The Link Between Environmental Health and Human Health

The environment has long been known to be linked to human health. The germ theory revolutionized both medicine and our views of environmental sanitation. Not surprisingly, global regions with poor sanitation have higher rates of infectious disease. However, being too clean may also have adverse effects on human health. Lastly, treating the environment poorly can also reciprocate itself on humans by promoting the emergence of novel diseases.

Regions of the globe with poor socioeconomic status and poor sanitation have levels of infectious diseases that not been observed in developed countries in a very long time. Such diseases include cholera, typhoid, polio, hepatitis, and numerous others. Through improved sanitation, enhanced personal hygiene, and education, these diseases are very small to non-existent in developed nations. Although these diseases are ranked high in importance by the World Health Organization, there is little concern about them in the United States.

In sharp contrast to this, asthma is becoming a major public health problem in developed countries, while it is almost non-existent in developing regions. The theory behind this is that individuals in regions with poor sanitation are exposed to more agents early on in life that balance the immune response. If an individual is too clean, when their immune system encounters and allergen, or an agent that stimulates the immune system, it may become over-stimulated. This theory is known as the hygiene hypothesis. The exposure to certain microbes early on in life is thought to modulate normal bacterial flora and also to help shape a balanced immune system (for more detail and examples see the hygiene hypothesis reference).

The health of the Environment, not just in sanitation terms, can also have an effect on human health. Deforestation, the movement of humans into unsettled regions of the globe, and mass animal farming is thought to be leading to the development of pathogens known as "emerging infectious diseases." A perfect example is the emergence of 2009 H1N1 influenza virus, also known as swine flu, that contained genes from the version of the virus that infects pigs. Scarier pathogens and disease examples include west nile virus, lyme disease, HIV, rift valley fever, and several others.

The link between the environment and human health is both logical and sometimes counterintuitive. Either way, humans need to find balance with the environment to learn how to best promote healthy living. Also, humans need to take care to respect the environment such that its damage does not reciprocate on mankind. Although this article focused on infectious disease, other forms of damage that include pollution and atmospheric damage can also have deleterious consequences for human health and need to be kept in consideration.

References:

Bloomfield SF, Stanwell-Smith R, Crevel RW, Pickup J. Too clean, or not too clean: the hygiene hypothesis and home hygiene. Clin Exp Allergy. 2006 Apr;36(4):402-25

Emerging Infectious Diseases. http://www.cdc.gov/ncidod/diseases/eid/. Accessed 3/30/2010.

Wastewater and excreta: Hazards or resources? http://www.who.int/water_sanitation_health/sanitproblems/en/index2.html. accessed 3/30/2010.