Cities in Latin America, which are home to 78 per cent of the region's population (UN, 1995a), are particularly vulnerable to environmental problems such as urban air pollution, water pollution, disposal of solid and liquid wastes, and industrial contamination. Domestic and industrial discharges in urban areas contaminate air, land, and water with nutrients and toxins. In turn, degraded air, land, and water harm flora and fauna and pose health risks to city dwellers. Although most of the megacities are affected in similar ways, data on urban environmental conditions are available mainly from a few large cities such as Mexico City, São Paulo, and Santiago. Much of this pollution stems from economic growth and industrialization, which have been highly concentrated in the large cities of the region, rather than from urbanization itself.
In the last decades, rural abandonment and poverty have accelerated the growth of urban areas. (See Figure 2.19.) Many of the cities in LAC were not conceived or planned for the current demographic densities. As a result, the sprawling megacities have generated peripheral belts of fragile human settlements, usually located in environmentally unsuitable areas such as hill slopes or floodable grounds. People living in these areas are particularly vulnerable to disasters and health hazards. Additionally, some of the larger cities, such as Mexico City and Santiago, are located in valleys and surrounded by mountain ranges, which exacerbate their urban pollution problems and make them inappropriate for further industrialization and urban expansion.
Air pollution is a constant fact of life for 81 million urban residents of Latin America, leading to an estimated 2.3 million cases of chronic respiratory illness every year among children, to 105,000 cases of chronic bronchitis among the elderly, and to nearly 65 million lost workdays (LAC CDE, 1992). Mexico City, São Paulo, and Santiago all have very high pollution indexes. Buenos Aires, Bogotá, Rio de Janeiro, and Caracas are not free of this problem either, although due to their geographical locations and climatic conditions they are less seriously affected (ECLAC, 1993a).
Mexico City has probably experienced one of the worst air pollution problems in the world. The weather and topography greatly hamper dispersal of the enormous volumes of pollutants that are emitted into the air, especially during the dry season (Gligo, 1995). World Health Organization guidelines for sulphur dioxide, suspended particulate matter, and carbon monoxide were all regularly exceeded in the city during the 1970s and 1980s (UNEP and WHO, 1992), although there has been a marked improvement over the past five years. According to estimates in 1992, suspended particulate matter in Mexico City from vehicles and other sources increased mortality rates about 0.038 per cent, and thus contributed to 6,400 deaths (Margulis, 1992). In addition, it was estimated that elevated ozone concentration contributed to the loss of around 6.4 million workdays a year, and that 29 per cent of children had unhealthy blood lead levels (Margulis, 1992). Similar patterns have been observed in many other cities of the region.
Two main factors are causing an increase in urban air pollution in the region: the mounting number of motor vehicles in use, and the expansion of industrial activity. Mexico City alone has more than 4.2 million motor vehicles (Cevalos, 1996), while in Santiago, the number of motor vehicles has tripled over the past 15 years (ECLAC, 1991). The use of motor vehicles produces more air pollution than any other single human activity, with an estimated 80-90 per cent of lead in ambient air coming from the combustion of leaded gasoline, despite the fact that unleaded gasoline has been introduced in most Latin American countries (WRI/UNEP/UNDP/WB, 1996). The growth of industrial activity has been especially marked in the larger countries and major cities. Following the slowdown in the 1980s due to economic stagnation, industrial activities are once again picking up (ECLAC, 1996), and with them, environmental pollution is increasing.
Although few countries aside from the smaller ones in the Caribbean face water supply problems on a national scale, many must deal with such problems in urban areas. Local water shortages are particularly acute in the region's megacities. The supply of drinking water is also a major environmental, technological, and financial challenge in many of the smaller cities.
Lima, Peru, for example, is located in an area where not enough water is available, which has forced the costly extraction of water from distant watersheds. In other large urban centres, water supply is based on the unsustainable exploitation of underground aquifers. In Buenos Aires, some 55 per cent of the population obtains its drinking water from underground sources, some of which have serious levels of pollution. In Mexico City, around two thirds of the water used in the city is obtained from aquifers at a rate of extraction more than double the recharge rate (Gligo, 1995).
The concentration and increases in urban population in the region have also generated difficulties in the supply of water of adequate quality. In most cities, piped drinking water is not available to everyone. The mounting demand for drinking water has outstripped its supply, causing serious problems (ECLAC, 1992). Access to safe water in the region is highly variable, ranging from 100 per cent for the urban dwellers of Cuba and Chile to 63 per cent for those in the urban areas of Ecuador (UNICEF, 1994). Some 10 per cent of urban households in Bolivia, 25 per cent in Ecuador, 30 per cent in Guatemala, and 13 per cent in Honduras are without access to piped water-inside or outside (UN, 1995a).
The absence of sewage treatment, especially in rapidly expanding urban areas, creates problems. Approximately 80 per cent of the urban population in the region has access to adequate sanitation and sewerage services (collection, but not treatment), although there is great variation among the countries-from 100 per cent in Chile and 97 per cent in Venezuela to 40 per cent in Bolivia and 56 per cent in Ecuador (UNICEF, 1994). This relatively high percentage of sewage collection coupled with the low share receiving any treatment before discharge into rivers, lakes, and seas has resulted in water quality problems not only in cities, but also on downstream areas, coastal areas, and beaches.
Many of the megacities, such as Mexico City and São Paulo-Santos, contain large concentrations of industry with correspondingly high levels of contamination. Such cities are often highly polluted and lack adequate social and sanitation infrastructure and proper policies for the treatment of hazardous industrial waste. At the same time, land pressures and urban poverty mean that communities are often built near industrial plants that dump their wastes into the rivers, the seas, or onto the nearby land, and that pollute the air. The inhabitants of these low-income neighbourhoods are consequently exposed to hazardous waste and face health risks.
In addition, increasingly stringent environmental standards in the industrial world, particularly in North America, have driven industries to transfer some of their most polluting technologies to developing countries such as Mexico (LAC CDE, 1992). The need to develop a local industry has forced many LAC countries to accept polluting technologies and, in some cases, also the transboundary traffic of hazardous wastes. The largest proportion of hazardous wastes coming into the region does so under the terms of agreements between the United States and Mexico. As of 1988, Mexico had accepted 30,000 tons of such waste for industrial recycling (ECLAC, 1993b).
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