Someone has to do it – clean the cat’s litter box or follow the dog around with a plastic bag and a scoop. We think of it mostly as keeping our streets and houses clean, but there’s another reason cleaning up pet waste is important: It helps keep contaminants out of our water supply.

The EPA reports that studies in the Seattle area showed that nearly 20% of the bacteria in water samples came from dogs. (Wild animals and farm animals are also responsible for a lot of water contamination, but most of us can’t do much about them.) Contamination from pets can include E. coli, parasites like roundworms, and, from cats, toxoplasmosis.

So, how do we keep these things out of the water supply? Mostly by keeping pet waste off the ground. The EPA recommends sealing it in plastic bags and putting it in the garbage (where this is allowed), flushing it down the toilet, or burying it under at least eight inches of soil.

If you bury pet waste – though this probably won’t be your regular disposal method – don’t do it in your vegetable garden. The parasites and other contaminants can cause problems there, too. For the same reason, don’t put pet waste in the compost.

A long grass area in your backyard may be useful for your dog. They’re naturally drawn to long grass, and it helps filter contaminants while the waste decomposes. The grass should be about six inches high.

There are more sophisticated solutions, like animal toilets for parks and homes. Right now I’m reading an interesting book called How to Toilet Train Your Cat.

But cutting down the harm from pet waste doesn’t really take special equipment or training. It’s within every pet owner’s reach.

(These tips came from the EPA fact sheet on pet waste.)