Thursday, July 10, 2014

Selected Readings on Human Health, Disease, and the Environment

The following are responses and summaries of various readings related to Human Health, Disease, and the Environment. 
Life Support: Urban and Transboundary Air Pollution
Since the Industrial Revolution people have been studying the effects of pollutants on lung disease.  During the Industrial Revolution entire communities of North America and Europe fell seriously ill or died from air pollutants.  These episodes were a result of air stagnation, which increased the concentration of pollutants in the atmosphere, more specifically those of sulfur dioxide and suspended particulates.  Because of these episodes scientists and governments began studying the adverse effects of pollution – identifying the sources of pollutants, and discovering exposure-response relationships, eventually leading to controls against pollution.  Because the air cannot be contained pollution is able to travel across borders.  Poorer nations generally have a greater problem with pollution than wealthier ones, especially due to the heavy use of coal for power and heating.  The countries which have found ways to reduce the emissions of pollutants from industry, power plants, and automobiles have created new problems via the formation of acids and ozone from their outputs.  The most common adverse health effects due to pollution are caused by sulfur dioxide, particulates, photochemical oxidants, ozone and nitrogen dioxide, and carbon monoxide.  Sulfur dioxide is a result of the combustion of fossil fuels such as coal and crude oil, generally affiliated with power plants and oil refineries.  Great reductions in the measurements of sulfur dioxide and related pollutants were achieved after the Clean Air Act of 1970s America.  However, the tall stacks which were implemented merely send the pollutants higher into the atmosphere where they are able to change into acid aerosols.  Particulates are the result of industrial activity which put off particles into the air which do not easily dissipate.  Particulate counts have been shown related with an increase in mortality rates.  Finer particles have been shown to be much more detrimental to respiratory systems than more coarse particles. In areas with high particulate levels deaths in children from respiratory illnesses is equally high.  In the developing world only infant diarrhea accounts for more deaths in children under the age of five.  Ozone and nitrogen dioxide are most commonly produced by sunlight on the output of automobiles.  When the amount of sunlight is greatest during the summer the greatest amount of ozone is produced.  The safest area to avoid exposure to ozone is indoors because ozone seems to be unable to contact surfaces chemically unchanged.  Carbon monoxide is another major automobile emission.  Many major U.S. cities have exceedingly unhealthy levels of carbon monoxide.  Carbon monoxide impairs the transport of oxygen throughout the cardiovascular system, the effects of which can be headache, dizziness, fatigue, and even death.  Poorer nations who use wood, crop residues, animal dung, and other carbon based fuels for cooking and heating are especially at risk for indoor pollution.  The government has failed greatly in studying the problem of pollution indoors.  Nations need to work together in finding solutions to the ever-growing pollution problem, as it is a global issue not only local one.

Water Quality and Water Resources
Over two million children die every year due to diarrhea related illnesses, often attributed to waterborne infections.  The greatest threat to the quality of water is waste disposal.  Increased quality of waste disposal will improve human health much more than trying to find cleaner water supplies.  The majority of human water consumption comes from surface water which is also the most susceptible to contamination by chemicals and pathogens.  Most of human water consumption is not used for drinking, as nearly seventy percent of the worlds water use is for the irrigation of agriculture and most home use is for the flushing of toilets, washing of clothes, showering, and small landscape and agriculture.  Much work has been put in to the development of legislation regarding the issue of point source contamination in drinking water, however due to poor enforcement point source contamination is still a problem especially in the developing world.  Chemical contamination seems to be the greatest threat to the safety of drinking water as it is not so easily destroyed by boiling.  Often water contaminated with chemicals requires additional treatment, usually by the use of activated charcoal or special ion exchange resins.  Bacteria contaminated waters most often cause diarrheal diseases, however since 1980 there have been no outbreaks of bacterial waterborne diseases in disinfected water supplies.  Though viruses and protozoa related illnesses are much more common as they are more difficult to eliminate.  Nitrates are a major issue in the contamination of water.  When ingested they are converted to a more toxic nitrite in the gastrointestinal tract.  These occur most often in rural areas where agriculture prevails and the majority of drinking water is obtained via ground wells because fertilizers are able to seep into the drinking table easily.  Though many of the worst pesticides have been banned for use for the last thirty years many of them can still be found in the water supplies, though it has yet to be proven that exposure to these contaminated waters increases the risk of cancer.  Radon, occurring natural in the environment, is able to seep into the water supply and cause increased risk of lung cancer through evaporation and inhalation, and increased risk of gastric cancer when ingested.  Arsenic also occurs naturally in the environment and can cause skin and lung cancer, skin hyperpigmentation and keratosis, vascular disease, and neurotoxicity.  Lead, though not used for municipal water systems for the last century, still persists and exposure can lead to decreased intelligence and behavioral problems in children.  Water usage is continuing to grow throughout the world all the while water sources continue to decline.  The relations between nations in areas of inadequate water supplies will likely suffer in the decades to come as populations’ water supply become more strained.  The world needs to become more efficient in its water usage to decrease the detrimental effect on the supply, perhaps using untreated or recyclable water in the circumstances where clean water is not a necessity.  A decrease in the consumption of meat products will also greatly reduce the amount of water used for agriculture, as the grain required for a pound of beef needs at least ten times as much water as an equal pound of grain for human consumption.
Ozone Depletion and Ultraviolet Radiation
Ultraviolet radiation is the cause of photochemical smog, bleaching of paints, and decay of plastics.  UVA is generally much less harmful than UVB radiation.  Chlorofluorocarbons put off by household substances are able to reach the stratosphere they release chlorine and bromine.  Due to this the amount of ozone in the stratosphere has been measure to have greatly decreased in temperate and polar zones during the last twenty years.  The effects the decrease in ozone has can be measure all the way down to the bottom of the marine food chain.  The increase in UVB radiation is not likely to increase the rate of sunburn in people because human skin can easily adapt to gradual change in UVB radiation, though it is believed that increased exposure can cause skin cancer, cataracts, and decreased cellular immunity.  UVB radiation causes damage to DNA and therefore increases the likelihood of cancer.  It has been shown that increased exposure to UVB radiation increases the risk of skin cancer.  Humans do need daily exposure to UVB radiation in order to maintain the levels of vitamin D in their systems, however overexposure can cause problems.  The occurrences of skin cancer is expected to reach its greatest level by the year 2060, when the ozone is predicted to be at its thinnest.  The cases of cataracts is expected to rise one half percent for every one percent decrease in the ozone layer.  UV exposure can be both beneficial and detrimental to skin diseases, however its causing of immunosuppression could cause a greater prevalence of cancers.  The increase in UVB exposure could affect humans indirectly by changes to the environment, though it would be difficult to quantify this.  Though efforts have been made to reduce the ozone depleting emissions of the world, it is difficult for more cash strapped developing nations to change without the help of the wealthier nations. 
U.S. Food Imports Rarely Inspected
The FDA is only able to inspect about 1.3 percent of imported foods which make it into the U.S. annually.  Experts believe that the FDA, and United States government in general, do not have the resources or manpower to effectively ensure the safety of the food which makes its way to our grocery store shelves. The rules and regulations regarding food safety practices in other nations outside of the United States and Western Europe are often poorly enforced if existing at all.  The food supply has become global and therefore the FDA is finding itself stretched too thin.  It must focus on the foods and producers which are most likely to be contaminated with potentially harmful bacteria and chemicals.  The problem arises when food that is not expected to be contaminated makes its way in without any inspection occurring at all, happening more often than believed.  China and other developing nations are the main cause for the contaminated foods which enter the U.S. as the laws regarding their inspection are often very lax in comparison to our own.  Just over the last ten years the U.S. consumption of Chinese exports has tripled.  China is only bested by Mexico in its suspicion by the U.S. food inspection services.  The FDA continues to have its budget reduced thereby decreasing the amount of food that gets inspected upon import.  The best way the consumer can insure the safety of their food, and reduce the load on the government agencies, is to buy food labeled as having been grown or acquired locally within our own borders.  The laws regulating the sell of local foods are much more stringent than those of imports and will thereby generally be a safer product.

Readings above may have been drawn from the following sources:
Six Modern Plagues and How We are Causing Them, Mark Jerome Walters; Shearwater Books, 2003, ISBN 155963992X
Life Support, The Environment and Human Health, Michael McCally, editor, MIT Press, 2002, ISBN 0-262-63257-8
Rx for Survival,  Philip Hilts, Pengquin Books.  ISBN 0-7394-6974-6
Emerging Infectious Diseases,  Stuart A. Hill, Pearson Eductation Inc., publishing as Benjamin Cummings.  ISBN 0-8053-3955-8
Under the Weather:  Climate, Ecosystems and Infectious Disease, National Research Council, National Academy Press.  ISBN 0-309-07278-6

This article originally written October 14th, 2008 for OU IPE 3913 - Human Health, Disease, and the Environment.

No comments:

Post a Comment