by Karrie Cooper
There’s a pesty side to the pesticides used in our homes, yards and gardens. A pesticide is any substance intended to prevent, destroy, repel, or mitigate pests. For example, insecticides kill insects, herbicides kill weeds, molluscides kill slugs, antimicrobials kill germs and fungicides kill plant diseases. Pesticides have “active” ingredients that actually kill and so-called “inert” or “other” ingredients, which can include surfactants, solvents, propellants, baits and other ingredients intended to make the product work better. In home pesticides, the active ingredients make up a very small part of the product, often 1% or less. Inert ingredients are really misnamed, because they aren’t necessarily chemically or biologically inert and can contribute substantially to the hazards of the product. Some are more toxic than the active ingredients.
While pesticides do their intended job well they can have unintended consequences. One concern is over how much of a given product is being used. We often think that more is better, but, in fact, this is not necessary. Excess amounts can wash off in rainwater and enter streams, wetlands, ponds, ground water and the surrounding sea. Significant problems can be caused to nearby aquatic plants, critters and animals that we wouldn’t choose to intentionally harm. Given that the islands have many areas with shallow soils and underlying bedrock or glacial hardpan the resulting increased runoff rates can increase the likelihood that these substances make their way into our waters. When they do they can interfere with the normal biological processes of freshwater and marine plants and animals. Most pesticides interfere with the nervous system of insects and many have neurological effects on Pacific salmon and other aquatic animals. Many pesticides disrupt the endocrine (hormonal) systems in fish affecting their reproduction and growth.
In July and August of 2008 a study was conducted by Kwiaht for the San Juan Nature Institute and reviewed by the Washington State Department of Ecology. Samples of water and sediment were taken from 32 lakes, ponds, streams, and sewer outfalls to determine whether household-use pesticides and their related surfactants “have accumulated to measurable levels, and whether they may already pose a threat to Pacific salmon and other aquatic organisms in the San Juan Islands”. The study focused on pyrethroid pesticides as an indicator for overall pesticide presence in local waters due to their common occurrence in the products sold locally. Levels of 1 part per billion are known to be toxic to salmonids and presumably to the “many aquatic crustaceans and larval insects that form the base of our freshwater and nearshore food chains”. The study found “widespread total pyrethroid pesticide levels of 1-2 parts per billion in San Juan County’s waters, with as much as 10-18 parts per billion at some sites.”
Recognizing the pesty side to pesticides should cause us to pause and determine whether there are other options to managing our yards and gardens in ways that support the health of our water and protect our aquatic resources. In coming weeks we will discuss alternative means to yard and garden care that are protective of our waters.
A consumer guide to lawn and garden products with detailed information and a review of 550 products is available in the grow smart, grow safe guide. A link to a PDF version of the guide can be found here
