas of road transport and marine transport, including public light buses, good vehicles, local and river vessels.

Please find our most recent response to the Government’s green transport policy here.

5.2 Explore Policy Tools to Encourage the Adoption of Onshore Power

We have found that cruise ships docked at Kai Tak Cruise Terminal, in close proximity to residential areas, have been emitting nitrogen dioxide of a level nearly nine times of the WHOAQGs (see details here).

The Chief Executive has announced plans to develop Hong Kong into a green maritime centre in the Policy Address in 2023 and 2024. The Government will invite tenders for the operation of the Kai Tak Cruise Terminal in the near future. We urge the Government to develop onshore power systems (‘OPS’) at cruise terminals and encourage the Government to explore policy tools to encourage cruise ships berthing in Hong Kong to use shore power, to eliminate emissions from the vessels while they are at berth.

Other key maritime regions have mandated or will mandate cruise ships to use shore power in recent years. In mainland China, shore power infrastructure has been expanding at a number of ports [9]. In the European Union, the revised Alternative Fuels Infrastructure Regulation made in the context of the ‘Fit for 55’ package requires container and passenger ships, including cruise ships, to use shore power at major ports by 2030, and those ports to construct shore power infrastructure by the same date [10]. Since 2014, California, U.S. has been mandating in phases cruise ships to connect to shore power [11] [12].

5.3 Curbing Ozone Pollution

The Environmental Protection Department announced earlier that the three-year study ‘Characterization of photochemical ozone formation, regional and super-regional transportation in the Greater Bay Area’ was completed in 2024 [13]. We recommend that the Government release the findings in the near future and, based on the findings, formulate policies to curb ozone pollution.

5.4 Tightening AQOs

To tighten the AQOs specified in the Air Pollution Control Ordinance, Cap. 311, the Administration has recently tabled the Air Pollution Control (Amendment) Bill 2024 in the Legislative Council. The Administration has proposed tightening only some of the AQOs; notably, it has proposed that those for nitrogen dioxide (averaged annually) and ozone (averaged over eight hours) should remain the same. As discussed above, nitrogen dioxide and ozone levels have been of particular concern.

We recommend that the AQOs for nitrogen dioxide (averaged annually) and ozone (averaged over eight hours) be tightened and set at at least interim target two
set by the WHO, and those for other pollutants to be further tightened. In the long term, the WHOAQGs should be adopted as local AQOs. Please find our full submission to the Bills Committee of the Legislative Council on this amendment bill here.

5.5 Collecting Data on Indoor Air Quality

While the Government has been monitoring ambient and roadside air quality systematically for many years, there is a lack of data about indoor air quality across Hong Kong, although we spend the majority of our time indoors. Studies conducted by CAN and other organisations with a relatively small sample size have suggested the need for further research, especially into carbon dioxide concentration levels at spaces frequented by children and PM2.5 pollution at subdivided units. For example, at one activity room for children at a non-profit centre in Sham Shui Po, we have recorded carbon dioxide levels exceeding 3,000 parts per million (ppm) continuously for two hours seven times over the course of 36 days from August to September 2024. This was three times the ‘good’ level under the Indoor Air Quality Certification Scheme for Offices and Public Places of the Environmental Protection Department (1,000ppm). Such high levels of carbon dioxide can cause headaches and nausea [14].

Besides, the Government relies on voluntary actions of the private sector to manage indoor air quality in Hong Kong. The major policy initiative about indoor air quality is the above-mentioned Indoor Air Quality Certification Scheme for Offices and Public Places, and only 2,250 spaces participate in it [15].

In the Clean Air Plan 2035, the Government states that it would monitor indoor air quality at selected sites with micro-sensors. We recommend that the Government conduct a study on the indoor air quality at various sites, particularly those frequented by vulnerable groups, such as children, the elderly and people with respiratory conditions. Such sites would include kindergartens, schools, elderly homes and inadequate housing spaces in Hong Kong.

Based on the data collected, the Government should formulate more rigorous measures to improve indoor air quality in Hong Kong.

Please find our full submission on the regulation of basic housing units with data and recommendations about indoor air quality here.

January 2025

Reference

[1] ‘Hedley Environmental Index,’ School of Public Health, The University of Hong Kong, accessed 14 January 2025, https://hedleyindex.hku.hk/en/historical-data.
[2] ‘Public consultation on Air Quality Objectives review launched,’ Hong Kong Government, 31 August 2023, https://www.info.gov.hk/gia/general/202308/31/P2023083100287.htm.
[3] Ibid.
[4] International Agency for Research on Cancer, WHO, ‘Agents classified by the IARC Monographs, Volumes 1–137,’ accessed 4 January 2025, https://monographs.iarc.who.int/list-of-classifications.
[5] Cui Guo et al., ‘Long-Term Exposure to Ambient Fine Particulate Matter (PM2.5) and Lung Function in Children, Adolescents, and Young Adults: A Longitudinal Cohort Study,’ Environ Health Perspect 127, no. 12 (2019): 127008, https://pubmed.ncbi.nlm.nih.gov/31873044/.
[6] Rakesh Gosh et al., ‘Ambient and household PM2.5 pollution and adverse perinatal outcomes: A meta-regression and analysis of attributable global burden for 204 countries and territories,’ PLoS Med 18, no. 9 (2021): e1003718, https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003718.
[7] Yuyuan Yi et. al, ‘Life Course Associations Between Ambient Fine Particulate Matter and the Prevalence of Prediabetes and Diabetes: A Longitudinal Cohort Study in Taiwan and Hong Kong,’ Diabetes Care, 48, no. 1 (2025): 93–100, https://diabetesjournals.org/care/article-abstract/48/1/93/157458/Life-Course-Associations-Between-Ambient-Fine?redirectedFrom=fulltext.
[8] ‘Air Quality in Hong Kong 2021,’ Environmental Protection Department, 2021, https://www.aqhi.gov.hk/common/api_history/english/report/files/AQR2021e_final.pdf.
[9] ‘Mainland China following the environmental protection trend and the number of shore power berths increased to 7,500 in 2021,’ HKFeature, 16 December 2023, accessed on 16 January 2025, HKFeaturehttps://hkfeature.com/local/%E5%85%A7%E5%9C%B0%E8%BF%BD%E7%92%B0%E4%BF%9D%E6%BD%AE%E6%B5%81-2021%E5%B9%B4%E5%B2%B8%E9%9B%BB%E6%B3%8A%E4%BD%8D%E5%A2%9E%E8%87%B37500%E5%80%8B/ (Chinese only).
[10] ‘Alternative Fuels Infrastructure,’ European Commission, accessed on 16 January 2025, https://transport.ec.europa.eu/transport-themes/clean-transport/alternative-fuels-sustainable-mobility-europe/alternative-fuels-infrastructure_en.
[11] ‘California approves updated “At-Berth” regulation, expanding efforts to cut pollution from ships in California ports,’ California Air Resources Board, 27 August 2020, https://ww2.arb.ca.gov/news/california-approves-updated-berth-regulation-expanding-efforts-cut-pollution-ships-california.
[12] In 2013 to 2015, there were discussions on the technical feasibility and a market demand assessment conducted by the Government about OPS in Hong Kong. It was assessed that the proposed OPS at the Kai Tak Cruise Terminal would be significantly underutilised in the foreseeable future due to the relatively small number of cruise vessels that could use OPS and that the OPS systems would be costly to install. ‘Provision of on-shore power supply at Kai Tak Cruise Terminal,’ Environmental Protection Department, paper for the Panel on Environmental Affairs of the Legislative Council (CB(1)895/14-15(03)), 2015, https://www.legco.gov.hk/yr14-15/english/panels/ea/papers/ea20150602cb1-895-3-e.pdf.
[13] ‘Overview of air quality unveiled,’ Hong Kong Government, 7 February 2024, https://www.news.gov.hk/eng/2024/02/20240207/20240207_153655_858.html.
[14] ‘Carbon Dioxide’, Wisconsin Department of Health Services, accessed 4 January 2025, https://www.dhs.wisconsin.gov/chemical/carbondioxide.htm.
[15] ‘Certified Premises List,’ Environmental Protection Department, accessed 14 January 2025, https://www.iaq.gov.hk/en/iaq-certification-scheme-certified-premises-list/.