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Chapter 1: Introduction - The Environment At Risk

Overview

  • Series Editor: Richard Riegelman

  • Essentials of Environmental Health: Third Edition by Robert H. Friis

  • Publication: Copyright © 2019 by Jones & Bartlett Learning, LLC

Learning Objectives

By the end of this chapter, the reader will be able to:

  • Describe how environmental health problems influence our lives.

  • Describe the potential impacts of population growth upon the environment.

  • State a definition of the term "environmental health."

  • List at least five major events in the history of environmental health.

  • Summarize employment opportunities in the environmental health field.

Environmental Quality

  • Maintaining environmental quality is a pressing task for the 21st century.

Environmental Health Threats

  • Trash fouling beaches.

  • Hazardous wastes, including radioactive wastes, leaching from disposal sites.

  • Ongoing episodes of air pollution.

  • Exposures to toxic chemicals.

  • Destruction of land through deforestation.

  • Global warming.

Population and Environment: The Three P’s

  • Principal determinants of health worldwide:

    • Pollution

    • Population

    • Poverty

Pollution

  • Sources:

    • Combustion of fossil fuels (Petroleum, Coal)

    • Dispersal of greenhouse gases into the atmosphere leading to:

      • Global warming

      • Change in distribution of insect vectors

Population

  • Overpopulation in developing nations exceeds the planet's carrying capacity.

  • World population may reach 10–12 billion during the 21st century, related to urban crowding.

Infectious Disease Epidemics

  • Avian Influenza A (H5N1): Outbreaks on poultry farms in Asia leading to mutations allowing human transmission, resulting in a pandemic.

  • Swine Flu (H1N1): Spread from North America to other parts of the globe, declared a pandemic by WHO.

Poverty

  • Linked to population growth.

  • Recognized determinant of adverse health outcomes.

Significance of the Environment for Human Health

  • Hazardous agents account for many forms of environmentally associated morbidity and mortality, including microbes, toxic chemicals, pesticides, and ionizing radiation.

Scope of Environmental Health Problems

  • Challenges include elevated blood lead levels, asthma prevalence, links to neurodevelopmental toxicity, and degraded air quality worldwide thought to significantly contribute to cancer development.

Environmental Risk Transition

  • Before Transition: Poor quality of food, air, and water.

  • After Transition: Emergence of new environmental problems like acid rain precursors, ozone-depleting chemicals, and greenhouse gases.

Population Growth

  • Increasing at an exponential rate.

  • Threat to overwhelm available resources and may cause periodic food scarcity and famine.

Causes of Population Growth

  • Increases in fertility, reductions in mortality, migration.

Trends in Population Growth

  • 6 billion people in 1999

  • 7.5 billion in 2017

  • Estimated 8 billion between 2018 and 2028, potentials for stabilization around 10 billion.

Population Dynamics

  • Interrelationships among variables influencing demographic makeup and population sizes.

Fertility

  • Total fertility rate (TFR): Number of children born to a woman by the end of childbearing.

  • U.S. fertility rate: about 2.0 births per woman (2012).

  • Estimated natural population replacement rate: 2.1.

Fertility Trends

  • Countries at/close to replacement rate:

    • North America: U.S., Canada

    • Asia: Japan, South Korea, Thailand, China

    • Europe: many countries.

  • Countries with TFR of 4.0: many Asian, Latin American, and African countries.

Demographic Transition

  • Alterations over time in a population’s fertility, mortality, and makeup.

  • Developed societies have progressed through three stages affecting age and sex distributions.

Three Stages of Demographic Transition

  • Stage 1: High fertility and mortality rates, small population.

  • Stage 2: Decreasing mortality rates, high fertility rates, rapid population increase.

  • Stage 3: Decreasing fertility rates, more even population distribution.

Epidemiologic Transition

  • Shift in patterns of morbidity and mortality from primarily infectious diseases to chronic, degenerative diseases.

Examples of Epidemiologic Transition

  • Cardiovascular diseases, cancer, neuropsychiatric conditions, injuries.

Consequences of Population Increases

  • Urbanization, overtaxing carrying capacity, food insecurity, loss of biodiversity.

Urbanization Trends

  • Proportion of urban residents: 5% in 1800, 50% in 2000, projecting 66% by 2030.

Factors Leading to Urbanization

  • Industrialization, food availability, employment opportunities, lifestyle choices, escape from political conflict.

Hazards of the Urban Environment

  1. Biological pathogens or pollutants.

  2. Chemical pollutants, including industrial wastes.

  3. Reduced availability and quality of natural resources.

  4. Physical hazards such as flooding and mudslides.

  5. Overcrowding and inadequate infrastructure.

  6. Natural resource degradation, impacting soil and water quality.

Carrying Capacity

  • Population that can be supported without environmental deterioration, limiting population size influenced by food availability, reproductive behavior, and infectious diseases.

Population Crashes

  • Overpopulation may disrupt essential life support systems, potentially leading to a species population crash.

Key Terms and Definitions

  1. Environment: The complex of physical, chemical, and biotic factors affecting organisms and ecosystems.

  2. Ecological Model: Interlinked determinants of health across an individual's life course.

  3. Ecosystem: A dynamic complex of communities and the nonliving environment interacting as a functional unit.

  4. Environmental Health: Addresses external factors impacting health and behaviors.

Historical Background

  • Hippocrates: Greek philosopher, focused on environmental influences on health.

  • Ancient Romans: Developed infrastructure for public health including water and sewage transport.

Current Hot Topics in Environmental Health

  • Environmental justice, global warming, nuclear power, pesticides and herbicides, war, and terrorism.

Careers in Environmental Health

  • Industrial Hygienist: Controls hazards affecting workers/community.

  • Toxicologist: Studies toxic chemicals' effects on health.

  • Environmental Health Inspector: Monitors compliance with regulations.

  • Food Safety Specialist: Ensures the safety of public food supply.

  • Vector Control Specialist: Manages disease spread by vectors.

  • Research Analyst: Conducts research on exposure risks.

  • Occupational Health Professional: Works on occupational health issues.

  • Environmental Lawyer: Aids in environmental policy and litigation.