A pesticide is defined as any substance or mixture of substances used to prevent, destroy, repel, or mitigate any pest. These include insecticides (affects insects), herbicides (affects plants and weeds) and fungicides (affects fungi). The main advantage of using pesticides is its ability to produce a high yield in crops. As a result, genetically modified crops (GMCs) that are pesticide-resistant have been developed to produce an even better yield. No one can deny the uses of pesticides for protection of crops in the field, thereby providing us with abundant, inexpensive and attractive fruits and vegetables. Yet, there is no such thing as a completely safe pesticide; its purpose is to kill and the question is who?
When DDT (dichloro-diphenyl-trichloroethane) was introduced in the 1940's, it marked the beginning of an agricultural and pest control revolution. It was used to control malaria, typhus, and other insect-borne diseases. However, as a result of overuse, many insect pest species developed resistance to DDT. Increasing concerns over health effects in humans and wildlife, and lessened effectiveness led to DDT being banned in many countries. Since DDT, thousands of new chemicals have entered the market as pesticides, out of which many have been proven to have many human health risks.
Contrary to popular belief, it is not only farmers and individuals who work closely with pesticides that are exclusively affected by pesticide exposure. In addition to accidental, suicidal and occupational exposures (during manufacturing, mixing, loading and harvesting), the general public can also be exposed as a result of off-target drift from spraying operations. Moreover, members of the general public who consume food items containing pesticide residues also ultimately fall prey to their unpleasant effects. Some research shows that living proximity to crop fields that use pesticides is a determinant of adverse health outcomes in some populations [1].
It has been thought that the biological effects are most lethal and immediate for accidental and suicidal poisonings while they are the least for the general population that consumes pesticide-contaminated food. However, over an average person's lifespan, chronic (long-term) exposure to a given pesticide or several pesticides can have many adverse health effects, even if they are consumed in minor amounts. These exposures are very more difficult to study due to lengthiness and confounding effects from other complex exposures.
Extensive studies have been carried out to determine the associations between exposure to pesticides and human disease. While overdose of many pesticides can result in immediate death, as with the case of pesticides used for suicides, pesticide toxicity in low doses over a long period of time are suspected to be associated with conditions such as malignant and benign tumors, nerve disorders, blood disorders, endocrine disruption and reproductive effects. Pesticide exposure is an emerging risk for several aging-related conditions such as Alzheimer’s disease [2]. The risk for developing these conditions has also been observed to be much higher amongst occupational users of pesticides, such as farmers. For example, the heavy metal cadmium, which is found commonly in fungicides and is also added to fertilizers, is known to be associated with the induction of chronic renal tubular disease and other kidney-related dysfunctions, particularly amongst members of farming communities.
Cadmium and other heavy metals, such as arsenic, and mercury are not the only culprits. Organochlorine insecticides such as DDT have been shown to directly and indirectly interfere with fertility and reproduction in both wildlife and laboratory species of animals. Organophosphate pesticides such as Chlorpyrifos and Diazinon have been detected in surface and groundwater, indicating that their effects go beyond agricultural land and can easily reach the general population [3]. While many organochlorine and organophosphate pesticides are being banned from the markets of developed countries, less developed countries continue to use them because they are relatively inexpensive to manufacture, highly effective and there’s an absence of substitutes. One of the biggest challenges here is the lack of sufficient data to determine associations and causality between pesticide exposure and long-term health effects.
As mentioned previously, the use of pesticides has several advantages for agriculture and crop management. Nevertheless, one cannot ignore the health hazards they can cause when abused and used under improper guidelines. Despite the recent development of second-and third-generation derivatives of the early chemical pesticides, all pesticides possess an inherent degree of toxicity to some living organism, otherwise they would be of no practical use. For farmers, emphasizing good handling techniques such as wearing protective masks, gloves and footwear when working in the fields and during spraying can mitigate a large proportion of the occupational exposure to pesticides. It is important that manufacturers also share the minimum volume of pesticide that can be sprayed in order to obtain the highest yield, which could minimize exposures to toxic agents. Using alternative pest control methods such as integrated pest management (IPM) and crop rotations can have a long-standing positive impact for safe food. Instead of scheduled routine spraying, using pesticides on an as-needed basis may also help lessen exposure levels.
It’s inevitable that global agricultural needs will continue to expand in the future. Therefore, it is essential that we establish safety frameworks to ensure that occupational and non-occupational exposures to pesticides can be accurately quantified so that potential adverse health outcomes can be identified early and mitigated in a timely manner.
It’s inevitable that global agricultural needs will continue to expand in the future. Therefore, it is essential that we establish safety frameworks to ensure that occupational and non-occupational exposures to pesticides can be accurately quantified so that potential adverse health outcomes can be identified early and mitigated in a timely manner.
Original of this article was first written by Dr. Dushani L. Palliyaguru for the Sunday Observer. It has been modified with updated content.
References
- Dereumeaux C, Fillol C, Quenel P, Denys S. Pesticide exposures for residents living close to agricultural lands: A review. Environ Int. 2020 Jan;134:105210. doi: 10.1016/j.envint.2019.105210. Epub 2019 Nov 16. PMID: 31739132. https://pubmed.ncbi.nlm.nih.gov/31739132/
- Yan D, Zhang Y, Liu L, Yan H. Pesticide exposure and risk of Alzheimer's disease: a systematic review and meta-analysis. Sci Rep. 2016 Sep 1;6:32222. doi: 10.1038/srep32222. PMID: 27581992; PMCID: PMC5007474. //pubmed.ncbi.nlm.nih.gov/27581992/
- Suratman S, Edwards JW, Babina K. Organophosphate pesticides exposure among farmworkers: pathways and risk of adverse health effects. Rev Environ Health. 2015;30(1):65-79. doi: 10.1515/reveh-2014-0072. PMID: 25741936. https://pubmed.ncbi.nlm.nih.gov/25741936/