November 1, 2017
The Minnesota Department of Agriculture, as the lead state agency responsible for pesticide environmental and regulatory functions, has made available its summary water monitoring report for 2016.
As in previous years, the report shows a very high degree of water resource protection while also providing reminders of the need to practice good pesticide application practices. The full report can be found at mda.state.mn.us/monitoring.
Recognizing the need to balance responsible pesticide use and protect ground and surface water resources, the MDA conducts one of the most rigorous monitoring programs in the nation. Laboratory and monitoring equipment has been upgraded in recent years, funded in part by the Clean Water Fund. As a result, the agency can monitor for more pesticides and pesticide degradates (the intermediate compounds formed as pesticides break down) and detect them at much lower levels than in the past.
Monitoring data are presented in nanograms per liter, the equivalent to parts per trillion. Some compounds can be measured at single-digit ppt, others at much higher levels. There is also a wide range of water quality benchmarks, ranging from a few hundred ppt to a half-billion ppt, depending on the toxicity of the compound.
For example, glyphosate can be detected at levels above 1,020 ppt. The groundwater reference value for glyphosate is 700,000 ppt, and the surface water reference value is 1.8 million ppt. And while glyphosate is used on more acres than any other compound, it was not detected in any groundwater samples in 2016. Glyphosate was detected in 23% of surface water samples, with a maximum value of 42,800 ppt, or 2.4% of its reference value.
Several other pesticides commonly used in crop production are frequently found. However, the vast majority of concentrations are far below reference values. The MDA monitors in both agricultural and urban settings with similar findings — the products used are often found in both environments, yet almost always at very low levels.
The MDA provides surface water results to the Minnesota Pollution Control Agency, which then uses the data to determine impaired waters listings. In 2016, of 1,029 samples, 12 exceeded surface water standards, some of which will lead to impaired waters designations. Eight of these exceedances were of chlorpyrifos.
Chlorpyrifos detections have averaged 5.6 per year, with a range from one to eight since lab methods were revised in 2008. Most of these detections occur in late summer, while most other pesticide detections occur earlier in the year.
These results serve as an important reminder to follow label directions for all pesticide applications, and especially as a reminder that some insecticide product labels also include larger setbacks from water than do most herbicides. Chlorpyrifos and some other insecticide applications require setbacks of 25 feet from water when making ground applications, 150 feet for aerial applications.
As part of their duties under the Minnesota Pesticide Control Law and the Comprehensive Groundwater Protection Act, the MDA program also provides best management practice information relating to pesticide use.
Along with the product label, these voluntary practice recommendations are intended to ensure the ongoing protection of water resources, and that crop protection products continue to be available. If you use crop protection products, it is in your best interest to learn and follow them.
Formo is executive director of the Minnesota Agricultural Water Resource Center.
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