One of Chile’s most intractable problems is air pollution, particularly in and around Santiago. In 2001, the journal Science ranked the capital as the second most polluted city in the Americas, after only Mexico City.

Santiago’s geography, similar to that of Los Angeles (California), does not help; it lies in a basin between the coastal range and an even higher Andean crest that blocks the dispersal of pollutants from smokestack industries, automobile emissions, and diesel exhaust from aging city buses, and dust from unpaved streets and roads outside the central city. Rain quickly washes some pollutants out of the atmosphere, but the long dry summer and the particularly stagnant autumn air often result in heavy haze.

Successive governments have had limited success in reducing polluting gases. Except in summer, there is a weekday restriction on vehicles without catalytic converters according to the last digit of their license plates, but when the Lagos administration placed limited restrictions on vehicles with catalytic converters on truly extreme days, rightist politicians and automobile owners protested vociferously.

Another political obstacle is that Gran Santiago (Greater Santiago) consists of 32 distinct boroughs, each governed by a mayor and administration whose constituents have very distinct ideas of what causes pollution and how to remedy it. Residents of the eastern suburbs, often wealthy professionals, argue that their new vehicles pollute less than the dirty diesel buses used by working-class commuters. While not entirely false, this argument overlooks the congestion created by large numbers of private vehicles, which increases the time that internal combustion engines spend idling.

A Lagos program known as Tran Santiago is getting some of the worst diesel-polluting buses off the streets, but implementation has been slower than expected. Other antipollution measures include bus-only lanes on the Alameda, the city’s major thoroughfare, and some other streets, as well as higher quality, lower sulfur diesel fuel.

The countryside, alas, is not free of air pollution. Agricultural burning is widespread and summer forest fires are common, especially in the heartland’s dry Mediterranean climate. In mining areas such as Chuquicamata, in the Norte Grande, Pacific westerlies blow billowing clouds of toxic tailings across the desert. In the Sur Chico, the main source is ash from firewood, used for heating and cooking even in cities the size of Temuco.

A different sort of air pollution is the deterioration of the Antarctic ozone layer, which has exposed both humans and livestock in far southern Chile to summer ultraviolet radiation. Though the gaping ozone hole is a global problem, Chileans suffer the consequences of its aerosol-triggered depletion.