A pesticide has been defined as “a substance or mixture of substances used to kill pests (US Environmental Protection Agency, 2007), and whose intention is for purposes of repelling, destroying, mitigating or preventing any pest (Graeme, 2005). In this case, a pest is taken to mean plant pathogens, molluscs, insects, mammals, nematodes, weeds, people, and even nematodes (for example, roundworms). A pesticide could be a biological agent (for example, a bacteria or virus), a disinfectant, a chemical substance, a disinfectant, or an antimicrobial agent.
Human beings have been using pesticides for purposes of crop protection prior to 2500 BCE. Elemental sulfur dusting, which was used in Sumer in the past 4500 years, has been recognized as the first ever known pesticide. During the 15th century, some poisonous chemicals which included mercury, lead and arsenic were being used as pesticides. During the 19th century, some two natural pesticides were discovered; rotenone, a derivative of tropical vegetable roots, and pyrethrum, which is a derivative of chrysanthemums (Miller, 2002).
DDT was discovered by Paul Muller, in 1939, and it soon proved to be quite effective as an insecticide, with a wide applicability around the globe. During the 1940s, synthetic pesticides started to be produced by manufacturers in large quantities, in effect gaining widespread application (Miller, 2005). According to Lobe (2006), the period between the 1940s and the 1950s has been regarded as “the pesticide era”. From this point moving on (since the 1950s), there has been a 50-fold increase in terms of the use of pesticides, with the result that on an annual basis today, approximately 2.3 million tonnes of pesticides gets used (Lobe, 2006).
Close to three quarters of all the pesticides that are produced on a global scale, find use amongst the economies that are already developed, even as the developing economies seek to enhance their usage (Miller, 2005).
Characteristics, toxic effects and mode of action of Organophosphate, Carbamate and Organochlorine pesticides
Organophosphate is a term used in reference to a group of chemicals that cause death to insects by way of disrupting both their nervous systems, and the brain. However, we have a number of acute health problems that are associated with those workers that have been found to handle these, and they include dizziness, nausea, pain, eye and skin problems, and also vomiting (Wilson, 1996).
On the other hand, carbamate in a similar fashion with organophosphates, operate on a mode of action that aims at suppressing enzymes known as cholinesterase, in effect having an impact on nerve impulse transmission of insects. With regard to toxicity, both the carbamate and the organophosphates have been seen to result in a nervous systems disruption of either a vertebrate, or an invertebrate, by way of cholinesterase enzyme inhibition. When we have an acute dose of these pesticides these act to lower the cholinesterase activity, with the result; that the normal transmission of nerve impulses gets impaired. As a result a nervous systems paralysis could result, causing death, mainly as a result of a failed respiratory system (Jaga & Dharmani, 2003).
Effects on the Environment
The use of pesticides is increasingly drawing a lot of concern in as far as environmental issues are concerned. More than 95 percent of herbicides that are spared, along with nearly 98 percent of the pesticides that are also sprayed, tend to reach to other destinations, other than those that they were initially intended to target. Such would include species not targeted, water, and air, food, and bottom sediments (US Environmental Protection Agency, 2007).
Pesticide drift takes place at such a time as when we have a suspension of pesticides in the air, often times in the from of particles. Such particles shall then be transported via the wind, to destinations other than where they were originally planned top target, in effect resulting in a potential contamination of such areas. Thus far, there is evidence to support claims that pesticides are slowly turning to be an emerging pollutant of water (US Environmental Protection Agency, 2007). Furthermore, we also have a number of pesticides that have since come to be referred to as “persistent organic pollutants”. These have been seen to play a significant role with regard to soil contamination.
Effects on Humans
Pesticides have the potential to pose danger to worker, consumers, or even bystanders at a time when these are being processed, during their shipment, or at the time of use. We have numerous studies involving farmers whose objective has been to assess the potential health effects to them. As a result of their being exposed to pesticides (Stallones & Beseler, 2002). According to joint estimates by the UN Environmental Program and WHO (World Health Organization), more than 3 million farm workers within the developing nations are at risk of severe poisoning, as a result of having contact with pesticides. Of these, about 18,000 have been noted to die due to pesticides-related complications (US Environmental Protection Agency, 2007).
The rise and fall of DDT
DDT refers to an organochloride, usually used as a spray on house walls for purposes of fighting against malaria. It has been in use from the 1950s. According to Dr. Arata Kochi, who is the malaria chief with WHO, “One of the best tools we have against malaria is indoor residual house spraying. Of the dozen insecticides WHO has approved as safe for house spraying, the most effective is DDT.” (12). Nonetheless, a study whose findings were released in October 2007, indicated a connection between on the one hand, DDT exposure amongst adolescent girls before puberty age and on the other hand, breast cancer (Stallones & Beseler, 2002).
Exposure to DDT has also been associated with poisoning. This happens why the insecticide gain access to the food chain of humans, thereby affecting tissues. According to scientific estimations, DDT, along with other pesticides that are categorized as organophosphates have sine 1945, helped to save more than 7 million lives of humans, through way of preventing the transmission of such diseases as sleeping sickness, malaria, typhus, and bubonic plague (Miller, 2002).
Nevertheless, there are cases of mosquitoes that are resistant to DDT have been reported (Das et al, 2001), thereby reducing its effectiveness. The Stockholm Convention that assessed the “persistent organic pollutants” banned DDT use in agricultural practices, due to what the convention termed as “a serious threat to biodiversity”.
Regulations governing pesticides in Canada and the US
The selling or the actual use of pesticides in a majority of the countries requires the approval of agencies of the government. For instance, EPA (Environmental Protection Agency) is the government agency charged with the responsibility of approving pesticide sale and use, in the United States. In this case, EPA categorizes pesticides into different toxicity classes, in addition to registering their sale and use, and ensuring that they bear a label on the directions for their use (US Environmental Protection Agency, 2007).
We nevertheless have those pesticides that EPA deems as being too hazardous to be directly sold to the public. These, often labeled as ‘restricted sue pesticides’, may only be purchased by certified applicators. Environmental and health concerns have seen 54 municipalities in Canada along with the whole Ontario and Quebec provinces impose restrictions on the utilization of synthetic lawn pesticides for cosmetic purposes (US Environmental Protection Agency, 2007).
Even as the regulations on pesticides varies from one nations to another, pesticides, along with the products that they are used ion, still gets to be traded from one country to the other. This is therefore a source of inconsistencies amongst the various countries. In a bid to curb such inconsistencies, FAO, in 1985, sought to embrace a code of conduct on the international use and distribution of pesticides. This code was based on voluntary standards, and was later updated in 2002 (Das et al, 2001). This is the only way to regulate the use and manufacture of pesticides, as they are a threat to the environment and human health, when misused. Nevertheless, we still need them so as to prevent or mitigate the prevalence of pests.
Das, R., Steege, A., Baron, S., Beckman, J., & Harrison, R (2001). “Pesticide-related illness among migrant farm workers in the United States”. Int J Occup Environ Health 7 (4): 303–12.
Graeme, M. (2005). Resistance management-pesticide rotation. Ontario Ministry of Agriculture, Food and Rural Affairs. (2005).
Jaga, K, & Dharmani, C. (2003). “Sources of exposure to and public health Implications of organophosphate pesticides”.Rev. Panam. Salud Publica 14 (3): 171–85.
Lobe, J. (2006). WHO urges DDT for malarial control strategies. (2006). Inter Press Service.
Miller, G. T. (2002). Living in the Environment (12th Ed.). Belmont: Wadsworth/Thomson Learning.
Miller, G. T. (2004). Sustaining the Earth (6th edition). Pacific Grove, California: Thompson Learning, Inc.
Stallones, L. & Beseler, C. (2002). “Pesticide illness, farm practices, and neurological symptoms among farm residents in Colorado”. Environ. Res. 90 (2): 89–97.
US Environmental Protection Agency (2007). What is a pesticide?
US Environmental Protection Agency. (2007). Pesticides and food: what the pesticide residue limits on food.
Willson, H. R. (1996). Pesticides regulations. Minnesota, Canada: University of Minnesota Press.