Herbicides and Pesticides

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Latest Edit: General 2013-06-20 (EDT)

The word "pesticide" is a general term that refers to any device, method, or chemical that kills plants, insects or animals that compete for humanity's food supply or are otherwise undesirable. Pesticides are environmental chemicals that include the following classes: insecticides, fungicides, herbicides, nematocides (elongated cylindrical worms), and rodenticides.[1] While some of the more toxic pesticides that were once used have been banned for use today, many of these chemicals are exported to assist developing countries (e.g. Mexico) It has been estimated that three million acute cases of pesticide poisoning occur per year, along with 20,000 deaths directly related to the misuse of pesticides in these countries. Many of these countries export produce that has been grown using pesticides to North America. Therefore the possibility of North American contamination is high. [2]

Classification of Pesticides

The World Health Organization examines and classifies the hazardous form of each pesticide based on the toxicity of the technical compound and on its formulations.

  • These hazard are assessed as they relate to the acute risk to health (the risk of single or multiple exposures over a relatively short period of time).
  • They are based on "acute oral or dermal toxicity that might be encountered accidentally by any person handling the product in accordance with the directions for handling by the manufacturer, or in accordance with the rules laid down for storage and transportation by competent international bodies." [3]

The World Health Organization Classification Scheme can be viewed at: http://www.who.int/ipcs/publications/pesticides_hazard_2009.pdf

Pesticides are often called "economic poisons” as they are a cost effective way of killing their intended target. Efficiency aside however, they are inherently toxic in nature.

Less Toxic Pesticides: Pesticides that are less toxic are classified as general use pesticides and can be used without a permit or license. They are usually found in the household (e.g. bathroom cleansers, bleach) and the pesticide registration number can be found on the product container.

Restricted Use Pesticides: More toxic compounds are called restricted use pesticides and their use requires a license. In some cases the restricted use materials have the same active ingredients as the general use materials, but at a higher concentration. [4]

Within the broader classes of products that exhibit a similar sort of action, (e.g.: weed killers, insect killers) there are further distinctions regarding the type of chemistry. For example, within the insecticide class there are synthetic compounds known as pyrethroids, organophosphates, and organochlorines.

  • Organochlorines: Chlordane and DDT are the most well known organochlorines. Their use in agriculture, and for home and commercial use began after World War II.
  • These compounds have low acute toxicity but after application remain in the environment and are known to cause a series of long-term environmental health problems.
  • These toxins remain in soil and tissues for a very long time, and they have been shown to have a harmful impact on animal endocrine systems.
  • Most organochlorines were phased out of use in the 1980s and replaced by organophosphate materials that are less persistent, but more acutely toxic.
  • Organophosphates: In the beginning of the 1990s organophosphates such as parathion began to be phased out through government actions, and voluntarily by the manufacturers. [4]

Mechanism of Action

A pesticide consists of an active ingredient combined with inert ingredients. The active ingredient kills the pests, while the inert ingredients facilitate spraying and coating the target plant.

  • Active ingredients were once distilled from natural substances but are now mostly synthesized in a laboratory
  • Common active ingredients include: Chlorine, oxygen, sulfur, phosphorus, nitrogen, and bromine
  • Inert ingredients can be a variety of substances depending on the type of pesticide being formed.
  • Liquid pesticides have traditionally used kerosene or some other petroleum distillate as a carrier, though water has recently begun to replace kerosene.
  • Emulsifiers (such as soap) are also added to distribute the active ingredient evenly throughout the solvent.
  • A powder or dust pesticide will typically contain: vegetable matter such as ground up nut shells or corn cobs, clays such as diatomite or attapulgite, or powdered minerals such as talc or calcium carbonate as a base.
  • Materials such as cornstarch or flour may be added to the pesticide in order to allow it to adhere better to the plant or soil. [4]

Risks of Pesticide Exposure

Article Chronic Pesticide Exposure in Farming Risks and Solutions, Vital Link; 2012 Fall

Even though a pesticide has been approved for use by the government, it does not mean that it doesn't carry significant risks to both the environment and to human lives. Pesticide regulation is often about balancing the risks of their use with their economic benefit, and sometimes chemicals will be kept in use if the economic benefit is seen to outweigh the human health risk. [5]

Health Risks

There are numerous health risks associated with pesticide exposure given their extremely toxic nature, including disruptions in the normal functioning of the nervous and endocrine system, and increased risks of cancer.

Article Multiple Pesticide Exposure Increases Lymphoma Risk, NMJ, [1], 2012 January
  • Pesticides have been linked to numerous types of cancer in humans: from breast cancer (DDT) to non-Hodgkins lymphomas and soft-tissue sarcomas (phenoxy herbicides).
  • The Environmental Protection Agency has identified 64 pesticides are potentially cancer-causing compounds
  • The National Research Council concluded that 80% of human cancer risk from pesticides is due to 13 pesticides used widely in the production of 15 important foods: tomatoes, oranges, lettuce, potatoes, apples, grapes, chicken, beef, carrots, beans, wheat, peaches, pork, soybeans and corn. [2]
  • Several studies have determined that farmers are at greater risk for lymphomas, leukemias, stomach, brain, skin and prostate cancer. [2]
  • Many large-scale studies in Canada, United State, Europe and New Zealand have demonstrated that the greater the exposure to pesticides the greater the risk for non-Hodgkins lymphomas [2]
  • A National Cancer Institute study in the U.S. indicated that children are as much as six times more likely to get childhood leukemia and brain cancer when pesticides are used in the home and garden. [6]
  • Parkinson's Disease
  • Miscarriage and birth defects
  • Nerve damage
  • Blocks the absorption of food nutrients.
  • Chronic low-level exposure to pesticides has been linked to symptoms such as:

Environmental Risk

The use of pesticides throughout North America is quite significant. For example, in the United States each year 1.2 billion pounds of pesticides and herbicides are sprayed or added to crops. This adds up to approximately 10 pounds of pesticides for every man, woman and child in America. [2]

While the application of pesticides is meant to target insects or other organisms, experts estimate that only 2% of the pesticide actually reaches its target and the reminder (98%) is absorbed into our air, soil, water and food supply. These airborne pesticides can damage nearby crops, plants, wildlife and domestic animals. [5]

Some examples of these adverse effects include:

  • Carbofuran (recently banned for most uses) was responsible for the near extinction of the burrowing owl.

  • Fenitrothion, which used in the budworm spray program in New Brunswick caused the extermination of the songbird populations in that province. Scientists from the Canadian Wildlife Service identified it as "environmentally unacceptable" and it was later taken off the market.
  • Wildlife in the Great Lakes region have been studied and exposure to pesticides have caused: enlarged thyroids, cancers, deformed bills, and the feminization of male animals.
  • Gulls’ eggs in the Great Lakes region were found to contain dioxin, a deadly substance contaminating phenoxy herbicides.

  • Evidence has shown that dogs from homes with lawns that have been sprayed with pesticides have a higher than average rate of the canine equivalent of lymphoma. [2] , [5]

Another key concern is that when pesticides are applied to kill the targetted pests they often kill the pests' natural predators in the process which only exacerbates the problem

  • In some cases, exterminating a pest merely allows another pest to take its place.
  • After a period of pesticide use insects can become resistant to the pesticide, so higher quantities and strengths pesticides must be used in order to do the job. [2]

Specific Consideration

Food Sources

It is best to buy organic foods wherever possible because these food sources are grown without the aid of any synthetic chemicals including fertilizers or pesticides. When buying organic products, make sure it’s labeled certified organic and find out who actually certified it - there are differences in quality and criteria around organic certification. This especially holds true for produce and meat as they can be the sources of many pesticides. [2]

  • When grain used for feed is grown with pesticides and then fed to livestock, pesticide residues accumulate in the animals' fatty tissue.
  • When humans consume the meat and dairy products derived from these animals, we're exposed to those same toxic ingredients.
  • Trim the fat from meat and skin from poultry and fish.
  • Many pesticides penetrate the entire fruit or vegetable and cannot be entirely scrubbed off.
  • Soak produce in a mild solution of additive-free soap or pure castile soap to remove surface waxes, fertilizers, fungicides and pesticides to try and reduce the overall toxicity to the body.
  • Peel the skin or remove the other leaves of the produce if it’s not certified organic. (This is sub-optimal as many of the nutrients are found in the skin.)
  • Eat a variety of foods from a variety of sources to help reduce the likelihood of exposure to a single pesticide

If you are unable to buy organic, then try to buy local produce that is in season as it is the next best thing.


Another way to reduce your exposure to pesticides is to find natural alternatives to pesticides for use on your lawn and garden. Following are some ideas:[7]

  • Crop Rotation: If you rotate crops every two years, you can greatly reduce some pest problems as this forces returning pests to feed on a plant they don't like as much and reduces the likelihood of their return.
  • Beneficial Species: Plant flowers that bloom in early spring as they will draw beneficial, predatory insects (lady bugs, lacewings, ground beetles and spiders) to the area and help keep the insect levels down. Examples of these flowers include: blue lace flowers, cone flowers and flowering herbs such as parsley, fennel, cilantro, dill and caraway.
  • You can also attract beneficial insects by spraying your garden with sugar water. Mix one part sugar to ten parts water.
  • Natural insect repellent: Make a home-made, natural pest spray by combining several cloves of garlic with one or two hot peppers and a quart of water and mixing it together in the blender.
  • Spray on infected plants as needed and from many angles to ensure thorough cleaning of the plant.
  • Use your hands: Many pests from are able to be plucked from plants with your hands or tweezers if you use a bit of patience and perseverance.
  • Slugs, snails, caterpillars and some beetles are both slow enough and large enough to be removed in this way.


In Canada, Pesticides are regulated by the Pest Management Regulatory Agency (PMRA), the branch of Health Canada that administers the Pest Control Products Act on behalf of the Minister of Health. This division receives input from Environment Canada, Agriculture Canada and Fisheries and Oceans Canada. [8]

  • Pesticides are reviewed every fifteen years or earlier if new information is discovered and as science evolves.
  • Health Canada requires companies and consumers to any adverse incidents regarding pesticides to them through their Incident Reporting Program.

  • Once on the market Health Canada is responsible for monitoring the use of pesticides through a series of education, compliance and enforcement programs. [8]

A province cannot decide to use a chemical if the federal government has not registered it, however each province does have its own registration process and can effectively ban the use of a pesticide in its own jurisdiction if it chooses to

  • For example, the pesticide 2,4,5 –T had been banned in the U.S., Sweden and many other countries but was registered for use in Canada by the federal government.
  • In the early 1980's Ontario, Saskatchewan and Quebec made independent decisions not to allow its use in those provinces recognizing the serious risks to human health this substance posed. [5]


  1. Encyclopedia Britannica Concise www.britannica.com
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Murray M, Pizzorno J (1997) Encyclopedia of Natural Medicine Three Rivers Press
  3. The WHO Classification of Pesticides by Hazard http://www.who.int/ipcs/publications/pesticides_hazard_2009.pdf Retrieved 14 March 2012
  4. 4.0 4.1 4.2 Hayes W Laws E (1991) Handbook of Pesticide Toxicology Vol 1 Academic Press
  5. 5.0 5.1 5.2 5.3 Sierra Club of Canada Pesticides Facts http://www.sierraclub.ca/national/programs/health-environment/pesticides/pesticid.html Retrieved 14 March 2012
  6. Maxcy-Rosenau L (1998) Public Health and Preventive Medicine Appleton and Lange
  7. Bradley F (2007) Rodale's Vegetable Garden Problem Solver Rodale Books
  8. 8.0 8.1 Health Canada Pesticides and Pest Management Consumer Health and Safety http://www.hc-sc.gc.ca/cps-spc/pest/part/index-eng.php Retrieve 14 March 2012