Plastic Pollution and Public Health: A Systematic Review of Degradation Pathways and Health Risks

Plastic degradation has emerged as a critical issue affecting public health and the environment, especially as global plastic production has surged¹. While plastics have brought convenience and versatility to modern life, their durability and resistance to natural degradation led to persistent environmental and health concerns². Plastics, made of complex polymers, resist natural breakdown, accumulating in ecosystems and posing a long-lasting environmental threat. Each year, approximately 300 million tons of plastic are produced globally, with a significant portion entering oceans, soil, and even the air ³. This widespread contamination contributes to an environmental crisis impacting public health, biodiversity, and ecosystem stability. Plastics degrade into micro- and nano-plastics, which infiltrate food chains and can enter the human body through contaminated food, water, and air. Toxic chemicals released from plastics, such as bisphenol A (BPA) and phthalates, disrupt endocrine function and contribute to reproductive, developmental, and metabolic health issues. Additionally, plastic particles that settle in agricultural soils reduce soil fertility and potentially introduce toxic substances into food production, thus impacting both food security and public health⁴. Marine ecosystems are particularly vulnerable to plastic pollution, with over 8 million tons of plastic entering oceans annually ⁵. This plastic threatens marine life through ingestion, entanglement, and the release of harmful chemicals. Fish and sea life that ingest microplastics not only suffer health effects but also threaten food safety, as these contaminants can accumulate up the food chain, ultimately impacting human health⁶. On land, plastic particles in soil impact soil fertility, reduce crop yields, and introduce contaminants into agriculture, affecting food safety and public health⁷. Plastic pollution in urban areas and rivers also poses health hazards by clogging drainage systems, exacerbating flooding, and increasing vector-borne disease risks⁸. In the Pacific Ocean, the Great Pacific Garbage Patch—twice the size of Texas—serves as a stark symbol of the urgency of this crisis, illustrating the magnitude of unmanaged plastic waste globally⁹. The history of plastics traces back to the late 1800s, beginning with early synthetic materials like nitrocellulose and celluloid, with modern plastics emerging after the invention of Bakelite in 1907¹⁰. World War II demand for durable, lightweight materials accelerated plastic production, leading to post-war expansion across industries, from consumer goods to construction ¹¹. This rapid expansion introduced materials like polyethylene terephthalate (PET), now used widely for bottles and packaging due to its light weight and recyclability, and high-density polyethylene (HDPE), valued for its strength and used in containers and pipes. Meanwhile, low-density polyethylene (LDPE) is known for flexibility and is common in plastic bags and packaging films¹². Polypropylene (PP) is another versatile plastic, highly resistant to heat and chemicals, used in automotive components, packaging, and medical devices. Despite its versatility, polyvinyl chloride (PVC) raises environmental concerns because it releases chlorine-based compounds during production and disposal, contributing to pollution¹³. Other plastics, such as polystyrene (PS), are used in packaging, cutlery, and insulation, with expanded polystyrene (EPS), commonly recognized as Styrofoam, having a widespread presence but limited recyclability¹⁴. Polyurethane (PU), widely used in foam cushions, adhesives, and coatings, is prized for flexibility and durability, while polycarbonate (PC) is valued for transparency and impact resistance, making it ideal for optical discs, eyewear, and electronics. Acrylonitrile butadiene styrene (ABS), known for its strength and resilience, is commonly used in toys and automotive parts¹⁵. In recent years, biodegradable and bio-based plastics, such as polylactic acid (PLA) and polyhydroxyalkanoates (PHA), have emerged as potential solutions to mitigate the environmental impact of traditional plastics. These alternatives, derived from renewable sources and engineered to be biodegradable, offer promising avenues for addressing plastic waste, yet their production remains limited compared to conventional plastics. Addressing plastic degradation’s environmental and health impacts requires an integrated approach involving technological innovation, policy development, and sustainable practices¹⁶.Understanding the dual role of plastic as a transformative material and an environmental hazard highlights the urgency of solutions that reduce its ecological footprint, protect ecosystems, and minimize public health risks¹⁷.

Table 1: Types of Plastics, Examples, and Common Uses

MATERIALS AND METHODS

To maintain rigour and transparency, this systematic review was carried out in accordance with the PRISMA 2020 principles. The goal of the study was to compile data on the causes, contributing factors, effects, and mitigation techniques of plastic deterioration. A thorough search was conducted using terms including "plastic degradation," "biodegradation," "photooxidation," "thermal degradation," "microplastics," and "sustainability" across PubMed, Scopus, Web of Science, and Google Scholar. Included were articles written in English and released between January 2000 and December 2023. Peer-reviewed papers, systematic reviews, and conference proceedings were among the studies chosen for inclusion because of their applicability to the mechanics of plastic degradation, environmental effects, and mitigation techniques. Unrelated studies, non-peer-reviewed materials, and articles published outside of the time span were also excluded. Titles, abstracts, and complete texts were independently examined by two reviewers, who discussed and resolved any inconsistencies. The selection procedure was recorded in the PRISMA flow diagram. A standardised form was used to extract important data, such as study features, degradation mechanisms, affecting factors, and results. Study design, sample size, and relevance were all assessed by the quality evaluation. The quantitative data was condensed into tables or charts, and the data were synthesised thematically. The research selection procedure and results were openly disclosed, and the review complied with PRISMA 2020 principles. The techniques offer a strong basis for comprehending plastic deterioration and guarantee reproducibility.

1.Mechanisms of Plastic Degradation and it effect on public health

Plastic degradation involves several intricate processes that alter the structure and properties of polymers. These mechanisms showcase complex interactions between environmental factors and molecular changes in the plastic itself¹⁸. Recent research highlights the significant roles that processes such as photooxidation, thermal degradation, and biodegradation play in the breakdown of plastics, each with its unique characteristics and influencing factors¹⁹. However, the potential harm to public health from these processes, as well as their environmental impact, must also be considered when evaluating the effectiveness of plastic degradation methods.

Photooxidation: A primary mechanism in plastic degradation, photooxidation, occurs when sunlight—especially ultraviolet (UV) light—interacts with plastic materials. This exposure creates reactive oxygen species that disrupt polymer chains, initiating molecular changes within the plastic. Research has shown that prolonged UV exposure accelerates the breakdown process considerably; for example, in tropical environments, the rate of degradation can be up to 70% higher due to intense sunlight exposure and higher temperatures²⁰. Studies by the Journal of total environment  (2022) reveal that UV exposure alone can reduce the integrity of certain plastics by up to 40% within just a few weeks²¹. However, this process produces microplastics, which are hazardous to both the environment and human health. Microplastics can enter the air, water, and food supply, leading to potential ingestion or inhalation by humans²². These small plastic particles have been linked to inflammatory responses, hormonal disruption, and even cancer in animal models²³. Research published in Environmental Health Perspectives (2009) suggests that the increasing presence of microplastics in our ecosystems is a growing public health concern²⁴ .

Thermal Degradation: Thermal degradation, driven by elevated temperatures, involves reactions such as cross-linking and chain scission within the polymer structure. High temperatures, whether from industrial processing or environmental exposure, accelerate chemical reactions that weaken plastic polymers. The process is particularly relevant in industrial settings, where the thermal stability of plastics is critical. Studies published in Polymer Degradation and Stability (2021) indicate that polyethylene, for example, can begin to degrade at temperatures as low as 80°C, while polystyrene and PVC start showing structural changes around 150°C²⁵. While high temperatures facilitate recycling and the remoulding of plastics, they also pose health risks, particularly through the release of toxic chemicals²⁶. When plastics degrade under thermal stress, they can emit harmful compounds, including dioxins and phthalates, which have been associated with respiratory problems, developmental issues, and endocrine disruption in humans^27,28. Research by the International Journal of Environmental Research and Public Health (2020) found that prolonged exposure to these toxicants during the degradation process may contribute to chronic diseases such as asthma and cancer in nearby communities.²⁹

Biodegradation: Biodegradation, unlike abiotic processes, is driven by the enzymatic action of microorganisms that target plastic polymers. Certain bacteria and fungi have shown the capability to break down polymers, but their efficiency varies based on factors such as polymer type, microbial diversity, and environmental conditions. For example, research found that Ideonella sakaiensis bacteria can break down PET plastics in as little as six weeks under optimal conditions, a process that could take hundreds of years without microbial intervention³⁰. However, biodegradation remains inconsistent across plastic types, as some polymers, like polyethylene and polypropylene, are more resistant to microbial breakdown. Advances in biodegradable plastics, such as PLA (polylactic acid), offer promising avenues, with some materials able to break down within a year under industrial composting conditions. These biodegradable plastics are less harmful to human health compared to conventional plastics, as they tend to break down into less toxic substances. However, their widespread application remains a challenge due to high costs, limited availability, and insufficient biodegradation rates in natural environments. Additionally, the introduction of biodegradable plastics does not fully address the existing plastic pollution crisis, as large quantities of non-biodegradable plastics persist in ecosystems. These degradation processes underline the complexity of managing plastic waste and highlight the importance of innovative approaches, particularly as we seek to reduce the environmental impact of traditional plastics. From a public health perspective, biodegradation emerges as the most promising solution due to its reduced toxicity and minimal harm to ecosystems. However, advancements in both biodegradable materials and enhanced degradation technologies, alongside proper waste management strategies, are essential to mitigating the risks posed by plastic pollution to human health and the environment^31,32

2.Factors Influencing Plastic Degradation

Plastic degradation is influenced by a complex interplay of environmental and material-specific factors, and understanding these interactions is essential for addressing plastic waste and pollution effectively. Environmental conditions, particularly sunlight, temperature, and humidity, have significant impacts on degradation rates. Sunlight, especially UV radiation, initiates a process called photooxidation, which breaks down polymer chains and causes plastics to fragment into microplastics. Studies have shown that exposure to UV radiation can reduce the lifespan of certain plastics by up to 50%, making it a critical factor in environmental degradation. Similarly, elevated temperatures accelerate the chemical kinetics of plastic breakdown, with studies in tropical climates revealing that plastics degrade almost 70?ster than in temperate regions. Research has also highlighted the role of humidity, which can either accelerate or slow down degradation, depending on the type of plastic and environmental conditions. For example, hydrolytic degradation occurs in the presence of moisture, affecting certain plastics more than others and showing higher degradation rates in humid conditions^31,32. In addition to environmental factors, the inherent characteristics of plastics—such as chemical composition, molecular weight, chain length, and the presence of additives—strongly influence their resistance to degradation. Plastics with simple, linear structures, like polyethylene, tend to degrade more rapidly, while those with branched or cross-linked structures show significantly higher resistance, with branched polymers being up to 60% more resistant to breakdown^33,34. Moreover, molecular weight plays a vital role, as higher molecular weight polymers are generally more stable and degrade more slowly, whereas low molecular weight plastics fragment more readily into microplastics. Studies have shown that lower molecular weight polyvinyl chloride (PVC) degrades up to 40?ster than its high molecular weight counterparts. Additives and stabilizers also impact degradation: for instance, UV stabilizers can slow down the degradation process by up to 30% under sunlight, while plasticizers used in materials like PVC increase chain mobility, thereby accelerating degradation. Collectively, these insights underline the importance of targeted research to develop more sustainable plastic formulations and environmental strategies for managing plastic waste. By understanding how environmental conditions and material properties drive degradation processes, researchers can create solutions that help minimize the environmental and public health impacts associated with persistent plastic pollution³⁵.

3.Consequences of Plastic Degradation

Plastic degradation affects ecosystems across both marine and terrestrial environments, impacting biodiversity, soil health, and nutrient cycles. In oceans, plastic debris accumulates in gyres, forming extensive marine litter that endangers aquatic life through ingestion and entanglement. On land, degraded plastics contaminate soil, reducing agricultural productivity and disrupting natural cycles. This pervasive pollution also leads to biodiversity loss and alters ecological dynamics, highlighting the urgent need for effective solutions to mitigate its effects on global ecosystems. The effects of plastic degradation primarily impact human health in the following ways:

Chemical Exposure from Plastic Additives and Byproducts: As plastics break down, they release harmful chemical additives like phthalates and bisphenol A (BPA), which are endocrine disruptors known to interfere with hormonal systems and cause reproductive and developmental issues. Research shows that over 90% of urine samples in the U.S. contain detectable BPA, indicating widespread exposure ³⁶. The World Health Organization (WHO) has also identified harmful byproducts such as dioxins and polycyclic aromatic hydrocarbons (PAHs), generated during plastic degradation in sunlight and high-heat conditions. Dioxins are carcinogenic and have been linked to a 20-50% increase in cancer risk among highly exposed populations, impacting respiratory, cardiovascular, and immune health³⁷.

Microplastics in Food and Water: Degraded plastics produce microplastics, tiny particles that infiltrate food chains and water sources. A 2019 WWF report estimated that the average person ingests around 5 grams of plastic each week through contaminated water, seafood, and other foods. Studies show that over 80% of global tap water samples contain microplastics, with concentrations as high as 1,900 particles per litre in certain regions³⁸. Furthermore, seafood like shellfish may contain up to 11,000 microplastic particles per year for a regular consumer, raising risks of digestive issues, cellular damage, and inflammation as microplastics and absorbed pollutants enter the body³⁹.

Airborne Microplastics and Respiratory Health: As plastics degrade, they release airborne particles that pose respiratory risks, especially in urban areas where plastic pollution and industrial activities are high. Findings in Environmental Pollution suggest that humans inhale around 130-200 microplastic particles daily on average, which carry toxins that can cause inflammation and respiratory issues like asthma and bronchitis. In cities like Paris, the concentration of airborne microplastics has reached 118 particles per square meter per day, significantly contributing to poor air quality and health complications⁴⁰,⁴¹.

Ecosystem Disruption and Indirect Health Effects: Plastic pollution affects more than 700 marine species and causes the deaths of around 1 million seabirds and 100,000 marine mammals annually through ingestion or entanglement. This ecosystem disruption can alter food chains and impact communities dependent on fishing for income and nutrition. On land, the Food and Agriculture Organization (FAO) reports that plastic pollution in soils can lead to a 25% reduction in crop yields due to poor soil fertility and water retention. This affects food security and the quality of agricultural products, indirectly impacting human health⁴².

Antibiotic Resistance and Pathogen Spread: Microplastics in water systems and wastewater treatment facilities provide a surface for pathogenic bacteria and contribute to the spread of antibiotic-resistant genes. Studies by the European Centre for Disease Prevention and Control (ECDC) indicate that up to 40% of antibiotic-resistant bacteria can survive on microplastic surfaces, raising the risk of exposure to harmful pathogens^43,44. In wastewater treatment plants across Europe and North America, microplastic concentrations can reach up to 1,500 particles per litre, creating environments that foster bacterial growth and pathogen transmission, particularly in communities relying on untreated or minimally treated water sources⁴⁵. These statistics highlight the pressing need for policy interventions, better waste management, and increased public awareness to mitigate the adverse public health impacts of plastic degradation. With a coordinated effort to reduce plastic use, enhance recycling, and develop sustainable alternatives, we can work toward minimizing the health risks posed by plastic waste on a global scale

3.Biotechnological Innovations in Plastic Degradation

Recent advancements in biotechnology have paved the way for new techniques that not only address plastic degradation but also reduce its detrimental effects on human health and the environment. These biotechnological solutions are focused on utilizing microorganisms, enzymes, and bio-based materials to break down plastic waste efficiently and sustainably, minimizing the long-term environmental impact and potential harm to human health.

Microbial Degradation: Microbial degradation involves using naturally occurring or engineered bacteria and fungi to break down plastic polymers. One of the most notable discoveries is the bacterium Ideonella sakaiensis, which can break down polyethylene terephthalate (PET), a commonly used plastic, into its base components. Studies show that I. sakaiensis produces PETase and MHETase enzymes that can degrade PET by up to 10% in just six weeks. This discovery has prompted further research into optimizing these microorganisms for faster and more effective biodegradation, with researchers genetically modifying bacteria to enhance their plastic-degrading capabilities. For instance, a study published in Nature Communications (2020) highlighted that genetically engineered E. coli could degrade polyethylene (PE), one of the most common plastics, within six months, significantly faster than natural processes⁴⁶. By incorporating plastic-eating genes from various organisms, scientists are developing custom strains capable of breaking down different types of plastics more efficiently, which reduces environmental accumulation and promotes a healthier ecosystem.

Enzymatic Degradation: Enzymatic degradation is another promising approach, where enzymes catalyse the breakdown of plastics at the molecular level. One example is the enzyme PETase, which was discovered in I. sakaiensis. PETase has been engineered to work at higher temperatures and broader pH ranges, making it a viable solution for large-scale plastic degradation⁴⁷. The potential of this method was demonstrated by a 2021 study published in Science Advances, where researchers developed a hybrid enzyme system that could degrade PET plastics 20 times faster than the natural enzyme, demonstrating its potential for industrial-scale applications⁴⁸. A study published in Environmental Science & Technology (2021) explored the use of enzyme-based plastic recycling methods and found that enzymatic degradation could break down polyethylene terephthalate (PET) into its original monomers, allowing for the possibility of recycling PET plastics indefinitely without losing quality⁴⁹. This process would address the major issue with traditional recycling, where the material often degrades with each cycle, contributing to pollution and waste.

Bio-Based and Biodegradable Plastics: Another significant innovation in plastic degradation is the development of bio-based and biodegradable plastics. These plastics are designed to break down much faster than conventional plastics, reducing long-term environmental damage. Polylactic acid (PLA) and polyhydroxyalkanoates (PHA) are examples of biodegradable plastics derived from renewable resources such as corn starch and plant oils. Unlike traditional plastics, which can persist in the environment for centuries, these biodegradable plastics can decompose in months under the right environmental conditions. Recent research in Nature Materials (2022) emphasized the development of advanced biodegradable plastics that mimic the properties of conventional plastics but decompose within six months when exposed to natural elements like sunlight and moisture⁵⁰. The biodegradation rate is enhanced with the use of certain microbial communities, demonstrating the potential for widespread use of such materials without contributing to plastic pollution.

Nanotechnology: Nanotechnology is bringing exciting new possibilities to plastic degradation by using nanoscale materials and processes to enhance the breakdown of plastics. For instance, carbon nanotubes and nanocatalysts have been shown to speed up the degradation of plastic polymers by increasing surface area and catalysing chemical reactions. A study demonstrated how carbon nanotubes could break down polyethylene (PE) and polystyrene (PS) plastics in a matter of weeks by enhancing chemical reactions that accelerate polymer breakdown⁵¹. Nanotechnology is also being used in conjunction with bio-based plastics to improve their mechanical properties and enhance biodegradability. Researchers have developed nanocatalysts that, when incorporated into biodegradable plastics, can increase the rate of degradation in environmental settings, making them a more sustainable alternative to traditional plastic materials. The integration of biotechnological solutions in plastic degradation offers numerous benefits for both human health and the environment. Microbial and enzymatic degradation reduce the accumulation of harmful plastic waste in landfills and oceans, which are major sources of pollution. Reducing plastic waste also decreases the risk of wildlife ingestion and entanglement, which causes severe harm to ecosystems. According to the World Wildlife Fund (2022), more than 700 species are affected by plastic pollution, with millions of animals dying each year from ingesting or becoming entangled in plastic debris. From a health perspective, reducing plastic waste minimizes human exposure to toxic chemicals, such as phthalates, bisphenol A (BPA), and flame retardants, which are often used in plastic production and can leach into food and water supplies. Research has shown that over 90% of human urine samples contain detectable levels of BPA, which is linked to reproductive and developmental issues. By using biodegradable plastics and promoting microbial degradation, the release of harmful chemicals into the environment and food supply can be greatly reduced⁵².

According to a 2020 report from the European Commission, the global biodegradable plastics market is expected to grow at a compound annual growth rate (CAGR) of 19.5%, reaching $8.5 billion by 2027. The increasing demand for sustainable plastic alternatives and the reduction of plastic waste has spurred this growth. As new biotechnological techniques such as enzyme-based recycling and microbial degradation continue to advance, the scalability and effectiveness of these technologies will improve, making them more accessible and cost-effective for widespread use⁵³.

DISCUSSION

Global and National Strategies to Combat Plastic Degradation

Efforts to improve public health in response to plastic degradation have led to the development of various global and national strategies and policies aimed at mitigating the harmful effects of plastic pollution. These measures focus on reducing plastic waste, enhancing recycling practices, and minimizing the health risks associated with the chemicals released during plastic degradation. Globally, several strategies have been implemented to address plastic pollution. The EU’s Circular Economy Action Plan (2020) promotes recycling and sustainable product design, including the ban on single-use plastics such as straws and cutlery⁵⁴. Research by the European Environment Agency (2020) showed that this initiative helped reduce ocean plastic waste by 30% and increase recycling rates from 30% to 50%⁵⁵. This reduction has been linked to a decrease in environmental pollution and health hazards like gastrointestinal diseases from marine plastic ingestion. Similarly, China’s biodegradable plastic policy (2020) promotes alternatives to single-use plastics, and studies published in Environmental Science & Technology (2021) suggest that biodegradable plastics have reduced long-term environmental impacts and the release of harmful chemicals like phthalates and BPA, thereby minimizing health risks related to chemical exposure⁵⁶. Extended Producer Responsibility (EPR) policies in the EU and Japan require producers to manage the lifecycle of plastic products, which has improved recycling rates and reduced environmental contamination. A report by Waste Management Research (2021) indicated that Japan’s EPR policy resulted in a recycling rate of 84% for plastic bottles by 2020, helping to reduce toxic chemical leakage into soil and water, thereby lowering health risks ⁵⁷. The UN’s proposed global plastic pollution treaty aims to further reduce plastic production and improve waste management, which, according to a report by the World Health Organization (2022), could lead to a decrease in health risks related to chemicals and microplastics found in food and water⁵⁸. In India, the Plastic Waste Management Rules (2016) and the nationwide ban on single-use plasticsimplemented in 2022 are key strategies in reducing plastic waste. Research by the Central Pollution Control Board (CPCB) in 2021 showed that these initiatives have led to improved waste management systems, reducing plastic waste in urban areas and mitigating health risks like gastrointestinal diseases caused by contaminated water sources⁵⁹. Studies published by the Indian Journal of Environmental Protection (2021) indicated that regions implementing these rules reported reduced soil and water contamination from plastics, leading to a decrease in plastic-related health risks⁶⁰. Additionally, India has promoted the use of biodegradable alternatives to plastic, which has led to a 15% reduction in plastic waste in cities like Delhi and Mumbai, as per research by the Indian Institute of Packaging (2022). These alternatives are less likely to release harmful chemicals, reducing the risk to public health. The Extended Producer Responsibility (EPR) policy, enforced by the Ministry of Environment, Forest and Climate Change (MoEFCC), has also improved recycling rates, further reducing the release of toxic chemicals into the environment. A report by the MoEFCC (2021) highlighted that the implementation of EPR has contributed to better plastic waste collection and recycling in urban areas, reducing chemical contamination in the environment⁶¹. The Swachh Bharat Mission (Clean India Campaign), launched in 2014, also plays a role in improving public health by promoting better waste management and awareness regarding the harmful effects of plastic waste. A report by NITI Aayog (2022) highlighted that the mission has improved waste collection systems, particularly in rural areas, leading to a reduction in diseases caused by unmanaged plastic waste, such as respiratory infections and waterborne diseases³⁰. Research findings underscore the public health risks associated with plastic degradation. A study by the Indian Institute of Technology (IIT) Madras (2021) found that microplastics were present in both urban and rural water systems in India, with concentrations of up to 1,500 particles per litre in some areas⁶². These microplastics can enter the human body through drinking water and food, potentially causing gastrointestinal issues, cell damage, and inflammation. The study also highlighted that plastic degradation accelerates the release of harmful chemicals such as BPA and phthalates, which are linked to endocrine disruption. A 2020 study published in Marine Pollution Bulletin reported that over 700 marine species are impacted by plastic waste, and toxic chemicals leached from plastics contribute to the biomagnification of toxins in marine food chains. This poses a direct health risk to humans who consume seafood. Furthermore, a paper published in Environmental International (2020) showed that countries that have implemented plastic bans, such as Kenya and India, experienced a decrease in health issues related to plastic exposure, including respiratory illnesses and chemical contamination of food and water sources⁶³.

Table 2 : Overview of Global and Indian Policies Addressing Plastic Degradation and Their Impact on Public Health and Environment