So far, we have learned that DDT is an extremely persistent chemical. It gets into the fats of organisms, and it stays there. But what makes it so dangerous to organisms? In this section, we'll discover how DDT works.

The current misunderstanding is that DDT kills by disturbing an organism's nerve cells.

All cells, including nerve cells, have a plasma membrane, which is the cell's outer boundary. Like an egg shell, the plasma membrane separates the inside of the cell from the outside. One important difference, though: The plasma membrane allows special substances to enter and leave the cell, (food, oxygen, water, etc.).


plasma membrane

The plasma membrane is made up mostly of lipids (fats). Remember that DDT is fat soluble, and so it will dissolve easily into the plasma membrane. In order to get into the plasma membrane, the DDT must open up the membrane slightly to make room for itself. DDT, unfortunately, opens up the membrane a little too much and causes the cell to leak.

Two things which will slip through these leaks are sodium ions and potassium ions.

CHEM WINDOW - Ions

For a nerve cell, the concentration of Na+ and K+ inside and outside of a cell are especially important, because they help determine when the nerve cell will fire its signals. After DDT gets into the plasma membrane, nerve impulses (signals) no longer fire when they are supposed to.

If you are not familiar with biology, nerve impulse tell the muscles when to contract and relax. Thus, when an organism is poisoned with DDT, it dies by either convulsions (random, uncontrolled contraction of the muscles) or paralysis (complete loss of muscle control).


This completes the Dangers of DDT.




Return to the beginning of the Pesticides unit.