In this highly industrialized era, agriculture and human health are key aspects that are never to be neglected as they anchor life on this planet. The agricultural sector is very key in the food and pharmaceutical industry among others where agricultural by-products are used. Humans are the dominant species and are working day in day out to ensure health is safeguarded to protect lives across the globe. Pesticides therefore become a critical resource to ensure high agricultural yields and the minimization of incidence and spread of vector borne diseases or any other pest induced diseases.
Approximately two billion people in the world work in the agricultural sector and use pesticides as a mechanism to guard their crops and livestock from pests. These include chemicals, bio-pesticides and biological agents, with chemical pesticides being the commonly used. Pesticides are used in manufacturing industries as a control measure especially the food industry under Food Safety Management Systems (ISO 22000) and Prerequisite Programs – Good Manufacturing Practices and Good Hygiene Practices among others. They are also used in homes as a public health measure to control insects such as mosquitoes and help in the fight against deadly diseases such as malaria. As much as there are different kinds of pesticides, the mostly widely used and highly recommended in terms of effectiveness are chemical pesticides. Contrary to them being a need in certain sectors, pesticides are some of the most harmful chemicals to the environment and human health in the after math.
Of the 12 listed dangerous persistent organic pollutants listed by the Stockholm Convention on Persistent Organic Pollutants “The Dirty Dozen”, 9 are chemical pesticides, DDT included. Persistent organic pollutants are chemicals that do not easily biodegrade and thus remain in the environment for decades after their use.
They accumulate in fatty tissues of exposed organisms and increase along the food chain, they have a variety of toxic endpoints, and can travel long distances from source areas through atmospheric or aqueous transport. DDT (Dichlorodiphenyltrichloroethane) is well known for its bioaccumulation and acute toxicity to non-target organisms to the extent where it has been banned and restricted in most countries. In Zimbabwe it is restricted and is only used for indoor residual spraying in malaria prone areas under the Malaria Eradication Programs. An environmental health conundrum.
The United States Environmental Protection Agency (EPA) spells out that pesticides are designed to kill, repel, attract, regulate or stop the growth of living organisms considered to be pests and there are what are termed target organisms. The fate of the pesticide after introduction into the environment is determined by a number of factors. Thus it finds itself exposed to non-target organisms with similar functionalities as target organisms and acts. Thereby posing harm. It is from this that pesticides have been concluded to have deleterious effects on the environment and human health.
The physical and chemical properties of a pesticide, soil, physical and environmental site conditions, management practices and climatic factors influence the behaviour and fate of pesticides. Pesticide introduction into the environment however differs. It can be through intentional application, disposal or accidental spills. These processes also determine pesticides movement and persistence. Physical, environmental and climatic factors are very important factors to take note of as these can allow for the adsorption, movement and spread of the pesticide in an area where the target organisms could be or further transport it where non target organisms can be affected, thus posing environmental damage. An example is that of fresh and groundwater bodies contamination especially with bio accumulating pesticides as this presents a ripple effect to consumers on the higher end of the food chain, the human beings. The fate of pesticides falls into 3 main categories adsorption, transfer and degradation and it important to understand the fate of pesticides in the environment for the proper handling, management and control of pesticide related cases.
The use of pesticides though beneficial in a number of ways is associated with far reaching costs both direct and indirect. The use of pesticides has ripple effects where not only one aspect of life is affected but all the other surrounding the initial are affected, obviously depending on the physical and chemical properties of the pesticide being used. Costs associated with pesticides are classified into 4 broad categories which are regulatory costs, human health costs, environmental costs and defensive expenditures.
Regulatory costs can be defined as costs associated with mandatory measures to prevent unnecessary pesticide exposure, remove residue pesticides to protect the environment and human health from the potential damage likely to be caused or to repair damage already inflicted. Examples include:
• Monitoring and decontamination of tap water
• Mandatory pesticide handling and disposal
• Public research and communication on new findings on how best to handle and manage pesticides
Human health costs are the costs on the wellbeing and life of humans exposed. Depending on the exposure route, exposure period, toxicity of the pesticide and sometimes the amount adsorbed by the human body, the fate of the exposed can be determined. Death can be instant, an acute illness can be experienced, a chronic one too. Some pesticides are also known to inhibit endocrine disrupting characteristic and thus fall under the EDCs (Endocrine Disrupting Compounds) whilst some will be carcinogenic, teratogenic, hepatotoxic among others. The cost on human health and life cannot be directly calculated. Medical costs are then used instead.
• Preventive medicine, annual check-up
• Medical bills for those suffering from the aftermath of exposure
Environmental costs are costs experienced from pesticide damage to the soil, plants, animals, aquatic life, algae and other microorganisms as well as pest resistance to pesticides. These costs can be local, regional or the impact can be felt large scale. Mostly environmental costs if not managed well have a ripple effect and stem off into other costs such as the cost on human health.
• Fresh and ground water bodies contamination
• Disruption of life and health terrestrial and aquatic organisms
• Soil degradation
• Pesticide resistance affecting yields and resulting in spread of diseases
• Pollination decrease affecting yields and plant life
• Spill incident clean ups to detoxify the environment either through containment or buffering
Defensive expenditures cover all expenses associated with the prevention to pesticide exposure. These can be implored as an emergency preparedness measure or as a measure to manage exposure after an incident. However it is mostly done as a defensive mechanisms well before an occurrence of any pesticide incident.
• Installation of containment systems
• Protective clothing purchasing
• Regular training of an emergency response and community communication
• Banning consumption of certain fresh foods from suspected areas, purchasing organic foods
• Purchasing and consumption of bottled water in areas where water contamination is suspected
The widespread application of pesticides has been favoured by the benefits they provide, in particular, they positively impact crop and livestock yields. They have also played a role in improving human health but in the later, pesticide residue gives rise to yet other environmental and health problems that could even be more devastating and get in the way of human life and sustainability, thus stirring a lot of controversy.
