**6. Environmental utility of propesticides**

Although commonly used structural modifications, carried out during routine structureactivity relationship studies and lead structure optimizations, affect both pharmacokinetics and pharmacodynamics, chemical alterations used in propesticide design are aimed to improve the biological profile by optimizing exclusively the pharmacokinetics of the toxicant. Potential advantages of a propesticide can be summarized as follows:

**i.** *Alteration of physicochemical properties.*

Altered physicochemical properties leading to improved stability, solubility, or lipophilicity influencing distribution in organism (systemicity).

#### **ii.** *Sustaining activity*

Delayed or sustained action due to the slow release of the active agent from its derivatives.

#### **iii.** *Increases selectivity*

Increased selectivity, that is, decrease toxicity toward non-target species, due to different metabolism of the parent compound and its derivatives.
