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Bioremediation for Sustainable Environmental Cleanup

7.2.4 Pyrethroids, Triazine, and Neonicotinoids

Pyrethroids are synthetic insecticides that are widely used in agriculture and the public health

sector. These are considered to be among the safer compounds currently available (Kolaczinski and

Curtis 2004). Pyrethroids are found in many commercial products used to control insects, including

household insecticides, pet sprays and shampoos (Nicolopoulou-Stamati et al. 2016). These include

permethrin, resmethrin, sumithrin, cypermethrin, chlorfenvinphos, deltamethrin, fenvalerate,

flumethrin and ivermectin (Huang et al. 2018). These compounds are neurotoxic, and extremely

toxic to fish and other insects but show less toxicity towards mammals and land birds (Kolaczinski

and Curtis 2004, Ray and Fry 2006). Triazines are widely used in agriculture as herbicides for

controlling weeds. Commonly used triazines are atrazine, simazine and ametryn. Among these,

atrazine is widely used as an herbicide, however, it has been banned from production to preserve

the environment (Nicolopoulou-Stamati et al. 2016). These herbicides are endocrine-disrupting

and carcinogenic, having long-term residual effects and creating health and environmental risks

(Zhang et al. 2021). Neonicotinoids are now the world’s most widely used insecticides (Hoshi

et al. 2014). It is water-soluble, easily absorbed by plants and transported throughout their tissues

for protection (Goulson 2013). Regularly known neonicotinoids are imidacloprid, thiacloprid and

guadipyr. Studies have concluded that these insecticides do not present a high risk to non-targeted

organisms; however, they can have possible adverse effects on the endocrine and reproductive

systems of animals (Bal et al. 2012).

7.3 Current Status of Pesticide Pollution

In the past decade, the global production of pesticides, or so-called plant protection products, has

been growing at a significant rate. In 1990, the production was 2.3 million tons, but in 2018, it

reached 4.1 million tons and this growth is expected to continue during the next decade (Degrendele

et al. 2022). While pesticides protect food production and cater to global food demand, they are also

ubiquitous environmental pollutants that negatively impact water quality, biodiversity and human

health (Landrigan et al. 2018). As a result of their toxicity and carcinogenicity, pesticides have always

been deemed potentially harmful to living systems and have been a matter of debate and concern.

Over the last few years, a high concentration of pesticides has been detected in environments such

as agricultural, forest regions and surrounding water, across the globe. Recent data reports by Tang

et al. (2021), documented the world geography of environmental risk of pollution by pesticides

in 168 countries. Worldwide, more than 70% of agricultural land is polluted by pesticides. The

risk of pollution was determined by pesticide residues exceeding the no-effect concentration in

the environment, and it was considered high risk if the residues exceeded this by three orders of

magnitude. In Figure 7.1, the land area subjected to low quantity and high variability of water

supply and high risk of pollution by pesticide mixtures is demonstrated for the top 30 high- and

low-income countries. About 34% of high-risk areas are in high-biodiversity regions, 5% are in

water-scarce areas, and 19% are in low- and lower-middle-income countries. Among the regions

of concern are South Africa, China, Australia and India due to high pesticide pollution risks, high

biodiversity and water scarcity. Therefore, in order to transition to a low-pesticide future, global

mandates for pesticide management and responsible food consumption should be implemented to

reduce pesticide application at a global scale.

7.4 Microbe Assisted Bioremediation and their Prospects

Bioremediation of pesticides can be achieved by using various biological systems, as microorganisms

(bacteria, fungi, cyanobacteria and algae) are major ways involved in the breakdown of pesticides.

Microbe-assisted bioremediation is considered eco-friendly and a green option for converting

pesticides into non-toxic or less toxic metabolites. It is a low-cost technology approach that is

generally accepted by the public and can be carried out most often on site (Azubuike et al. 2016).