Understanding & Assessing Threats to Environmental Health

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  • 0:06 Enviornmental Health Threats
  • 0:50 Risk Assessment
  • 2:42 Assessing Risk
  • 4:55 Risk Management
  • 6:07 Lesson Summary
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Lesson Transcript
Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

In this lesson you will learn how threats to environmental health are assessed. You will also learn how management decisions are made based on such threats and their risks.

Environmental Health Threats

In another lesson, we learned about environmental health, which involves understanding hazards that impact human health and ecological systems. The hazards that affect environmental health come from physical, chemical, biological, and cultural sources. However, just like they come from a variety of sources, they also have varying effects.

This leads scientists to ask a number of questions. How do we know which chemicals to restrict or ban? How do we fight disease? How do we protect people from natural disasters such as earthquakes and floods? These are certainly not easy questions to answer! In order to understand what actions need to be taken to minimize the impacts of environmental health threats, we need to understand the risk of such threats.

Risk Assessment

When understanding environmental health, it's important to determine which substances and activities are most dangerous and which are safe. This is done through risk assessment, which is the measurement and comparison of the risk involved in an activity or substance. What this means is that problems are identified and then compared with the risk of other similar activities or substances. Risk assessment involves a number of different processes that all work together to determine the overall risk. Let's look at assessing risk for a chemical substance as an example.

In another lesson, we learned about the dose-response curve, which involves controlled laboratory experiments to understand the toxicity and effects of a substance. The tests involved in a dose-response study tell scientists how toxic a substance is, what effects it has on the organism and how much of the substance causes these effects.

Dose-response experiments are done on lab animals, so the information that scientists get from them have to be extrapolated to human-sized levels, which allows for safety standards to be set. The risk assessment from dose-response studies also takes into account how likely exposure is for a certain population, how often the exposure would be, the concentration of the exposure and the length of exposure time. So, in other words, for any given population the when, where, how much, how often and how long all goes into determining how risky an activity or substance is.

You can see how complicated risk assessment is! This is just one example for one type of risk assessment. The main point is that risk assessment involves many different ways of looking at a problem and identifying all of the factors that threaten environmental health.

Using Human Health to Assess Risk

While the previous example was a risk assessment based on predictions of future occurrences, risk can also be assessed by learning from the past. Human studies are great ways to understand environmental health threats because instead of using lab animals and extrapolating to humans, we can learn from human issues directly.

Epidemiology is a large-scale comparison among groups of people to determine causes, effects, and patterns in human disease. Epidemiological studies compare groups of people who have been exposed to a certain hazard to a group of people that has had no exposure. These studies often span long periods of time (some studies are decades long), and over that time, they measure any deaths or other health problems that occur. If there are higher rates of death or illness in the group exposed to the hazard, this tells scientists that the hazard is most likely the cause of the problem.

This is much like any other scientific experiment: one group is the control (the non-exposure group) and one is the experimental group (the hazard group). The difference is that epidemiologists do not purposefully expose people to hazards - they simply take advantage of the chance to learn from these exposures and hopefully prevent people from becoming sick in the future.

A very famous epidemiological study was done by Elizabeth Guillette in the Yaqui Valley in northwest Mexico. There is quite a bit of farming done in this area, and synthetic pesticides are highly used on crops in the valley, while the farmers in the foothills preferred not to spray their crops with pesticides. Guillette wanted to know what the effects of pesticides were on children, so she compared the development of children in the valley to the development of children in the foothills.

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