Sunday, January 31, 2010

Environmental threats to human health

Health is becoming a core value in all aspects of our daily activities from the products we use, to the places we go and the choices we make in our daily life.Health is a product of complex interactions between the external environment, individual behavior and inherited traits.Environmental problems have taken center stage in the 21st century and will present enormous challenges to human health ,national economy, public security and natural resources for generation to come.The human activities affect the earth at a global scale in complex, interactive and accelerating ways.There is a growing evidence that human health is negatively effected by a polluted environment.The World Health Organization (2003) in a press release stated that “ there is growing evidence that changes in the global climate will have profound effects on the health and well-being of citizens in countries throughout the world”.Hippocrates  was the first to relate disease like malaria to environmental and social ecosystems such as season, diet and living conditions. The environment is fragile. It is easily damaged by human activities through pollution and many other forms of abuse. The survival of humanity is threatened by three major crises : Environmental crisis, Food crisis and Energy crisis.

Profile of Environmental Degradation

The environment, which sustains human life, is also a veritable source of ill health for many of the world’s people. Chronic environmental degradation threatens people worldwide and undercuts the livelihoods of at least half a billion people. Environmental health problems vary dramatically from region to region, reflecting geography, climate (heat and humidity) and a country’s level of economic growth and social development. Many environmental health problems are associated with poverty and a lack of essential resources like sufficient and clean water, food, shelter, fuel and air. In many developing countries, both pesticides and feces may contaminate drinking water; air pollution may arise both from the household burning of biomass fuels and the industrial use of fossil fuels.

Environmental impact on human diseases

World Health Organization (WHO) has estimated that as much as 23 percent of the global burden of disease is associated with environmental factors. Every year nearly 3 million people die of air pollution – more than 80% of them of indoor air pollution and more than 5 million die of diarrhoeal diseases caused caused by water contamination. Environmental change and its attendant health impacts are driven by many factors including population growth, increased consumerism, agricultural intensification, industrialization, urbanization, transportation and rising energy use.

Definition of Environmental Health

World Health Organization ( WHO 1993) defined as the “ Environmental health comprises those aspects of human health, including quality of life , that are determined by physical, chemical, biologic, social and psycho-social factors in the environment”.
Environmental health refers to the theory and practice of assessing, correcting, controlling and preventing these factors in the environment that potentially can adversely affect the health of present and future generations (WHO,1993).
Environmental health relates to ecological factors, human activity ( production or consumption) and human behavior that impact socioeconomic condition and environmental life support systems and potentially affect the well-being of present and future generations by increasing human disease, injury, conditions and premature death. Thus any external factors that negatively affects human health can be considered an environmental health hazard. 

Poverty and Health Risks

Poverty has harmful environmental and health effects. Poor people are unable to secure the basic  necessities for a healthy life – adequate food ,water, clothing, shelter and health care. Poor people are more likely to live in an unhealthy environment.Pollution and environmental degradation have a severe impact on the poor people. In rural areas and urban slums, inadequate shelter, over- crowding, lack of adequate safe water and sanitation, contaminated food and indoor air pollution are the greatest environmental threats to human health. These conditions are often compounded by poor nutrition and lack of education, which make people more vulnerable to environmental health risks. Often , unhygienic living conditions spread diseases such as typhoid, cholera, malaria and hepatitis. Exposure to infectious and chemical agents can stunt physical growth, impair cognitive skills and hamper educational participation and performance, thereby reducing the future potential of individuals, and perhaps , of society as a whole.

Kinds of Environmental Health Hazards

In general , environmental change can degrade human health either directly by exposing people to harmful agents or indirectly by disrupting the ecosystems that sustain life. Environmental hazards to health fall into two broad categories. The first is the lack of access to essential environmental resources like clean water, food , shelter, fuel and air. The second category is exposure to hazards in the environment. The quality of human life is directly related to the quality of the environment. Man is subjected to a variety of environmental hazards such as :

  • · Physical hazards
  • · Chemical hazards
  • · Biological hazards
  • · Psychological / sociological hazards

Physical Hazards

Climate and weather have a powerful impact on human health and well being. Climate change directly affects human health through temperature and weather extremes. A number of indirect impacts are likely to arise from changes in precipitation and temperature patterns, which may disturb natural diseases, harm agriculture and freshwater supplies. These indirect effects may, in the long run, have greater cumulative impacts on human health than the direct effects.
Global warming may increase the number and severity of heat waves and produce large changes in the frequency of extreme weather events such as hurricanes (cyclones), violent thunder storms, and wind storms. These induced natural disasters cause a heavy burden in the destruction of lives and property. High temperature speed up the life cycles of both mosquito and the disease organisms. Climate change will affect plant pests and diseases in the same way as it affects infectious disease agents. The long – term danger to human health from climate change will be the disruption of natural ecosystems, which provide an array of services like food, materials and medicines that ultimately support human health.
The extreme weather events can directly affect human health through injuries and deaths from trauma and drowning. Loss of housing, sanitary facilities, social structure and contaminating existing water supplies can lead to increased transmission of communication disease. Transmission of vector borne disease typically increase because the disrupted conditions favor vector breeding and human contact. In the long term, mental strain and physical illness may result from economic losses due to damage to agriculture and livestock. Other examples of physical hazards include radiation, temperature extremes and excessive noise. Radiation may be ionizing or non-ionizing; natural or man-made. Man-made ionizing radiations are produced from nuclear explosives, nuclear power, medical and dental radiography and occupational exposure.
Anthropogenic activities discharge fine particulates containing organic as well as inorganic compounds into the atmosphere.The sources of particulate matter include motor vehicle emissions, power generation, industrial combustion, construction and demolition activities. Larger particles tend to deposit in the extra-thoracic and upper tracheobronchial region whereas small particles show greater deposition in the deep lung. Ultra fine particles are able to pass directly into the circulatory system leading to heart and lung diseases.

Chemical Hazards

Exposure to chemical agents in the environment through air, water, food and soil has been implicated numerous adverse health effects from cancer to lung disease and brain damage to birth defects. Exposure to pesticides can lead to symptoms of acute poisoning such as headaches, allergies, dizziness, skin problems or blurred vision. Other acute responses include chemical burns, paralysis, blindness and even death. Long-term pesticide poisoning will lead to suppression of body’s defense, reproductive damage and various cancers. Persistent Organic Pollutants (POPs) are long-lived organic compounds (e.g. DDT) that become more concentrated as they move up the food chain. The adverse health effects from POP exposure may include immune dysfunction, neurological disorders, reproductive anomalies, behavioural abnormalities.Volatile organic compounds(VOCs) are a diverse group of easily evaporated organic compounds such as octane,benzene and toluene that may be toxic at high exposure levels. VOCs are found in paints, paint thinners, lacquers, hair sprays, perfumes, oven cleaners and dry cleaning liquids.VOCs can cause eye and skin irritation and in high concentrations damage the liver , kidney or central nervous system. The Endocrine disruptors are a group of chemicals that can alter the critical hormonal balances required for a proper health and development at all stages of life. Common hormone disruptors include phthalates (found in some cosmetics and plastics), Bisphenol A ( found in a type of plastic in tin can linings and some water bottles) and DDT(a pesticide).Exposure to these hormonally active agents has been linked to early puberty, impaired fertility, impaired males fetus sexual development and some cancers.

Biological Hazards

Environmental pathogens are defined as microorganisms that normally spend a substantial part of their life cycle outside human hosts, but when introduced to humans cause disease with measurable frequency. They are carried in the water, soil, air, food and other parts of the environment and can affect almost every individual on the planet.Environmental conditions increase the biological organism’s ability to thrive or spread. Of all the infectious diseases, diarrhea has perhaps the clearest links to the environment. Diarrhea is spread by both bacteria ans viruses through contaminated food or water. Diarrhea diseases arise through contact with human faces and are spread by fecal oral route. Cholera and hepatitis A and E are generally spread by contact with water or food contaminated with human feces. Diarrhea diseases are the worlds major cause of infant mortality. Studies estimate that the provision of clean water and basic sanitation would reduce the incidence of diarrhea by 50 per cent, cholera by 90 per cent, sleeping sickness by 80 per cent and Guinea worm infestation by 100 percent (UNEP 1987).                                         

Psychological and sociological Hazards

Noise, overcrowding, lack of privacy, traffic congestion; lack of open space have social and psychological consequences.


Understanding the complex links between the environment and health is important. To date, however, little research has been conducted on how much environmental factors add to the world’s burden of ill health. Conditions in both the global and the local environment are critical to our health and well-being. Indeed, environment – related risks can be deadly: each year, infectious diseases linked to environmental conditions kill one out of every five children in the poorest regions of the world. Implementing preventive actions to reduce environmental threats to health risks will entail devising public policies, educating society and making financial investments for health care.One of the best opportunities to improve health through preventive action is to improve the household and community environment. Such actions include expanding access to clean water, sanitation and hygiene education. 
There are 3 key requirements for developing a sustainable community:
Ecological Health - use nature’s productivity without damaging it.
Community Health -foster social well-being, through the promotion of fairness,equity and co-operation.
Individual Health – secure food,shelter,health care,education etc. for everyone.
Sustainable development is human development that is ecologically sustainable. The development is based on peace, economic development, social betterment and effective national governance.Its aims are human freedom, opportunity and higher quality of life.


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