Authors: Bhadra A H, Anwesha Sengupta, Aliahad Altaf Melani, Sai Malavika, Chanchal Rathee, Chennaboina Komal Sai Siddardha, Rutuja Buchewad ABSTRACT Plastic pollution in freshwater systems is an escalating environmental concern, with implications for ecosystem integrity, water quality, and public health. This paper reviews research on microplastic and macroplastic contamination in aquatic environments and empirically examines how plastic waste generation and economic development relate to freshwater quality in Indian states from 2016 to 2021. Using an unbalanced state-level panel of 75 observations, the study applies a fixed-effects regression model with Biological Oxygen Demand (BOD) as the dependent variable, state-level plastic waste generation as a proxy for plastic contamination, and Gross State Domestic Product (GSDP) as an indicator of economic development. The findings show a statistically significant negative association between GSDP and BOD, suggesting that higher economic development is associated with improved freshwater quality, likely through better wastewater treatment and regulatory capacity. In contrast, plastic waste generation is not significantly associated with BOD, indicating that conventional water-quality indicators such as BOD may not adequately capture the environmental effects of plastic pollution. The study highlights the need for more comprehensive monitoring frameworks, including plastic-specific indicators, and finer-grained spatial analysis to better understand the distribution and impacts of plastic contamination across Indian freshwater systems. Keywords: Microplastics, Macroplastics, Wastewater Treatment, Drinking Water, Plastic Waste Management, Freshwater quality; Plastic waste generation. INTRODUCTION Plastic is a material that is essential in today’s society due to its light weight, durability, and low cost (Wagner et al, 2014, as cited by Yang et al, 2021). It is used widely in many industries, including packaging, construction, healthcare, agriculture, textiles, and more. But the growing amount of plastic waste accumulated and disposed of in an improper way has posed serious environmental risks globally. Every year, tons of plastic waste are dumped into rivers, lakes, groundwater, and oceans, where plastics persist for extended periods of time because they break down very slowly. The plastic pollution in aquatic environments is typically divided into macroplastics (larger than 5mm) and microplastics (smaller than 5mm). Macroplastics are made up of larger plastic products like bottles, bags, food containers and fishing gear, while microplastics are either fragments of larger plastic products or manufacturing products like cosmetic microbeads and synthetic textile fibers. Plastic pollution in all forms pose a risk to water quality and aquatic ecosystems. Water bodies are important vectors for pollution coming from urban, industrial, and agricultural sources to larger water bodies. Plastics can end up in sediments, and then be transferred to the food chain as they travel through rivers and lakes. Plastic contamination is not just a problem, but recent studies depict that microplastic presence is indicated in groundwater and drinking water (Duan et al, 2021). These results have led to implications posed about ecological sustainability and potential human health risks. In addition to surface water and sediments, microplastics have also been found in packaged and bottled drinking water (Marin et al, 2023), which means that direct concerns have been about human ingestion via the food chain as well as through the consumption of drinking-water-safety problems, rather than just an ecological one. Thus, the purpose of this literature review is to explore the current research on microplastic and macroplastic contamination in water bodies. It highlights the main sources of pollution, transport pathways, contamination of various aquatic environments, the effects of urban land-use and usage patterns, environmental and human health impacts, and existing management and removal strategies and identifies areas where further research is needed. THEORETICAL FRAMEWORK To explain the observed relationships, this study relies on three theoretical ideas-the Environmental Kuznets Curve (EKC), the source-pathway-receptor model of pollution, and the ecological sustainability/ecosystem-services paradigm. First, the EKC hypothesis suggests a particular income-environment relationship according to which environmental degradation rises until a given level of aggregate income is surpassed and begins converging downwards as income keeps growing (Grossman and Krueger, 1995). This is a reasonable explanation for the negative and statistically significant association between SGDP and BOD found in this study because the latter is a measure of organic waste and municipal sewage. The turning point income level could be considered the threshold beyond which increased urbanization, regulatory oversight, and capital intensity counteract the polluting pressures of growth. Thus, the phenomenon driving the association between SGDP and BOD in this study aligns with the EKC in that the former partially offsets the negative implications of the latter for water quality. Next, in terms of the source-pathway-receptor (SPR) conceptualization of pollution, the present findings indicate that the SPR in which receptor organisms are freshwater macro- and meiofauna is responsible for the association between BOD and SGDP found in this study. The fact that a similar SPR with plastics as the source, pathway, and receptor failed to show a comparable association suggests that the BOD test is only sensitive to organic waste as the receptor part of the SPR. Therefore, the lack of a similar relationship for plastic waste in this study is explained by the BOD’s insensitivity to the latter’s presence in water. Finally, the ecological sustainability/ecosystem-services approach emphasizes the importance of freshwater bodies as regulators, providers, and supports of life and biodiversity (Millennium Ecosystem Assessment, 2005). From this viewpoint, both plastic waste and organic sewage represent stressors with varying modes of action that diminish the regulating and supporting capacity of freshwater ecosystems. Thus, with regard to the findings of this study, the EKC-driven association between SGDP and BOD fits within this theoretical framework in that both are negative influencers of freshwater ecosystem integrity. Meanwhile, the SPR framework is also compatible with the results in that both plastic waste and BOD represent three different parts of an SPR – in this case, acting as a source, pathway, and receptor. Overall, the study’s findings are compatible with all three theoretical frameworks used for this study. REVIEW OF LITERATURE All reviewed studies report several sources of aquatic exposure for plastics. One of the key contributors is urban areas where plastic accumulation takes place, and where municipal waste is not
