Understanding the chemical and physical characteristics of a pesticide allows the applicator to make better decisions about which pesticide active ingredient and/or formulation to use for a particular situation. Two chemical characteristics of interest are water solubility and volatility. The more water soluble a pesticide is, the greater the potential for runoff and leaching. The more volatile a pesticide is, the greater the potential for drift.

When a pesticide is highly water soluble the pesticide remains dissolved in the water as it moves around in the environment. Less water soluble pesticides deposit in the soil or on plants more quickly and are less likely to move around in the environment. Because highly water soluble pesticides tend to move around in the environment, they are more likely to contaminate nearby rivers, lakes, streams, wells, and storm sewers, especially following heavy rainfall or excessive irrigation. If soils are sandy or if ground water tables are close to the surface, highly water soluble pesticides are not a good choice for use in these areas. This is because the dissolved pesticide has a greater chance of moving into groundwater.

The physical form of a pesticide or pesticide formulation can also travel throughout the environment. Pesticides formulated as granules, for instance, can be easily carried by wind or water into undesirable areas.