Q: Used motor oil is a big contributor to the pollution in our waterways and drinking water. How can I make sure I am not contributing to this problem?

– John Eckerle, Jupiter, Fla.

A: Motor oil leaked from individual vehicles – or outright dumped by homeowners and commercial garages – constitutes a significant percentage of storm water runoff, the precipitation that runs off of roads and parking lots and finds its way into local bodies of water.

These pollutants include not only leaked motor oil (which may contain toxic substances such as lead, benzene, zinc, or magnesium) but also fertilizers, insecticides, plastic debris, cigarette butts, paints, solvents, sediments, and other hazardous waste.

Topsoil and natural vegetation would ordinarily filter out many of these pollutants, but the impermeable pavement that covers much of the surface where these pollutants originate allows it to flow into storm drains and then into streams, rivers, lakes, and the ocean. There, it may poison marine life – which we might eat – as well as riparian or coastal ecosystems.

This pollution also finds its way into underground aquifers that supply drinking water, so reducing it is a human health measure and could also save municipalities millions of dollars in costs associated with drinking-water treatment facilities.

While government agencies try to craft and implement development and zoning standards to help reduce storm water runoff problems caused by commercial and industrial entities, there is still much that individuals can do to reduce storm-water impact as well. According to the US Environmental Protection Agency (EPA), 40 percent of all oil pollution in the United States comes from the improper disposal of used motor oil by individuals. One quart of motor oil can pollute 250,000 gallons of water.

The EPA recommends keeping on top of car maintenance to prevent and repair leaks and disposing of used motor oil and other automotive fluids and batteries at designated drop-offs or recycling locations (consult Earth911.org to find one near you). Many gas stations or garages will recycle used motor oil for you. Also, it is preferable to wash your car at a commercial carwash instead of in your driveway. By law, carwashes must treat their wastewater before disposing of it.

Besides handling and discarding your motor oil responsibly, cutting back on or eliminating fertilizers and pesticides from your lawn or garden will also reduce your negative impact.

And don’t overwater your lawn, as that can create extra runoff as well. If you are embarking on a residential landscaping project, try to incorporate permeable pavement (which allows runoff to percolate through it into the soils below), rain barrels to collect water, and rain gardens, grassy swales, and driveway-side vegetative strips – all planted with region-appropriate native plants, of course – to help filter out contaminants before they hit the storm sewers.

Got an environmental question? Write: EarthTalk, c/o E – The Environmental Magazine, Box 5098, Westport, CT 06881. Or e-mail: earthtalk@emagazine.com.