Airborne particulates have been in the news in Hong Kong again, as the air is so thick with them that even clear skies are whitish rather than blue (hah! - so much for the government's Action Blue Sky Campaign - launched w fanfare; seems to have vanished amidst the smog); and HK Chief Executive Donald Tsang expressed the view that while they do impact visibility, the particulates may not affect human health!
[June 2012 update: Donald Tsang about to leave office, in shameful manner given his propensity for expensive overseas trips and utter lack of empathy for most Hong Kong people; failed to make good on his promise to introduce new AIr Quality Objectives before leaving office. I'll put more info on air pollution and health in other threads, including Dirty Air is Dangerous Air.]
This was a curious opinion on Donald's part, since the EPD notes - in report on HK air quality during 2005:
RSP [Respirable Suspended Particulates] at high levels may cause chronic and acute effects on human health, particularly the pulmonary function, as they can penetrate deep into the lungs and cause respiratory problems. These effects are enhanced if high RSP levels are associated with higher levels of other pollutants, such as SO2. The smaller particulates in RSP have a major impact on visibility.
Well, Mr Tsang, even though you perhaps don't read your own government's reports, I hope you'll have time to review this thread, maybe contribute a post or two, for I'll try n find some info on airborne particulates and associated health risks.
First: there are various sources of these particulates, but main concerns are with particulates from vehicle exhausts, power stations (and factories). Larger particulates tend to be filtered by our noses; but smaller ones - below 10 microns (10 micrometres) - can pass on through respiratory tracks, even penetrating deep into our lungs (and lung tissues). These Respirable Suspended Particulates (RSP) are classified by World Health Organisation into two types: PM10, for particles 2.5-10 microns; and PM2.5, for those smaller than 2.5 microns. In Hong Kong, seems Environmental Protection Department only considers all RSPs, below 10 microns. WHO notes that studies have been consistent in showing RSPs have health impacts, primarily on respiratory and cardiovascular systems. And, impacts found at levels even close to "background" levels (ie without exhaust fumes etc) - so there isn't really a fully safe lower limit for RSPs. -
This info from 2006 air quality guidelines (pdf) file, available from WHO site at: http://www.who.int/phe/health_topics/outdoorair_aqg/en/" title="http://www.who.int/phe/health_topics/outdoorair_aqg/en/">Air quality guidelines
Through assessing several studies, the WHO has suggested the following Air Quality Guideline for Respirable Suspended Particles (PM10) - 20 microgrammes per cubic metre WHO guidelines note:
These are the lowest levels at which total, cardiopulmanary and lung cancer mortality have been shown to increase with more than 95% confidence in response to long-term exposure to PM2.5.
So, how does Hong Kong fare? Not well at all. Our Air Qualilty Objective is 55 Î¼g/m 3 - almost three times the new WHO guideline. In 2005, even this modest objective was exceeded at six general and three roadside stations; and all stations - including Tap Mun, well outside the city, at mouth of Tolo Channel, recorded RSP at levels more than double those of the new WHO guideline. The worst monitoring station for RSP during 2005 was in Causway Bay, with a whopping annual average of 84 Î¼g/m 3. [2005 report info, was available from Air Quality Reports[/url] ] That's well above the 70 Î¼g/m 3 of the WHO's Interim target-1 for RSP reduction: at around this level, according to the WHO: These levels are associated with about a 15% higher long-term mortality risk relative to the AQG level. The worst one-day average for RSP in 2005 was recorded in Tung Chung, with 217 Î¼g/m 3.