They come from outside, they come from inside, and they shouldn't be ignored.
Back in the days when people started getting seriously worried about air pollution, it was known as smog, a portmanteau of smoke and fog. If you look at the Wikipedia entry, it lists the main components as carbon monoxide and nitrogen oxide, and at the end of a long list, mentions "particles."
In the last few years, however, there has been increasing recognition of particulate matter (PM) as THE serious problem. The really tiny particles, PM2.5, are probably the worst. They get deep into the lungs and can even pass through into the circulatory system. The World Health Organization estimated in 2005 that "fine particulate air pollution (PM2.5), causes about 3% of mortality from cardiopulmonary disease, about 5% of mortality from cancer of the trachea, bronchus, and lung, and about 1% of mortality from acute respiratory infections in children under 5 years, worldwide."
Now, writing in his blog Energy Vanguard, Allison Bailes describes how PM2.5 tops the list of indoor air pollutants. He shows a slide from a presentation by Dr. Brett Singer which shows PM2.5 as being worse than all those other pollutants we have been talking about for years, from VOCs to formaldehyde to radon.
It estimates the DALY (disability adjusted life years) lost due to the pollutants per 100,000 people; DALY are a useful measurement of the estimated years of healthy life lost. The fact that PM2.5 is the biggest hazard in our homes should be making us do a serious rethink about how we design our homes and our cities.
The single biggest source of PM2.5 is the exhaust, tire and brake wear from cars and trucks; in cities, it is generally higher outside the home than inside. Health Canada recently advised:
Indoor levels of PM2.5 should be kept as low as possible, as there is no apparent threshold for the health effects of PM2.5. It is impossible to entirely eliminate PM2.5 indoors, as among its sources are essential and everyday activities, such as cooking and cleaning, as well as infiltration from outdoor sources, over which residents have little or no control. However, any reduction in PM2.5 would be expected to result in health benefits, especially for sensitive individuals, such as those with underlying health conditions, the elderly or children.
But there are things that we can do to control outdoor sources. We can build really tight houses with very little infiltration, and supply fresh air that is filtered, like in most Passivhaus designs.
At the city level, we have to start thinking about where people live; what were they thinking in Toronto, permitting all those condos to almost hang over the expressways? How do they allow people to live so close to highways where the particulate levels are so high? If gasoline and diesel powered cars are killing so many people, why are we not even talking about limiting their use in cities?
Meanwhile, in the home, don't do this.
- As Allison Bailes suggests, we should ALWAYS use a kitchen exhaust fan that is vented to the exterior (those filters on recirculating fans will not catch PM2.5).
- The stove and hood should be installed on a wall, not an island. Use the back burners first.
- Use an electric range, not gas.
- I know it is unpopular but I am going to flog this again: I cannot understand why people would put a VOC and particulate generating stove in the middle of their living space. Open kitchens are not good for air quality.