A Closer Look at Glufosinate Ammonium Safety: What You Need to Know

Glufosinate ammonium, a non-selective herbicide, is widely used in weed control in orchards (such as papaya, banana, citrus, and waxberry), economic crops (tea gardens, mulberry fields, coffee plantations, and cowpea fields), land reclamation, non-cultivated land weed control, herbicide-resistant crops (corn, cotton, soybeans, sugar beets, etc.), forests, and pastures. Without a doubt, glufosinate ammonium is a herbicide that becomes inert upon contact with the soil. Glufosinate ammonium rapidly degrades in the soil through microbial action, with leaching in most soils not exceeding 15 centimeters. Soil moisture content affects its adsorption and degradation, ultimately releasing carbon dioxide. Its half-life is 3-7 days. After stem and leaf treatment, approximately 10%-20% of the compound and degradation products remain in the soil for up to 32 days, but by 295 days, residue levels are nearly zero. Glufosinate ammonium has a half-life of 433, 693, and 533 days in buffered solutions with pH values of 5.0, 6.9, and 9.3, respectively, and remains stable under weak acidic and weak alkaline conditions. Temperature significantly influences its hydrolysis, with higher temperatures leading to faster degradation. Under xenon lamp exposure at 4,500 hours and 8,300 hours, the half-lives are 1155 and 866 hours, respectively. Under UV light at 360 and 254 nm wavelengths, the half-lives are 462 and 40 hours, respectively, demonstrating the pronounced effect of light intensity and wavelength on glufosinate ammonium photodegradation. Therefore, it is evident that glufosinate ammonium can persist in the soil and eventually enter water bodies and the human body. The following is further research on the safety issues of glufosinate ammonium.

Introduction to Glufosinate Ammonium

The mechanism of action of glufosinate ammonium primarily involves inhibiting the phosphoenolpyruvate carboxylase kinase and glutamine synthetase enzymes in the shikimate pathway. These enzymes are crucial in key metabolic pathways in plants and microbial cells. Glufosinate ammonium acts by accumulating ammonium ions, inhibiting glutamine synthesis. Glufosinate ammonium is a non-selective, contact-action herbicide that disrupts plant detoxification processes by inhibiting glutamine synthetase, leading to nitrogen metabolism disruption, excess ammonium accumulation, chloroplast disintegration, and, consequently, inhibition of photosynthesis, ultimately causing weed death. It can be used on all crops (as long as it does not contact the crops directly; inter-row spraying requires additional covers or shields). When applied as targeted spray treatment on weed stems and leaves, it is effective for weed control in a wide range of crops, including fruit trees, row crops, vegetables, and non-cultivated land, capable of quickly killing over 100 species of grasses and broadleaf weeds, particularly effective against some noxious weeds that are resistant to glyphosate, such as Johnsongrass, goosegrass, and pigweed, making it a nemesis of grass and broadleaf weeds. It does not exhibit the same selectivity as other herbicides and does not cause root death in plants. According to reports, glufosinate ammonium can control the infection of rice sheath blight and reduce the formation of colonies. It exhibits high activity against fungi causing sheath blight, sclerotinia stem rot, and stem rot disease and can simultaneously control weeds and fungal diseases in glyphosate-resistant transgenic crops. When applied at normal rates in glyphosate-resistant soybean fields, it has a certain inhibitory effect on soybean bacterial blight, delaying or inhibiting bacterial growth.

Environmental Impact of GA

Zhejiang University in China conducted several tests to demonstrate the impact of glufosinate ammonium on aquatic plants and organisms.

1. In preliminary tests, acute toxicity of glufosinate ammonium to microalgae was measured at concentrations ranging from 3.5 to 112.0 mg/L. The results showed that 95% glufosinate ammonium technical material had minimal impact on microalgae biomass at 24, 48, and 72 hours within the tested concentration range, with LC50 values exceeding 100 mg/L. It was classified as low toxicity.

2. Acute toxicity tests on Daphnia Magna were conducted with glufosinate ammonium technical material at concentrations ranging from 0.1 to 102.4 mg/L, and the results indicated that Daphnia Magna showed no specific symptoms within the first 8 hours of exposure. After 8-24 hours of exposure, poisoned Daphnia Magna exhibited sluggish responses to stimuli and slow swimming. Between 24-48 hours of exposure, poisoned Daphnia Magna displayed even slower responses at high concentrations. At concentrations of 6.4 and 102.4 mg/L, only one Daphnia Magna died at 48 hours, resulting in a 5% mortality rate. Therefore, it can be concluded that the LC50 values for Daphnia Magna at 24 and 48 hours are both greater than 102.4 mg/L, indicating low toxicity of 95% glufosinate ammonium technical material to Daphnia Magna.

3. In preliminary tests, glufosinate ammonium was tested for acute toxicity to zebrafish over 96 hours at concentrations ranging from 0.1 to 102.4 mg/L. Zebrafish showed no specific symptoms within the 0-96 hour period of contact with the test substance. Across the tested concentration range, no zebrafish deaths occurred. The LC50 values for 95% glufosinate ammonium technical material in zebrafish were greater than 102.4 mg/L, indicating low toxicity to zebrafish. These experiments demonstrate minimal harm to aquatic organisms when glufosinate ammonium enters water bodies.

Part Three: Health Impacts of GA

Glufosinate ammonium is metabolized relatively quickly in the human body and does not easily accumulate. According to relevant research, glufosinate ammonium has low acute toxicity to humans, but prolonged exposure may pose certain health risks. Therefore, when using glufosinate ammonium, it is important to observe protective measures to avoid direct skin contact and inhalation of glufosinate ammonium aerosols.

Studies have indicated that glufosinate ammonium not only inhibits GS (Glutamine Synthetase) in plant organisms but can also exert irreversible inhibition and disrupt GS-related processes in animal organisms, affecting nitrogen metabolism. Sinceglufosinate ammonium has a structure similar to glutamate, which plays a role in regulating the nervous system, it occupies the enzyme-binding site of glutamate during metabolism, leading to metabolic disruption and resulting in neurotoxic effects. Peak blood ammonia concentration can serve as a predictive factor for neurotoxicity in poisoned individuals. Extensive animal experiments have shown that low doses of glufosinate ammonium can affect the brain development of newborn animals; animals exposed to lethal doses of glufosinate ammonium exhibit symptoms of toxicity such as hyperactivity, tremors, respiratory disturbances, drooling, and seizures.

Part Four: Safety Standards and Regulation of GA

In the current scenario, glufosinate ammonium faces certain restrictions or bans in some countries and regions, such as the European Union, the United Kingdom, and Morocco, due to its potential hazards to the reproductive system. This means that in these areas, farmers and agricultural practitioners are required to adhere to strict regulations to ensure that the use of glufosinate ammonium does not have adverse effects on the environment and human health.

However, in other countries, glufosinate ammonium continues to be widely used and is considered an effective herbicide. When using glufosinate ammonium, one of the key considerations is to ensure proper application rates. Overuse can lead to the accumulation of residues in the soil and water, potentially posing risks to the ecosystem.

To maximize the safe use of glufosinate ammonium, agricultural practitioners need to follow specific usage guidelines and recommendations typically issued by agricultural departments and regulatory agencies. This includes proper application techniques, appropriate personal protective measures, and maintenance of spraying equipment. Additionally, farmers need to adhere to the instructions on product labels to ensure the safe and effective use of glufosinate ammonium.

In summary, the use of glufosinate ammonium is influenced by regional regulations, and farmers and agricultural practitioners must comply with local regulations and take necessary measures to ensure its safe and effective use in agricultural practices. This helps minimize potential environmental and health risks.