NEW YORK (TheStreet) -- The main ingredients in a wide array of agricultural and consumer insecticides produced by Bayer Group (BAYRY) and Syngenta (SYT) have long been suspected of contributing to the collapse of honey bee populations. While the companies deny their products are the cause, new studies suggested widespread use of those insecticides could be having a much broader impact on untargeted insect and bird populations.

The debate is reshaping public policy around the world on insecticides to a degree not seen since DDT was banned and, as a result, threatens about 20% of Bayer's revenue. 

The most recent study, the results of which were published in the journal Nature, was based in the Netherlands and found that areas where the active ingredient imidacloprid was evident in higher concentrations in the surface water showed a correlating annual decline in the local population of bird species:

At imidacloprid concentrations of more than 20 nanograms per litre, bird populations tended to decline by 3.5 per cent on average annually. Additional analyses revealed that this spatial pattern of decline appeared only after the introduction of imidacloprid to the Netherlands, in the mid-1990s. . . .

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Imidacloprid is one of class of chemicals known as neonicotonoids and is used in a variety of products, including insecticides and herbicides.

Our results suggest that the impact of neonicotinoids on the natural environment is even more substantial than has recently been reported and is reminiscent of the effects of persistent insecticides in the past. Future legislation should take into account the potential cascading effects of neonicotinoids on ecosystems.

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Bayer CropScience, a unit of Germany-based Bayer, originated the use of neonicotinoids, including imidacloprid, as insecticides, developing them in labs in the late 1980s and marketing them beginning in 1991. The technology began to take off in the 2000s. The unit's products now are almost entirely focused on crop protection based on neonicotinoid treatments and the unit's sales provided 8.8 billion euros ($11.9 billion) or 22% of Bayer Group's total revenue for fiscal 2013.

By Bayer's estimate, over 90% of corn seed used in the U.S. is treated with neonicotinoids. Most of that is distributed by Monsanto (MON) .

Bayer CropScience took immediate issue with the Nature article in a rebuttal posted on its Web site. The company said the article "does not demonstrate that there is a causal link between the use of neonicotinoids and the development of bird populations in Europe. Neonicotinoids have gone through an extensive risk assessment which has shown that they are safe to the environment when used responsibly according to the label instructions."

In an interview with TheStreet, David Fischer, a scientist with Bayer CropSciences in North Carolina, dismissed the study.

"You can have a lot of correlations that don't necessarily imply a cause and effect relationship," he said. "You can correlate the number of babies in Europe with the number of storks on rooftops."

The Netherlands study noted that its scientists do not know the exact mechanism behind bird declines they associate with the concentrations of imidacloprid, but theorize that the toxins in insects are affecting the food supply of the birds. The study's lead author made that point in an email exchange with TheStreet.

"This could be food shortages (owing to high levels of imidacloprid in the surface water) possibly affecting breeding performance, possibly local recruitment, possibly mortality and so forth," Caspar Hallman, a Ph.D. candidate at Radboud University in the Netherlands, said. "Some bird species could be eating contaminated insects too, and for some of the species even coated seeds. We simply can't say at the moment."

However, Fischer insisted that to be harmful to birds concentration levels of imidacloprid would have to be above 100 parts per million -- far higher than those cited in the study. Similarly, the levels found in surface water noted by the study were not high enough to affect the birds' food supply.

"Therefore, there is no reason to expect that imidacloprid is reducing the availability to birds of insects emerging from these aquatic habitats," Fischer said.

An important factor overlooked in the recent scientific research, Fischer said, is how much safer neonicotinoids are compared to previous insecticides.

The chemical DDT, once used to spray crops and city streets to kill harmful insects, was famously banned in the 1960s as a result of the outcry from environmentalists and scientists, spurred initially by the work of science author and researcher Rachel Carson, whose findings were summarized in the 1962 book, Silent Spring. The movement that was launched in the fight to ban DDT eventually resulted in the creation of the Environmental Protection Agency in 1970.

Organophosphates, or so-called "soft pesticides," served as replacements for DDT but also had a broad impact on the immediate environment, killing birds and other creatures.  

"[T]hey didn't stick around as long [as DDT], but they were a lot more toxic, directly toxic to wildlife," Fischer said, adding that he considers the development of neonicotinoids "a major milestone.  ... an order of magnitude less toxic," he said.

The Netherlands study was instigated by evidence compiled and published by scientists weeks earlier concluded that neonicotinoids were impacting the environment more than previously believed. This has led the Natural Resources Defense Council to petition the EPA to withdraw its approval for neonicotinoids.

Bee Buzz

Bayer CropScience's ubiquitous corn seed treatments contain imidacloprid. From the seed coating, the chemical permeates the entire plant as it grows, spreading into the soil. As insects and worms eat the treated plant, the toxin binds to their nervous receptors, eventually causing death. This direct effect seems limited to insects, worms and certain types of birds, like the house sparrow.

The treatments came under fire when they were connected to Colony Collapse Disorder among bees. Farmers depend on bees for pollination of crops and the large die-offs have quickly gained international attention. While Bayer insists doses of the toxin found in plants are too small to affect bees, researchers suspect a link, possibly through a buildup of the toxin over time, its transference in the air or its interaction with other chemicals in the environment. Imidacloprid has not been proven as a direct cause of CCD, but remains a prime suspect and scientists in Europe and the U.S. are conducting tests to determine its role, if any.

Last year, in response to scientific studies and public concerns, the European Union issued a two-year ban on certain neonicotinoid insecticides. The policy affects Bayer products and Syngenta's Cruiser insecticide, which uses a different neonicotinoid, thiamethoxam. Syngenta claimed the affected product was not implicated in the bee research, which raised concerns regarding dust in the air from "a competitor" product.

Not all neonicotinoid insecticides were banned by the E.U., Fischer said, and the effect on Bayer, assuming the ban is eventually lifted, will be limited. However, in an email to TheStreet, he noted, "A study issued January 2013 by the Humboldt Forum for Food and Agriculture (HFFA) concluded that suspension in the EU of neonicotinoid technology would result over a five-year period in loss of 17 billion euros and 50,000 jobs."

Risk of Bans Elsewhere

Imidacloprid has proven so successful as a pesticide that it has been adopted in many consumer uses well beyond farmers' fields. It is the active ingredient in Bayer's Advantage flea and tick medicine for pets, along with termite treatments, tree and shrub care products and others.

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The chemicals have been proven safe for mammals and Fischer insisted there is no risk to humans or pets. However, the authors of the Netherlands study are skeptical. Although stipulating that he was not an expert on the effects of consumer insecticides, Hallman said, "We (as a research team) are particularly worried about the negative effects these chemicals have on our ecosystem once they have leached into the environment. Prohibiting contact of non-target organisms with chemicals designed specifically to kill insects is a MUST to our opinion."

Such concerns about neonicotinoids, coupled with their widespread use, are also attracting the attention of other government regulators. Ontario recently announced it is weighing regulations to tamp down widespread use. The current petition of the EPA and environmentalists' lobbying efforts point to the possibility of U.S. federal government action. 

Should a ban on neonicotinoids or Bayer's imidacloprid products, in particular, be enacted in the U.S., Bayer CropSciences and Bayer Group could see a significant hit. The loss of sales of treatments for corn seed alone would be huge. The fallout would likely also directly impact sales at Syngenta and Monsanto.

Regarding the prospect of a U.S. ban for Bayer, Fischer said, "I'm not allowed to discuss our sales figures. It's something that certainly gets our attention, let's just say that."

Fischer insisted that concerns about neonicotinoids are misguided, the result in part of flawed scientific studies, and that his company would not be producing these products if it thought they were harmful to wildlife and the environment.

"We want to get the truth out," he said.

-- Written by Carlton Wilkinson in New York

Follow @CarltonTSC