Thirty dogs will have radon detectors attached to their collars as part of a study into the effects of the odorless gas.

"We hope to find an association between radon exposure and lung cancer in dogs and, therefore, in humans," said Purdue University veterinarian Robert Teclaw. "The long-term goal is to find out if dogs can serve as warning signals on environmental hazards to humans."Dogs were chosen because they are in the house as much or more than people, who work outside the home, and because they have a shorter lifespan. Any health hazards from radon will show up earlier in the animals than in humans.

Dog owners in Tippecanoe County, where Purdue is located, have begun fitting their pets with the collars, which will be worn for three months. The detectors weigh less than an ounce and are the size of a silver dollar. Film inside the detector is sensitive to ions emitted by radon. Radon coming in contact with the film will leave tell-tale tracks.

Radon is a colorless, odorless, radioactive gas that comes predominantly from the decay of radium, which occurs naturally in the soil and can accumulate in a house. Exposure over a long period of time has been associated with lung cancer and other health risks.

The owners also will be asked to keep diaries of where the dogs spent their time and how long they were in each area of the house. The radon level in the house will be measured separately.