Glyphosate: A review of its global use, environmental impact, and potential health effects on humans and other species

Glyphosate, [N-(phosphonomethyl) glycine], was synthesized in 1950 and patented as a chemical chelator, capable of binding metals such as calcium, magnesium, and manganese. Glyphosate’s ability to bind to manganese was later found to inhibit an enzyme used by plants and bacteria for biosynthesis of three amino acids found in all proteins, and the commercial value of this property led to the development and marketing of glyphosate as a broad-spectrum herbicide. In 1974, the Monsanto Chemical Company introduced the herbicide as Roundup™, a formulation of glyphosate and adjuvants. Roundup™ was originally used for weed control in specific farming and landscaping operations and around power lines and train tracks. Following introduction of Roundup Ready™ seeds, in the 1990s, glyphosate use increased significantly. Although Monsanto’s patent on glyphosate expired in 2002, the widespread and growing use of Roundup Ready™ seed globally and competitive glyphosate marketing by other chemical companies have led to glyphosate’s significant increase in the environment. Concerns about potential adverse effects have also grown. While, at present, many regulatory agencies have determined that there is little risk of adverse health effects to the general public or to farmworkers using proper handling techniques, the International Agency for Research on Cancer (IARC) assessing hazard data on glyphosate identified it in 2016 as a category 2A carcinogen (likely to cause human cancer). Response to this classification has been divided: The agribusiness industry has been forceful in its opposition, while other experts support IARC’s classification. The following article examines these issues. It also examines the basis for regulatory decisions, controversies involved, and questions of environmental justice that may or may not be addressed as glyphosate continues to be used.