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Written by Professor Omar Hasan Kasule Sr.
MODULE OUTLINE
8.1 ENVIRONMENTAL EXPOSURES
8.1.1 The Environmental Problem
8.1.2 Environmental Pollution
8.1.3 Epidemiological Studies
8.1.4 Risk Assessment and Management
8.2 OCCUPATIONAL EXPOSURES
8.2.1 Introduction
8.2.2 Occupational Hazards and Diseases
8.2.3 Occupational Health Studies
8.2.4 Prevention of Occupational Disease
8.3 NUTRITIONAL EXPOSURES
8.3.1 Introduction
8.3.2 Incidence and Prevalence of Malnutrition
8.3.3 Diseases Associated with Malnutrition
8.3.4 Assessment of Nutritional Status
8.3.5 Epidemiological Studies of Nutritional Exposures
8.4 RADIATIONAL EXPOSURES
8.4.1 Over-View
8.4.2 Radiations: Types, Sources, and Measurement
8.4.3 Effects of Radiation
8.5 OTHER EXPOSURES
8.5.1 Biological Markers
8.5.2 Genetic Exposures
8.5.3. Pharmaceutical Agents
UNIT 8.1
Learning Objectives
· Sources of air pollution: indoor pollutants, out-door pollutants
· Sources of water pollution: municipal sewage, industry
· Sources of soil pollution: solid waste, hazardous waste, sewage
· Types of eco-poisons: pesticides and PCB
· Prevention of pollution: primary and secondary
Key Words and Terms
· Acid rain
· Air pollution
· Dental waste
· Drug residues
· Eco-poisons
· Environmental health
· Environmental degradation
· Environmental engineering
· Environmental ethics
· Environmental exposure
· Environmental health
· Environmental impact analysis
· Environmental law
· Environmental medicine
· Environmental monitoring
· Environmental policy
· Environmental pollution
· Environmental protection
· Food microbiology
· Food parasitology
· Green-house effect
· Hazardous substance/waste
· Inhalation exposure
· Maternal exposure
· Maximum permissible exposure level
· Medical waste
· Natural disasters
· Noise and vibration
· Occupational exposure
· Paternal exposure
· Pest control
· Refuse disposal
· Smoke
· Soil pollution
· Vehicle emissions
· Water micro-biology
· Water pollution
UNIT OUTLINE
8.1.1 THE ENVIRONMENTAL PROBLEM
A. Definition and Scope of Environmental Epidemiology:
B. Ecology
C. Population and the Environment
D. Background to the Environmental Problem:
E. Effect of the Environment on Health
8.1.2 ENVIRONMENTAL POLLUTION
A. Air Pollution
B. Water Pollution
C. Soil Pollution
D. Eco-Poisons
E. Others: Food, Animals and Plants
8.1.3 EPIDEMIOLOGICAL STUDIES
A. General
B. Exposure Assessment
C. Measurement of Outcome
D. Confounding
E. Priorities in Environmental Epidemiology Research
8.1.4 RISK ASSESSMENT and MANAGEMENT
A. History
B. Definition of Risk Assessment
C. Risk Management
8.1.1 THE ENVIRONMENTAL PROBLEM
A. DEFINITION AND SCOPE OF ENVIRONMENTAL EPIDEMIOLOGY:
Environmental epidemiology is a sub-discipline that studies environmental causes of human disease and how to prevent those diseases. It seeks to establish exposure-disease relations and to change them. The environment consists of all those substances and phenomena that have an impact on human health and disease at all stages of the human lifespan. The environment can be physical, chemical, biological, social, political, and cultural. Environmental hazards enter the body through the respiratory tract, the alimentary tract, and the skin. Most environmental exposures that have an adverse effect on health are involuntary. The discipline of environmental epidemiology was first concerned with infectious diseases. It later expanded into air, water, and soil pollution. Its scope is now quite wide including: physical and environmental causes of disease, air pollution, water pollution, soil pollution (solid wastes, chemicals, mining, radiological), eco-poisons (e.g. DDT) food toxins, and bacterial infections. The concept of total exposure is used to describe the multi-media exposure in environmental epidemiology i.e. exposures from several and not one source of exposure. Where environmental causes can not be eliminated, environmental epidemiology helps set safe exposure limits. Reducing risk is by restrictions and regulation. Conservation of natural resources may be the definitive approach.
B. ECOLOGY
Ecology is the study of the organism and its environment. The interaction can be described in several modes. Humans interact with energy systems either in the food web or non nutritive energy systems (fossil, electrical, and nuclear). Humans interact with biological systems in the biosphere. They interact with geophysical systems like the earth, water, and the atmosphere. They also interact with biological systems of the biosphere. Human civilization has created systems that were unknown in primitive society and with which humans have to interact such as the built environment (home dwellings, factories, water systems, sewage systems, communication systems, and transport systems), technological activities (manufacturing, mining, energy production), residues and wastes (domestic waste, manufacturing waste, transport waste like CO and HC, and wastes as a result of energy generation). Humans have to interact with environmental hazards that are either natural or are a result ot human activity. Natural disasters may be geophysical such as earthquakes or meteorological such as cyclones, hurricanes, typhoons, and volcanic eruptions. They cause psychosocial stress, and injuries, property losses. The victims are in urgent need of water, food, and shelter. Biological hazards arise as a failure of environmental sanitation. They are disease-causing organisms that may be water-borne, food-borne, or vector-borne. The water borne hazards are polio, HAV, salmonella spp, shigella spp, cholera, E. Histolytica, and G.lamblia. Food-borne outbreaks are caused by viruses, bacteria, or protozoa. Vector borne hazards arise due to conditions that encourage the breeding of vectors (mosquitoes, fleas, lice, ticks, etc): standing water, overloaded sewage, and improper handling of wastes. Mosquitoes in particular thrive in mismanaged irrigation waters, water in discarded automobile tyres. Open drains are breeding places for rodents. Chemical hazards are mostly man-made and may be solid, liquid, or gaseous. Physical hazards are extremes of temperature, humidity, noise, vibration, tools and equipment. Heat causes heat stroke and heat exhaustion. Extreme cold causes hypothermia. Life at high altitude is difficult because of shortage of oxygen. Drowning in water causes death. Electric shocks cause extensive tissue damage. Noise and vibration have physical and psychological effects. Noise is defined as unwanted sound. Noise is annoying. It disturbs sleep, conversation, rest and home life. Besides annoyance, noise impairs hearing, causes stress, causes emotional problems, and reduces concentration which increases the risk of unintentional injury. Construction noise is temporary. Traffic noise is permanent but peak hours vary. Sound meters are used to measure the frequency and amplitude of sound which are expressed in decibels. Noise pollution is controlled by legislation to control sources of noise, education, and environmental change (padding, and ear plugs). Vibration usually accompanies noise. The sources of vibration are: industry, construction, road traffic, and the supersonic boom of aircraft.
C. POPULATION AND THE ENVIRONMENT
Carrying capacity is the amount of resources (air, water, shelter, etc) in a given environment needed to support a population of a given size. Population doubling time is directly proportional to the annual population growth rate. The doubling times in years for various growth rates is as follows: 0.5% - 140 years, 1.0% 70 years, 2.0% 35 years, 3.0% 24 years, and 4.0% 17 years. Population increase can result into environmental degradation if the carrying capacity is not increase proportionately. A higher population is associated with production of more waste and therefore more air and water pollution, higher energy demands which leads to higher fossil fuel use and hence pollution, higher food demand, less land for agriculture, less living space per person, less available resources leading to crime and war, higher health care demand, higher housing demand. Population increase is controlled naturally by starvation, epidemics or wars or artificially by contraceptives.
D. BACKGROUND TO THE ENVIRONMENTAL PROBLEM:
The earth consists of the lithosphere (land mass) and the hydrosphere (water mass). The biosphere is part of the earth in which life exists. The ecosystem is biotic and abiotic. It is dynamic as evidenced by the carbon, nitrogen, phosphorus, and energy cycles. The current problems facing the biosphere are: waste disposal, destruction of ecosystems, and desertification. The ozone layer protects against ultra-violet rays. This protective layer is being depleted by hydrocarbon release into the atmosphere. Environmental health emergencies: chemical spills, earthquakes, floods, forest fires, landslides, and radioactive spills. Population growth leads to environmental degradation unless special measures are taken. More people use more of the natural resources which if not replaced will be deleted. Energy consumption is increasing. Fossil fuels cause air pollution. Alternative fuels such as nuclear power, geothermal power, solar power, and the biomass do also have environmental risks. Industrialized nations have more per capita energy consumption than the less developed countries and hence have more pollution. Increasing industrialization leading to ecological damage, exposure to chemical & physical hazards. Pesticides used in agriculture, noise, and radiation are other causes of the environmental problem. In response to the increasing environmental degradation, special laws have been passed in many countries. An environmental impact statement is now required before approval of new industrial developments.
E. EFFECT OF THE ENVIRONMENT ON HEALTH
Carcinogenesis:
Environmental epidemiology is concerned with investigation of chemicals that are toxic or carcinogenic. Environmental carcinogens are chemical or radiation. They cause mutagenesis by changing the DNA molecule or the DNA structure. The mechanisms of mutagenesis are: break, base substitution, intercalation, and frame shift. DNA repair often repairs the damage but may fail in some cases. Testing of mutagenicity is by in vivo animal tests or in vitro. Reproductive teratogenesis/toxicity: paternal or maternal exposure.
Toxicology operates using three laws: the dose makes the poison, chemical agents have specific effects, and humans are animals. When chemicals come into contact with the human they are absorbed, distributed, metabolized, and excreted. Differences among humans in susceptibility are not understood. Toxicology tests the safety of chemicals and helps set environmental standards.