Monday, July 27, 2009

How Green is Your Lawn- The Use of Pesticides

From the beginning of recorded time humans have utilized pesticides to protect their crops and food stores. Humans tried many substances as pesticides; toxic chemicals were tried in the 1600’s. Arsenic, mercury and lead were applied to crops to kill pests; the fact that these substances also killed larger animals including humans resulted in their abandonment for use as pesticides. One of the results of chemical development during World War II was the widespread manufacture and use of pesticides after the war. With the use of pesticides and herbicides to control unwanted pests came dramatic changes in agriculture and the agricultural business model and increasing crop yields in excess of 10%. Pesticides including herbicides and insecticides are used to control harmful and annoying organisms. They can be used to protect from diseases carried by mosquitoes or parasites. Herbicides can be used to kill invasive weeds in gardens, parks and public spaces, to clear roadside weeds, trees and brush. They are also used to prevent algae from taking over ponds and pools. Pesticides are used to control termites and mould that can damage buildings and homes. Pesticides are used in grocery stores and food storage facilities to prevent mice and insects that infest food such as grain. Much of our very clean and sanitary American life is the result of pesticide use. Each use of a pesticide carries some associated risk and controlled and limited use of these pesticides is believed to reduce the risks to a level deemed acceptable by the US EPA.

DDT became the most widely used pesticide in the world in the 1950’s. It’s potential to do harm was not fully recognized until, the 1960’s when it was identified as the cause of diminished populations of eagles, hawks, gulls and other birds. DDT use was banned. The recent reemergence of support by the World Health Organization for the use of DDT to prevent malaria is an example of the questions raised by pesticide use. The WHO argued that used sparingly DDT was the most effective method to control the spread of malaria and that saving human lives from malaria was more important than potential impact to lesser species. DDT’s potential as an endocrine disruptor was not full appreciated at that time and it has recently been implicated in increased incidence of breast cancer in women exposed before or at puberty in the California study. The wide spread use of herbicides and their potential presence in water resource was also ignored. The fate and transport model for understanding chemicals added to the environment has not always been fully appreciated. However, by the 1980’s alachlor, atrazine, cyanazine and metolachlor (all common corn and soybean herbicides) were being detected in surface water and near surface groundwater. The US EPA began to restrict use of these herbicides, too, and they were phased out over the next decade.

A new generation of herbicides was developed during the phase out period encouraged by the US EPA. The newer herbicides were applied at much lower levels, broke down more quickly in the environment and were less toxic to animals. Applying ounces of herbicides per acre that broke down in days rather than pounds of chemicals that persisted for weeks or months was a victory to the US EPA. These new herbicides were based on sulfonylurea an imidazolinone. The lower concentrations of the new herbicides and their breakdown products rendered them virtually invisible in water. We could not detect them and assumed they were not present. Now it seems that the degradation products of these new herbicides are far more persistent in the environment that originally believed or hoped.

Recent studies have documented endocrine disruption in a wide variety of marine gastropods, frogs, and fish associated with exposure to low levels of non specific endocrine disrupting chemicals of unknown sources. The current state of analysis only allowed the documentation of EDC presence. EDCs are a structurally diverse group that includes natural and synthetic estrogens, alkyl phenols surfactants, phthalates, bisphenol A, brominated flame retardants and some pesticides. Studies in recent years have documented a wide occurrence of endocrine disrupting compounds (EDCs) throughout aquatic ecosystems. This could indicate non-point sources of contamination from run off or an additive effect, which may have serious implications for US water quality. Suspect EDCs are used in large quantities by consumers and industry. Domestic and industrial wastewater and agricultural run-off are believed to be the major sources of EDCs today. The impacts of trace concentrations of EDC on wildlife do beg the question about the potential effects on humans. Drinking water is not tested for minute quantities of endocrine disrupting chemicals; we simply do not have the knowledge of what to look for nor the technical ability to identify all the trace contaminants of that nature.

In April of 2009 the US EPA issued the Final List of Initial Pesticide Active Ingredients and Pesticide Inert Ingredients to be Screened Under the Federal Food, Drug, and Cosmetic Act as potential endocrine disruptors. Pesticide runoff is a large contributor of known pollutants to the watershed. Maybe we should be re-examining the risks associated with what is now known as conventional agricultural practices, and embrace (at the very least) the best management practices for controlling environmental release of agricultural chemicals and waste. Several Provinces in Canada are in the process of banning the use of herbicides for ornamental lawn use.

1 comment:

  1. Hi, Elizabeth. I wanted to thank you for posting the information about the ad hoc committee meetings. You have done a great job of condensing our day-long discussions into something that's easily understandable. I will direct some of the people in the industry who are interested in this to your blog.

    Also, this entry on pesticides is fascinating. I didn't realize that some were classed as EDCs. As a Master Gardener with our local office of cooperative extension, I work with homeowners to help educate them about proper use of lawn chemicals and how to reduce the amount they use. We have a program called Grass Roots in which the homeowner can have one of us come to their property to measure the lawn area, take soil samples for nutrient analysis, and determine what (if any) fertilizer or pesticides they may need to achieve an acceptable lawn. We try to steer them away from the idea that they need a "golf course" look toward a more ecologically sound lawn. (Not that any lawn is truly "green!")

    Do you know what progress has been made on this screening? Has the EPA made a determination regarding the potential for contamination with EDCs by these pesticides?

    This is a newly emerging area of concern and I'm glad you are staying on top of it. I will check back here often to see what news you have gathered.

    Sandra Gentry