Demographic impact
The rate of increase is massive, with 1,000 migrants arriving a day from urban areas. The majority of the migrants tend to by young males, leading to an imbalance in the population structure.
Social impact
As the city's population has increased, people have tended to remain in similar areas, leading to a characteristic land-use pattern. The wealthiest districts are in the west, while developers sold large tracts of unserviced land in the east to low-income families.
In 1954 the Federal District forbade further subdivision of land within the city limits, leading to informal settlements in Naucalpan, Ecatepec and Netzahualcoyotl. However, there is still a desperate shortage of dwellings - in 1994 it was estimated around 800,000 houses were required.
Access to healthcare attracts many to the city in the first place but there is uneven distribution of facilities, with most hospitals and clinics found in the centre and west. The social security system does not cover most who work in the informal sector, so many can scarcely afford medical bills.
Some 60% of Mexico City's population live in what were originally illegal settlements. Much is poor quality and high density with few services.
The government does little to change this situation. Newcomers are treated as transients from rural areas who have strayed temporarily into town. They are described as 'marginal', belonging neither to the urban economy, nor to the place where they live.
One of the major social consequences of urban sprawl is the loss of the "Sense of Place". Urban Sprawl can turn a landscape which once was considered special into something that reflects the "geography of nowhere" (Kunstler, J. H., 1998). Kunstler claims that the "geography of nowhere" created by sprawl destroys the unique character of the urban and rural communities as activities which once took place in the center of Toronto have been segregated and dispersed in the periphery. The result is that miles of undifferentiated landscape are created where civic values are undermined, and individuals in those new subdivisions become alienated from their neighbours (Kunstler, J. H., 1998).
The process of suburbanization leads to greater social and to a lesser degree racial inequalities in Toronto. This social diversification takes place because of the flight of job opportunities from the city to the suburbs which the poor and minorities cannot afford. Thus, sprawl has devastating impacts on the poor and minorities left behind in the city core.
Economic impact
Mexico City is very much a primate city, producing 28% of the country's industrial output, 49% of manufacturing and 68% of financial services.
There are well over 7 million economically active people within Mexico City. There is a constant inflow of rural migrants, who inevitably end up working as street vendors, unskilled workers in the clothing and show industries, or cleaners. The national minimum wage is $2.50, though most are pleased with any small wage they are given.
Foreign multi-national companies like Daewoo are attracted to Mexico City by the large cheap labour force. Tourism is another major foreign currency earner.
The inflow of rural migrants in search of employment makes the job situation acute, and unemployment is high.
Environmental impact
"Through the dense clouds of automotive exhaust the sun appeared only as a remote, flickering ball". That was how Marco Morelli described the air pollution on a typical day in Mexico City.
In 1994, the World Health Organisation declared that air quality in Mexico City was only acceptable on 20 days in the year. Some 4 million vehicles, together with 40,000 factories pump over 12,000 tonnes of gases, pollutants and particulates a day.
Two million people suffer from diseases caused by air pollution, as well as increasing incidence of allergies, cardiovascular diseases and cancer. 98% of the population suffer from deformation and inflammation of the nasal passages.
The air pollution problem is exacerbated by the temperature inversions which occur when cold air sinks down from the surrounding mountains, trapping the pollutants below at ground level. The reduced oxygen level causes incomplete combustion of gasoline. So automobile exhausts and industrial pollution can create a great smog, especially when the phenomenon of thermal inversion occurs.
Another contributing factor is the dumping of hazardous waste on open sites. The city produces 40% of all Mexico's hazardous waste, some 2.48 million tonnes per year. With no legal landfill sites and just 5 recyclers, waste is dumped in any available open space, for example Rincon Verde in the west. The site produces dangerous air and water pollution, when chemicals are leached into the water table.
Water supply is another problem. Mexico City consumes 60,000 litres of water per second, 80% of which is groundwater. Having overpumped the Mexico Valley aquifer, it is now necessary to pump water up to 180km from Cutzamala at much higher cost. Some 40% of water entering the city's supply system disappears en route, due to cracked and leaking pipes, illegal tampering and the lack of water meters. A vicious circle has developed, with the service so poor that the water companies cannot recoup their costs from users, and the derived income so low that the service can't be improved.
In Toronto, cost of sprawl is not only economic and social but also environmental. First sprawl causes natural resources to be consumed at a greater rate. Natural lands are converted into residential areas at unsustainable rates. Sprawl pushes farmers off their land and onto less productive land, forcing them to harvest a greater area than before in order to produce the same amount. As low density houselots encroach on the outlying areas, the agricultural landscape which surrounds Toronto is ruined.
