Professor David Mortensen tells Vermont committee paraquat’s toxicity, volatility prompt concern; offers alternatives

Professor David Mortensen, a retired weed-science researcher who chaired the Department of Agriculture, Nutrition and Food Systems at the University of New Hampshire, told a Vermont committee on April 9 that the herbicide paraquat presents acute risks for applicators and potential exposure for nearby residents and urged the panel to weigh those risks as it considers H.739, a bill to prohibit paraquat’s sale and use.

Mortensen described decades of field experience applying paraquat by backpack and said the compound produced rapid, noticeable effects on workers he called “knockdown” reactions. He cited toxicology metrics to explain his concern: “The LD50 is 150 milligrams per kilogram of body weight,” he said, noting that most other herbicides fall in the 2,000–10,000 mg/kg range. He argued that the herbicide’s acute toxicity, combined with real-world difficulty following label guidance on buffers and personal protective…