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close this bookDiversity, Globalization, and the Ways of Nature (IDRC, 1995, 234 p.)
close this folder8. Protecting air quality
View the document(introduction...)
View the documentAir and its principal contaminants
View the documentProcesses of contamination in industrial and urban areas
View the documentCurrent and future trends

Processes of contamination in industrial and urban areas

Since its first stages of development, the industrial revolution caused episodes of acute air pollution in many cities. The air-quality problems in parts of Europe (London, the Ruhr basin, and the Moselle basin) during the last decades of the 19th century and first decades of the 20th century are well known. A similar situation developed in the northeastern United States (in Detroit, Pittsburgh, and New York), in Los Angeles, and in the largest industrial areas of Japan.

Eventually, in many cities, control measures (such as improved combustion and the use of filters) were implemented and noxious emissions were significantly reduced. Air pollution remains a problem, however, and most industrial zones in developed countries are also zones of poor air quality.

In Third World industrial and urban areas, air contamination became a problem later than in developed countries, but in cities like Sao Paulo, Mexico City, Santiago, Shanghai, Bangkok, Bombay, and Manila, conditions have been a “nightmare” for some time. Some Asian countries, such as China and India, owe this situation to their overdependence on coal. In other cases, air degradation is the combined result of the geographic concentration of high-emission industries and inadequate controls.

The case of Sao Paulo

Sao Paulo is located on the divide of the Serra do Mar about 60 kilometres from the Atlantic Ocean, at 650 to 1 200 metres above sea level. The dominant wind is from the southeast, with some influence of sea breezes because of the city’s proximity to the ocean. The dispersion of air contaminants is slow during the winter as a result of frequent atmospheric inversions.

The worst contamination in the Sao Paulo region occurs in Cubatao, which is a valley 45 kilometres from the city on the Serra do Mar escarpment. The peaks of the Serra do Mar, which are a maximum of 1 000 metres above sea level, and the neighbouring Morrao and Quilombo hills enclose the basin, reducing air circulation. This area was selected as the site for many industries that were creating a critical situation in terms of air quality. At one time, Cubatao was one of the most contaminated areas of the world. Recently, an antipollution campaign has resulted in considerably lower levels of contaminants.

Because industrial sources are increasingly regulated, a higher proportion of current pollution can be blamed on vehicles. In 1990, Sao Paulo contained about 3.5 million vehicles, of which 1.5 million were using gasoline; 1.5 million, alcohol; and 250 thousand, diesel fuel (CETESB 1992). Vehicles also produce most of the carbon monoxide, hydrocarbons, nitrogen oxides, and some sulphur oxides (Table 4). Industries are responsible for most of the aerosols and sulphur oxides. Diesel vehicles cause the most pollution, followed by gasoline-powered vehicles. Alcohol-buming engines appear to be relatively environmentally friendly. Because of an overconcentration of the population and an increasing number of vehicles moving at slower speeds in traffic jams, it is likely this situation will continue.

Table 4. Emission levels of pollutants (‘000 tonnes per year) from vehicles and industry in metropolitan Sao Paulo.












































Note CO, carbon monoxide; HC, hydrocarbons) NO, nitrogen oxides; SOx, sulphur oxides) MP , particulates.

Source: CETESB (1992).

The case of Los Angeles

For some time, metropolitan Los Angeles, the second largest urban area in the United States, has suffered from one of the worst cases of polluted air in the world. Its air violates federal health standards regarding levels of ozone, carbon monoxide, nitrogen dioxide, and fine particulates. The poor air quality is a direct result of a sustained increase in population, automobiles, and industrial activity. The population of the Los Angeles area tripled from 4.8 million in the 1950s to the current level of 14 million; at the same time, the number of vehicles increased by a factor of four from 2.3 million to 10.6 million. Some of the main sources of air pollution are motor vehicles, trash incinerators, barbecues, paints, dry cleaners, industrial coatings, and commercial ovens (Lens and Kelly 1993).

In 1947, heavy industries, foundries, motor vehicles, and backyard incinerators were identified as the sources of air pollution. The effects were most acute during periods of meteorological inversion, which are rather common on the Pacific coast of southern California. By 1953, Los Angeles’ smog rivaled that of London.

To solve the problem, the Beckman Commission (chaired by Arnold 0. Beckman of Beckman Instruments) was formed. It proposed five measures to decrease air contamination:

· Reduce hydrocarbon emissions;

· Set standards for automobile exhausts;

· Promote the use of trucks and buses that bum liquified petroleum gas instead of diesel fuels;

· Curtail the growth of the worst-polluting industries; and

· Ban the open burning of trash.

The recommendations of the commission developed into a general air-quality management plan for the region. An important step occurred when regional governments joined to form the South Coast Air Quality Management District (AQMD), with jurisdiction in Los Angeles, Orange County, Riverside, and part of San Bernardino. All American cities were to meet the standards set by the Federal Clean Air Act by 1987, although no one believed this would be possible for Los Angeles. Some of the measures that were implemented included:

· Banning of trash incinerators;

· Using vapour-recovery equipment to transfer petroleum products;

· Using nonreactive solvents in industries using ozone-producing solvents (such as construction, auto manufacturing, and dry cleaning);

· Improving the quality of gasoline (by eliminating their lead content, for example);

· Installing devices in automobiles to prevent the emission of hydrocarbons; and

· Using catalytic converters.

As a result of these measures, any new car sold in California emits only 10% of the pollutants it emitted in 1970. In 1987, incentives were offered, to companies with more than 100 employees, to encourage car-pooling and increase the number of people per car from 1.13 to 1.24. Despite these advances, the situation is still serious (Table 5). The main contributor is the motor vehicle (47% of hydrocarbons, 70% of nitrogen oxides, 90% of carbon monoxide, and 60% of sulphur oxides), followed

Table 5. Daily emission of pollutants in the Los Angeles area.


Amount (tonnes)



Nitrogen oxides


Carbon monoxide


Sulphur oxides




Source: Lents and Kelly (1993). by industries (26% of hydrocarbons, 18% of nitrogen oxides, and 30% of sulphur oxides).

According to the AQMD, the poor quality of the air is affecting the health of the population, increasing the annual costs of health-care systems by about $9.4 billion (tents and Kelly 1993). About 15 million person-days are lost as a result of respiratory disease, and there is an increased risk of dying prematurely from exposure to particulates. According to this report, Los Angeles’ failure to meet ozone standards is also costing 18 million person-days as a result of restricted activity, 65 million person-days from chest discomfort, 120 million person-days from coughing, 180 million person-days from sore throats, and 190 million person-days as a result of eye irritation.

Such data continue to prove that there is a basic problem that remains unsolved: the unsustainability of contemporary macrourban systems. Los Angeles is the perfect example.

The case of Mexico City

Mexico City is one of the most problematic areas in terms of atmospheric contamination. It is situated in a valley that is about 2300 metres above sea level and, consequently, the content of available oxygen in the air is 23% lower than at sea level. The population of the valley is over 16 million, with approximately 2.5 million vehicles, and 30 thousand hydrocarbon-burning industries. The valley burns 43 million litres of hydrocarbons daily 54% by vehicles, 28% by industries,

11% for domestic use, and 7% in thermoelectric plants. The high population density and intensive economic activity have gradually increased the amount of carbon monoxide, carbon dioxide, lead, sulphur, ozone, and nitrogen oxides in the air throughout the valley.

A large air-purification plan (Programa Integral contra la Contaminacion Atmosferica en la Zona Metropolitana de la Cuidad Mexico, PICCA), costing 4.7 billion dollars, has recently been launched. Its purpose is to reduce air pollution in the Mexican valley. Today, the trend of increasing air contamination has been stopped or even reversed. Improvements in the quality of fuels and adding catalytic converters to car engines under the program have had a positive effect. The air in the city is monitored automatically by 32 stations and manually at 19 stations. According to recent data, most atmospheric contaminants are below maximum allowable levels most of the time (except for ozone levels, which remain high).