Particulates, Indoor Air Pollution and Environmental Justice

Why particle size is everything. Airborne particles are classed by diameter. PM10 — dust, pollen, road grit — is caught in the nose and throat. PM2.5 — smoke, soot, combustion products — is small enough (a human hair is about 28 of them wide) to reach the alveoli, where it lodges and inflames. Ultrafine particles below 0.1 µm cross into the blood and reach the heart and brain. The health effects are mostly chronic: asthma, chronic bronchitis, heart attacks, strokes, lung cancer and premature birth, accumulating over years rather than in one episode, which is why they are under-recognised and hard to attribute. The World Health Organization estimates around seven million premature deaths a year from outdoor and indoor air pollution combined — more than from malaria, tuberculosis and HIV together.

Indoor air: the largest single source most people never mention. About 2.3 billion people cook on wood, charcoal, crop waste or dung in enclosed kitchens without chimneys. PM2.5 inside such a kitchen can be ten to fifty times the outdoor level, and the exposure falls on whoever tends the fire for hours a day — overwhelmingly women and the young children with them, in low-income countries. Roughly three million premature deaths a year result. Level-1 solutions replace the fuel: liquefied petroleum gas, electricity or biogas, which need subsidy and a distribution network to reach the poor. Level-2 solutions keep the fuel but vent the smoke: improved stoves with chimneys, ventilation. Improved-stove programmes have often failed because the stoves did not fit local pots, changed the taste of food, broke without spare parts, or were used alongside the old fire — a reminder that a technical fix without the social fit is not a fix.

Environmental justice. Pollution does not fall evenly. Land near motorways, factories, ports and waste sites is cheap because it is polluted, the poor move there because it is cheap, and then bear the pollution: in most cities the poorest districts have the worst air and the least political voice to change it. The people who cause pollution — car owners, factory owners, consumers of the products — are usually not the people who breathe it — pedestrians, children, the elderly, the poor, and those downwind or in the next province. A policy can reduce total pollution while worsening its distribution: banning old vehicles without providing alternatives removes the transport of the poor and leaves the rich driving; relocating a factory moves the exposure to a community with less power to object.

How to evaluate an air-quality policy. Ask five questions: does it reduce concentrations of the pollutant that is actually causing harm here; at source or at the end of the pipe; for whom — does exposure fall for the most exposed group; who pays, and can they afford it; and what reaction will it provoke. A policy that scores well on total tonnes removed but badly on who benefits is not a good policy, and examiners increasingly reward answers that say so.