Zequanox: Is it safe to use in Alexandria area lakes to combat zebra mussels?
Zequanox kills zebra and quagga mussels, according to experts in the field. But are the current studies sufficient to determine whether it is safe for humans recreating in and around Alexandria area lakes?
Dr. Daniel Molloy, retired scientist from the New York Museum Cambridge Research Institute, recently visited Alexandria to discuss using the biopesticide Zequanox to combat zebra mussels in Alexandria area lakes.
What is the mechanism that causes the mussels to die?
Molloy did not have a specific answer, but offered a comparison.
"I drive a car," he said. "I don't understand all the mechanisms of how it works, but I know it has a safety record. That is the best analogy I can come up with."
Dr. Sarahann Rackl weighed in. She is the project manager at Marrone Bio Innovations, the commercial developer of Zequanox.
Rackl explained the bacteria used in Zequanox, pseudomonas fluorescens, causes "hemorrhaging and killing of the digestive gland through the mussel."
A French study recently analyzed the bacteria's potential effects on humans and its link to Crohn's disease, which involves inflammation of the digestive tract in humans. The November 2010 report concluded that pseudomonas fluorescens were able to alter intestinal barriers.
Molloy explained that lake water is already teeming with thousands of bacteria.
"The thing is, it is already in your milk and it is alive," he said.
Rackl said metabolism was at the heart of the mechanism that kills the zebra mussels specifically and not other animals.
"A lot of it has to do with the way that each organism, including humans, is metabolizing differently," she said. "It is a very specific metabolic interaction between the zebra mussel and the bacteria. We know there are multiple compounds that cause the reaction."
Rackl was not familiar with the French study.
Is it safe to apply Zequanox in open lake waters where people swim and fish; and will people suffer ill effects if they eat the lake fish?
Molloy reiterated that dead strains of the bacteria would be used. He believes it would be safe for humans and other aquatic life.
"Whether the cell is live or dead has no bearing on it because it is intoxication," he said. "It is not infection."
There is a catch.
The active ingredient in Zequanox, the bacteria pseudomonas fluorescens, does not kill zebra mussels naturally, according to Molloy.
"You have to have an artificially high density of the cells, but in terms of the impact on the lake I don't see - these are dead cells - you are adding some organic material," he said.
According to Rackl, a maximum of 200 mg per liter as dry cell weight could be used.
How much more bacteria would be used than is found naturally in the water?
"It would be significantly higher," Rackl said, but explained calculating the increase was difficult. "It is dead so you can't measure it the same."
Molloy said numerous "non-target" species were tested with Zequanox and no mortality issues were discovered.
According to Marrone Bio Innovations, trials indicated tested fish could not tolerate high levels of the live bacteria, but dead cells did not harm fish.
Mallards fed 2,000 mg/kg doses showed no mortality and Zequanox was classified as "practically non-toxic to mallard" with larger doses, according to Marrone's report.
Studies conducted by Marrone on blue mussels and six native North American unionid clams showed no mortality after being exposed to the bacteria.
"The promise of this, their specificity [to zebra mussel death], is enormous," Molloy said.
"The product quickly degrades like all microorganisms do when they die," Rackl explained. "It is not capable of bioaccumulating. This product is safe for humans and animals to drink directly from the water."
Rackl also said she believed waters treated with Zequanox would be safe to swim in and fish would be safe to eat.
"It's not like the chemicals currently on the market," she said. "The objective is to change the paradigm of chemicals in the environment to limit the chemical profile with safer alternative biopesticides."
Can you explain why the bacteria would specifically harm the zebra mussels but not other organisms?
Rackl said the Environmental Protection Agency required completion of a mammalian toxicity package.
"It was submitted - we passed everything," she said. "We are all good to go." Rackl said they found no mammalian or human toxicity concerns connected with Zequanox usage.
Is Zequanox safe for persons with immune deficiencies such as people undergoing chemotherapy or those with AIDS?
"Anyone who is immunocompromised has to be cautious anywhere they are," Molloy said and reiterated that they would be dealing with dead cells.
Rackl said, "For pathogenicity, you have to have a live microbe. There is no risk to an immune-compromised person."
Dick Osgood, certified lake manager, offered his opinion.
"You don't drink the water and so on and so forth, so the risk is so far down the line."
Osgood went further.
"In my opinion, this stuff is safe," Osgood said. "Not just this, but this stuff categorically, certainly in comparison to almost everything else you look at."
What are the effects of allowing Zequanox to disperse into the rest of the lake after testing?
"We know of nothing now," Molloy said. "There is no organism that we know of that could be impacted...There are a million species of organisms out there - no commercial product is tested against everything - so far the track record is excellent."
Molloy said he has worked with the bacteria since 1995.
"I have had it in my eyes," he said. "I have had it in cuts on my hand... This is not an organism I'm concerned about...I don't have a problem letting it drift."
Will the lakes be left open during testing?
Yes, according to Bonnie Huettl, Douglas County Lakes Association president.
Osgood believed the Department of Natural Resources would impose some requirements.
"I would be really surprised if one of those was to shut down the lake," he said.
"We should know how far it can go in terms of being used," Molloy said. "This is what we are trying to define. It's not the panacea that you put a little drop in the end of this lake and all the mussels will die. No. It is going to take money to buy the Zequanox to apply it."
Huettl said that while most of the public response to testing Zequanox was positive, some had reservations.
"There have been some people who have decided before knowing anything that it is not good to put things in the water and, oh, my gosh, you're killing our lakes - where none of this is true," she said.
Osgood added, "This reaction, that is a vocal minority, always happens no matter what you are proposing."
Dennis Bitter, a chemical engineer and sales manager at Marrone, said testing with Zequanox was conducted in a quarry in Indiana.
"It was not as successful as we really needed it to be," he said, but explained he believed the results were related to an inappropriate delivery system, rather than the product itself. Rackl agreed.
"What money we do have is being focused on the power industry and industrial industry," Bitter explained.
Bitter's understanding about Alexandria's role in the production of Zequanox differed from that described by Huettl. Bitter explained that Marrone was not planning to build a plant manufacturing Zequanox in Alexandria. "We are looking at somewhere in the Great Lakes region," he said.
Bitter said Marrone is speaking with groups from several states that are interested in Zequanox, but were trying to lower the cost.
"Based on the literature, [the bacteria pseudomonas fluorescens] is not a concern to public health," Rackl said. "[Marrone Bio] will not produce anything that is not environmentally safe."