Many pesticides are relatively soluble in water, whereas others attach strongly to soil particles.
Pesticides are transported from the land surface to streams through a combination of subsurface drainage, surface runoff, and soil erosion. Infiltration of rain and irrigation water facilitate transport of pesticides to ground water. Because of their uses, VOCs are typically associated with urban environments. Examples of VOC sources include leaky underground storage tanks and emissions from automobiles. In drinking water, they may be carcinogenic or otherwise harmful to human health.