One widely-used insecticide, rotenone, has for years been thought to be very safe and environmentally friendly.  In addition to being used in the garden to kill insects, rotenone is commonly used to spread on stock ponds and lakes to kill unwanted fish. For example, if you want to stock your pond with good game fish like bass or catfish, you first kill off all existing fish that might compete with the new species. State fish and wildlife agencies in the past have frequently recommended using rotenone in this way to kill the unwanted species. Click here for example for more information.
Rotenone has been used to kill off wild fish in lakes and ponds, so that they can be stocked with "good fish" like bass and catfish

How does rotenone kill fish?
At first, we thought it coated the gills, making it hard to exchange gas (oxygen and carbon dioxide).

Now we know that rotenone poisons the energy production process in cells

Do you know anyone with these symptoms?
  • limbs tremble, especially the hands
  • walking is slow and difficult, feet shuffle
  • voice is weak
  • face loses expression
  • condition develops usually around age 50 and gets progressively worse

These are the symptoms of "Parkinson's Disease." You may have an older relative with this disease. You have likely seen someone with this condition. Over one million people in the U.S. have it and over 50,000 new cases are diagnosed each year. 

Parkinson's disease seems more common now than it used to be, although we don't have good data to prove that. Maybe people just talk about the disease more now. But maybe something in the environment is causing it. Studies of this possibility show that there is a correlation between the number of people who get Parkinson's Disease and the number who live in rural areas, drink well water, and use pesticides. Showing a correlation does not prove the cause, but it should serve as a warning.

Scientists have tested rotenone in experimental animals.  When animals are given very low doses over many days, they develop signs of Parkinson's Disease. Examination of their brains shows a selective death of cells in the same place in the brain where cells die in human patients with Parkinson's Disease. The most recent study has shown that the death of nerve cells seems to be indirect. In cell cultures of neurons, with and without the normal supporting cells (glia), the researchers found that rotenone was most toxic when the supporting cells were present. When exposed to rotenone, one type of glia cell makes a highly toxic form of oxygen that acts as a poison on the nearby nerve cells. And it turns out that the neurons that die in Parkinson's Disease are especially vulnerable to the toxic form of oxygen.  That is why signs of disease first show up as Parkinson's Disease.

[See also the lessons on the nervous system]

Of course, we don't have a good way to know if the dose that the experimental animals received is equivalent to what humans get from occasional use of rotenone. Humans also do not usually get exposed to rotenone day after day, which was the case in the animal studies.  Rotenone does not persist in the environment, as is the case with many pesticides.

More about Parkinson's Disease
More about rotenone 

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Wash garden food that has been sprayed with insecticide.  Insecticide can accumulate in teh body and become toxic.


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