20 Microplastics in Our Oceans and Drinking Water
Microplastics in the Environment and Ecosystems
As mentioned earlier, microplastic particles are primarily composed of degraded polyethylene plastics. These materials are among the most widely produced and used plastics globally, commonly found in packaging, shopping bags, food containers, and even personal care products such as exfoliating scrubs and toothpaste. Due to their widespread use and light weight, polyethylene plastics frequently escape waste management systems and enter the environment. Once released, they are extremely resistant to degradation. Exposure to sunlight and physical stress causes them to fragment into smaller and smaller pieces—eventually forming microplastics—but the underlying chemical structure remains intact. These microplastic particles are small enough to pass through most water filtration systems, making their way into oceans, lakes, and even municipal drinking water supplies. (JC)
In today’s consumer economy, plastic consumption has surged dramatically. Its low production cost, resistance to corrosion, and versatility make it an attractive material for countless industries. From packaging and textiles to automotive parts and electronics, plastic is integral to modern life. Approximately 400 million tons of plastic are produced every year, yet only about 9% is recycled (United Nations). The rest ends up in landfills, water systems, or the natural environment. This overwhelming accumulation presents a growing threat to ecological systems, particularly aquatic environments, where plastic can persist for centuries. (JC)
The industry that contributes significantly to plastic pollution in aquatic systems is commercial fishing. Plastic has become a staple material for fishing gear, including nets, lines, ropes, floats, and traps. These tools are favored due to their strength, durability, and flexibility. However, this same resilience becomes a liability when gear is lost or discarded. It’s estimated that between 40% and 80% of ocean litter is composed of plastic, much of it originating from fishing operations (Alberghini et al., 2020). Ghost fishing—when lost nets continue to trap marine organisms—poses an additional threat to biodiversity (National Oceanic and Atmospheric Administration). As fishing gear degrades, it breaks into microplastic fibers and fragments that spread throughout the water column and seafloor. (JC)
Illegal, unreported, and unregulated fishing exacerbates the problem. In these operations, there is often little accountability, and plastic waste is routinely dumped into the ocean rather than properly disposed of. Even in legal fisheries, recycling infrastructure is limited, and damaged gear is frequently discarded rather than reclaimed. These practices contribute to the widespread contamination of marine ecosystems and highlight the urgent need for stricter regulations, sustainable gear alternatives, and international cooperation. (JC)
Once microplastics enter the marine food web, they begin affecting organisms at every trophic level. Plankton—tiny, drifting organisms that form the base of the oceanic food chain—have been shown to consume microplastics at alarming rates. These plastic particles can physically block digestion, reduce energy intake, and ultimately lead to death. Plankton are also eaten by a wide array of marine animals, including small fish, shellfish, and coral, thereby transferring microplastics up the food chain. Coral reefs, which are already vulnerable to climate change and ocean acidification, suffer additional stress from microplastic contamination. When corals ingest plastic particles, they experience reduced growth, tissue damage, and increased disease susceptibility. In some cases, corals starve due to a false sense of satiety caused by plastic ingestion. (JC)
The collapse of coral reef ecosystems has far-reaching consequences. Coral reefs protect coastal communities from storm surges and erosion, support a high level of marine biodiversity, and contribute to global climate regulation. As reefs decline, the services they provide diminish, leaving human populations more vulnerable to environmental instability. Reduction in coral reefs contributes to warmer oceans, sea level rise, and changing weather patterns dramatically altering ecosystem function (National Oceanic and Atmospheric Association, 2024). Similarly, fish and shellfish that consume microplastics not only face health issues such as organ damage and reproductive failure but also pose a risk to human health. While gutting and filleting can reduce some exposure, studies have shown that microplastics and associated toxins can migrate from the digestive tract into muscle tissue—the part of the fish most commonly eaten by humans. (JC)
Smaller species like anchovies, sardines, and shellfish are often consumed whole, including their digestive systems, which raises the likelihood of direct human ingestion of microplastics. Research has also found plastic particles in salt, bottled water, and even fruits and vegetables irrigated with contaminated water, indicating that the problem is not limited to seafood. (JC)
Figure 3.1- Sources of Plastic in the Ocean (National Oceanic and Atmospheric Administration, 2024)
Microplastics in Water Systems
Recent studies have revealed a disturbing presence of microplastics in both tap and bottled drinking water, raising significant concerns about water safety, human health, and the effectiveness of current water treatment systems. Research found that a single liter of bottled water can contain an average of 325 plastic particles and 5.5 liters of plastic in tap water (Mason et al., 2023). This contamination is particularly alarming for high-risk populations, including communities with limited access to advanced water filtration, individuals with weakened immune systems, and populations living near industrial or agricultural zones. The presence of microplastics in water raises long-term questions about potential links to inflammation, endocrine disruption, and other chronic health issues, especially since many of these particles are small enough to enter human cells. (JC)
Microplastics can enter freshwater systems through multiple routes, making contamination difficult to control. One major pathway is urban and industrial runoff. During rainfall, microplastics from landfills, roads, and littered areas are washed into rivers, lakes, and reservoirs, which serve as sources of drinking water. These particles originate from a variety of sources, including degraded plastic packaging, synthetic clothing fibers, and tire wear particles from vehicles. (JC)
Another significant contributor is water discharged from manufacturing plants. These industrial effluents often contain microbeads from personal care products, microfibers from textile production, and plastic pellets used in the creation of plastic goods. When factories release untreated or insufficiently treated wastewater into nearby waterways, these particles travel downstream, eventually making their way into drinking water sources. This ongoing discharge highlights gaps in industrial regulation and waste management practices. (JC)
Agricultural activities also contribute substantially to microplastic pollution. The use of plastic mulch films, synthetic fertilizers, and sewage sludge as fertilizer introduces plastic particles directly into the soil. Over time, these microplastics leach into groundwater reserves—the same aquifers that supply many communities with drinking water. Unlike larger debris, microplastics are small enough to infiltrate deep into the soil, often bypassing natural filtration layers and entering aquifers with minimal resistance. (JC)
Water Filtration
Most public water treatment systems go through a multi-step system to ensure the safety of drinking water. This process is designed to remove contaminants and derbies, making water safe for consumption. These steps include coagulation, flocculation, sedimentation, filtration, and disinfection. The first step is coagulation where chemicals such as salt are added to the water. These salts neutralize the negative charges of dirt and other particles forming larger particles called flocs. The next step to this process is flocculation which involves mixing the water to encourage larger flocs. The third step in this process is sedimentation where water sits undisturbed which allows the heavy flocs to sit at the bottom due to gravity. Separation occurs here that removes a significant number of solids. After sedimentation, filtration occurs where the clear water on top passes through filters composed of materials like sand, gravel, or charcoal. These filters are designed to remove remaining particles, including parasites, bacteria, viruses, and dissolved chemicals. Some treatment plants employ advanced filtration methods such as ultrafiltration, which uses membranes with very small pores to remove even smaller contaminants, or reverse osmosis, particularly when treating recycled or saltwater. The final step involves disinfecting the filtered water to eliminate any remaining pathogens. Common disinfectants include chlorine, chloramine, or chlorine dioxide. These chemicals not only disinfect the water at the treatment plant but also maintain a residual level to prevent microbial growth as water travels through distribution pipes to consumers. (CDC, 2024). (JC)
While water filtration is meant to remove various impurities and ensure that water is safe to drink, it doesn’t always ensure safety when it comes to eliminating microplastics—especially the tiniest particles that slip through conventional treatment systems. Most municipal water treatment plants are equipped to handle common contaminants like sediments, bacteria, and chemical residues through steps such as coagulation, sedimentation, filtration, and disinfection. However, microplastics present a unique challenge. (JC)
Conventional filters—often made of sand, gravel, or charcoal—aren’t specifically designed to trap particles as small as some microplastics. While advanced filtration technologies like ultrafiltration, nanofiltration, and reverse osmosis can remove many of these particles, they’re not used in all public systems due to cost and infrastructure limitations. (JC)
Additionally, even when water leaves the treatment plant relatively free of microplastics, contamination can occur after treatment. Water may pick up microplastics as it travels through aging plastic pipes, or when it is stored or transported in plastic containers. Even household plumbing systems and filters can contribute to microplastic content if made from degrading plastic materials. (JC)
With no global standards yet mandating removal, and limited testing in place, many water systems may not even be measuring how many microplastics make it through the treatment process. Ultimately, while modern water treatment significantly improves water quality and protects public health, it isn’t always capable of fully addressing emerging pollutants like microplastics—especially as plastic pollution continues to rise. (JC)
Bottled Water and Microplastics
While many consider bottled water to be much cleaner alternative to tap water, it is still not free from microplastic contamination. Several factors contribute to this contamination. (JC)
Most bottled water is stored in containers typically made out of plastic. Since bottled water can be stored much longer, it allows for the gradual degradation of plastic material into the water. The breakdown of this plastic can occur due to several reasons, including exposure to heat, UV radiation, mechanical stress, and prolonged storage times, all of which accelerate microplastic release into the water. (JC)
Bottled water often undergoes physical stress, including pressure from sealing, stacking, and movement. This stress can cause microplastics to mix into the water. Additionally, heat exposure is common for plastic bottles as they are often in high-temperature environments such as warehouses. Exposure to sunlight or fluctuating temperatures can further promote the release of microplastics into the water. Bottles rubbing against one another during packaging, storing, and handling can lead to small amounts of plastic wear contributing to contamination. (JC)
Over time, the degradation of plastic due to extended storage can also increase the presence of microplastics. Chemical interactions between the plastic and the water, especially in older bottles, may accelerate particle release. Studies suggest that even opening and closing a plastic bottle repeatedly can shed microplastic particles into the liquid. As bottled water remains a major source of hydration worldwide, further research is essential to assess health risks and develop solutions to minimize microplastic exposure from packaging materials. (JC)
Health Implications
The presence of microplastics in drinking water raises significant concerns for both human health and environmental sustainability. Although research limits full understanding of what is occurring, health effects of microplastic ingestion is still developing. Initial findings suggest that exposure to these particles may pose serious risks. One major issue is the potential for microplastics to accumulate in the digestive system and internal organs, leading to inflammation and cellular damage over time. Since microplastics are not easily broken down by the body, their prolonged presence can contribute to chronic irritation and physiological stress. (JC)
In addition to their physical impact, microplastics introduce hazardous chemicals into the body. Many plastics contain harmful substances such as bisphenol A (BPA), phthalates, and heavy metals, which can leach into the bloodstream upon ingestion. These chemicals are known endocrine disruptors, meaning they interfere with the body’s hormonal balance and regulatory systems. Prolonged exposure to such substances has been linked to an increased risk of cancers, reproductive disorders, and metabolic diseases. As microplastics travel through the body, they can also act as carriers for other toxic pollutants, amplifying their potential harm. (JC)
Beyond chemical exposure, microplastics disrupt the digestive system, particularly by irritating the gastrointestinal tract and altering the gut microbiome. A balanced microbiome is essential for proper digestion, immune function, and overall health. However, ingesting microplastics can cause an imbalance between beneficial and harmful bacteria, potentially leading to chronic digestive issues and weakened immunity. Furthermore, some microplastic particles serve as hosts for harmful bacteria and pathogens, increasing the likelihood of microbial contamination and infection. As these risks become more apparent, understanding the full extent of microplastic exposure and its long-term health effects is crucial for public health protection. (JC)
Figure 3.3- Health Implications of Microplastics (Yuan et al., 2022)
Despite mounting evidence that microplastics pose serious risks to environmental and human health, significant gaps in scientific research, regulatory policy, and public awareness continue to delay meaningful action. One of the most fundamental challenges lies in the absence of a standardized definition and classification system for microplastics. Without a globally accepted framework that identifies variables such as particle size, shape, chemical composition, and safe concentration limits, researchers struggle to compare findings, and policymakers are left without the tools to develop coherent regulations. This inconsistency results in fragmented data and piecemeal responses that fail to reflect the scale of the problem. (JC)
This lack of consensus not only complicates scientific study but also hampers risk assessment and public health preparedness. While emerging studies have linked microplastic exposure to biological effects such as inflammation, oxidative stress, endocrine disruption, and cellular damage, much of the existing research remains preliminary. Longitudinal studies that explore chronic exposure, accumulation in human tissues, and potential links to long-term diseases are still largely lacking. As a result, national and international agencies remain hesitant to establish enforceable thresholds for acceptable levels of microplastic contamination, leaving drinking water systems unregulated and public health protections incomplete. (JC)
This scientific uncertainty has direct and troubling implications. Microplastics are now being detected in drinking water supplies worldwide—in both tap and bottled water. Studies have shown that bottled water may contain hundreds of plastic particles per liter, and some analyses suggest microplastic presence in treated tap water as well. Yet in the absence of safety standards, consumers remain unaware of the levels of exposure they may be facing daily. Even advanced water filtration systems at treatment plants, designed to remove sediment, chemicals, and bacteria, often lack the capacity to effectively remove microplastics. (JC)
Beyond direct ingestion through drinking water, microplastics enter the freshwater ecosystem through multiple pathways. Industrial discharge, including wastewater from textile, plastic, and cosmetics manufacturing, releases large quantities of microplastics—such as microbeads and synthetic fibers—into rivers and streams. Runoff from landfills and urban surfaces during rainfall can also carry plastic waste into water bodies. In agricultural regions, the use of biosolids (sewage sludge) as fertilizer and plastic mulch films introduces microplastics into soil, which can then seep into groundwater over time. Many of these particles are small enough to bypass standard filtration methods, making their way into public water systems. (JC)
Detection methods for microplastics in water are not yet fully standardized, and existing techniques vary widely in sensitivity. Larger particles are more easily identified, while smaller microplastics often go undetected. This makes accurate tracking and assessment of exposure levels extremely difficult. Without clear detection protocols or enforceable monitoring benchmarks, water quality regulators are unable to effectively assess contamination or implement remediation strategies. This is especially concerning in regions with underfunded infrastructure, where basic water treatment is already a challenge. (JC)
Technological solutions to reduce microplastic levels in water do exist. Membrane filtration, activated carbon systems, advanced oxidation processes, and reverse osmosis have shown promise in capturing or breaking down microplastics. However, these methods are expensive, energy-intensive, and difficult to implement in large-scale public systems without significant investment and political will. Upgrading existing infrastructure in both developed and developing countries will require coordinated support from governments, industries, and environmental organizations. (JC)
Equally important are preventive measures that reduce plastic pollution at its source. Single-use plastics, improper waste disposal, and unchecked industrial emissions are the root contributors to microplastic contamination. Policies focused on banning or restricting the use of single-use plastics, incentivizing sustainable product design, and requiring companies to take responsibility for plastic waste could significantly curb environmental plastic leakage. International collaboration is crucial here—since plastic pollution crosses borders through oceans, rivers, and atmospheric systems, isolated national efforts will be insufficient to tackle a problem of this scale. (JC)
Public engagement and consumer awareness also play a vital role. People can reduce their personal contributions to microplastic pollution by avoiding single-use plastics, opting for reusable products, supporting sustainable brands, and properly disposing of plastic waste. Transitioning to biodegradable or compostable packaging made from natural fibers or plant-based materials can also help lessen dependence on petroleum-based plastics. Furthermore, public pressure on governments and industries can drive policy change, research funding, and infrastructure development. (JC)
While microplastics in water systems are a grave concern in themselves, they also represent just one dimension of a much larger issue: the infiltration of microplastics into the food chain. Water is a gateway through which microplastics move into marine and terrestrial ecosystems, where they are absorbed by plants, consumed by animals, and eventually ingested by humans. Aquatic organisms—ranging from plankton to fish regularly consume microplastics suspended in water, mistaking them for food. These plastics then bioaccumulate up the food chain, introducing plastic particles and associated toxic chemicals into human diets. (JC)
The transition from contaminated water to contaminated food is not only seamless—it is accelerating. Studies have identified microplastics in sea salt, honey, fruits and vegetables, and a wide range of seafood commonly consumed worldwide. As water sources become more polluted, the likelihood that microplastics are making their way into every stage of food production increases. For this reason, addressing water contamination is not just about clean drinking water—it is a necessary step in safeguarding the broader food system. (JC)
*Note: AI was used in this section to create outline, find sources, create reference list, and to proofread the chapter. All paragraphs were hand-written at first and then plugged into AI to correct grammar errors and provide a better structure for the flow of information.