What are Pesticides, and How are They Absorbed in Our Environment

The term “pesticide” is a composite term that includes all chemicals that are used to kill or control pests. In agriculture, this includes herbicides (weeds), insecticides (insects), fungicides (fungi), nematocides (nematodes), and rodenticides (vertebrate poisons). Agriculture is one of the few activities where chemicals are intentionally released into the environment because they kill things.
About 50,000 pesticide products are now registered for use with the U.S. Environmental Protection Agency (EPA), but the number of those used extensively is smaller. These pesticides are commonly classified according to their intended target organism (as mentioned above) and according to their intended use (for example, defoliants, desiccants, fumigants, and plant growth regulators).
The assessment of human-toxicological effects of a pesticide emitted into the environment implies a cause-effect-chain linking emissions to impacts through four steps: environmental fate, exposure, effects, and damage analysis.
The fate of pesticides in the environment is varied. Pesticides dissipate at varying rates. Simple chemicals often dissipate more quickly than complex chemicals.
The physical and chemical properties of pesticides influence their potential to harm the environment. The most important properties to know are:

Degradation – Ability to break down in the environment
- the longer a pesticide takes to degrade, the greater the risk for water contamination
- generally, complex chemicals like some organophosphates last longer since they can’t be broken down readily by soil microbes
- soil conditions that provide excellent habitat for microbial growth may also lead to more rapid rates of degradation
Volatility – Ability to move into the air, eg., hormone herbicides
Solubility in Water – Abilitty to leach into groundwater, e.g., metachlor can leach more readily than atrazine
Adsorption – Binding characteristics with soil particles, e.g., triazines bond to soil particles
Absorption – Ability to move into organisms or structures
Bio-Accumulation – Ability to accumulate in body tissues.