City street during hard rain

All too often, we hear about oil spills and toxic waste sites polluting the environment. Although very concerning, we can at least pinpoint the source where these pollutants originate. However, that is not the case for nonpoint source pollution.

Nonpoint source (NPS) pollution happens when rain or snowmelt carries pollutants to waterways or into the ground and comes from diffuse sources. As runoff moves, it gathers contaminants in its path. Water is a great way to clean clothes or dishes because it suspends unwanted particles and takes them with it. Unfortunately, water does the same with pollutants, contaminating lakes, rivers, oceans, and groundwater.

According to researchers at the University of Missouri, NPS pollution is also a significant threat to safe drinking water. Although the Clean Water Act has successfully reduced significant pollution at its source, it has done little to curb NPS pollution.

“Large amounts of nitrates and nitrites, such as those found in fertilizer, can cause negative health effects such as blue baby syndrome,” said Robin Rotman, assistant professor at the MU School of Natural Resources. “Nonpoint source pollution can lead to toxic algae blooms; pesticides and herbicides also contain carcinogens that can threaten human health.”

Because preventing NPS pollution is critical for promoting water quality and protecting wildlife, it is vital to address. Let’s examine common sources so we can identify opportunities to mitigate them.

Lawn, Garden, and Agricultural Chemicals

Fertilizers commonly find their way to waterways, promoting the growth of microorganisms and causing dissolved oxygen levels to plummet. Without sufficient oxygen, fish and other aquatic species suffocate. Likewise, pesticides also wash into waterways, making the water unfit for human consumption and unsafe for wildlife.

Applying pesticide in yardSolutions

To prevent pesticides from entering waterways, use regenerative and organic gardening techniques in your yard. Learn about nontoxic pest control methods or at least utilize integrated pest management, only using pesticides when absolutely necessary. Seek out natural fertilizers and soil amendments such as compost and seaweed. Also, when possible, eat organic foods to discourage the use of pesticides and synthetic fertilizers on farms.

Household Chemicals

Some households dispose of chemicals such as paint, used oil, antifreeze, drain cleaner, ammonia, bleach, upholstery cleaner, swimming pool chemicals, and other household chemicals down storm drains. This practice pollutes water supplies since storm sewers typically lead directly to lakes, rivers, and wetlands without being treated. Also, deicing salts wash into waterways and harm plants and aquatic life.

Likewise, washing a car at home does the same thing because all the cleaning products, grime, and oil typically find their way into the stormwater system without being adequately treated. Again, this wreaks havoc on ecosystems and causes toxins to accumulate.


If possible, avoid buying harmful household chemicals altogether. If necessary, purchase the smallest quantity necessary and properly dispose of chemicals through household hazardous waste (HHW) collection locations, not storm drains. If your community has no programs or locations for the collection of HHW, encourage your local government to start them. Remember that storm drains empty directly out in waterways, so we should only use them for rainwater and snowmelt.

Avoid washing your car in your driveway or on the street. Instead, seek out environmentally friendly car washes that capture and process water, protecting the environment. Find them by looking for the WaterSavers designation.

Litter and Pet Waste

Street litter regularly makes its way into stormwater drains, making its way to rivers, lakes, and oceans; tons of plastic waste ends up in our oceans every year. Unmanaged pet waste will also wash into our waterways; it may contain phosphorus, nitrogen, fecal coliform bacteria, and parasites. Even laundering synthetic fabrics causes microplastics to enter waterways through discharge water.

Litter trapped in storm drain


Ensure that waste is correctly disposed of and support local cleanup initiatives that pick up trash. Encourage others to follow suit, especially children, by educating them about the harmful effects of plastics and waste in our environment. When possible, wash synthetics in cold water using a short cycle, and consider purchasing a microfiber ball for laundry, helping prevent microplastics in waterways.

Stormwater Surges

Impervious surfaces, such as parking lots, roads, compacted gravel, buildings, and other built surfaces often cause stormwater surges that lead to more polluted runoff. Unfortunately, it is hard to prevent all sources of nonpoint source pollution from cars, neighbors, construction sites, etc., but you can reduce runoff on your property.


Try to avoid having impervious surfaces on your property; they encourage runoff by preventing water from seeping down into the ground. For example, reduce the length and widths of driveways and parking areas when feasible. Or instead of paving paths in your garden, use porous pavers, which allow some water to filter into the soil beneath. Encourage similar actions in your community, perhaps through your local government or workplace.

Remember that roofs also create runoff, but some actions can reduce that as well. For example, plant a green roof, use rain barrels, or plant a rain garden to help prevent runoff, thermal pollution in waterways, and stormwater surges.

Taking on all these actions can seem overwhelming. Address the most impactful and easy solutions first, and then adopt more over time. Our collective efforts shape water quality for humans and all life that depends on safe water supplies.

This article was originally published on January 18, 2022.

By Sarah Lozanova

Sarah Lozanova is an environmental journalist and copywriter and has worked as a consultant to help large corporations become more sustainable. She is the author of Humane Home: Easy Steps for Sustainable & Green Living, and her renewable energy experience includes residential and commercial solar energy installations. She teaches green business classes to graduate students at Unity College and holds an MBA in sustainable management from the Presidio Graduate School.