The Environmental Protection Agency is ordering clearer labels for all “spot-on” flea and tick treatments applied directly to dogs’ and cats’ skin, and will consider banning the products if pet deaths and illnesses linked to them don’t decline.

The Wednesday announcement came 15 months after the Center for Public Integrity revealed serious problems with pyrethroid-based spot-on treatments. Pyrethroids are typically used in less-expensive products sold at grocery stores and by other retailers. About 1,600 deaths were reported to the EPA over a five-year period—as well as seizures, heart attacks and gastrointestinal illnesses—in animals treated with pyrethroid-based products, the Center investigation showed.

Steve Owens, EPA assistant administrator for the Office of Prevention, Pesticides and Toxic Substances, said the number of reported incidents connected with all spot-on products jumped from about 28,000 in 2007 to 44,000 in 2008. “We found that a number of the current labels have insufficient warning statements on them,” Owens said during a media teleconference. “Sometimes the labels were hard to read and the warnings were buried in the text.”

Owens classified most of the 44,000 incidents in 2008 as minor, but said there were about 600 reported deaths. An expert veterinary team convened by the EPA analyzed the data and concluded that small dogs were particularly vulnerable to adverse reactions – probably because the doses they were given were too high — as were cats when they were mistakenly given products formulated for dogs. “The existing label warnings against the use of dog products on cats are simply not working,” Owens said, leading to potential misapplication. A report on 2008 incidents reviewed by the EPA can be found here.

From this point on, Owens said, the agency will allow only conditional registration of new spot-on products, which means they could be pulled off the shelves quickly if problems were suspected. The EPA is also restricting the use of “certain inert ingredients that may be contributing to adverse incidents,” he said.

Owens said that the labeling changes will be made over the next few months. If they don’t help reduce the number of incidents, he said, “We will take more significant action going forward. We will remove products from the market if we have to. We will not register products going forward.”

Asked if he believes the products are generally safe, Owens said, “I think in most cases, yes,” although he added that the EPA plans to require more detailed incident data from manufacturers.

James Terbush, founder of BioSpotVictims.org, a website for pet owners who believe their animals were harmed by spot-on products, said he was disappointed with the EPA’s action. “They’re going to have to do more than change the labels,” Terbush said. “These products are really too dangerous to be on supermarket shelves. People use these too casually.”

A group representing manufacturers of the affected flea and tick treatments said it had no objection to the EPA plan. “Pets are an important part of many people’s lives, and these products are designed to help protect pets from dangerous diseases that can be transmitted by fleas and ticks,” Chris Cathcart, president of the Consumer Specialty Products Association, said in a statement. “While it is uncertain how some of the announced changes will play out within the industry, the end result will help provide consumers with increased confidence that they can to continue use these products safely and effectively.”

The Center reported in December 2008 that many problematic spot-on products contained active ingredients from the pyrethroid family of chemicals. Over a five-year period, the Center found, the EPA received more than 25,000 reports of adverse reactions to these products. However, it was unclear how many of the 2008 incidents reviewed by the EPA involved pyrethroids, which are synthetic relatives of pyrethrins, extracted from the chrysanthemum plant.