We all do. Polluted runoff is the cumulative result of our everyday personal actions and our local land use policies. Here's a brief rundown on the causes and effects of the major types of pollutants carried by runoff. Pathogens are disease-causing microorganisms, such as bacteria and viruses, that come from the fecal waste of humans and animals. Pathogens wash off the land from wild animal, farm animal and pet waste, and can also enter our waterways from improperly functioning septic tanks and leaky sewer lines.
Nutrients are compounds that stimulate plant growth, like nitrogen and phosphorous.
Under normal conditions, nutrients are beneficial and necessary, but in high concentrations, they can become an environmental threat. Nutrients in polluted runoff can come from agricultural fertilizers, septic systems, home lawn care products, and yard and animal wastes. Sand, dirt and gravel eroded by runoff clog ditches, culverts and drain pipes and create the potential for flooding. Poorly protected construction sites and unpaved roads can be major sources of sediment. Toxins are created by a wide variety of human practices and products, and include heavy metals, pesticides and organic compounds like TCE and PCBs.