Who is the target?
Pesticides are primarily used in agriculture to protect crops and livestock. They consist of insecticides, herbicides and fungicides designed to prevent, destroy and repel pests. The killing of primary pests with pesticides has paved the way for secondary pests to come to the forefront. Since 1945 overall pesticide use has risen 3,300%, while overall crop loss due to insects has risen only 20%. Of the 2.5 million tons of pesticides used worldwide each year, less than 0.1 % reaches the target pest. In other words, 99% of the applied pesticides are not achieving their goal and are being released into the environment. Many will persist for years and travel far from the area of application, exposing humans to these harmful substances.
Residues of pesticides remain in or on the treated food we consume. Drinking water can be contaminated as runoff or leaching can occur through the soil and persist for decades. The use of pesticides on lawns, gardens and ornamental plants can often lead to exposure in the home. Personal insect repellants and flea and tick products on pets are also sources of exposure. As a bystander, you can easily be exposed to these products in public areas such as schools, parks and recreational areas.
The toxicity and the amount of pesticides a person are exposed to can have a direct influence on their health. For instance, a pesticide with a low toxicity and high exposure may cause similar risks as a pesticide with higher toxicity and low exposure. The accumulated exposure to multiple substances can have greater impact than their individual effects. The damage to the body could increase exponentially for each pesticide we come in contact with. The health effect of most pesticides has been assessed yet the combination of these products is far from being fully understood.
The health and safety of pesticides can greatly depend on the type of pesticide. Some of the main pesticides include:
Organophosphates: a group of insecticides used in both agricultural and non-agricultural sites. They were originally developed in the early 19th century and some were used as chemical weapons (nerve agents) in World War II. These pesticides disrupt an important enzyme responsible for regulating a critical neurotransmitter in the body, acetylcholine, which can lead to damaging effects on the nervous system. Several of these pesticides have been discontinued and restricted in residential use.
Carbamate: a group of pesticides used in homes, gardens and agriculture. They can affect the function of acetylcholine by disrupting an enzyme responsible for its regulation. The enzyme effects are usually reversible.
Organochlorine: an insecticide commonly used in the past. Many have been removed from the market due to their damaging effects on health and their persistence in environment (e.g. DDT and chlordane). Soil-based DDT is incorporated into grasses growing in the soil, into cattle consuming the grass and eventually into the milk and fat tissue of cows. The half-life of DDT ranges between 4-30 years.
Pyrethroid: pesticides developed as a synthetic version of the naturally occurring pesticide found in chrysanthemums, known as pyrethrin. They have been modified to increase their stability in the environment. Some synthetic pyrethroids are toxic to the nervous system.
Arsenic based pesticides: discontinued in the U.S. but still widely available in certain countries. Homes and farmers have leftover supplies that remain to be a risk. Arsenic has life-threatening effects in the body specifically to the central nervous system, blood vessels, kidney and liver.
Mercury based fungicides: mainly used as seed protectants. Many mercury compounds have been prohibited for several years. Among the most toxic pesticides ever developed. Severe and often fatal neurological disease have occurred when mercury-treated grains have been consumed directly or through the meat of animals fed mercury-treated seeds.
Pesticides can have a variety of effects especially on the nervous system. Some pesticides may be carcinogens, while others may affect hormones and the endocrine system in the body. One important factor in uptake and storage of chemicals is whether they are water or fat soluble. Water soluble compounds have a low potential for bioaccumulation as they do not easily enter cells. Fat loving chemicals pass more easily into the body’s cells through the cell membrane where they can accumulate in fatty tissues. Fat soluble compounds do not need to be re-sprayed following a rainfall as opposed to water soluble. The National Human Adipose Tissue Survey identified multiple pesticides stored in human fat tissue (please refer to Chemicals and Solvents for more information). Numerous studies have also shown persistent levels of chlorinated pesticide residues, including DDT, in breast milk that correlated directly with the level in maternal adipose tissue. In the body, when detoxification pathways are working efficiently, we can effectively deal with some exposure to pesticides. With increased exposure, the body removes the toxin from the blood, but stores the chemical in fat; therefore when fat reserves are called upon to provide energy, the chemical is remobilized and released back into the bloodstream leading to toxic effects. The negative impact pesticides can have in our body is alarming.
Food can often be a large source of contamination. The Environment Working Group (EWG) offers a Shopper’s Guide to Pesticides in Produce that determines which fruits and vegetables have the most pesticide residues (please refer to www.ewg.org for more information). Produce with a thin skin are more susceptible to contamination through absorption of the pesticide.
12 Most Contaminated Produce Items
- Sweet Bell Peppers
- Grapes (Imported)
12 Least Contaminated Produce Items
- Sweet Corn (Frozen)
- Sweet Peas (Frozen)
- Kiwi Fruit
Another tool is the Interactive Toxic Home. An excellent and fun resource to see the common toxins that are present in different areas and rooms in the home (you can access the interactive site at www.everydayexposures.com). With the many possible sources of pesticides in our environment, it is important to stay informed and try to limit your exposure.
- Crinnion, W. Environmental Medicine, Part 4: Pesticides – Biologically Persistent and Ubiquitous Toxin
- Routt Reigart, J & Roberts J.R. Recognition and Management of Pesticide Poisonings. 5th edit. 1999. United States Environmental Protection Agency. United Book Press, Baltimore, MD.