Most people think that all pesticides are chemical poisons. However, in most countries, the definition of a pesticide is much broader and includes any substance or mixture of substances intended for preventing, destroying, repelling or mitigating any pest. Pesticides are usually chemicals, but can include devices and even organisms. Plant regulators, defoliants and desiccants are other products often classified as pesticides. A pest is usually considered to be any organism that is destructive, or troublesome to its host, or carries disease to plants, animals, or humans. Common examples of pests are insects, rodents, weeds, fungi, bacteria and viruses.
Pesticides have a range of toxicity to humans, but because they are designed to kill or adversely affect living organisms, most pesticides pose some risk to humans, animals, or the environment - particularly if they are used incorrectly. They are, however, considered by most farmers to be a useful tool for protecting their crops and therefore used widely. Below are links to some articles with more complete definitions of pesticides. The next lessons will talk in more detail about the health and environmental risks associated with their irresponsible use.
Almost every chemical poses some risk to human health if used incorrectly. Pesticides - chemicals designed specifically to have an adverse effect on a target organism(s) - are particularly prone to create potential health risks to humans and non-target species. The good news is that the risks can be greatly minimized if proper precautions are taken - the most important being to avoid exposure.
The other important point to remember is that not all pesticides are equally dangerous. Just swallowing a teaspoonful of a very toxic pesticide can cause a serious or even fatal reaction. Other pesticides, however, are arguably less toxic than common table salt. The degree of risk (hazard level) associated with pesticides is usually defined using the following equation:
Risk = Toxicity x Exposure
Where: Toxicity is a measure of how harmful or poisonous a pesticide is and Exposure is a measure of the contact you have with the pesticide.
Toxicity is a measure of the ability of a pesticide to cause harmful effects. Toxicity depends on:
Pesticide exposure occurs when you get a pesticide in or on your body. The toxic effect of a pesticide exposure depends on how much pesticide is involved and how long it remains in contact.
Pesticides can cause three types of harmful effects: acute effects, chronic effects, and allergic effects. An Acute effect is the toxic response that results from a single dose or exposure to a pesticide. A Chronic effect is the toxic response that results from repeated exposures to small doses of a pesticide over a longer period of time. An Allergic effect is a harmful effect that some people develop in reaction to a substance that does not cause the same reaction in most other people.
It is probably safe to assume that all of you know what is meant by the environment - literally everything around us including air, soil, water, plants, animals, houses, restaurants, office buildings, and factories and all that they contain. Over the past few years, the public, national governments, international organizations, farmers and agricultural professionals alike have become much more concerned about how we humans are affecting the environment. The effects of agricultural pesticides on the environment are specifically worrisome to many. If used irresponsibly, they have the potential to cause harm to the environment. However, the good news is that when proper practices are observed the environmental risks are quite small.
The degree of environmental risk associated with any particular pesticide depends on a number of factors. Here are some of the most commonly mentioned:
Some natural processes also influence the impact of a pesticide on the environment. The most important of these include:
The International Code of Conduct on the Distribution and Use of Pesticides is perhaps the most important response to minimizing the risks associated with pesticides discussed in the previous lessons. The first release of this document was developed in 1985 by the Food and Agriculture Organization of the United Nations (FAO) in consultation with United Nations agencies and other organizations. It has recently been revised and the revised version was adopted by the Hundred and Twenty-third Session of the FAO Council in November 2002. The Code is based on internationally agreed upon technical guidelines and is aimed at reducing the hazards associated with the marketing and use of pesticides. It is of particular value in countries that do not yet have adequate control infrastructures. The Code sets standards for pesticide management; testing; reducing health hazards; regulatory and technical requirements; availability and use; distribution and trade; information exchange; labeling, packaging, storage and disposal and advertising. It is fully supported by the international crop protection industry.
Everyone concerned about the responsible use of pesticides should have at least a general understanding of what the Code advocates and what its implications are for professionals in various sectors. If you don't have a copy available you can use your browser to download an online copy at the following Website:
An analysis of the extent to which the code is being implemented in countries around the world: