Pesticides and Ornamental Gardens

On Thursday, July 30th the Wall Street Journal published an article by Gwendolyn Bounds entitled “Death by Mint Oil: Natural Pesticides.” As Ms Bounds points out more and more pesticides, herbicides and insecticides derived from naturally occurring substances are now commercially available. Some of the more natural pesticides were introduced in the 19th century, and are based on, pyrethrum which is derived from chrysanthemums, and rotenone which is derived from the roots of tropical vegetables. Others like boric acid (used to kill amongst other pests termite colony invasion inside homes and ant hills) and soap salts are just older and though modesty less effective are believed to be far less toxic. These older, naturally occurring chemicals are a step back, but believed to be even safer than the new generation of herbicides developed during last quarter century encouraged by the US EPA. Those newer herbicides were applied at much lower levels, broke down more quickly in the environment and were less toxic to animals. The new generation of herbicides was based on sulfonylurea and imidazolinone. Now it seems that the degradation products of these new herbicides are far more persistent in the environment that originally believed or hoped and we are looking once more at older, natural solutions.

Pesticide' is a broad term, covering a range of products that are used to control pests. The slug pellets, ant powder, weed killers, and rat and mouse baits that you may use in your everyday life are all pesticides. Other pesticides you may have heard of including: insect killers (insecticides), mould and fungi killers (fungicides), weed killers (herbicides), slug pellets (molluscicides), plant growth regulators, bird and animal repellents, and rat and mouse killers (rodenticides). Often people only think of pesticides as chemicals, but they include a very large range of different types of products. Some as described above are natural, while many are altered versions of natural chemicals.

In Canada there is a growing movement to ban the use of pesticides for ornamental use. Town by town, Provence by Provence bans are appearing. Ontario and Quebec have banned the pesticides use for cosmetic purposes on lawns, vegetable and ornamental gardens, patios, driveways, cemeteries, and in parks and school yards. There are no exceptions for pest infestations (insects, fungi or weeds) in these areas, as lower risk pesticides, biopesticides and alternatives to pesticides exist. More than 250 pesticide products are banned for sale and over 95 pesticide ingredients are banned for cosmetic uses. Pesticides, including herbicides, insecticides, fungicides, and rodenticides, used to simply prevent blemishes and other imperfections on private and public lands are referred to as the cosmetic (or ornamental) use of pesticides in these regulations. The question is should we be following the Canadian lead in this?

Though there has been no direct evidence linking pesticides with the exception of nitrogen to diseases in humans, an increasing number of health and environmental groups are claiming that these chemicals do indeed impact human health. A wide range of chemicals are used to treat everything from pests to mold in household gardens. One of those is 2, 4-D, used by cereal crop producers and commonly found in household weed killers. It has been the subject of an extensive study by Health Canada which determined that, when used properly, it is safe. Organizations like the Sierra Club and the Canadian Cancer Society, which strongly support a ban on cosmetic use of pesticides and herbicides, disagree. However, no specific research linking the currently used ornamental pesticides to disease in humans was found.

The only documented study to find a disease link to 2,4-D was done in the United States, a 1991 National Cancer Institute study examined dogs whose owners' lawns were treated with 2,4-D four or more times per year. The study found those dogs had double the risk of developing canine malignant lymphoma than dogs whose owners do not use the herbicide. Overall, it appears that the Canadian ban on cosmetic use of herbicides and pesticides is based on an emotional and logical belief that cchildren may be more at risk of developing health problems from pesticides because:

• Their activities lead to more exposure e.g., playing in the grass, putting their hands or toys in their mouths.
• They are closer to the ground and breathe in higher amounts of pesticides.
• Proportional to their weight, they breathe in more air and consume more food and drink than do adults.
• Their immature metabolic systems cannot break down toxins as effectively as adults.
• Their bodies are rapidly growing and developing and potentially impacted more strongly by endocrine disruptor effects.

While I certainly do not know if a ban on ornamental use of pesticides will prevent disease in children, I wonder what the downside of reducing use would be. (For full disclosure purposes I have the third to worst lawn in my neighborhood, I apply no chemicals to my lawn and never water. However, I do hope to improve the lawn by aerating and over seeding annually and applying my compost. So far, not so good despite soil analysis that showed decent soil composition.)