So-called biodegradable poop bags may be leaving some dog owners with the mistaken impression that simply leaving them scattered along walking trails isn’t doing any harm.

Think again says Dalhousie University School for Resource and Environmental Studies professor Tony Walker who has studied the issue.

Walker says leaving dog waste, either loose or in poop bags, in the general environment can result in a number of environmental and health hazards.

He says dog poop contains parasitic worms that can be harmful and even cause blindness in humans if inadvertently ingested. Dog poop is also a source of nutrient enrichment if it makes its way into waterways and can contribute to harmful algal blooms.

He says poop bags marketed as “biodegradable” may also leave pet owners with the mistaken impression that they do no harm in the environment, when in fact, Walker says, they need to be disposed of properly.

He says many poop bags still contain up to 25 per cent fossil fuel-based plastics, and when they eventually break down, they break down into micro plastics.

Walker says the best way to dispose of poop bags is to carry it home and dispose of it with your household garbage.