The region has a highly urban population. In 1950, 43 per cent of the total population lived in urban areas but this had risen to 73.4 per cent by 1995 (see graph opposite). Most of the urban population lives in large cities such as Mexico City (16.5 million people), São Paulo (16 million) and Rio de Janeiro (10 million). Buenos Aires, with nearly 12 million people, and Santiago, with 5 million, house 34 per cent of the population of Argentina and Chile (WRI 1996). While urbanization itself does not necessarily have negative socio-economic or environmental impacts, unplanned urban growth has led to the development of outer and inner city slums, many of which lack basic services.
Increasing population density and economic activity have led to increased pollution in many cities. Santiago, for example, is now one of the most polluted urban areas in the world; the main sources of air pollution are urban transport, and small and medium-sized industries (IMO 1995). Air pollution is causing severe respiratory problems among city dwellers, with higher rates of pneumonia than in many other cities, and many premature deaths from respiratory diseases. Treatment costs are high and there are productivity losses due to absenteeism (O'Ryan 1994). Mexico City, São Paulo and Bogota are also suffering from severe air pollution. The Brazilian programme of adding alcohol to gasoline has, despite reducing carbon dioxide emissions by some 30 per cent and decreasing air pollution, not been sufficient, and São Paulo now restricts private car circulation, as do Mexico City and Santiago. In São Paulo and Rio de Janeiro, 27 million people are exposed to high levels of particulate air pollution estimated to cause 4 000 annual cases of premature mortality (CETESB 1992).
Lead emissions are also a major problem. The main sources of exposure are emissions from vehicles that use leaded gasoline, industrial production, particularly of paints and batteries, and food. The effects of leaded gasoline are felt most in urban environments. Residents of areas with high levels of traffic generally have a much higher level of lead in the blood than those exposed to less traffic. However, over the past decade or so, the lead content of gasoline has been decreasing in most countries, and lead-free gasoline has been introduced. Countries with the largest share of lead-free gasoline are Brazil (100 per cent), Costa Rica (100 per cent), Guatemala (80 per cent) and Mexico (46 per cent) (Christopher and others 1996).
Until the mid-1970s, poverty was generally more common in rural areas than in urban ones. In the 1990s, however, regional statistics show that 65 per cent of poor households are in urban areas (World Bank 1996). During 1990-94, the level of urban poverty fell from 33 to 24 per cent in Chile, and from 12 to 6 per cent in Uruguay (CEPAL 1996). In Buenos Aires, 17 per cent of the population live in households with unsatisfied basic needs (overcrowded households, inadequate housing, poor access to clean drinking water and sanitary infrastructure) compared to 22 per cent in the 1980s (La Serna and others 1997).
Unplanned growth in urban areas has most effect on the poor, who often lack proper water supplies and sanitation services, even though these are generally well developed in urban areas. Unplanned growth has other environmental effects associated with inadequate means of disposing of wastewater, a demand for water that exceeds supply, and the pollution of groundwater.
The topographic position of most Latin American cities makes it difficult to use conventional methods of water and sewage treatment, and collection of solid wastes. In Central America, a study of 158 urban centres with more than 10 000 residents showed that industrial and domestic wastes were not treated before disposal (Incer 1994). Caracas, La Paz, São Paulo, Rio de Janeiro and Lima, among others, have serious sanitation problems. In Brazil, sewerage networks reach only 49 per cent of the urban population. Lack of water and sanitation in Brazil's urban areas is estimated to cause some 8 500 cases of premature mortality per year (Barros and others 1995).
The disposal of solid waste is also problematic. Only 30 years ago, the generation of solid waste per capita was 0.2-0.5 kg a day while it is now 0.5-1.00 kg a day. The problem lies not only in the quantity but also in the quality and composition of the wastes, which have changed from being dense and almost entirely organic to voluminous and increasingly non-biodegradable, with a higher percentage of toxic substances. In 1995, Latin America was generating approximately 275 000 tonnes a day of solid urban waste. A fleet of 30 000 trucks and 350 000 m3 of land a day would be needed to collect and bury this garbage in a sanitary fashion. In reality, the region's waste disposal facilities are composed of 35 per cent sanitary landfills and 25 per cent semi-controlled landfills (PAHO 1995). The other disposal facilities do not comply with minimum norms and are best regarded as no more than rubbish dumps.
Progress has been made but only in a few large cities that, because they are so big, distort the statistics and lead to unwarranted optimism. In reality, the situation in other cities is grim. In Brazil, a national survey found that 57 per cent of cities have open garbage dumps, 14 per cent have controlled landfills, and 28 per cent have sanitary landfills or other adequate methods of waste disposal. In Chile, 78 per cent of waste disposal facilities are sanitary, as are 30 per cent in Mexico. In other countries, such as Bolivia, Ecuador, Peru and most Central American nations, there are no sanitary landfills outside the capital cities, although both Bolivia and Colombia have interesting programmes for medium-sized cities (PAHO 1995).
In most Caribbean countries, increased population and per capita incomes, altered patterns of consumption, and the rapid development of the tourism and industrial sectors have led to fast rates of growth in waste generation. In 1994, the volume of waste disposed of at the major landfills in Trinidad and Tobago was 44 per cent more than in 1979 whereas population increase over the same period was only 30 per cent (Goddard 1997). The quality and composition of the waste has also altered significantly, becoming much less biodegradable. Increasing amounts of plastics, aluminium, paper and cardboard packing cases are being used and disposed of by households and businesses.
Urban populations are growing very rapidly. For example, in the Brazilian states of Rondonia, Para and Mato Grosso, and in Santa Cruz de la Sierra in Bolivia, the urban population has been doubling every decade (WRI 1997). In the Brazilian cities of Manaus and Belém, the population grew by more than 65 per cent in the past decade (IBGE 1991). Although the rates of growth of large cities declined in the 1990s, the problem is now moving to the medium-sized cities. Increases in income in countries such as Chile, for example, have changed consumption patterns in favour of more intensive use of the environment. Higher income is accompanied by increased consumption and more waste. In Santiago, for example, areas with higher income levels produce 1 kg of waste per inhabitant a day, while the poor areas generate 0.5 kg (Escudero 1996).
It seems likely that over the next decade water problems will be moderated but not solved by investment in sanitation programmes. Urban air pollution, in spite of special governmental programmes, may remain high because of the increase in the number and use of private cars, the main source of air pollutants. No significant reductions are expected in industrial wastes and emissions because of the magnitude of the problem, and the time and resources needed to implement effective policies.