National Toxicology Program

In the past 20 years, the NTP has primarily used rodents in studies to determine the potential carcinogenic hazard for chemicals that occur in the workplace or environment. Because rodent cancer studies are costly and required years to complete, the NTP continues to investigate other animal models that may offer advantages in terms of time, cost, and mechanistic information.

Several small fish species have been suggested to be more sensitive for detecting carcinogens in assays that would be less expensive and faster than rodent studies. Since large numbers of small fish can be easily maintained in a limited space, this model appeared to offer real advantages to the NTP.

The NTP chose to initiate studies in fish as an exploration of alternate or additional models for examining chemical toxicity and carcinogenicity. The two species chosen for study were guppy (Poecilia reticulata) and medaka (Oryzias latipes), both of which are hardy, easily maintained, and have a low occurrence of background lesions. (see NTP Technical Report TR-528)