NGO Green Power has urged the Hong Kong government to better regulate ozone precursors as hot weather exacerbates air pollution across the city.

Chemical compounds – such as nitrogen oxides, methane, Volatile Organic Compounds (VOC) and carbon monoxide – form ground-level ozone by reacting in the lower atmosphere in the presence of sunlight. Ground-level ozone attacks and inflames lung tissue, but reducing underlying pollutants prevents harmful smog.

According to a Sunday press release, Green Power’s director, Cheng Luk-ki, said VOCs – which are emitted through oil and gas operations, petrol evaporation and chemical solvents – should be better regulated.

See also: How extreme heat became the deadliest silent killer among world weather disasters

“In the future, the public’s health may be affected by both high temperatures and air quality at the same time,” the press release said.

Last week, Hong Kong sweltered amid a days-long heatwave. Whilst rain brought some respite over the weekend, the Observatory predicts highs of 35 degrees Celsius by the end of this week.

Cooling measures for hottest areas

Green Power’s review of Hong Kong’s air quality situation in 2025 found that 15 air quality monitoring stations recorded “a total of 2,080 hours at High, Very High and Serious levels – collectively referred to as ‘High Risk (HR) hours.'”

See also: How Hong Kong’s elderly face deadly heat inside cramped cage homes

Cheng said Hong Kong was affected by a northern Chinese dust storm last April, pushing up the statistics. However, the NGO also noted that overall air quality has been improving thanks to the city’s diversification away from coal towards natural gas, as well as efforts to tighten emission standards for fuel-powered vehicles.

The director said he had analysed last summer’s Air Quality Health Index data, and found that the nine days ranked as “high risk” all saw temperatures exceeding 29 degrees Celsius, “demonstrating a strong connection between heat and air quality.”

He warned that hot weather will become more frequent, as he urged the authorities to take action in the territory’s hottest districts.

The NGO recommended cooling measures in Tuen Mun, Tai Po, North District, Yuen Long and Tung Chung, “such as increasing greenery coverage, revitalising local rivers, and incorporating more ventilation corridor designs.”

See also: How extreme heat became the deadliest silent killer among world weather disasters

Hong Kong has already warmed by 1.7 degrees Celsius since the Industrial Revolution, research NGO Berkeley Earth says. Heat and humidity may reach lethal levels for protracted periods by the end of the century, according to a 2023 study, making it impossible to stay outdoors in some parts of the world.