Atrazine

What is atrazine?

Atrazine is a colorless, crystalline substance that is poorly soluble in water. It was introduced in 1958 by Ciba-Geigy (now Syngenta) under the trade name Gesaprim as a systemic triazine herbicide. Atrazine works by blocking photosynthesis in plants. It inhibits the enzyme plastoquinone reductase, which is responsible for the transfer of electrons in the light-dependent reaction of photosynthesis. This prevents the formation of ATP and NADPH, which are required for carbon fixation in the light-independent reaction.

What are the advantages of atrazine?

Atrazine has the advantage of being effective against a wide range of monocotyledonous and dicotyledonous weeds that can reduce crop yield and quality. It is particularly effective against weeds such as hen's millet, goosefoot, chamomile, burdock and thistle. Atrazine has a long duration of action and can be applied before or after crop emergence. It is absorbed through the roots and leaves of the weeds and distributed throughout the plant body. It has a selective effect, which means that it only damages certain plant species, while others are more tolerant.

What are the disadvantages of atrazine?

Atrazine also has some disadvantages that have led to its ban in many countries. One of the most important disadvantages is the risk to groundwater from atrazine residues. Atrazine remains in the environment for a relatively long time and can enter the groundwater through leaching or seepage. The half-life of atrazine in the soil is 6-10 weeks. The Drinking Water Ordinance in Germany sets a limit value of 0.1 micrograms per liter for atrazine. Compliance with this limit requires extensive monitoring and purification of the water.

Another disadvantage of atrazine is the potential harm to non-target organisms such as animals and humans. Atrazine can cause irritation of the skin and mucous membranes and, at high exposure levels, can lead to symptoms of poisoning such as anorexia, vomiting, diarrhea, ataxia and convulsions. The acute oral LD50 of atrazine for rats is 2500-3080 mg/kg body weight. No specific data are available for dogs, but it can be assumed that they are similarly sensitive as rats.

In addition, there is evidence that atrazine may have carcinogenic and endocrine effects. Animal studies have shown that atrazine can increase the risk of breast, prostate and testicular cancer. Atrazine can also disrupt hormone production and lead to the feminization of male animals. This was observed in frogs, for example, which showed increased activity of the enzyme aromatase, which converts testosterone into oestrogen, as a result of atrazine.