Environmental diseases

The environment is intimately associated with human health, illness and mortality. Environmental exposures to potentially hazardous agents such as microbes, toxic chemicals and metals, pesticides and ionizing radiations account for many of the diseases of humans, animals and plants. The concept of ‘environmental disease’ is usually applied to illnesses from chemical exposure due to environmental pollution. In other words illnesses and conditions caused by factors in the environment are collectively called environmental diseases. Pesticides, chemicals, radiation, air pollution and water pollution are some of the man-made hazards that are believed to contribute to human illnesses. Human beings made the global commons air, water and land into the global dustbins of human wastes.

Exposures to environmental pollution remain a major source of health risk throughout the world. Globally an estimated 24 percent of the disease burden (loss of healthy life years) and an estimated 23 percent of all deaths (premature mortality) was attributed to environmental factors. Among the children 0-14 years of age, the proportion of deaths attributed to the environment was as high as 36%. Of the 102 major diseases covered by the World Heath Report in 2004, environmental risk factors contributed to disease burden in 85 categories. Poor air quality contributes to cancers, cardiovascular diseases, asthma and other illnesses. Poor water quality can lead to gastrointestinal illness, neurological problems and cancer. Pollution is one of the biggest global killers, affecting over 100 million people.

Globally the two groups of people that are most affected by environmental diseases are the rural poor and the urban poor who live in slums.  About 25-50% of the world’s urban population live in extreme poverty. They lack basic necessesities for a decent life such as adequate housing, drinking water, sanitation or garbage collection. About 75% of the rural households in India burning wood, dung cakes and crop residues for cooking. Epidemiological studies in developing countries have linked exposure to indoor air pollution from biofuels with four major categories of illnesses: acute respiratory infections (ARI) in children; chronic obstructive lung diseases such as asthma and chronic bronchitis; lung cancer and still-births and other problems at birth. Rural coal smoke exposures seem to increase lung cancer risks by a factor of nine or more. Lung cancer in China is attributed to high levels of coal smoke. 

One recent study in Colombia found women exposed to smoke during cooking were more than three times more likely suffer from chronic lung disease. In developed countries, energy efficiency improvements make houses relatively airtight, reducing ventilation and raising indoor pollution levels. Increasing numbers of urban homes and buildings are now ‘air tight’ which can lock in bio-allergens (dust mites, moulds, cockroaches, insect droppings or animal dander) and also irritants (dust, odours from oil paints, room fresheners) and other pollutants. These urban environmental conditions may lead to ‘sick – building syndrome’ (SBS). A number lifestyle changes in living conditions in the indoor environment such as carpeting, upholstered furniture, mattresses, humidifiers and air conditioning make it easier for dust mites and moulds to thrive.

An estimated 500,000 women and children die in India each year due to indoor air pollution (IAP) – related causes, which is 25% of the estimated IAP-related deaths worldwide (World Bank Report). A report of WHO in 2002 showed that 36% of lower respiratory infections were attributable to solid fuel use alone and 1% of all respiratory infections to outdoor pollution.

Causes of environmental diseases

Industrial growth, urbanization and the increasing use of synthetic organic substances have serious and adverse impact on the environment. Population growth indirectly driving climate changes by contributing to deforestation, overgrazing, soil erosion and desertification. Overuse of land may lead to a drop in food production, depletion of natural resources and a rise in pollution.  Chemical fertilization, chemical control of insect pests and weeds, mechanization and irrigation all have an impact on the land environment. The land vegetation and organic matter had been reduced about one-third. ‘Formerly man had been part of nature’ said Lynn White Jr. and ‘now he was the exploiter of nature’. Man dominates all other living creatures and exploits all available natural resources. He has been working as an agent of all environmental degradation and now he becomes its prime victim.

Types of environmental diseases

1.    Vector – borne diseases – transmitted through insects e.g., malaria, dengue fever, encephalitis, schistosomiasis.

2.    Vessel – borne diseases – transmitted through some kind of vessel e.g., a cup, water, food, milk, blood etc. e.g., diarrhoea, dysentery, cholera.

3.    Air – borne diseases – transmitted through air medium e.g., flu, tuberculosis, measles, heart and lung diseases and cancer.

Malaria is strongly connected to environmental factors such as climate, rainfall, irrigation and sanitation. Malaria is caused by the blood parasite plasmodium. This parasite is transmitted by the bite of an infected female anopheles mosquito. An estimated 42% of the global malaria burden could be prevented by environmental management.

World Health organization (2002) estimated that 88% of all causes of diarrhoea globally were attributed to water pollution, sanitation and hygiene. About 18% of the world’s population still lacks access to safe drinking water and nearly 40% have no access to proper sanitation.

Examples of environmental diseases

Air pollutants have both acute and chronic effects on human health. Urban air pollutants can cause or exacerbate cardiovascular disease, cancer, allergies, asthma and lung disease. Benzene, nitrogen dioxide and small particulate matter can cause damage to the bone marrow and the immune system.  Air pollution is shown to be the cause for 1 in 10 deaths due to lung cancer. Air borne particulates increase the severity of asthma attacks, lung disease and chronic obstructive pulmonary disease (COPD). Exposure of humans to air pollutants may be a cause for acute respiratory distress syndrome (ARDS), sick building syndrome (SBS), multiple chemical sensitivities (MCS), and chronic fatigue syndrome (CFS).

Water – and food – borne diseases that result in diarrhoea or dysentery are the leading cause of environment – related health problems in the world. The primary diarrheal diseases include amoebiasis, cholera, giardiasis, and other protozoal diseases; samonellosis, shigellosis, typhoid and paratyphoid fevers and viral diseases. These diseases collectively cause more than 16% of the global environmental disease burden (58 million DALYs per year) and 13% of deaths (1.7 million per year).

Human health effects of heavy metals in soil include brain and nervous system damage, kidney damage, liver toxicity and birth defects.

Ultraviolet and other ionizing radiations are very damaging to cell components and DNA and they trigger development of cancerous tumours.

Quotes for reflection

“Pollution of the environment  is the root cause of all human health problems”.

"Environmental pollution is an incurable disease. It can only be prevented."
                                                                                 -Barry Commoner.