The agriculture sector plays a vital role in Bangladesh's economy and food security. According to Bangladesh Bureau of Statistics' 'Yearbook of Agricultural Statistics-2019', this sector contributes about 14.23% to the country`s Gross Domestic Product (GDP) and employs around 40.60% of the total labour force.
The fertile soil with a warm and humid climate in Bangladesh fosters the ideal condition for high yielding varieties of crops.
As the yield of crops is increasing, the infestation of pests, fungi, mites, rodents and herbs etc. also heightened. According to a study by FAO, the estimated loss in crop yields due to attacks from pests and diseases ranges from 15% to 25% (annually) in Bangladesh and this may vary from season to season.
To deal with these infestations, farmers generally use pesticides. In Bangladesh, the most commonly used pesticides include insecticides, rodenticides, miticides etc. According to BBS, the yearly use of pesticides was 38,691.86 Metric Ton for the year 2018.
Most of these pesticides contain toxic chemicals such as aldrin, dieldrin, heptachlor, chlordane, DDT, mirex, toxaphene etc. And the ultimate fate of these agricultural pesticides is to be deposited into the environment and the human body.
But how do these chemicals penetrate our environment and worse, the human body?
The dominant mode of entry for agricultural pesticides into air, water, soil, plant etc. is through washout, leaching, deposition, wind drift, adsorption, erosion and absorption etc.
For instance, the atmospheric transportation of pesticides is through drifting and wind movement. The pesticide droplets can be drifted 10 miles in a windy condition when the droplet size is less than 130µm.
Pesticides may be transported through the wind erosion of soil. Large pesticide particles can transport by rolling of eroded soil and smaller particles can be transported by air.
On the other hand, the transportation of pesticides through water is by point source and nonpoint source such as rain washout, runoff through drains and spills etc.
Pesticides can also travel long distances through contaminated plants, animals and human bodies. The ultimate fate of these pesticides is accumulation on the surface, groundwater and land by deposition, leaching and precipitation.
Sometimes it can also enter the human/animal body directly by inhalation. The pesticides on the soil surface can be directly absorbed by the plant roots and then it may be absorbed or synthesised by the animal body and may even enter the human food cycle through consumption of these contaminated plants.
Pesticides in the water sources may end up getting absorbed by the aquatic plants, aquatic animals, aquatic microbes etc. These contaminated chemicals can also enter the food web. Consequently, we can find traces of pesticides in rainwater and also in groundwater.
There are multiple effects of pesticides on both the human body and the environment.
In the environment, the volatile organic compounds in pesticides can react with other chemicals and can form tropospheric ozone, which is a pollutant.
The air drifted droplets may have an impact on the health of forests, the wildlife and eventually the human body.
These pesticides contaminate the supply of water and soil which affect aquatic life, wildlife (bird, amphibians, mammals etc.) and degrade the fertility of the soil, inhibit the tree growth, decline of pollination, destruction of ecological and ecosystem balance etc.
The pesticides can enter into the human body directly by inhalation, absorption through the body or consuming the pesticide-contaminated water, plant, animal etc.
The persistent exposure of pesticides to the human body increases the risks of lung cancer, asthma, birth defects, tumours, genetic changes, blood and nerve disorders, endocrine disruption, coma or death.
Many alternative and remedial actions can be adopted to reduce the use of pesticides such as manual removal of weed, manual traps for rodents, the biological trap for pest, removing breeding place of pest, pest resistance crop, include biocontrol agents as predator bird for pest, implant native crop species etc.
Sex pheromones (SP), integrated pest management (IPM) and genetically modified plant (GM) are widely used throughout the world to control pests.
In addition to the use of pesticides, biological management is the best possible solution and it is ecologically, economically and environmentally viable.
The authors are from Jahangirnagar University.
Disclaimer: The views and opinions expressed in this article are those of the authors and do not necessarily reflect the opinions and views of The Business Standard.