Sunday, November 23, 2014

Every Breath You Take

BANGKOK – Fearsome stories about migrating Indonesian haze, post-Diwali smog in northern India, and the return of the “airpocalypse” in China tell of Asia’s recent air-pollution woes. Not confined to Asia, outdoor particulate pollution claims over 3.1 million lives worldwide every year, five times the number of deaths from malaria and slightly less than double the current AIDS death rate.

Airborne pollutants, especially fine particles (smaller than 2.5 microns, or roughly the width of a strand of a spider web), enter deep into the lungs and from there enter the blood stream, causing cardiopulmonary disease, cancer, and possibly premature births. Just how significant are these health risks?

Unfortunately, discussion of the subject is often opaque. Poor air quality is often described as reaching a certain “AQI” (Air Quality Index) level, or as being a certain degree above a particular World Health Organization standard. But the general public might better understand the situation if it were framed in terms that compare easily with more familiar hazards.

For instance, the immediate risks of breathing polluted air could be described in terms of the “micromort,” the unit representing a one-in-a-million chance of dying. An average person on an average day faces a risk of roughly one micromort from non-natural causes. This provides a useful starting point for comparison: the risk of scuba diving, for example, is around five micromorts per dive; sky diving is ten micromorts per jump; and giving birth in the United Kingdom is around 120 micromorts. By comparison, breathing in Beijing on its most polluted days equals approximately 15 micromorts.

But the more troubling risks from air pollution arise from chronic exposure. This can be expressed in terms of “microlives” – a unit developed by Cambridge statistician David Spiegelhalter to describe a person’s cumulative risks over a lifetime. One microlife represents 30 minutes of an average young adult’s expected lifespan. The average person uses up about 48 microlives per day; but lifestyle affects how fast one expends one’s microlives.

Settling in smoggy Beijing will use up roughly an additional 2-3 microlives per day, implying a reduction in life expectancy of almost three years. Living in Hong Kong or Santiago, Chile, will cost one additional microlife per day, whereas daily life in New Delhi, one of the world’s most polluted cities, costs an estimated 4-5 microlives.

By comparison, smoking four cigarettes a day will cost the smoker around two microlives, roughly equivalent to living in Beijing. But the aging clock can also be slowed down – 20 minutes of daily exercise will extend life expectancy by two microlives per day (unless done in the smog), and drinking two or three cups of coffee daily saves an additional microlife per day. Furthermore, recent research suggests that some, if not all, of the microlives lost from living in Beijing could be recovered by moving to, say, Vancouver, with its pristine air.

Besides skipping town, one can mitigate at least some of the risks by limiting one’s exposure on particularly hazardous days. If citizens had access to current air-quality data, they could choose to take protective measures, such as minimizing physical exertion, staying indoors (ideally in filtered air), and wearing a mask (an N95-rated mask, at a minimum, not a surgical mask).

Unfortunately, air-quality information, especially for the most pernicious fine particles, is not easily available in many highly polluted cities. But such monitoring is not beyond the reach of developing countries, because the necessary equipment is not prohibitively expensive. Ideally, air-quality data should be collected, translated into easily understandable language, and widely disseminated in real-time via social media so that city dwellers can take appropriate action (particularly important for vulnerable individuals). In this regard, China has made big strides, providing a good example for other developing countries to follow.

Of course, governments should not stop at monitoring; they should take active measures to reduce air pollution. Against the pressure of Asia’s rapid urbanization and industrial development, this will take sustained effort, involving complex policy decisions and painful economic trade-offs.

Making air-quality information available to all – essentially democratizing the data – allows people to engage better in the debate on what sacrifices are acceptable in the fight against air pollution; it also provides basic input for desperately needed research into the health effects of these new highly polluted environments. These far-reaching health effects, in addition to the immediate benefit of empowering citizens to protect themselves, should spur even the most financially strapped governments to start a transparent air-quality monitoring campaign today.

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    1. CommentedWalt French

      This article suggests that virtually all the risk from air pollution comes from microparticles.

      But pollution standards also address chemicals, especially hydrocarbon smog, which made LA so unbearable, making one's eyes smart. I wouldn't think masks do one scintilla of good against these, which I assume heavily factor in industrial pollution in China.

      Can experts tell us? Are the chemicals a cancer, lung irritation or other long-term risk? Is ANY mask that people realistically wear, a bit of good against them?

    2. Portrait of Michael Heller

      CommentedMichael Heller

      “former science adviser to the US Ambassador to Japan” huh?
      says ...
      “drinking two or three cups of coffee daily saves an additional microlife per day” huh?
      b… b… but …

      It's probably not the caffeine. Based on studies of decaf coffee, Dr Hu, who really knows, says “I think we can safely say that the benefits of coffee are not likely to be due to caffeine," Hu says. Huh said that?
      Frank Hu, MD, MPH, PhD, nutrition and epidemiology professor at the Harvard School of Public Health

      Why means green tea with much higher antioxidant than coffee probably keeps folk in Hunan or Hubei safer. Hu would agree? By the way, Santiago in Chile (historically very democratic) has been giving out this micro-particle information for a decade at least online and in the press. As far as I can tell it hasn’t done a micro-bite of good. Santiago is as polluted as ever. In fact pollution levels are said to have doubled between 2000-2010.

      People aren’t stupid you know. They can see the dirt when they blow their noses. They weigh up the risks (rural poverty vs urban prosperity). Now if you could come up with some really useful and reliable research data …. like, for example, wearing surgical masks on a bicycle doesn’t stop PM10 (that refers to particulate matter as opposed to pre-menstrual countdown). Hu'd a thought it?