Pesticides include a broad category of chemicals that are used to kill specific living organisms or pests such as:

• herbicides for plants
• insecticides for insects
• fungicides for fungi and mold

Where do pesticides come from?

The source of pesticides are humans.  Large scale production of synthetic pesticides began in the 1940's.  Currently in Wisconsin, over 90 pesticides were reported as being used with about 75% being used by agriculture.⁶⁶  Here in Portage County there at least 45 chemicals being used on agricultural crops.  In addition to agriculture, industry and homeowners also use pesticides.

After application, pesticides can:

1. evaporate into the air

2. runoff into surface water

3. enter the soil

1. taken up by plants
2. broken down into other chemicals by sunlight, microorganisms in the soil, or chemical reactions
3. attach to soil particles
4. leach into groundwater

4.  stays on the plant surface

What factors increase leaching or groundwater contamination?

"Whether pesticides that leach into the groundwater pose a hazard to humans or animals depends on the toxicity and concentration of the compounds and how they 'degrade' or break down as they move through the soil." ⁶⁷  The factors that increase groundwater contamination include: 

• pesticide properties such as high water solubility, low adsorption (the ability of a pesticide to remain in the soil), and  high persistence (how long it takes for the chemical to degrade)
  
• soil characteristics such as high permeability,  high porosity, no soil compaction, low amounts of organic material, and high amounts of sand and gravel content
  
• site conditions such as shallow depth to groundwater, high amount of precipitation, and excessive irrigation
  
• management practices such as poor timing of pesticide application, not  incorporating the pesticide into the soil, poor handling of the chemical, and solely relying on chemicals for pest control

Once the pesticides reach the groundwater, breakdown continues, but at a much slower pace.

What laws govern pesticide use?

Currently, no laws exist that regularly requires pesticide applicators or their clients to report the pesticides being applied.  The existing laws for pesticide management are regulated by the Department of Agriculture, Trade, and Consumer Protection under ATCP 29 through ATCP 35.