Atrazine is one of the most widely used herbicides in the US and Australian agriculture. Pure-atrazine is a white, odorless powder that is not very volatile or flammable. Atrazine is the main active ingredient in 21 herbicides in US alone (Mercola, 2016). In Australia, atrazine is utilized to control weeds in lupin and Triazine Tolerant (TT) canola. Furthermore, it is also used to control weeds in Lucerne, grass seed, pasture, and potatoes. In conservation tillage farming systems, atrazine is introduced for weed control in established seedbeds prior to planting sorghum, wheat, peas, or lupins. In the US, it is used for control of certain annual broadleaf and grass weeds (Worthing,1991). It can be applied by spraying onto the targeted area through ground spray or agricultural aircraft. The decision for the appropriate choice of application will be determined by the distance from waterways, the size of the area, the topography of the area, available machinery as well as product label restrictions. Atrazine is manufactured from cyanuric chloride that has been treated with ethylamine and isopropyl amine. It effectively binds with plastoquinone-binding protein in photosystem II which death of the targeted plants through starvation. For it to be effective it has to be absorbed by the targeted plant and this is done through the roots of weeds and then transported to the actively growing tips and leaves. It is here where it binds with plastoquinone-binding protein and disrupts the process of photosynthesis. Once photosynthesis has been inhibited in all the active areas of the weed, the plant begins to slowly die. Atrazine, through photolysis and microorganisms, can be degraded in surface water. Moreover, hydrolysis and microbial degradation can also occur in soil, depending mainly on temperature, moisture, and PH. The half-lives of the products of degradation; metabolites are greater than 100 days at 20 º C for surface water and 20-50 days at 20-25 º C in the soil as long as the conditions are met (USEPA, 1988). The rates of degradation of atrazine are inversely proportional to the depth and as a result, they are quite stable in groundwater. In soil, atrazine products are of the chloro-s-triazine metabolites mainly found in water, unsubstituted amino metabolites, and triazine. The latter metabolites are formed much later and maybe mineralized completely. Recent monitoring data of concentrations of atrazine in groundwater and surface water show declining levels and incidences of detection of atrazine and its chloro-s-triazine metabolites compared to earlier data. Despite having this information, it is important to continue monitoring the levels of atrazine metabolites in water so as to prevent its effects. A lab experiment on atrazine effects was done and solutions containing atrazine were administered to rats. The C-labelled atrazine was quickly and almost completely absorbed by all the rats, sex and dose notwithstanding. Radioactivity was spread throughout the body. 93% of the administered dose was excreted within 7 days primarily via urine (approximately 73%) and through feces (approximately 20%) and the rest via bile. More than 50% of the metabolites were excreted within the first 24 hours. From the lab experiment, it was noted that atrazine was of low acute toxicity to the rats that were exposed orally with a median lethal dose. Generally, the consistent toxic effects noted across all species are reduced body weight gain as well as food intake, a slight decrease in erythrocyte parameters, an increase in liver weights, and splenic hemosiderin deposition. Long-term studies were also done and the reduced body weight gain and food intake and a slight decrease in erythrocyte parameters were notable effects just like in the short-term studies. Moreover, in other studies, majorly for carcinogenicity in ovariectomized Sprague-Dawley rats, showed that the carcinogenic mode of action of atrazine in the rats is related to ovarian function. Atrazine effects on the human body are relatively mild, however, they can alter the neurotransmitter and neuropeptide function regulating LH and secretion of prolactin and consequently result in adverse effects during critical periods of development such as pregnancy loss, delayed puberty in males and females and decreased suckling-induced prolactin release in lactating dams. The conclusion for the lab was that atrazine, when used in accordance with the label recommendations, poses no undue hazard to users and is unlikely to contaminate waterways to an extent likely to be hazardous to human beings.
References
Mercola, J. (2016). Atrazine — Second Most Commonly Used Herbicide in the U.S. Retrieved from https://articles.mercola.com/sites/articles/archive/2016/06/21/atrazine-herbicide.aspx
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