Do you know what's in your pet's food?

One study says you could be feeding your little bundles of joy dozens of toxins.

Denver-based non-profit Clean Label Project took hundreds of the best-selling pet foods and testsed them for more than 130 contaminants.

Then, the brands were given a rating out of 5 stars here.

Executive Director Jackie Bowen says she was shocked by their findings.

"We find things like pesticide residues, things like BPA or BPS that are plasticizers--things like cadmium. Things that would be found in smoking cigarettes" says Bowen.

Cadmium can cause liver damage, high blood pressure, and kidney damage in pets.

For owners that feed their cats tuna, the study warns that mercury levels in some brands can cause neurological impairments.

"These animals are eating the same thing every day, 2 to 3 times a day. So, when you think about things like mercury and the whole nature of how mercury can bioaccumulate in fish....for us it's a matter of in these small animals weighing nine to twelve pounds, seeing the potential for adverse health effects because of this heavy metal contamination", says Bowen.

They found that pet brands made with turkey had the least amount of toxins and those made with fish the most likely to have toxins.

Blind tests were completed at 2 independent labs to confirm the results were fair and accurate.

Clean Label Project is set to release a similar study on baby food later this Spring.