Can green consumers be trusted? Maybe not.

A new study to be published in a forthcoming issue of Psychological Science has found that just being around green products can make consumers behave more altruistically. But buying those same products can have the opposite effect.

Researchers found that while consumers who were simply exposed to green products tended to act more altruistically, consumers who actually purchased green products were more likely to "cheat and steal" than those who purchased conventional products.

The research found buying products that claim to be made with low environmental impact can set up "moral credentials" in people's minds that give license to selfish or questionable behavior.

"This was not done to point the finger at consumers who buy green products. The message is bigger," says Nina Mazar, a marketing professor at University of Toronto's Rotman School of Management and a self-admitted green consumer. "At the end of the day, if we do one moral thing, it doesn't necessarily mean we will be morally better in other things as well."

Because purchasing green products affirms individuals' values of social responsibility and ethical consciousness, the study predicts that "purchasing green products will establish moral credentials, ironically licensing selfish and morally questionable behavior."

What's next, a burgeoning black market for compact florescent light bulbs and low flow toilets?

Tom Kraeutler is the AOL'S Home Improvement Editor and co-author of "My Home, My Money Pit: Your Guide to Every Home Improvement Adventure." He delivers green home improvement tips each week as host of The Money Pit, a nationally syndicated home improvement radio program. He has never been known to so much as steal an organic carrot.