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A class of pesticide linked to declining populations of bees was found year-round in major tributaries to the Great Lakes, and some scientists say the finding suggests the substances also could pose a danger to fish, birds, and aquatic insects.
A recent study by the U.S. Geological Survey detected neonicotinoid pesticides in 10 Great Lakes tributaries throughout the year, although the levels were highest during the growing season. The study is the first to gather a year’s worth of field data on levels of the insecticides in major waterways—in this case, rivers feeding the world’s largest group of freshwater lakes.
“At these levels [of pesticides detected] it may not cause severe consequences today, but we could start seeing issues down the line with aquatic invertebrates,” said Michelle Hladik, a USGS research chemist and lead author of the study, published Jan. 19.
Neonicotinoids are the most widely used class of insecticides in the world, with large-scale application primarily as a seed-coating for row crops including corn, soybeans, and beans.
The most common neonicotinoid products are manufactured primarily by Bayer and Syngenta. Both companies said the USGS study and others around the world do not indicate a risk for the aquatic environment.
“It is critical to understand that the mere detection of a pesticide, or other chemical does not imply any risks to aquatic insects,” Bayer Crop Science said in a statement to Bloomberg Environment. “In fact, there was nothing new about the monitoring data presented—it is consistent with data from earlier USGS monitoring programs and publications. These results are good news about the quality of our waterways.”
Likewise, Syngenta said the threats posed to aquatic species have already been evaluated and cleared by regulators.
“EPA requires more than 120 different baseline studies to assess pesticide safety to humans, wildlife, and the environment,” Syngenta said in a statement to Bloomberg Environment. “Syngenta’s neonicotinoid, thiamethoxam, has undergone more than 1,600 studies to establish its safety.”
When introduced in the 1990s, neonicotinoids were touted for their selectivity, targeting only insects with little direct harm to mammals or birds. But environmentalists say the reality has proven to be much more complex.
“We are now playing catch up for a chemical that has been on the market for decades,” Jay Feldman, executive director of Beyond Pesticides, a Washington, D.C.-based advocacy group, told Bloomberg Environment. “The ecological reviews of neonicotinoids are wholly inadequate and have allowed contamination which is devastating to the aquatic food web.”
In the U.S., neonicotinoids are currently not restricted at the national level, although several states, including California, Maryland, and Minnesota, have issued restrictions on the sale and use of the pesticides to protect pollinators.
The Environmental Protection Agency is currently considering an application by Syngenta to allow its neonicotinoid, thiamethoxam, to be used on many of the most widely grown crops in the U.S. If approved, it would allow the pesticide to be sprayed on 165 million acres of wheat, barley, sorghum, corn, alfalfa, potato, and rice.
Syngenta’s application came the same day that EPA drastically lowered the aquatic life benchmarks for another popular neonicotinoid—Bayer’s imidacloprid—down to 385 nanograms per liter for “acute exposure,” and 10 nanograms per liter for “chronic exposure.” The prevoius benchmarks were 34,500 nanograms per liter for acute exposure and 1,050 nanograms per liter for chronic exposure.
According to the USGS study, while imiacloprid did not exceed EPA’s acute benchmark during the sampling of water in the Great Lakes area, it did exceed the benchmark for chronic exposure 33 times for individual water samples during the year-long testing.
Hladik said that while chronic exposure measurements may not cause significant impacts in the lab, in nature they could potentially cause issues like decreased reproductivity, growth rates, and movement in some species.
“I think what our research is pointing to is there are probably low-level exposures on a constant basis,” in some aquatic environments. “So the question now becomes, ‘Are there long-term effects?’ And we don’t quite know the answer to that.”
The three most common neonicotinoid products are imidacloprid, manufactured by Bayer and sold under the brand names Admire, Advantage (flea & tick for dogs), Confidor, Goucho, Marathon, Merit, Premeir, Provado, and Bayer Advanced; clothianidin, also manufactured by Bayer and sold under the brand name Poncho; and thiamethoxam, manufactured by Syngenta and sold under the brand names Actara, Crusier, Dividend, and Platinum.
The EPA is currently re-evaluating the benchmarks for thiamethoxam and clothianidin.
Neonicotinoids work by absorbing into a plant and spreading through the vascular system, which makes the pesticides easy to use while limiting exposure to the surrounding environment. But they can also materialize in pollen that bees pick up and return to the hive, weakening the colony. Dust from seed coatings can also shake off and affect bees.
“A lot of the press and research has focused on bees, maybe because they’re cute and fuzzy—it’s a little harder to get interested in a water flea,” said Hladik.
But smaller aquatic invertebrates form the basis of a food chain for larger animals, she said
“The lethal concentration that kills 50 percent of individuals for mayflies is less than 1 part per billion,” said Dave Goulson, a professor of biology at the University of Sussex, England.
This, said Goulson, suggests that the current focus by regulators on pollinators may be missing a bigger environmental hazard, especially if of the solutions being considered are to simply swap out neonicotinoids for pesticides with even greater pollution hazards.
When originally approved by EPA in 1994, neonicotinoids were viewed as a good replacement for more dangerous organophosphate pesticides, which posed a danger to agricultural workers. And they excelled at eliminating pests.
“It was a game-changer for us,” said Steve Twynstra, who farms about 4,000 acres west of London, Ontario, Canada. “Prior to neonics, our higher-value specialty crops, like beans and cereals, were very susceptible to damage from leaf hoppers and aphids,” he told Bloomberg Environment.
Once he had access to neonicotinoids, Twynstra said he was able to drastically reduce the amount of spraying he did on his farm. “And because we’re are able to use such a small amount of active ingredient, it was much cheaper, and safer, than what we used before.”
Those economics, however, are changing. A year after Ontario’s bee industry recorded the loss of more than 50 percent in 2013, the province issued new regulations designed to reduce the use of the insecticides by 80 percent over two years.
Last fall, Health Canada, the national public health authority, came to a preliminary conclusion that imidacloprid should be banned almost entirely after finding it was building up in surface water and groundwater and killing aquatic insects. A final decision is expected late this year.
In the European Union, the European Commission is expected to vote in the coming months on a proposal to extend a 2013 neonicotinoid ban for flowering crops to all outdoor crops.
And in a reversal of a previous position, the U.K. recently announced it would support a total agricultural ban when the European Commission votes.
Regardless of the outcome of the vote, France is slated to ban all neonicotinoid use in the country beginning in September.
What these developments might ultimately mean for pesticide manufacturers remains an open question.
“In the crop chemicals industry, when you stop selling one product, you create a lot of profit for another,” said Jason Miner, an analyst for Bloomberg Intelligence who tracks the chemical sector.
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