Consumers will want to wash their reusable bags more frequently after reading the results of a study commissioned by the plastics industry warning of health risks associated with the bags.

At a time when shoppers are being encouraged to forgo plastic bags for more environmentally friendly totes, the Canadian Plastics Industry Association hired two independent labs to conduct what it says is the first study of reusable bags in North America.

The study, released Wednesday, found more than 30 per cent of the bags came back positive for bacterial contamination. It also showed 40 per cent had yeast or mold, and some of the bags had intestinal fecal bacteria embedded in their surfaces.

The study also warns of other potential health problems if the reusable bags are used to carry gym clothes or diapers in addition to groceries.

"The unacceptable presence of coliforms, that is, intestinal bacteria, in some of the bags suggests that all meat should be double-packed in a first-use bag to prevent accidental leakage or drips into the reusable bag," the study recommends.

With files from The Canadian Press