Air Pollution: Beware the beast in the air

Don't label it the haze; PM2.5, or fine particle air pollution, is a real killer
Michael Chee Straits Times 29 May 10;

AS THE cool months of the year draw to a close and the hot and dry months approach, most Singaporeans will be bracing themselves for the return of the annual deluge of fine particle air pollution from regional fires.

Media channels have already begun to manage expectations of the annual recurrence of this 'nuisance' and we have been forewarned that this year may be a bad one for the haze.

On May 10, the American Heart Association issued an update to a statement first made in 2004 concerning the association between particulate matter air pollution and cardiovascular disease.

It stated that in the intervening period, numerous studies have expanded our understanding of this association and its impact on human lives. The report focused particular attention on PM2.5 pollution.

PM2.5 pollution is so called because of the 2.5 micron (a micron is 1/1000th of a millimetre) size of the particles.

Unlike larger particles that can be trapped in one's nose and upper airway passages, PM2.5 gains direct entry into the deepest reaches of the lung, right onto the gas exchanging surface through which oxygen enters into our bloodstream, literally invading one's inner space and wreaking slow but sure health havoc.

PM is not a single substance, but a mixture of multiple compounds, including elemental and organic carbon, transition metals, nitrates and sulfates.

Whenever South-east Asian cities are enshrouded with enough PM to obscure visibility, governments dutifully inform persons to stay indoors to avoid short-term cardio-respiratory problems.

There has been data for some time now that a one standard deviation (around 33 per cent) increase in PM2.5 over a single day is associated with an approximately 1 per cent increase in premature mortality within a few days.

Long-term exposure leads to greater risk than short-term exposure and several independent researchers in the United States, Germany, Norway, Britain and France have now shown this.

The consensus from several cohort studies is that there is an approximately 10 per cent increase in all-cause mortality (death), most of this arising from an increase in cardiovascular causes.

As you might suspect, the impact of PM2.5 invasion is greater than that for the larger PM10 grade particles that are tracked by the PSI measure used in Singapore.

In the short term, the developing bodies of babies and children and the ageing insides of elderly persons are the most vulnerable.

They can manifest with asthmatic attacks or breathing problems.

Deposits build up in blood vessel inner linings and can give rise to heart attacks and stroke.

The risk of lung cancer is also increased. A part of the lung's immune system (macrophages) is adversely affected.

The risk of premature death is increased.

There are quantifiable, evidence-based estimates for these endpoints. None of these sobering facts is really new. But perhaps, because these effects tend to be delayed, they tend to be ignored.

If someone were to release a small bomb in a city, killing 50 people, we can be certain of a strong military grade response.

To contain alarm over what was impossible to control some years ago, we have been persuaded to believe in the 'safe', 'moderate' and 'unhealthy' categories of air pollution.

In truth, risk rises continuously as a function of particle density. As with blood pressure, there is no true 'safe' level of exposure to PM2.5, only what the trade-off between economics and tolerance for human suffering will bear.

Regrettably, after decades, burning of forests, fields and plantations persists at visibly unhealthy levels.

Is there ever an excuse for businesses to continue harming the community in a quietly lethal manner?

If not, those who have reason to benefit directly or indirectly from abetting such activities should take stock of the harm they are inflicting on themselves and their loved ones, as well as the potential political and legal fallout from liability claims should the new data on health risks be ignored.

Additionally, what is needed is for the average person to wake up and say 'enough', to agitate for change and to promote awareness that the effects of PM2.5 can be likened to forcibly breaking into and entering another person's private space.

We can collectively contribute financially to the education and economic improvement of would-be fire-starters (governments and NGOs already do this, though their activities are largely unheralded).

Finally, the media and regional governments would do well to desist from obscuring the monster by calling it 'the haze' - a term most have come to associate with woolly ineffectiveness and which fosters continued acceptance of the status quo.

Call the beast by its real name and know that it will kill.

Make no mistake about it: You could be the next statistic in a journal of epidemiology if the required actions fall short. PM2.5 - our ugly, inconvenient truth.

Do something about it.

The writer leads the Cognitive Neuroscience Laboratory, part of the Neuroscience and Behavioral Disorders Programme of Duke-NUS Graduate Medical School.