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April 26th, 2015:

Hong Kong’s elderly face special air pollution risk, unique study finds

Research over 13 years shows a link between fine particles and increased death rates

A groundbreaking tracker study offers evidence for the first time that the fine suspended particles known as PM2.5 lead to a higher death rate among elderly people in the city.

Conducted by a team from the University of Hong Kong’s School of Public Health, the study successfully tracked more than 60,200 elderly Hongkongers for 10 to 13 years, from 1998 to 2011, and analysed the mortality rate in correlation to the levels of PM2.5 where they lived. There are participants from all 18 districts.

Its results were published yesterday in journal Environmental Health Perspectives.

“There have been studies on the lethalness of PM2.5 and other pollutants but no data at all in Asia … this study provides new evidence on mortality from the long-term effects of being exposed to PM2.5 among the elderly,” said HKU associate professor Dr Wong Chit-ming, of the School of Public Health, who led the study. “This refutes [claims] that perhaps Asians are less susceptible to the effects of PM2.5.”

The study – which used Nasa satellites to narrow down PM2.5 levels by square kilometre – was the first of its kind in Asia not just Hong Kong, and was rare worldwide in its scope and detail, Wong said. While most overseas studies compare different cities, HKU’s examined Hong Kong in detail, and can therefore give more accurate results specific to the city.

The study is also relevant as Hong Kong grapples with a fast-ageing population.

Every 10-unit increase in PM2.5 correlated to a 22 per cent hike in deaths by cardiovascular causes, a 42 per cent increase in coronary heart disease and a 24 per cent increase in strokes.

The study took into account participants’ individual variables – health records, income, education level and lifestyle habits such as smoking – as well as the socio-economic status of the communities in which they lived, Wong said. The variables were factored in to the calculations.

There were around 16,000 deaths from natural causes during the study. The report stated that survival was highest among those who were exposed to the least amount of PM2.5, and “markedly lower” for those with high exposure.

The World Health Organisation sets 25 micrograms per square metre as the maximum 24-hour average concentration for PM2.5. Hong Kong averages 40 to 50, while mainland readings often surpass 100.

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