September 5, 2011

The effects of the environment on health have long been recognized. In the United States, industrial growth and increasing urban population centers in the mid-19th century resulted in concern about the water supply and sewage management. Furthermore, increasing use of coal-burning furnaces and the subsequent soot and cinders in the air led to public fear and, ultimately, organization of public policy to address these problems. State and local health boards were used to improve public sanitation with clean drinking water the first priority. Adequate sewage treatment was also a priority, although, due to economic limitations, strategies for sewage treatment were slower to be adopted.

In the latter part of the 19th century, the problems of air pollution were addressed by common councils of large industrial cities. States would authorize cities to regulate smoking nuisances (if the states were to do anything). The local ordinances developed took a variety of forms including modest fines for dense smoke emissions to responsibility of an owner to eliminate smoke emissions from his/her facility. Other ordinances prohibited the use or sale of coals with certain ash and sulfur content. The enforcement of these laws was difficult as the agencies had little resources for enforcement. As air pollution increased in the first half of the 20th century, county air pollution agencies replaced city smoke inspectors. Finally, in 1955, the federal government got involved through the Air Pollution Act of 1955.

In general, environmental protection up to the 1970s was largely left up to the states. However, public concern over national and international environmental conditions led to increasing federal government involvement and the development of statutory requirements. The states were allowed to develop more stringent standards, but were required to at least meet the standards set forth by the federal government. Policies enacted by the federal government include the National Environmental Policy Act; the Federal Insecticide, Fungicide, and Rodenticide Act; the Toxic Substances Control Act; the Clean Air Act; the Clean Water Act; and the Safe Drinking Water Act to name a few.

Environmental epidemiology, which is the study of the effect of the external environment on health, examines a broad range of factors. In addition to examining associations between water and air quality to health, environmental epidemiology is also concerned with diseases associated with vector-borne and soil-borne contaminants. Vector-borne illnesses are those that stem from a nonhuman carrier of disease organisms and are generally of greater concern in developing countries compared to industrialized countries. Mosquitoes, flies, rats, and mice can all spread disease to human populations. Of particular concern is malaria, which is spread by mosquitoes. Malaria is one of the most widespread vector-borne diseases. Soil-borne parasites also pose a health threat. Soil-borne parasitic diseases include ascaris (roundworm), hookworm, whipworm, strongyloides, and animal nematodes.

Environmental epidemiology can also examine how health is affected by people’s work environment and living environment. Approximately 137 workers die each day from job-related diseases, more than eight times the number of workers that die from job-related accidents. These illnesses may be caused by a variety of substances including poisonous chemicals, dyes, metals, and radiation. Also, there has been increased attention to the association between place of residence and health. While some of this association can be attributed to factors such as air/water pollution and lead exposure, other factors related to place of residence are considered to have effects on health outcomes. For example, resources such as easy access to medical care, education, transportation, health and welfare services, and police protection are all expected to have important effects on health. In addition, networks of community support and the behavioral norms in an area are thought to play a role in health outcomes. The location of stores that sell nutritious foods, alcohol, and cigarettes can have an effect on health as can the amount of advertising for these products (i.e., billboards) in an area. Finally, for infectious diseases, the prevalence of diseased people in the area and the amount of contact with these people are important in predicting transmission of infectious disease.

Studies of the environment and health are complicated not only by traditional concerns in epidemiological studies such as confounding, but also by specific difficulties of environmental studies. Exposure assessment is a vital part of environmental epidemiology but exposure assessment is often inadequate. Sometimes there are no documented exposure data for individuals who are at risk. Even when exposure information exists, it is often not complete. For example, several different pieces of information on the exposure are often needed including the intensity and frequency of contact as well as routes of entry into the body. Studies of communities exposed to environmental contaminants are also problematic. Again, often the exposure is poorly defined. Furthermore, people living in the area around an exposure may be small in number thereby limiting the range of outcomes that can be studied. Similarly, often the endpoints of interest are rare and/or have a long latency period. Publicity of the situation may influence reporting of exposure and/or an atmosphere of fear or anger may make studying the effects difficult.

Many associations between environmental exposures and disease have been noted in spite of these limitations, although some of these associations are controversial. Cadmium, lead, and other heavy metals found in the environment have been associated with osteoporosis, which is characterized by fragility of the bones. Autoimmune diseases, such as multiple sclerosis, rheumatoid arthritis, scleroderma, and systemic lupus erythematosus (SLE), also have links to environmental exposures. These diseases, which are more common in women than in men, have been linked to certain pharmaceuticals and solvents. Specifically, lupus has been associated with both hydrazine (an industrial chemical) and tartrazine (a food additive). Certain cancers have been associated with radiation, natural and man-made chemicals, and sunlight. Black lung (or pneumoconiosis) occurs when particles such as asbestos, silica dust, graphite dust, coal dust, and the like damage sensitive areas of the lung, which subsequently leads to scar tissue. More commonly, pollutants and chemicals in the air are known triggers for asthma.

Uranium can damage living tissue and a single high dose can be fatal. While most people will not come into contact with uranium, miners and medical professionals who work with x-rays need to take precautions against uranium exposure. Finally, in the 1970s, scientists discovered that the use of diethylstilbestrol (DES) in pregnant woman could lead to cancer in the reproductive organs of the daughters of these women. Consequently, the use of DES and other synthetic hormones during pregnancy has ceased. However, there is concern that other chemicals and man-made pesticides may have similar effects.

While efforts at the local, state, and national level have addressed clean water, air, sewage management, and cleanup of hazardous waste sites, less money has been spent on addressing health risks from chronic low-level exposures to hazardous substances. Several low-level exposures are of particular concern. Pesticides are widely used in the United States, with more than 1 billion pounds of synthetic organic pesticides produced each year. Specifically, PBCs and DDT have been known to affect the immune system, the neurological system, and the endocrine system, and some researchers have speculated that these pesticides are a promoter of breast cancer. The use of PBCs has declined over the years, although concern about residual levels of PBC still remains.

Another pollutant of concern is mercury. Mercury is a widespread persistent air pollutant and organic mercury (a mercuric compound) has been found in the aquatic food chain. Both are of concern to pregnant women, since levels that would produce no or minimal symptoms in the mother have been found to have consequences for the fetus. Two other pollutants that have received increased attention over the years are asbestos and lead. Asbestos can be found in a variety of items including insulation, floor tiles, shingles, and fire-resistant dry wall. While it is rare for asbestos to be installed today, previous exposure or exposure during asbestos removal, renovation, or maintenance of buildings are of concern. Asbestos fibers enter the body through inhalation or ingestion of the fibers, which subsequently become embedded in the respiratory or digestive system. This inhalation or ingestion of the fibers may cause disabling or fatal disease.

Lead is another pollutant that has received increased attention. Lead is most commonly found in homes in lead paint chips that have separated from the wall, which may be pulverized into dust. Lead also exists in homes in lead pipes and some ceramic food containers with lead glazing. Lead exposures have been associated with negative reproductive effects in men and women and long-term exposure of lead in children has been associated with reductions in cognitive abilities and shorter attention spans. It has been suggested that levels of lead in children have been declining over the years, perhaps in part to increased attention to this issue.

The environment, defined in multiple ways, plays a major role in the health of the population. Air and water quality, containment of hazardous wastes, and vectors that transmit disease are all important environmental factors. Additionally, health is also affected by one’s environment, more broadly defined, meaning “their work environment and their place of residency.” There has been increased involvement in the monitoring of the safety of our environment and increased understanding of the specific aspects of the environment that are associated with detrimental health effects. It is hoped that continued study and monitoring of these factors will result in a healthier population overall.

SEE ALSO: Pregnancy, Women in the Workforce

Suggested Reading

Blumenthal, D. S., & Ruttenber, A. J. (1995). Introduction to environmental health (2nd ed.). New York: Springer.

Macintyre, S., Ellaway, A., & Cummins, S. (2002). Place effects on health: How to conceptualise, operationalise and measure them? Social Science and Medicine, 55, 125-139.

National Research Council (U.S.). Committee on Environmental Epidemiology. (1991). Environmental epidemiology. Washington, DC: National Academy Press.

National Research Council (U.S.). Committee on Environmental Epidemiology. (1997). Environmental epidemiology (Vol. 2). Washington, DC: National Academy Press.

Nolan, L. (2001). Our environment, our health. Association of Women’s Health, Obstetric and Neonatal Nurses, 5(6), 25-29.

Talbott, E. O., & Craun, G. F. (1995). Introduction to environmental epidemiology. Boca Raton, FL: Lewis.

WHO Commission on Health and Environment, and World Health Organization. (1992). Our planet, our health: Report of the WHO Commission on health and environment. Geneva: Author.


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