Environment & Science

New poison ban that aims to protect wildlife may hurt pets

An assortment of rat control products are offered at a Los Feliz home and garden store.
An assortment of rat control products are offered at a Los Feliz home and garden store.
Jed Kim

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John Tegzes was in the pesticides aisle at a Los Feliz home and garden store recently, looking at all the options available for killing rats. It’s a visit he makes a few times a year.

Tegzes doesn’t go, because he has a recurring rodent problem. He goes, because he’s doing homework as a veterinary toxicologist. By seeing which rodent poisons are offered, he can prepare himself to know how to treat pets that may end up eating them.

“It helps me to anticipate the types of cases that might be coming in, in the next couple of months to a year,” said Tegzes, who teaches at Western University of Health Sciences in Pomona.

Because he makes these visits so regularly, Tegzes is attuned to the trends in rodenticide offerings. On this most recent visit, he noticed that there were no products containing second-generation anticoagulant rodenticides, some of the most powerful toxins used to control rat infestations.

It’s no surprise that the products would be absent from shelves, since they were just days from being banned from consumer sale in California. The ban, which goes into effect Tuesday, sets new rules designed to keep the poison from entering the food chain and damaging wildlife such as raptors, bobcats and mountain lions.

While the rodenticide ban is expected to cut down on accidental exposures, many feel it does not do enough to protect wildlife. That's because licensed exterminators will still be able to purchase and use the product. Also, it only restricts four compounds — brodifacoum, bromadiolone, difenacoum and difethialone — out of the toxins that exist on the market.

An effective killer

Anticoagulant rodenticides work by keeping the blood in a rat from clotting. The poisoned animals die from uncontrolled internal bleeding. 

Second-generation anticoagulant rodenticides are especially powerful and longer-lasting compounds that have had the unintended result of building up in predators that eat the afflicted rats. Scientists have found the chemicals in the livers of coyotes, bobcats and mountain lions.

“The second generation compounds are a huge issue for wildlife, and we are most frequently detecting those compounds in the livers,” said Laurel Klein Serieys, who recently received a doctoral degree from the UCLA Department of Ecology and Evolutionary Biology.

Serieys has studied rodenticides and their impacts on bobcats for eight years. Over the course of the study, she found that 88 percent of bobcats had been exposed to rodenticides.

“I have found evidence of the poisons impacting immune function in the bobcat, and we think the impacted immune function does explain their increased susceptibility to mange,” Serieys said.

Part of the problem with rodenticides is that they are widespread throughout the environment. The Department of Pesticide Regulation estimates that up until now, more than 200,000 pounds of rodenticides containing one of the banned chemicals, brodifacoum, have been sold in California a year.

Too weak a ban?

Anti-rodenticide advocates have said that while the consumer ban will remove a lot of toxins from the environment, use by licensed exterminators still poses a threat.

“Roughly 40 to 60 percent of the problem of the poisons comes from consumers, and 40 to 60 percent, very roughly, comes from the professional exterminators or pest control companies,” said Joel Schulman of Poison Free Malibu, an advocacy group looking to raise awareness around rodenticides.

Exterminators acknowledge they do little to keep rats who eat their poisoned bait from escaping outdoors. But they say the ban will be effective because they're trained to use the product correctly.

“You just have a total different level of stewardship that is not even comparable,” said James Steed, a member of the trade group Pest Control Operators of California.

Steed, who also owns Neighborly Pest Control in Sacramento, said that licensed exterminators make judgments as to which pest control strategy they should use in each situation. He said that means not using second-generation anticoagulants near wild lands — a consideration that the average homeowner probably doesn’t take into account.

“We have all of this scrutiny over what we do, all of this liability,” Steed said. “Yet, when I go to the Home Depot, I look at an aisle that’s 50-feet long, six, seven feet high with pesticide choices.”

Schulman’s other major complaint about the ban is that it leaves other rodenticides on the market, including first-generation anticoagulant compounds and ones that target other biological systems within animals.

“There’s so much of this stuff,” Schulman said. “There’s an ocean of poisons in the environment.”

Schulman points out that it was first-generation compounds that were recently found in P-22, the mountain lion in Griffith Park. Also, a homeowner’s dog recently ate some first-generation bait that had been set out in the park.

“It’s like having a bowl of hydrofluoric acid in your house. It’s just so dangerous,” Schulman said. “People should just be really terrified.”

Unintended consequences

Both the cougar and the dog were treated and survived, but their examples point to an unintended consequence that may arise as a result of the ban. While it seeks to protect wildlife, the ban may mean more fatal encounters between the remaining commercially available rat poisons and household pets.

Tegzes said dogs commonly get exposed to anticoagulant rodenticides. But he said that a readily available antidote for those toxins means that 90 percent of dog exposures end happily.

The bad news is now that the ban’s in place, homeowners may turn to pesticides for which there is no known antidote. Tegzes has already noticed a big change in what’s being sold at stores. Only one product he surveyed had an anticoagulant component. Several others had a compound called bromethalin, a neurotoxin that causes swelling around the brain.

“This is the one that we’re really worried about and concerned that this one does not have an antidote,” Tegzes said. “If a dog or cat were to be poisoned, and they develop clinical effects from it, it’s very, very difficult to successfully treat them.”

He said it takes a lot of bromethalin to kill a dog, but he’s worried the substance will become more abundant as people look for a new way to rid their homes of mice and rats.