Selective control means that the target weeds are controlled, with little or no injury to corn and sorghum crops. Atrazine is well tolerated by actively growing corn or sorghum, which absorb and metabolize the herbicide, deactivating it. In 1959, atrazine was registered as an approved herbicide in Kansas. It is still widely used because it is economical and effectively controls many weeds, reducing the risk of crop losses due to weed interference. Its use can also reduce or eliminate the need for inter-row cultivation of corn and sorghum fields.
Toxicity is measured in different ways.
Acute oral toxicity is a measure of how poisonous or toxic a substance is when swallowed as a single dose. If we assume the acute oral toxicity is the same in humans as in laboratory rats, then a 150-pound person would have a 50 percent probability of death by poisoning by ingesting about 0.75 pound of atrazine in a single dose. In comparison, 0.5 pound table salt or 2.5 ounces aspirin would produce the same probability of death by acute poisoning. The reason atrazine is effective for weed control, but relatively nontoxic to animals, is that it inhibits photosynthesis in susceptible species of plants. Photosynthesis is the process that occurs in green leaves and stems of plants, whereby light energy is converted to chemical energy, or carbohydrate.