In an effort to allow farmers greater use of weed killers at higher concentrations, one company genetically engineered certain crops to be highly resistant to its weed killer. This would allow farmers to control weeds without harming their crops.

The company could then sell its special seed each season, as well as selling a lot more weed killer.

Studies have found much higher concentrations of weed killers in these crops. This is important because weed killers are associated with a number of deadly diseases, including cancer.

And unlike other pesticides that are used mainly for commercial agriculture, weed killers use extends to millions of homes, golf courses, and public facilities.

A growing number of studies are showing that weed killers may cause significant damage to human DNA, mitochondria, and immune cells.

Worst of all, they do so in doses far below those occurring in agriculture.

Many earlier studies were either paid for by the manufacturer of the product, or tested only one ingredient — glyphosate. Recent studies have shown that other chemicals used in weed killers add to their toxicity.

In addition, one of the breakdown products of glyphosate, called AMPA, causes considerable DNA damage.

Studies have also shown that AMPA is a significant endocrine disrupter, meaning that it can interfere with estrogen and testosterone function.

A French study reported in the journal “Toxicology” found that weed killers produced gene damage and were anti-estrogenic and anti-androgenic at doses below those used in agriculture.

The researchers concluded that weed killers should be considered carcinogens and mutagens, and are harmful to reproduction.

Other pesticides are also linked to a high incidence of cancer, especially lymphomas, which are increasing more rapidly than any other type of cancer, especially among people in their 30s.

From the late 1970s until 1992 there was a 50 percent increase in lymphomas, with the greatest incidence occurring in the farm belt of the Midwest.

The strongest links to cancer occurred with:

• Phenoxyacetic acids (especially 2,4-D)

• Organochlorines (chlordane, DDT, lindane and toxaphene)

• Organophosphates such as diazinon, dichlorvos, and malathion

These are all commonly used pesticides — not only in commercial agriculture, but also in homes.

You should be especially concerned about a pesticide called 2,4-D, which is commonly used in pasture lands, lawns, and golf courses. It is strongly linked to non-Hodgkin’s lymphoma.

In 1992 alone, the Environmental Protection Agency (EPA) estimated that 40 million to 65 million pounds of this chemical were used in the U.S. alone.