Slow-release pesticide will help prevent aquifer pollution

Date:03-26-2009

Scientists in the Institute of Natural Resources and Agrobiology of the Spanish National Research Council (CSIC) have developed a method to encapsulate and slowly release pesticides. The new development allows prevention of leaching, as well as the volatilization of their molecules. Fewer applications are then needed, with positive effects on the contanimation and pollution of aqifers and soils in force of an excessive and uncontrolled release of pesticides and herbicides into the environment.

One of the effects of the application of pesticides and herbicides in agriculture is the pollution of aquifers: irrigation waters abìnd rainfalls carry the toxic substances along the soil profile, causing it to leach into the underground till they reach the aquifers.

Another problem is that when applying pesticides by spray part of their molecules are volatilized. Failure to comply with strict security measures implies risk for people who repeatedly apply the compounds as they are exposed to the neurotoxic effects of some of these substances.

Tomas Undabeytia, principal investigator of this project, explains that the new method encapsulates the pesticide in lecithin liposomes or vesicles, which in turn are  fixed on the surface (adsorption) of clay. The final product is a complex that combines liposomes, pesticide and clay and, at a first glance, looks like clay powder. This complex, which is dispersed in water, allows the chemical compound to be slowly released, as it is fixed to the clay. This also prevents the compound to be washed away by irrigation water or rainfall to subsurface layers and aquifers.

Although the formulation has been designed for agricultural products, it could be applied to other areas, such as mosquito lotions. The components of this formulation, the lipid to form liposome and the clay mineral, are classified by the Environmental Protection Agency of USA (USEPA) as substances of minimal toxicological concern.

One of the major advantages of this system, as the authors explains, is that this formulation can be applied to molecules of pesticides of any kind, either hydrophobic, or acidic or basic.

Safety problems with pesticides are not trivial. The EU has recently adopted new rules to restrict the use of chemical compounds that pose a risk to health and the environment.

The new regulations forbid, among other things, production of pesticides that may be carcinogens or affect human health. Some of the compounds that are used at the farm level are very neurotoxic and, although they degrade after a few days, humans and wildlife exposed while the molecules are still active can be affected.

Suppression at once of the current substances is not possible, so the EU strategy aims at reducing or replacing existing products by less harmful formulations.