A new and improved method to test carcinogen risk has been developed by researchers at Oregon State University.
They said that trout can be a superior animal model than laboratory rats, and other traditional methods of assessing the risk of carcinogens.
"The whole foundation of modern toxicology is that the dose makes the poison," said George Bailey, an OSU distinguished professor emeritus of molecular and environmental toxicology.
"You can die from eating a few tablespoons of ordinary table salt at one time, but that doesn't mean that table salt is a poison at the doses that humans normally consume.
"With compounds that we know can cause cancer, the real question is how much is too much.
"What we have found is that traditional approaches to making that evaluation, which are almost always based on studies done at very high doses with laboratory rodents, may not always give us answers that are reasonably accurate," he added.
Researchers are usually trying to determine what can cause cancer at levels considered unacceptable.
However, the age-old problem they have faced is the cost and laboratory logistics making it virtually impossible to test millions of rats.
"When using rodents, it simply was not possible to study larger numbers of animals, the cost was too prohibitive," said Linus Pauling Institute at OSU.
The Oregon State University researchers have revealed that rainbow trout may for many purposes be as or more accurate in determining what compounds, at what levels, can pose a risk of human cancer.
They have pioneered the use of trout for studies of this type for 40 years, and researchers believe that it may now be time to greatly expand the use of that research.
"We can do experiments with trout in large numbers at very low cost, about 5 percent of what a rodent study would cost," she said.
"For most studies of carcinogens, exposing 2,000 rodents would be a huge project. For us, working with 2,000 trout is a pilot study," she added.
The OSU scientists recently completed the largest study ever done with animals in toxicology, exposing 40,800 trout to what's considered an "ultra-low" dose of dibenzo-a,l-pyrene, a chemical that can cause liver cancer and is part of a broad field of toxic compounds called polycyclic aromatic hydrocarbons, or PAHs.
The study determined that a tolerable threshold for human exposure to this toxic chemical would be 500 to 1,500 times higher than is outlined by the Environmental Protection Agency.