The many causes to non point source pollution in a shopping area include:
- Shopping malls typically have large parking lots. Precipitation that falls on the lot runs off and carries along oil and rust from the cars, as well as salt used for melting ice. Without a well maintained stormwater drainage system all of this finds its way into the watershed.
- Parking lots generate almost 16 times as much runoff as an undeveloped meadow.
- Herbicides are often used to control plant growth around parking lots.