Study linking pollution to all kinds of cancer should prompt greater efforts to clean the air
Hong Kong must convince neighbours in Guangdong and others that the use of cleaner marine fuels will be to the benefit of all
Evidence linking air pollution with cardiopulmonary disease and lung cancer is well documented. The results of a 13-year, Hong Kong-based study by teams of local and British researchers are good reason for heightened concern. The study found that fine-particulate pollution caused mostly by road and maritime traffic is putting elderly Hong Kong people at risk of dying from all kinds of cancer.
The researchers, from the universities of Hong Kong and Birmingham, recruited 66,280 people aged 65 or older between 1998 and 2001, and followed their mortality outcomes up to 2011. They found that every 10mg per cubic metre of increased exposure to tiny airborne particulates known as PM2.5 increased the mortality rate of elderly residents from any cancer by 22 per cent. This included a 42 per cent higher risk of dying from cancer of the upper respiratory tract, a 35 per cent greater risk of dying from cancer of digestive organs such as the liver, bile ducts, gall bladder and pancreas, and, for women, an 80 per cent heightened risk of dying from breast cancer.
The study was confined to Hong Kong. There is therefore great interest in determining whether other urban populations may be at the same risk. A graphic accompanying our recent report showed that Hong Kong has made impressive strides in reducing total air pollution from all causes, but marine and roadside fine-particulate pollution remain potent contributors. The World Health Organisation’s recommended limits for 24-hour and annual concentrations are 25mg and 10mg per cubic metre respectively. Hong Kong’s limits are less stringent at 75 and 35 and often exceeded.
To put the health issue into perspective, Dr Thuan Quoc Thach of HKU’s school of public health says pollution is just one risk factor for cancer, with others such as diet and exercise “more significant and modifiable”. However, the government needs to report on and review its voluntary policies and incentives for retiring old, polluting heavy vehicles and buses from our roads.
Maritime pollution presents a different problem. Since July 1, ocean-going vessels have been required to switch to low-sulphur fuel within local waters – but not Pearl River Delta waters – under a new law to improve air quality. Air pollution knows no boundaries. The importance of getting Guangdong and others on board to improve air quality has long been recognised. The HK-UK joint study should prompt redoubled efforts to convince our neighbours of the benefits of cleaner skies.