Glyphosate-based herbicides

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Glyphosate herbicides are usually made of a glyphosate salt that is combined with other coformulants that are needed to stabilize the formula and allow penetration into plants.

Background[edit]

Monsanto's glyphosate-based herbicide Roundup was first developed in the 1970s. Between 1985 and 1996, Monsanto reduced the price of Roundup by 50%. Between 1990 and 1996 sales of Roundup have increased by around 20% per year.[1] As of 2015 it is used in over 160 countries.[2] Roundup is used most heavily on corn, soy and cotton crops that have been genetically modified to withstand the chemical, but in 2012 glyphosate was used in California to treat other crops like almond, peach, cantaloupe, onion, cherry, sweet corn and citrus.[2]

Monsanto is the largest producer of glyphosate-based herbicides, but formulations from other manufacturers are available that use different inert ingredients.[3] Other glyphosate-based formulations include Bronco, Glifonox, KleenUp, Ranger Pro, Rodeo, and Weedoff.[4][5] As of 2010, more than 750 glyphosate products were on the market.[6]

In 2014, the EPA approved Enlist Duo which was developed by Dow AgroSciences, despite widespread opposition. This herbicide combined two active ingredients: 2,4-D and glyphosate. Enlist Duo is intended for use with genetically modified crops that have also been developed by the Dow Chemical subsidiary. The initial approval was limited to the states of Illinois, Indiana, Iowa, Ohio, South Dakota and Wisconsin.[7] However, in 2015, during the course of litigation the EPA found out that Dow had told the United States Patent and Trademark Office that Enlist Duo offers "synergistic herbicidal weed control." The EPA requested additional clarification about the "synergistic effects" and sought to reverse its approval pending a full review of the new information provided by Dow.[8][9] In 2016, the 9th Circuit rejected the EPA's petition to vacate its approval of the herbicide.[9]

Inert ingredients[edit]

Surfactants, solvents and preservatives are inert ingredients that are commonly added to glyphosate-based herbicide formulations.[10] Polyethoxylated tallow amine (POEA) is a surfactant added to Roundup and other herbicides that helps the glyphosate penetrate the plant surface.[3] Some surfactants that are added to herbicide formulations may increase glyphosate's toxicity.[11]

The names of inert ingredients used in glyphosate formulations are usually not listed on the product labels. In 1997 the USDA listed the contents of the following formulations: Accord (45.5% glyphosate and 58.5% water), Rodeo (53.5% glyphosate and 46.5% water), Roundup (41.0% glyphosate, 1.5% related organic acids of glyphosate, .5% isopropylamine, 15.4% POEA, and 41.6% water) and Roundup Pro (41% glyphosate, 14.5% phosphate ester neutralized ethoxylated tallow amine and 44.5% water).[12]

Regulatory history[edit]

European Union[edit]

In the European Union the active ingredient, glyphosate, is approved at the supranational EU level and is governed by Regulation No 1107/2009. Specific glyphosate-based formulations, like Roundup, are regulated at the Member State level.[5]

As part of the process to renew glyphosate's license under EU regulations, a 2013 systematic review by the German Federal Institute for Risk Assessment (Bfr) of epidemiological studies of workers exposed to glyphosate formulations found no significant risk,[vague] stating that "the available data are contradictory and far from being convincing".[13] In 2015, as part of the ongoing renewal process, the European Food Safety Authority (EFSA) published a final risk assessment on 12 November 2015 stating that glyphosate met EU-level regulatory standards. Despite classifying glyphosate as non-carcinogenic, this report also acknowledged that some of the co-formulants added to glyphosate based pesticides "appeared to have toxic effects higher than the glyphosate itself", noting POEA in particular. The conclusion of the final EFSA assessment was that glyphosate met EU-level regulatory standards, but individual formulations would have to be evaluated by member states.[14]

United States[edit]

Glyphosate products are among the most commonly used in aquatic applications, but because some formulations contain an inert ingredient that may be toxic to fish and amphibians, only glyphosate products that are labeled for aquatic use can be used.[15][16] Aquatic formulations using the isopropylamine salt of glyphosate include Glypro (also called Rodeo, Aquapro, and Accord Concentrate)[17] and Shore-Klear.[18] Refuge is also approved for aquatic applications; the active ingredient in this formulation is the potassium salt of glyphosate.[18][19] There are a few aquatic formulations that already include a surfactant that are registered for aquatic applications including GlyphoMate41 and Shore-Klear Plus, but most aquatic formulations do not include surfactant. The composition of surfactants is proprietary and non-disclosed, but low-toxicity surfactants that are labeled for aquatic use are available for aquatic tank mixes.[20][16]

Acute Toxicity[edit]

The lethal dose of different glyphosate-based formulations varies, especially with respect to the surfactants used. Formulations that include the surfactant POEA are more toxic than other formulations, especially for aquatic species.[21]

Human[edit]

The acute oral toxicity for mammals is low,[21] but death has been reported after deliberate overdose.[22][23] Ingestion of Roundup ranging from 85 to 200 ml (of 41% solution) has resulted in death within hours of ingestion, although it has also been ingested in quantities as large as 500 ml with only mild or moderate symptoms.[24] Consumption of over 85 ml of concentrated product are likely to cause serious symptoms in adults including burns due to corrosive effects as well as kidney and liver damage. More severe cases cause "respiratory distress, impaired consciousness, pulmonary edema, infiltration on chest X-ray, shock, arrhythmias, renal failure requiring haemodialysis, metabolic acidosis, and hyperkalaemia" and death is often preceded by bradycardia and ventricular arrhythmias.[22] The surfactants in formulations generally do not increase the toxicity of glyphosate towards humans.[22][clarification needed]

Skin exposure to ready-to-use concentrated glyphosate formulations can cause irritation, and photocontact dermatitis has been occasionally reported. These effects are probably due to the preservative benzisothiazolin-3-one. Severe skin burns are very rare.[22] Inhalation is a minor route of exposure, but spray mist may cause oral or nasal discomfort, an unpleasant taste in the mouth, or tingling and irritation in the throat. Eye exposure may lead to mild conjunctivitis. Superficial corneal injury is possible if irrigation is delayed or inadequate.[22]

Aquatic[edit]

Glyphosate formulations with POEA are generally more toxic to aquatic animals then terrestrial animals. Glyphosate formulations that include the surfactants POEA and MON 0818 (75% POEA) may have negative impacts on various aquatic organisms like protozoa, mussels, crustaceans, frogs and fish.[21]

References[edit]

  1. ^ "Top-selling herbicide not close to withering". Wall Street Journal. 1996-01-08. Archived from the original on 2018-08-13. Retrieved 2018-08-12. 
  2. ^ a b "What Do We Really Know About Roundup Weed Killer?". National Geographic News. 2015-04-23. Archived from the original on 2018-08-13. Retrieved 2018-08-13. 
  3. ^ a b News, Crystal Gammon, Environmental Health. "Weed-Whacking Herbicide Proves Deadly to Human Cells". Scientific American. Archived from the original on 2018-08-13. Retrieved 2018-08-12. 
  4. ^ Vaida, Bara. "Does This Common Pesticide Cause Cancer?". WebMD. Archived from the original on 2018-08-13. Retrieved 2018-08-13. 
  5. ^ a b Sihtmäe, M.; Blinova, I.; Künnis-Beres, K.; Kanarbik, L.; Heinlaan, M.; Kahru, A. (2013-10-01). "Ecotoxicological effects of different glyphosate formulations". Applied Soil Ecology. 72: 215–224. doi:10.1016/j.apsoil.2013.07.005. ISSN 0929-1393. Retrieved 2018-08-13. 
  6. ^ National Pesticide Information Center. Last updated September 2010 Glyphosate General Fact Sheet Archived 2015-10-13 at the Wayback Machine.
  7. ^ "EPA Approves Dow's Enlist Herbicide for GMOs". Scientific American. Archived from the original on 2016-05-24. Retrieved 2018-08-15. 
  8. ^ "Busted: EPA Discovers Dow Weedkiller Claim, Wants It Off The Market". NPR.org. Archived from the original on 2017-08-25. Retrieved 2018-08-15. 
  9. ^ a b Callahan, Patricia. "Court clears way for revival of worrisome weedkiller". chicagotribune.com. Archived from the original on 2018-06-11. Retrieved 2018-08-15. 
  10. ^ News, Crystal Gammon, Environmental Health. "Weed-Whacking Herbicide Proves Deadly to Human Cells". Scientific American. Archived from the original on 2018-08-13. Retrieved 2018-08-12. 
  11. ^ Gupta, Ramesh C.; Gupta, Ramesh Chandra (2012-03-29). Veterinary Toxicology: Basic and Clinical Principles. Academic Press. p. 843. ISBN 978-0-12-385926-6. 
  12. ^ Glyphosate: Herbicide Information Profile Archived 2018-04-07 at the Wayback Machine., USDA Forest Service, February 1997
  13. ^ Renewal Assessment Report: Glyphosate. Volume 1. Report and Proposed Decision. December 18, 2013. German Institute for Risk Assessment, pages 64-65. Downloaded from http://dar.efsa.europa.eu/dar-web/provision Archived 2009-01-30 at the Wayback Machine. (registration required)
  14. ^ Bozzini, Emanuela (2017-03-23). Pesticide Policy and Politics in the European Union: Regulatory Assessment, Implementation and Enforcement. Springer. pp. 85–86. ISBN 978-3-319-52736-9. 
  15. ^ Helfrich, Louis; Weigmann, Diana; Hipkins, Patricia; Stinson, Elizabeth. "Pesticides and Aquatic Animals: A Guide to Reducing Impacts on Aquatic Systems". Virginia Cooperative Extension. Retrieved 16 August 2018. 
  16. ^ a b Langeland, K A; Gettys, Lyn A. "Safe Use of Glyphosate-Containing Products in Aquatic and Upland Natural Areas": 4. 
  17. ^ [www3.epa.gov/pesticides/chem_search/ppls/062719-00324-20150820.pdf Glypro Herbicide EPA 2015 product label]
  18. ^ a b Wisconsin Department of Natural Resources - Glyphosate Chemical Fact Sheet
  19. ^ Refuge Herbicide EPA 2011 product label
  20. ^ Lembi, Carole; Botany, Purdue; Pathology, Plant. "Identifying and Managing Aquatic Vegetation": 19. 
  21. ^ a b c Van Bruggen, A. H. C.; He, M. M.; Shin, K.; Mai, V.; Jeong, K. C.; Finckh, M. R.; Morris, J. G. (2018-03-01). "Environmental and health effects of the herbicide glyphosate". Science of The Total Environment. 616-617: 255–268. doi:10.1016/j.scitotenv.2017.10.309. ISSN 0048-9697. Retrieved 2018-08-15. 
  22. ^ a b c d e Bradberry SM, Proudfoot AT, Vale JA (2004). "Glyphosate poisoning". Toxicological Reviews. 23 (3): 159–67. doi:10.2165/00139709-200423030-00003. PMID 15862083. 
  23. ^ Sribanditmongkol P, Jutavijittum P, Pongraveevongsa P, Wunnapuk K, Durongkadech P (Sep 2012). "Pathological and toxicological findings in glyphosate-surfactant herbicide fatality: a case report". The American Journal of Forensic Medicine and Pathology. 33 (3): 234–7. doi:10.1097/PAF.0b013e31824b936c. PMID 22835958. 
  24. ^ Talbot AR, Shiaw MH, Huang JS, Yang SF, Goo TS, Wang SH, Chen CL, Sanford TR (Jan 1991). "Acute poisoning with a glyphosate-surfactant herbicide ('Roundup'): a review of 93 cases". Human & Experimental Toxicology. 10 (1): 1–8. doi:10.1177/096032719101000101. PMID 1673618.