There is a natural background level of heavy metals in soils and sediments, but there are many places in the world where those levels are much higher as a result of metal mining and refining.
Why is this important?
Heavy metals are both essential for life (iron, copper, zinc and others) and toxic at elevated levels. And these levels are high enough to have significant impacts on both human health and the environment. The problem with metals is that they do not degrade -- they are with us forever. Some of them become sequestered in our bodies and stay there for a lifetime.
Except in extreme cases, heavy metal toxicity has symptoms that can easily be confused with other sources: malaise, anemia, and other symptoms are common. On this page we have some information about heavy metals. Much of the work was developed in response to the heavy metals plume from the ASARCO smelter in Tacoma Washington, but the information is useful for anyone who lives where the heavy metals are elevated.
The key thing to do is: know if there is a problem, and take action to mitigate it if there is one.
- Heavy Metal Handbook: A Guide for Healthcare Practitioners
- A study performed on Vashon Island showed that native plants excluded arsenic and lead, but took up cadmium: Preliminary phytoremediation results on Vashon Island
If you live in contaminated areas, it is prudent to take precautions to limit your exposures. Here are several useful fact sheets:
If you want to check the levels of these metals in your soil see: Soil Sampling for Lead, Cadmium and Arsenic