The Effect of Population Density on Personal Health

"If current predictions of population growth prove accurate and patterns of human activity on the planet remain unchanged, science and technology may not be able to prevent either irreversible degradation of the environment or continued poverty for much of the world." This statement, written in a 1992 status report issued jointly by the U.S. National Academy of Sciences and the Royal Society of London, reflects the concerns the scientific community has for the future of our planet if the set course remains the same. Clearly, technology is not considered to be the panacea that will block all negative consequences of degrading the environment. While nature, when given the opportunity, will recover and overcome much of the damage done, there is a limit to which it is capable of rebounding.

Population Density

Issues that surround population growth and how to control its progress are complicated and involve societal mores, religious beliefs and economic factors. During the past 300 years, the world's population has grown at an exponential rate. Six billion people live on the planet today. As illustrated by the graph, there were only two billion people in 1930, but by 1960, just 30 years later, there were three billion. In 1975, only 15 years later, the population reached four billion. In the 12 years between 1975 and 1987, it grew to five billion. Projections indicate that the population may hit the ten billion mark by 2020.

Degradation of the Environment

While humans have always impacted the environment in the quest to improve their quality of life, the scale and rate of changes made during the past 50 years have had profound effects. Declining fish catches, falling water tables, progressive depletion of the ozone layer, eutrophication, and fresh water scarcity are all indications that the environment is undergoing significant change due to industrialization and population growth. Societal demands and an increase in population have stretched or exceeded the carrying capacity of many ecosystems.

The United States: Population Density and Resource Management

How is the environment affected, especially in urban areas, as the United States continues to grow by 2.5 million people annually? Cities have had to devise methods to efficiently and effectively manage resource availability and consumption as well as the disposal of various kinds of waste. At present, heavily populated areas are undergoing significant changes. The increase in population in the United States in certain areas has placed a strain on one of our most important resources-water. Although the United States enjoys a plentiful renewable water supply, averaging almost 10,000 cubic meters per person per year, sometimes regional demands for water exceed the water supply. For example, the U.S. population is not evenly distributed throughout the country, as 46% of the population in the United States live in or near coastal regions.

Safe Drinking Water and Health

There is no such thing as naturally pure water. As the "universal solvent," water dissolves more substances than any other liquid. In nature, all water contains some impurities. As water flows in streams, sits in lakes, and filters through layers of soil and rock in the ground, it dissolves and/or absorbs many of the substances with which it comes into contact.
Some of these substances are harmless. In fact, some people prefer mineral water because they feel that minerals give it an appealing taste or health benefit. However, at certain levels minerals, just like man-made chemicals, are considered contaminants and can make drinking water unpalatable or even unsafe. The sources of contaminants might be your neighborhood or your own home, or they might be many miles away at the purification plant. Surface water (collected from a river or lake) can become contaminated by industrial wastes, farm runoff, storm water runoff, acid deposition and human and animal wastes. Although some natural cleansing may take place when water is exposed to sunlight and certain microorganisms, intervention to restore the water quality usually takes place at the water treatment facility before it is sent to residents within a municipality. Surface water accounts for approximately 56% of water used for domestic purposes. Groundwater, while somewhat better protected because it is collected from deep within the earth, is also subject to contamination. Leaking underground storage tanks, careless disposal of household hazardous wastes, leachate from landfills and septic tanks, agricultural chemicals and waste can adversely affect the quality of groundwater. Some natural cleansing occurs as the water moves through the various soil and rock layers. However, when groundwater becomes contaminated, it is usually more costly and difficult to restore its quality than it is to restore the quality of surface water. Groundwater sources supply about 44% of all water used for domestic purposes in the United States.
	When chemicals and microorganisms contaminate the water supply, there is always a potential risk to the health of both humans and other living things. Certain cancers, birth defects, nervous system disorders and circulatory problems have all been linked to some of the chemicals that may contaminate drinking water.
The EPA has set safety standards for more than 80 contaminants that may occur in drinking water and pose a risk to human health. These contaminants are placed into two groups according to the health effects that they may cause. Acute effects occur within hours or days of the time that a person consumes a contaminant. An example of such an acute effect was the 1993 outbreak of cryptosporidiosis in Milwaukee where over 400,000 people became ill from the city's drinking water. Chronic effects occur after people consume a contaminant for many years in amounts that exceed safe levels. The drinking water contaminants that can have chronic effects are chemicals (such as solvents and pesticides), radionuclides (such as radium), and minerals (such as arsenic). Examples of chronic effects of drinking water contaminants are cancer, liver or kidney problems, or reproductive difficulties.

Status of Drinking Water in the U.S.

Today, the United States has one of the safest water supplies in the world. However, national statistics don't tell you specifically about the quality and safety of the water coming out of your tap. That's because drinking water quality varies from place to place, depending on the condition of the water source from which it is drawn and the treatment it receives.
The U.S. Environmental Protection Agency sets maximum levels of a contaminant in drinking water at a level at which no known or anticipated adverse affect on health of persons would occur, and which allows for an adequate margin of safety (check the EPA website for more information).