Movements of people whether from rural to urban areas or from one country to another often alter the characteristic epidemiological disease profile, and at the same time new diseases appear or old ones reemerge. Such is the case of HIV/AIDS, tuberculosis, yellow fever, dengue, and Lyme disease.
For example, large-scale migrations to Costa Rica in the 1980s, stemming from conflicts in other Central American countries, produced a palpable increase–especially along border areas–in the prevalence of malaria and other infectious and parasitic diseases. At the same time, urbanization is associated with changes in diet and exercise that increase the prevalence of obesity with increased risks of type II diabetes and cardiovascular disease.
Among migrants, mobility-related risks include poverty, vulnerability to sexual abuse and exploitation, dangerous working conditions and separation from social support networks. Many of these conditions affect the most vulnerable segment of the population: women, children and the elderly.
The reproductive system of pregnant women is especially vulnerable to environmental contaminants. Each step in the reproductive process can be altered by toxic substances in the environment that increase the risk of abortion, birth defects, fetal growth and perinatal death. Many studies have shown that exposing pregnant women to carbon monoxide can damage the health of the fetus. In addition, the developing fetus is susceptible to environmental factors – for example through the mother’s exposure to toxic substances in the workplace.
Children are especially susceptible to disease when they are born and develop in an environment characterized by overcrowding, poor hygiene, excessive noise, and a lack of space for recreation and study. They suffer not only from a hostile physical environment, but from stress and other factors such as violence that such environments create.
The more obvious ill effects of urban life–emotional stress, loss of family structure, congested traffic, noise, environmental pollution– affect people from all incomes. Many city dwellers take for granted access to basic public services, such as drinking water supply, housing, solid waste disposal, transportation, and health care. For the poor, however, these are either deficient or nonexistent. Instead, those in poverty zones usually receive an extra dose of environmental pollution, since industries tend to cluster in outlying areas where regulations are more lax.
Particularly in cities, motor vehicles are an important source of air pollution. In addition, they can be a significant cause of pedestrian injuries and fatalities. The pollutants that originate from motor vehicles, particularly nitrogen oxides, hydrocarbons, ozone, and particulate matter, account for a substantial proportion of air pollution in cities and serious impact on health.
Lead particles released as a result of gasoline combustion pose a significant potential threat to children, whose behavior and psychological development can be affected. In Mexico City, a city notorious for its air pollution, children are exposed to several million tons of contaminants.
Yet Mexico City’s pollution problem is hardly unique; virtually every major city in the Western Hemisphere is fighting the same battle. Residents of Santiago, Chile, are afflicted with a host of chronic respiratory infections caused by large concentrations of particulate pollutants in the atmosphere, whose persistence is, in turn, facilitated by the area’s unique topographical and climatic circumstances.
The crowded urban neighborhoods combined with poor sanitary conditions and inadequate waste removal create conditions favorable to the spread of infectious diseases.
The overcrowded housing in the slums expose the urban poor to high rates of infectious diseases such as pneumonia, tuberculosis and diarrhea. As a result, the proportion of children dying from infectious and parasitic diseases in poor households in Africa, Asia and Latin America is several hundred times higher than in households in Western Europe or in the United States.
The environmental, social and economic situation at home is, in turn, influenced by the general social, economic and political situation. The rules, regulations, and laws governing a particular city or country will be a reflection of the priority that the government attaches to providing good services and a healthy environment to the population.
Given the serious effects that urbanization can have on health, it is essential to include health considerations into policy making. Because many of the negative effects are suffered by the poor and minorities, it is equally essential to view the challenges incorporating considerations of social justice and equity. The economic situation is a key determinant in the decision, resolve and capacity of the authorities to tackle environmental problems more effectively.
As Herbert Girardet, an expert on urban sustainability has stated, “If we are to continue to live in cities, indeed if we are to continue to flourish on this planet, we will have to find a viable relationship between cities and the living world –a relationship not parasitic but symbiotic, or mutually supportive.”
– In this blog series, Dr. Cesar Chelala explores the many challenges presented by urbanization, the impact of urban migration, challenges to health, and challenges of providing clean water. – Ed.
Cesar Chelala, MD, PhD, is an international public health consultant and a writer on human rights issues and foreign affairs.
NNNIIICCCEEE!!!
environments are the sources of each and everything,