Scientists reject neonic-DDT comparisons

Power of social media | Belief is growing online that neonicotinoid seed treatments are as dangerous to wildlife as DDT

Something that is repeated often enough will eventually be assumed to be true, says Joe Schwarz, director of McGill University’s Office for Science & Society.


If Schwarz is right, North Americans may soon think that neonicotinoids are just as dangerous as one of history’s most notorious chemicals.


That’s because environmental groups, activists and some scientists are now comparing the class of insecticides used as a seed treatment on canola, soybeans and corn to DDT. 


In August, treehugger.com ran the headline “Neonicotinoids are the new DDT” with an article on its website, echoing a Guardian story on the same topic published earlier in the year. 


However, Keith Solomon isn’t buying it.


“In no way is it (comparable). DDT was very persistent. It was metabolized into a metabolite called DDE that was even more persistent,” said Solomon, professor emeritus in the U of G’s School of Environmental Sciences.


“And it also bio-magnified through the food chain. It (DDT) dissolved very easily in fat and moved up through the food chain. All of that led to issues, at least in birds. At the top of the food chain, humans, it never got to levels that were considered to be hazardous.”


In contrast, neonic insecticides don’t build up in a bird’s tissues and organs if an insect is exposed to it and the bird eats the insect.


“They will definitely not move up through the food chain. They don’t have those properties and they’re nowhere near as persistent as DDT,” Solomon said.


Christy Morrissey, a University of Saskatchewan toxicologist who studies neonics, said Solomon is right.


DDT contaminated small organisms and then accumulated to high levels in the birds, fish and animals that ate the smaller creatures.


“The neonics will not bio-accumulate in organisms. So you’re not going to look at food chain transfer,” she said.


Still, Morrissey said it is valid to compare neonics to DDT because the scale of use is extraordinary and residues do remain in the soil for years.


“The parallels between DDT are being drawn because DDT was extremely persistent. It turns out that at least some of the neonics are very persistent as well,” she said. 


“For clothianidin (a Bayer CropScience neonic) … the breakdown for 90 percent of it to be gone (from soil) is closer to 12 years.”


Morrissey, who is studying how neonics affect prairie ecosystems, said 27 million acres of western Canadian farmland were treated with neonics in 2012. In the rest of Canada and the United States, nearly every soybean and corn seed is treated, which represents nearly 175 million acres. 


“For single products (insecticide), I don’t think anything has been used this commonly,” she said.


“That’s a huge scale of use for a compound that lasts a long time.”


Neonics wash into water bodies during rainstorms because they remain in the soil and are water soluble. Morrissey’s research has determined that many wetlands within or near agricultural land in Saskatchewan have troubling concentrations of neonics.


“It’s staying in the soil and then as soon as the snow melts or it rains … it’s just running off the fields and into these ponds.”


As a result, neonics are killing aquatic insects and non-target insects in the soil, which Morrissey said reduces the food supply for birds and other animals that depend on insects.


“Insects, on the whole, are declining, and we’re seeing similar parallels in bird populations … in some cases very, very severely,” she said.


Neonics aren’t solely responsible, she added, but are likely contributing to the problem. 


However, Morrissey doesn’t think neonics should be outlawed like DDT. 


“I won’t go so far as promoting an outright ban,” she said.


“I think pesticides have a place, including the neonics.”


Instead, she thinks growers should adopt more sophisticated practices rather than use neonics as insurance against crop pests.


“(We need) serious reconsideration of the chemical’s application rates, the types of crops it is used on and controlling its use in proportion to the pest problem,” she said. 


“We used to have integrated pest management practices and that’s gone completely out the window.”