Molecular Soil Biology 2024, Vol.15, No.3, 118-128 http://bioscipublisher.com/index.php/msb 122 5.4 Case study: water contamination and ecosystem disruption in a rice-growing area A case study conducted in the Deduru Oya River Basin, Sri Lanka, assessed the concentration of pesticide residues in water associated with rice ecosystems and their potential impacts on environmental health. The study found that several pesticides were overapplied, leading to high environmental risks, particularly from 2-methyl-4-chlorophenoxyacetic acid and diazinon. These chemicals posed significant threats to fish, amphibians, insects, and beetles, with adverse outcomes ranging from physiological stress to mortality (Figure 2) (Gamaralalage et al., 2021). The findings highlight the need for adopting environmental health indicators and regulating pesticide use to balance food security with ecosystem sustainability. By understanding the pathways and impacts of pesticide runoff, leaching, and bioaccumulation, we can develop better management practices to mitigate the adverse effects on water quality and aquatic ecosystems. The assessment using the Environmental Impact Quotient (EIQ) method shows that the variation in pesticide use across different plots leads to significant changes in ecosystem impacts. For example, MCPA has the highest Environmental Impact Quotient among all the pesticides studied, indicating a very high potential hazard to ecosystems. At the plot level, the environmental impact is greater in upstream areas, while it is relatively smaller in midstream areas. Overall, the excessive use of these pesticides poses a significant threat to local biodiversity, particularly to the growth, behavior, and survival of fish, insects, and amphibians. To reduce the adverse effects on ecosystems, the use of highly harmful pesticides should be restricted, and farmers' awareness of the rational application of pesticides should be increased. 6 Consequences for Human Health 6.1 Direct and indirect exposure to pesticides Direct exposure to pesticides primarily occurs through dermal contact and inhalation during pesticide application. Farmers often use knapsack sprayers, which can lead to significant dermal exposure, especially when protective measures are not adequately adopted (Wong and Brown, 2020). Indirect exposure can occur through contaminated water sources and residues in soil and crops. For instance, in the Babol Roud River in Northern Iran, high concentrations of diazinon, carbaryl, and butachlor were detected in water samples, posing risks to both human health and the environment (Jolodar et al., 2021). 6.2 Health risks for farmers and nearby communities Farmers and nearby communities face various health risks due to pesticide exposure. Common symptoms reported include skin irritation, eye irritation, cough, dizziness, nausea, and diarrhea (Vieira et al., 2016). In severe cases, there have been instances of death and serious illness due to intentional or unintentional ingestion of pesticides. The lack of education and awareness about safe pesticide use exacerbates these health risks. Protective measures such as wearing protective clothing, goggles, masks, gloves, and boots can significantly reduce these risks. 6.3 Pesticide residues in rice and implications for consumers Pesticide residues in rice can pose significant health hazards to consumers. Studies have shown that pesticides like chlorpyrifos, butachlor, and fipronil remain in the soil and can be absorbed by rice plants, leading to residues in the harvested grains (Selvaraj et al., 2014). The presence of excessive pesticide residues above tolerance levels can lead to chronic health issues for consumers, including potential carcinogenic effects. Monitoring and regulating pesticide use are crucial to ensure food safety and protect consumer health. 6.4 Case study: human health impacts in regions with intensive rice cultivation In regions with intensive rice cultivation, such as the Mae Chaem District in Northern Thailand, the use of pesticides has led to significant human health impacts. The study found that lowland rice fields, which use more agricultural inputs, had the highest impact on human health and freshwater ecotoxicity (Toolkiattiwong et al., 2023). Similarly, in Punjab, Pakistan, a study reported various health issues among rice growers due to pesticide exposure, including skin and eye irritation, cough, dizziness, and nausea (Elahi et al., 2019). These findings highlight the urgent need for sustainable farming practices and effective pesticide management to mitigate health risks in such regions.
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