Chapter 17 Flashcards
Review Questions
Why are some substances, such as radon gas, cobalt or selenium potentially hazardous?
Certain elements, molecules and minerals (i.e. arsenic), whether they are dissolved in water or not, are a medical hazard because they cause illness in living things.
For example, Mercury causes mental illness.
These potentially hazardous substances are usually released from a rock formation as a result of a natural process (i.e. radioactive decay) or as the rock/mineral weathers.
What controls the distribution of substances in the environment?
- The geological source - the rock it came from
- Climate, which controls weathering
- Biology - This controls weathering and the distribution of these substances after they are released.
What is the major problem with determining the health risk of substances?
The major problem is determining how much is harmful and what the effect are. Effects can be short or long term.
What is meant by background level when it comes to medical geological hazards such as mercury and lead?
The background level of potentially harmful substances refers to the concentration that occurs naturally.
Explain the medical hazard associated with radon gas.
Radon Gas is a naturally occurring radioactive gas emitted by some rocks, mainly metamorphic.
The hazard is that in high enough concentrations, it can cause health problems such as cancer - ex: Elliot Lake Ontario.
Why is arsenic so hazardous to human health?
Arsenic affects many parts of the human body as it is a poison.
In what kinds of deposits is arsenic found in the natural environment?
Arsenic is found in arsenopyrite, an iron sulfide mineral that precipitates under anaerobic conditions, Anaerobic means no oxygen. Arsenic in arsenopyrite is common in black shales. This is a fine grained layered clastic sedimentary rock that formed in deep, still water, often in the ocean.
Explain the arsenic hazard in Bangladesh.
The presence of Black Shale in the Himalaya Mountains is a source of arsenic. The climate in the area promotes weathering. The large rivers between the mountains and the coast transport arsenic south of the population centers.
As a result there is a high, unhealthy concentration of arsenic in the local groundwater. Groundwater is a major source of drinking water.
