HKU Bulletin May 2009 (Vol. 10 No. 2)

8 9 The Poor Hurt More on Bad Pollution Days The Depar tment of Communi ty Medicine and Department of Microbiology, in collaboration with the Hospital Authority and the Chinese Universi ty of Hong Kong, showed the excess risk could be more than double in high-versus low-deprivation areas, depending on the pollutant, after correlating the SDI with readings from the government’s air pol lution monitoring network and mortality rates. “We know already that mortality is affected by air pollution but we wanted RESEARCH says. “Air pollution is an important cause of injust ice and this aspect should be given serious consideration by policy makers.” The study was conducted as part of an on-going regional project, Public Health and Air Pollution in Asia (PAPA), which was initiated in 2004 with funding from the US Health Effects Institute. It is quantifying air pollution risks in major cities, including Hong Kong, Shanghai, Wuhan and Bangkok. Apart from looking at air pollution and social deprivation, Wong and his colleagues also led a study for PAPA to look at how influenza modifies the health effects of air pollution in Hong Kong. A significant effect was found chiefly for ozone, which, when combined with higher influenza levels, increased excess mortality for respiratory disease by 0.59 per cent and for chronic pulmonary disease by 1.05 per cent. The researchers also observed higher hospitalization rates. “These are substantial changes compared with the magnitude of air pollution effects of around one per cent estimated in most studies,” Wong says. Both the influenza and the social depr ivat ion studies were publ ished recen t l y i n Env i r onmen t a l Hea l t h Perspectives . People in deprived areas have higher mortality rates from air pollution, says study. P eople living in socially deprived areas in Hong Kong are more likely than their better- off neighbours to die from exposure to air pollution. The finding was made in a study that links air pollution to a Social Deprivation Index (SDI), originally devised about 10 years ago to determine health care needs in the community. N New Terretories Kowloon Lantau Island Hong Kong Island MAP KEY SDI Categories 1 - Low social deprivation 2 - Middle social deprivation 3 - High social deprivation Sub-urban Area are more likely to smoke, they exercise less and their nutrition is not so good. These reduce their biological capacity to withstand environmental hazards that cause inflammatory changes and make them more vulnerable to the risk of air pollution,” he says. The study looked at levels of four di fferent ai r pol lutants and tracked readings for several days afterwards, to see if there was a lagged impact. It also considered respiratory and cardiovascular mortality separately, as these have both been linked to higher air pollution levels in other studies. Mortality rates in middle and high- SDI areas were higher during pollution episodes, and high-deprivation areas suffered particularly when nitrogen dioxide and sulphur dioxide emissions rose. For example, the day after a high sulphur dioxide pollution episode, the excess risk of cardiovascular death was more than three times greater in a high SDI area than that for people in low-SDI areas (2.88 per cent excess deaths for every 10 micrograms increase of sulphur dioxide in high-SDI areas, against 0.89 per cent in low). This could translate into hundreds of deaths each year, depending on the frequency of pollution episodes. “This is a social justice issue,” Wong to quantify it for those who are deprived. These people are not only economically deprived, they are also more vulnerable to environmental problems,” Dr Wong Chit Ming, Associate Professor of Community Medicine, says. The SDI i ncorporates data on unemployment, households earning a low income, people with no schooling, one-person households, people never mar r i ed and households l i v i ng as sub-tenants. “People in high-deprivation areas