A first assessment of glyphosate, 2,4-D and Cry proteins in surface water of South Africa

Abstract

Agriculture plays a vital role in the South African economy, as well as in the production of maize for food. Genetically modified maize is transformed to encode for crystalline (Cry) proteins found in Bacillus thuringiensis (Bt) and is referred to as Bt maize. Ingestion of specific Cry proteins causes the death of target insects that cause harm to maize plants. Bt crops, along with herbicides such as glyphosate and 2,4-dichloro- phenoxyacetic acid (2,4-D), are widely adopted as part of the South African farming regime that aims to increase crop yield and reduce costs of production. As chemical compounds used in agriculture often end up in water sources, their presence should be monitored. There are many such monitoring programmes worldwide, but not in South Africa. We screened surface water sources in a maize-dominated agricultural area in the North West Province in South Africa for the presence of Cry1Ab, glyphosate and 2,4-D using enzyme-linked immunosorbent assays (ELISAs). Cry1Ab was not detected at any site; glyphosate was below the limit of detection at most of the sites but one sample had quantifiable traces of glyphosate; and 2,4-D was detected at all the sites. The concentrations of 2,4-D exceeded those for drinking water according to European guidelines, thus highlighting the need for regular monitoring of these compounds. Many people depend on untreated water resources, which may be contaminated by toxic agricultural chemicals. This report is the first on levels of these target compounds in South African water systems.

Significance:

• This report is the first on the presence of glyphosate, 2,4-D and Cry1Ab in the South African aquatic environment.
• Concentrations of 2,4-D in South African surface waters exceed the European guideline for drinking water, indicating a risk to people using these water sources.
• These preliminary results highlight the need to regularly monitor for the presence of glyphosate, 2,4-D and Cry1Ab in water resources in South Africa.