If you enjoy a leaf or two of Taraxacum officinale (that is, dandelion) in your salad, you are certainly among the minority. And if you savour your ants when they are chocolate covered, well, enough said. For the most part, our society prefers a green lawn, without yellow polka dots, and our chocolate "pure", without the added protein boost of a "pest", thank you very much.

Pest season is well underway. We typically solve our pest problems with one or two applications of our favourite pesticide product and, poof, our pests disappear. Who needs Harry Potter? Well, we do—maybe not only to get rid of the pests themselves but to get rid of the residues left lingering on lawns and gardens. Eventually these chemicals seep their way through our local watersheds into ground and surface water supplies.

Pesticides harm human health through acute pesticide poisoning, reproductive effects, and chronic health effects. Pesticides also affect the health of aquatic ecosystems, upon which depends human health. Before reaching for your next can of pesticide we urge you to consider the broader effects of this action on your health and the health of your environment and neighbours.

What is a pest?

A pest is an organism which causes disease and competes with people for food, or causes discomfort (SRD 2002). Because dandelions and ants are harmless to humans, definition of particular pests is clearly subjective. For the most part, pests are what humans define as pests.

What is a pesticide?

Pesticides are chemical compounds used to control pests. They include insecticides, herbicides, fungicides, and other materials designed to kill or control pests.

What are some pesticide benefits?

Pesticides help increase crop yields and control some species of disease-carrying pests, including malaria-carrying mosquitoes.

How do I come into contact with pesticides?

Pesticides may be ingested, inhaled, or absorbed through the skin. Ingestion occurs directly through food or water sources which have been sprayed with pesticides, or indirectly through foods that have accumulated pesticides in their tissues through long-term exposure. Drinking water can be contaminated with pesticides.

Exposure can occur in a variety of locations, such as while working on agricultural farmland. Exposure at home is also common through the use of pet flea collars, treatments for scabies and lice, treatments for home infestations of insects, and treatments for garden and lawn infestations of weeds and insects.

Even if your home is pesticide free, exposure can occur in one's own environment. Your neighbours may use pesticides on their lawn and gardens—and there is no guarantee they are using them properly. Golf courses, public parks, hospital grounds and other public areas might also be using pesticides (though, in public places, pesticides are more than likely to be applied in the prescribed manner). Regardless of the location, pesticides—whether used in your backyard or in agriculture—eventually run off into ground and surface water, exposing entire populations of organisms, including humans, to the poison.

What are the risks from pesticide exposure?

1. Acute health risks: Poisoning

David Boyd, an environmental lawyer who authored the recently released report Northern Exposure (2007), found that 6 000 Canadians—almost half of them children—suffer acute pesticide poisoning every year, although none were fatal. In Alberta, there were 1 021 cases of pesticide poisoning in the year April 2005 to April 2006; 461 cases involved children under the age of six (Boyd 2007, 8). Provinces with large populations of farmers were found to have the highest per-capita incidence: 33 per 100 000 for Saskatchewan and 30 per 100 000 for Alberta. The report is the first comprehensive national survey on the issue of acute pesticide poisonings in Canada. Because no national standards exist for collecting pesticide poisoning data in Canada, these findings most likely fall below the actual incidence of poisonings. Only cases brought to the attention of poison control centres are reported.

2. Reproductive risks: Pre-term Births

Boyd's study follows on the heels of an American study out of Indiana University School of Medicine that found pre-term birth rates peaked when pesticide and nitrate measurements in surface water were highest, from April through July. Pre-term birth rates were lowest when pesticides and nitrates (found in fertilizers) were lowest, from August to September. The Indiana study considered more than 27 million live births in U.S. between 1996 and 2002 (Winchester 2007). Other reproductive effects linked to pesticide exposure include increased miscarriage, fetal death, infertility, intrauterine growth retardation, and birth defects (OCPS 2004, 173-174). Because the ova (or eggs) of a female fetus are produced while in the womb, the effects of pesticide exposure can affect not only the female infant but her children, the next generation (Boyd 2007).

3. Chronic health risks

Pesticides are designed to kill something. The mechanisms for doing this involve disruption of processes inside the cell. The ability of the chemical to do this means that it can also disrupt human cell processes.

(Sanborn 2003) A Canadian study undertaken in 2004 by the Ontario College of Physicians and Surgeons (OCPS) examined the potential chronic health effects on humans from pesticide exposure. These risks include development of certain types of tumours, non-Hodgkins lymphoma, leukemia, chromosomal abnormalities, skin diseases, neurological diseases, and reproductive effects (OCPS 2004, 4). Specific findings of the report included the following:

• A positive association between pesticide exposure and leukemia (OCPS 2004, 51)
• Residents who were more often subject to drift from aerial spraying experienced a substantially higher proportion of mental and emotional symptoms than those who were not subject to such drift (OCPS 2004, 87)
• "...occupational exposure to agricultural chemicals may be associated with adverse reproductive effects including: birth defects, fecundability, fetal death and intrauterine growth retardation (OCPS 2004, 117). Both paternal and maternal exposure increases these health risks.
• A link between the pesticide 2,4-D and Non-Hodgkin's Lymphoma (NHL) (OCPS 2004, 38).
• In 2003, NHL researchers Hardell and Erikson identified a decline of NHL in countries where the herbicide 2,4-D has been banned for over ten years. Their analysis concluded that 5% (3.0-7.7%) of NHL is attributable to chlorphenoxy herbicide and chlorophenol exposure (OCPS 2004, 175). 2,4-D is used in Alberta.
• The elderly can exhibit chronic neurological diseases that have been related to long-term pesticide exposure. These include Parkinson's disease, amyotrophic lateral sclerosis, and Alzheimer's disease (OCPS 2004, 173-174).

Increasingly there are concerns about the effects of estrogen-mimicking chemical compounds in our environment, such as a commonly used type of pesticide called organophosphates (Colburn et al. 1993). Organophosphates include herbicides alachlor and atrazine; atrazine is commonly used throughout Alberta. These compounds mimic the estrogen hormone and thereby disrupt the endocrine system in humans and wildlife. The endocrine system regulates hormones secreted through a series of glands, organs, and tissues, and their receptors; and it plays an important role in reproduction, child development, and the control of other bodily functions.

Pesticide risks to aquatic and terrestrial ecosystems

Ecologists were among the first scientists to reveal that pesticides killed and deformed the offspring of non-target organisms, including beneficial insects and plants, wildlife and humans (Schindler 2003). Rachel Carson's book, Silent Spring, published in 1962 was the first time toxic effects to wildlife were connected with pesticide accumulation in the food chain. Carson's discovery eventually led to this first batch of "broad spectrum" pesticides (such as DDT) being banned in North America.

Unfortunately, many of those pesticides continue to persist in our environment, their residues being carried across oceans by the atmosphere where they condensed and accumulated in colder environments such as in Canada's Arctic and in high altitude alpine regions (Schindler 2003). As glaciers and permafrost melt, accumulations of these chemicals can be released.

The effects of newer pesticides are only beginning to be understood. For example, atrazine causes sexual abnormality in frogs and its use might have unacceptable impacts on the environment and human health (Hayes et al. 2002). Atrazine has been banned in Europe because of irreversible harm to exposed wildlife and threats to human health. Atrazine is commonly used in Alberta for weed control.

A common herbicide with estrogen-mimicking properties is glyphosate, also called Roundup. Glyphosate, especially in combination with certain surfactants added to make pesticides "stick" to the weeds, has estrogenic effects and is moderately persistent in water and not removed by normal drinking water processing (PAN 1999).

Pesticides in Alberta

A 2005 study by Alberta Environment found that pesticides are commonly found in Alberta's surface waters. In most cases, the report found, pesticide concentrations were within the range prescribed by law to be safe and surface water quality guidelines were exceeded in less than 30% of the samples taken. The report could not determine the actual significance of low levels of pesticides to aquatic ecosystem health. Accordingly, the Report could not exclude local chronic effects of pesticides on aquatic life and some sensitive crops. The report notes there are also no guidelines for over half of the pesticides detected in Alberta surface waters (AENV 2005).

The herbicide 2, 4-D was the most frequently detected herbicide in Alberta's surface waters, occurring at a much lower detection frequency in Alberta's northern basins (Hay, Slave, Peace, Athabasca, and Beaver river basins) than in its southern basins (North Saskatchewan, Battle, Red Deer, Bow, Oldman, and South Saskatchewan river basins, and Sounding Creek basins).

Irrigation returns and urban streams had the highest frequency, number, and concentration of pesticides, especially from March to September where June and July are peak months. The study attributed the results to the combined effects of seasonal hydrology of the river (snow melt, runoff and rainfall occurring early in the spring) and seasonal agricultural activities (peak pesticide application period occurring mid-summer). The highest concentrations of pesticides coincided with rain following shortly after the main period of pesticide application. This increase was due to both runoff and atmospheric deposition.

In South Saskatchewan River Basin (SSRB), researchers are examining the Bow, Oldman, and Red Deer Rivers for the presence of estrogenic compounds and their effects on aquatic species. They have established that a species of fish, a minnow known as the longnose dace, is exhibiting signs of reproductive impairment, which has been linked to the presence of estrogenic compounds in their aquatic environment. The sources of these compounds include not only pesticides but compounds that are commonly found in PVC plastics, common plasticizer, and wood derived sterols (wood preservatives) (Jackson and Jeffries 2006).

Sources

Alberta Environment (AENV). 2005. Overview of Pesticide Data In Alberta Surface Waters Since 1995. Prepared by: Anne-Marie Anderson, Ph.D., P.Biol. Environmental Monitoring and Evaluation Branch, Alberta Environment.

Boyd, David. 2007. Northern Exposure: Acute Pesticide Poisoning in Canada. David Suzuki Foundation.

Carson, Rachel. 1962. Silent Spring. Houghton Mifflin.

Colborn, Theo, Frederick S. vom Saal, and Ana M. Soto. 1993. Developmental effects of endocrine-disrupting chemicals on wildlife and humans. Environmental Health Perspectives. Vol. 101: 5. pgs. 378-384.

Hayes, TB, A Collins, M Lee, M Mendoza, N Noriega, AA Stuart, and A Vonk. 2002. Hermaphroditic, demasculinized frogs after exposure to the herbicide, atrazine, at low ecologically relevant doses. Proceedings of the National Academy of Sciences (US) 99:5476-5480.

Jackson, Leland J. and Ken Jeffries. 2006. Human impacts on water quantity and quality in the South Saskatchewan River Basin and challenges to policy development. Presentation, Department of Biological Sciences, University of Calgary.

Ontario College of Physicians and Surgeons (OCPS). 2004. Pesticides Literature Review.

Pesticide Action Network. 1999. Glyphosate.

Sanborn, Margaret. 2003. Pesticides disrupt brain development & reproduction. Update Spring 2003. Testimony of Dr. Margaret Sanborn to Parliamentary hearings re: proposed Federal Pest Control Products Act (testimony reprinted in part).

Schindler, David. 2003. Scientists must be more social. June 19, 2003. Express News. University of Alberta

Sustainable Resources Development (SRD). 2002. Management of invertebrates.

Winchester, Paul. 2007. Pesticides, fertilizers linked to US premature births. Presentation at Pediatric Academic Societies' annual meeting, Toronto, Canada, May 7, 2007. Indiana University School of Medicine.

Additional reading

Alberta Environment website contains a number of sources about pesticides: http://environment.gov.ab.ca.

Rachel Carson Council Inc. promotes alternative, environmentally benign pest management strategies to encourage healthier, sustainable living.

Northwest Coalition for Alternatives to Pesticides. Though this website is more specifically directed to the Pacific Northwest, it includes tips for pesticide free gardening for many common pests.

Patterson, K. 2007. Canada raising limits on pesticide residues. May 08, 2007. CanWest News Service.

Patterson, K. "Kids Often Pesticide-Poisoning Victims: Doctors" (June 21^st, 2007) CanWest News Service, online:

Pesticide Action Network North America (PANNA). Primarily U.S. based though loaded with information about current developments in pesticide research and politics.

Sanborn, M. et al. 2002. Identifying and managing adverse environmental health effects: 4. pesticides. CMAJ 166(11):1431-6. A peer reviewed article in Canada's premiere medical journal, this article is written in a clear and accessible manner.