Ranking Sri Lanka among the World’s Top Mismanaged Waste Polluters: Does Model Data Change the Story?

Abstract

The accumulation of Mismanaged Plastic Waste (MPW) in the environment is a global concern. The amount of waste generated by countries is estimated using globally available data layers and/or empirical surveys. Unlike globally available metadata, MPW estimates based on empirical surveys allow for better visualization of amounts, potential pathways, and hotspots. A model study conducted in 2015, based on global metadata, ranked Sri Lanka in fifth position among the world’s worst mismanaged plastic offenders. However, there is significant uncertainty in the source data on waste generation and the parameters used for model prediction, such as plastic usage (5.1 kg per person per day), since Sri Lanka is predominantly a service-based country with limited plastic-based manufacturing industries. The source data for plastic usage has been derived from a very limited study, biased toward waste hotspots that have not been verified. Our empirical data has shown that population density, one of the key parameters used for global ranking, is a weak predictor of debris densities. Therefore, we argue that the given plastic leakage data and the ranking is an error. Therefore, Sri Lanka’s position in the global ranking deserves reconsideration. Further, we propose the need for model predictions that rely on global metadata to be backed by robust and unbiased designed surveys that are based on empirical data and undergo intense baseline data verification to generate more precise predictions on litter quantities.

1. Introduction

Plastics are synthetic or semi-synthetic polymers that have transformed not only the manufacturing industry, but also the everyday life of human beings. Their unique characteristics, such as low weight, durability, water resistance, and versatility in molding, make them extremely useful. However, the rapid development of the plastic industry has caused immeasurable harm to the environment, since these synthetic polymers are technically developed to resist degradation, and only a handful of microbes in nature can break them into simple molecules. Discarded plastics become post-consumer-managed plastic waste, while the rest ends up as MPW. MPW is plastic material that is littered, improperly disposed of, or dumped in uncontrolled landfills [1]. In 2019, global plastics production reached 370 million tons, with China being the world’s largest plastic producer (31%), and Asia becoming the biggest plastic-producing region in the world (51%) [2]. In total, 60% of the plastics produced have a lifespan of 1–50 years, or even more [2]. Therefore, the extensive use of plastic products results in the accumulation of non-degradable solid waste in the environment.

Since the early 1970s, the amount of plastic pollutants in the ocean has increased exponentially due to population growth, urbanization, and the rapid development of industrial activities. Presently, plastics contribute to 80% of marine debris worldwide. In 2010, it was estimated that 4.8 to 12.7 million metric tons (equivalent to 1.7–4.6%), out of the 275 million metric tons of plastic produced in 2010, ended up in the ocean [3].

Marine litter can be land-based, shore-based, or ocean-based. Land-based litter is carried to the coast from inland areas via wind, canals, drains, streams, wetlands, and rivers [4,5,6]. Shore-based litter is primarily generated through tourism-related activities, fisheries, and coastal residents. Ocean-based litter is primarily the floating debris carried to the coast by water currents and accelerated by seasonal winds [7], and mostly generated via fisheries, merchant ships, cruise liners, and recreational activities such as diving, boating, etc. Studies have shown that the largest proportion of plastic emissions reaching the ocean is via river flow [8]. Another study [9] demonstrated that the majority of municipal plastic waste (91%) is transported via watersheds larger than 100 km², suggesting that rivers are major pathways of plastic litter to the ocean. Therefore, attempts to model MPW should include debris flow through rivers for a better understanding of this process [9].

Debris can accumulate in the marine environment due to a variety of factors, including beach typology, the persistence of a physical barrier, the time of monsoon, the distance from urban centers, the tourism industry, the fishing industry, improper solid waste management systems, the lack of recycling facilities, the lack of public awareness, etc. The adverse effects of marine debris on wildlife, humans, and the environment are well documented [4,10,11,12,13,14,15,16,17,18]. Marine plastic debris can cause even more damage as it gradually decomposes into microplastics and gets ingested by marine organisms, including fish [19].

Sri Lanka is an island with a 65,610 km² land area, comprising picturesque landscapes and enormous faunal and floral diversity. The island’s 1340 km long coastline with sandy beaches makes the country a popular tourist destination. Around 35% of the total population and 65% of industrial infrastructures are located in five out of the nine coastal provinces [19]. In total, 80% of the tourism industries rely on the coastal region. The topology and the location of Sri Lanka in the Indian Ocean make the island prone to the accumulation of debris. Islands generally experience the acute effects of debris accumulation due to their proximity to debris-concentrating gyres [19], and due to the tendency of debris to naturally accumulate via ocean currents; this all contributes significantly to the marine debris load. The common practice of waste disposal in Sri Lanka is open dumping in selected dump yards [19]. Municipal, urban and other local councils are legally responsible for municipal solid waste collection and management.

This study was conducted to determine whether Sri Lanka’s position in ranking among the world’s top mismanaged waste offenders is correct. The objective of this study was to scientifically discuss the importance of conducting empirical surveys on-ground, versus extracting information from global data layers for estimating mismanaged waste amounts. This article presents the different types of methodologies practiced to estimate the amounts of mismanaged debris worldwide, demonstrates the important findings, and discusses the importance of using robust and unbiased designed procedures to estimate MPW.

2. Estimating Marine Litter

A variety of methodologies have been adopted to assess the amounts of marine debris, as well as MPW. Most of the plastic leakage studies are based on calculations made from the outcomes of surveys primarily conducted at the coast, with limited geographic boundaries [7,20,21,22,23]. Some studies rely on globally available proxy data, and some also focus on empirical data [3,19,24,25,26,27,28]. In 2021, the importance of globally available proxies was emphasized, along with the empirical data for predicting the amounts of MPW [24].

Numerous studies have investigated the amount of debris at the local scale, regional scale, and global scale. Some studies are carried out along the coast [7,22,29], some along rivers and at river outlets [4,5,6], and some at specific sites of preference [17,20]. Some studies discuss the existing level of pollution [7,10,11,12,15,16,17,18,19], some studies use available data to derive predictions for the future [3,25], and some studies go further and develop ranking systems based on plastic leakage [3,24,25].

The World Bank has projected the per capita waste generation for 2025, based on expected growth in population and economic growth rates (GDP) [25]. The study used information collected from official government publications, reports by international agencies, and articles in peer-reviewed journals, acknowledging the fact that waste estimations can differ at regional levels due to the influence of single countries, such as China, India, and the United States. South Asia was ranked fourth among the seven regions, according to total waste generation per day.

In 2015, Sri Lanka was ranked fifth among the top twenty countries losing MPW to the world’s oceans, only behind China, Indonesia, The Philippines, and Vietnam [3]. The study estimated the annual input of plastic to the ocean by combining available data on the solid waste generated by coastal populations with a model that used the population density and economic status of a country to estimate the amount of land-based plastic waste entering the ocean. In this study, mismanaged waste is defined as material that is littered or inadequately disposed of. The term “inadequately disposed” was further clarified as “not formally managed, including disposal in dumps or open uncontrolled landfills where it is not fully contained”. The mass of waste generated per capita annually, the percentage of waste that is plastic, the percentage of plastic waste that is mismanaged, and the potential of mismanaged plastic waste to enter the ocean as marine debris have been computed using the best available data, though the origin and enumeration of these waste data remain unclear. Population growth data have been used to project the increase in mass in 2025. The study suggests that annual waste generation is a function of population size, with the top waste loads tending to be for the countries with the largest coastal populations.

The Commonwealth Scientific and Industrial Research Organization (CSIRO) works on a combined approach in developing the first empirical baseline study to predict marine debris loads [24]. Their main focus was on South-East Asia, since this region has been identified as an area losing high levels of waste to the environment [3]. The project aims to identify links between land-based waste management and pollution entering the marine environment. One of the studies based on the CSIRO model has assessed and compared the impact of different factors on plastic waste generation, using empirical data collected from seven countries/territories, including China, Kenya, South Africa, South Korea, Sri Lanka, Taiwan, and Vietnam. The program conducted in each of these countries is a comprehensive modeling-based study for predicting the anthropogenic debris loads that are reaching the ocean from inland, using empirical data. Survey locations were selected to include a variety of covariates, including population density, land use type, road and transportation networks, etc. In Sri Lanka, four different survey methods (inland surveys, coastal surveys, river surveys, and trawl surveys in coastal waters) were conducted in 2019, and a total of 300 transects were completed in 86 sites [26]. Inland survey locations were selected using a stratified random sampling design, and Geographic Information System (GIS). Coastal sites were located between Kalpitiya to Galle in approximately 10 km intervals along the coastline. River sites were selected considering the ease of access, and trawl surveys were performed at the mouth of the Maha Oya River using a Neuston net with a mesh size of 330 µm. At each site, a site information sheet was completed [24], and 3–6 transects were conducted. Debris items were recorded in the information sheet in each distance interval, stating size class, if whole or fragmented, and material type. The analysis of debris loads used a combination of empirical data and a variety of local and global proxy layers.

Marine debris, stranded on 22 beaches along 1340 km of the coastline of Sri Lanka, was surveyed in December 2016 using a standard quadrat method to quantify the density and composition of the macro debris (>25 mm) [7]. In this descriptive study, any manufactured or processed solid waste material that enters the marine environment from any source was considered marine debris. In each beach, 3 quadrats (10 m × 10 m) were surveyed and large debris (>25 mm) was categorized according to the origin (local or foreign), type (i.e., end-consumer products, packaging material, fishery-related material, and industrial materials other than fishery), and material (i.e., plastic, metal, glass and ceramic, processed wood, and other). Small debris (5–25 mm) was surveyed using beach sand samples and classified into the same material groups as large debris. Plastic debris was further categorized into types (i.e., hard, foam, and fiber) to find possible sources. Furthermore, to identify the influence of beach typology on the quantity of stranded marine debris, the relative proximity to a river mouth or city, the presence of a wall or barrier next to the beach, and monsoon impacts were considered.

Macro debris (>2.5 cm) on Kadolkele mangroves in Negombo lagoon, Sri Lanka was surveyed in 2017 [20]. A standard quadrat method was used and debris was classified according to material type (plastics, metal, glass and ceramics, rubber, cloth, wood, paper and cardboard, and others). Plastic materials were further classified into packaging items, fishing items, and consumer items. Another study in the same year (2017) investigated plastic pollution on the west coast during the southwest monsoon, inter-monsoon, and northeast monsoon seasons [21]. The study area contained fishing sites, recreational establishments, and industrial areas, as well as river discharging outlets. Surface water samples were collected horizontally using a floating net with a 300 µm mesh size for floating plastic debris. Sieved debris items were categorized according to size [i.e., small-micro (0.3–1 mm), large-micro (1–5 mm), meso (6–20 mm), and macro (21–100 mm) plastics], shape (i.e., filaments, fragments, and films), and color (i.e., black, white, transparent, and colored). The abundance of plastics was enumerated in numbers, and weights per cubic meter.

Plastic pollution in the southern coastal belt of Sri Lanka was investigated by studying twelve beach sites representing tourism, recreation, and fishing in 2018 [22]. Trawl surveys were conducted using a Neuston-type sampling net with a mesh size of 380 µm, representing three monsoon seasons (south-west monsoon, inter-monsoon, and north-east monsoon) to enumerate macro and meso (>4000 µm), and micro (4000–250 µm) plastic debris. Sieved debris was categorized according to the size (i.e., macro, meso, and microplastics), shape (fibers/filaments, films, sheets, fragments, granules, polystyrene foams, and rod), and color (i.e., blue, light blue, brown, green, orange, pink, purple, red, transparent, yellow, and white), and size measurements were made using imaging software. Fourier-Transform InfraRed (FTIR) spectroscopy was used to validate the polymer types.

3. Study Findings

Different studies have reported a great degree of variation in debris composition, amounts, and sources of debris in Sri Lanka. International Coastal Cleanup data between 2008 and 2013 [23] reported that plastic bags are the most abundant type of beached debris (22.68%), followed by paper bags (14.35%) and plastic bottles (10.97%). More than 74% of the debris was produced from beach-based recreational activities, while 15.48% was produced by waterways and ocean-based activities [23]. The first island-wide marine debris survey revealed that only 0.9% of the debris was of foreign origin and more than 90% was local [7].

In another study [27], municipal waste in Sri Lanka was categorized as biodegradable: 62%, paper: 7%, polythene and plastic: 6%, wooden: 6%, glass 2%, and other 17%. A recent report [19] classified solid waste composition as kitchen waste: 74.6%, garden waste: 4.8%, paper and cardboard: 7.8%, soft plastic: 4.2%, hard plastic: 0.9%, textiles: 1.0%, rubber and leather: 0.4%, metal: 0.9%, glass: 1.7%, ceramics: 0.5%, hazardous waste: 0.4%, e-waste 0.2%, and miscellaneous: 2.7%. The World Bank report [25] classified Municipal Solid Waste (MSW) in Sri Lanka as organic: 76%, paper 11%, plastic: 6%, glass: 1%, metal: 1%, and other: 5%. This indicates that 75–80% of municipal solid waste is biodegradable, while 25–20% of non-biodegradable waste may be left untreated in Sri Lanka.

According to Jambeck et al. [3], 14.6 million of the coastal population in Sri Lanka produces 0.24–0.64 million metric tons (MMT) of plastic debris per year, with the highest waste generation rate of 5.1 kg/person/day in the world. The amount of mismanaged plastic waste was calculated as 1.59 MMT per year, which accounts for 5% of the global mismanaged waste. Further, the report indicated that 84% of the waste generated in the country is mismanaged. China is highlighted as the largest mismanaged-plastic producer (8.82 MMT/year) with the highest coastal population (262.9 million), while the United States is ranked twentieth, producing 0.28 MMT/year of mismanaged plastics with a coastal population of 112.9 million. Sri Lanka was ranked fifth, producing 1.59 MMT/year of mismanaged plastic waste, despite possessing the second smallest coastal population among other candidate countries (i.e., South Africa: 12.9, Pakistan and Sri Lanka: 14.6, Algeria: 16.6, Morocco and North Korea: 17.3, Burma: 19.0, Egypt: 21.8, Malaysia: 22.9, Thailand: 26.0, Nigeria: 27.5, Turkey: 34.0, Vietnam: 55.9, Bangladesh: 70.9, Brazil: 74.7, The Philippines: 83.4, United States: 112.9, Indonesia: 187.2, India: 187.5, China: 262.9). However, another publication stated that 2.7 million of the urban population of coastal cities generates approximately 0.75 kg/person/day of solid waste, totaling 2026 metric tons per day (approximately 0.74 MMT/year) in Sri Lanka [28].

The World Bank report [25] included Mismanaged Solid Waste (MSW) generation data by country and projections for the year 2025 (see

Table 1. MSW generation data for Sri Lanka (in 2010, and projections for 2025). In 2010, the MSW generation rate is reported as 5.1 kg/ppd, while for 2025, it is projected as 4 kg/ppd.

Sri Lanka
Economic status	Lower Middle Income (LMI)
Region	South Asia Region
Total Urban Population in 2010	2,953,410
MSW generation per capita per day in 2010	5.1 kg/ppd
Total MSW generation in 2010	15,068 tonnes/day
Total population in 2025	20,328,000
Urban population in 2025	3,830,000
MSW generation per capita per day in 2025	4 kg/ppd
Total MSW generation in 2025	15,320 tonnes/day

for a summary of information related to Sri Lanka).

The report compared solid waste generation by region and the country’s income level. Among the regions, South Asia (including Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan, and Sri Lanka) reported, comparatively, the lowest annual solid waste amount; meanwhile, Organization for Economic Co-operation and Development (OECD) countries reported the largest annual solid waste amount (

Table 2. Waste generation by region [25]. OECD countries with the highest total urban population reported the largest average per capita waste generation rate; however, the Middle Eastern and North African regions, with the lowest total urban population, did not report the lowest average per capita waste generation rate.

Region	Total Urban Population (Million)	Annual Solid Waste Generation (Million Tons/Year)	Per Capita Waste Generation Rate Range (kg/Person/Day)	Average per Capita Waste Generation Rate (kg/Person/ Day)
Organization for Economic Co-operation and Development (OECD)	729	572	1.10–3.7	2.2
Eastern and Central Asia (ECA) (except for eight countries in the region)	227	93	0.29–2.1	1.1
Latin America and the Caribbean region (LCR)	399	160	0.1–14	1.1
Middle East and North Africa region (MENA)	162	63	0.16–5.7	1.1
East Asia and the Pacific region (EAP)	777	270	0.44–4.3	0.95
Africa region (AFR)	260	62	0.09–3.0	0.65
South Asia Region (SAR)	426	70	0.12–5.1	0.45

). The largest per capita solid waste generation rate was reported as being produced by the islands of the Caribbean (14 kg/person/day), whereas the lowest was reported from the African region (0.09 kg/person/day). The daily combined generation rate of MSW in South Asia, East Asia, and the Pacific is stated as being 1 million tons per day.

The lower-middle-income countries ranked third according to the average per capita waste generation rate, reporting 0.79 kg/person/day (

Table 3. Waste generation by country income level [25]. Countries with high-income levels reported the largest average per capita waste generation rate, while countries with low-income levels reported the lowest average per capita waste generation rate.

Income Level	Per Capita Waste Generation Rate Range (kg/Person/Day)	Average per Capita Waste Generation Rate (kg/Person/Day)
High	0.70–14	2.1
Upper Middle	0.11–5.5	1.2
Lower Middle	0.16–5.3	0.79
Lower	0.09–4.3	0.60

).

The island-wide marine debris survey [7] reported that the average number of large debris (>25 mm) collected was 4.1 ± 9.2 items per square meter of the beach (175 ± 538 g by weight). The average number of small debris (5–25 mm) reported was 158 ± 170 items per square meter of the beach (18.6 ± 21.6 g by weight). Packaging material was the most abundant debris type (55.1% by number), followed by end-consumer products (25.1%) and fishery-related debris (19.5%). The dominant material type was plastic (93.3% of large debris and 98.7% of small debris by number). Sampling sites exhibited a huge spatial variation in debris densities (i.e., 0.1 item/m² at Kudawa beach, Northwestern province, and 38.8 items/m² at Kudawella beach, Southern province), highlighting the importance of incorporating beach typology when generalizing debris calculations. Coastal winds, ocean currents and tides, beach type, and monsoon cycles were suggested as drivers of debris densities. A similar study [29], conducted on recreational beaches in Mumbai, India, reported that the mean abundance of plastic was 68.83 items per square meter (7.49 g/m²). Microplastics dominated (41.85% by number) among the other size classes of plastics. The effect of long-shore currents towards the South, the number of beach visitors, its proximity to the population center, and high onshore wind speeds were suggested as drivers of debris densities.

The macro debris survey conducted in Kadolkelle, Negombo [20], reported an overall mean abundance (±SD) at the location of 2.57 ± 1.37 items/m². Plastics were the dominant debris type (73%). Among plastic debris, packaging items (68%) were significantly more numerous than fishing items and consumer items. The retention of large plastic items by the aerial root system of mangroves was highlighted as the main factor that affected debris accumulation.

The study conducted in the Southern coastal belt of Sri Lanka [22] reported a mean density of 0.23 ± 0.13 macroplastic items/m³. The overall mean density of microplastics was reported as 17.45 ± 3.35 items/m³. Filamentous macroplastics were abundant (70%), while 99.37% of microplastic debris was composed of microfilaments. The impact of monsoonal conditions and anthropogenic activities were suggested as reasons for different debris densities.

The mean (±SE) abundance of plastics (0.30–100 mm) in the coastal waters off Colombo was reported as being 140.34 ± 13.99 items/m³, with a range of 7.92–655.64 items/m³ by number [21]. By weight, the mean (±SE) abundance of plastics (1–100 mm) was reported as 0.66 ± 0.16 mg/m³, with a range of 0.00–8.19 mg/m³. Plastic filaments dominated (61%), followed by fragments (25%) and films (14%). The population density, river discharges, meteorological conditions, and turbulence were suggested as reasons for site-wise debris density differences.

CSIRO surveys across 86 sites altogether detected 14,173 pieces of debris in Sri Lanka [26]. Unknown hard plastics (16%) and soft plastics were the most abundant fragment debris, while thin-film carry bags were the least abundant. Bottle caps/lids (23.4%) and plastic bottles (12.4%) were the most abundant whole debris, while unknown/glass items were the least abundant. Coastal surveys reported the highest debris density (2.94 items/m²) and, on average, reported 57.93 debris items per linear meter of the coastline. The study estimated that the total debris load along the Sri Lankan coast was over 77 million items, assuming the number of debris items per linear meter of the coastline representing the entire 1340 km coastline [26]. Inland surveys reported a total of 3477 items, equivalent to an average of 1.18 pieces of debris/m². River surveys reported a total of 2123 items, equivalent to 14.74 pieces of debris in a linear meter of the river bank; trawl surveys reported a mean debris density of 90,474.7 items/ km², where soft plastic was the most abundant debris type (63.6%).

A CSIRO-led publication [24] discussed the ranking of candidate countries based on mean debris loads (

Table 4. Ranking of candidate countries based on mean debris loads, based on the CSIRO-developed empirical survey method [24]. The highest debris load in inland surveys was reported from South Africa, while the lowest was reported from South Korea.

Country/Territory	Mean Debris Items/m2	Rank (among the Study Country)
South Africa	2.05	1
Mainland China	1.51	2
Taiwan	1.33	3
Vietnam	1.21	4
Sri Lanka	1.18	5
Kenya	0.59	6
South Korea	0.40	7

).

The study [24] further discussed whether population density can be considered a proxy for debris densities, using empirical data. The surveyed countries were ranked based on the country coefficient in the model and compared with the existing rank [3]. Sri Lanka was ranked sixth among seven countries, based on the country coefficient in the model (

Table 5. Comparison of rankings derived from Jambeck’s study [3] and CSIRO study [24]. The contrasting difference in ranks can be observed in the two models.

Country/Territory	Waste Generation Rate According to the Study from 2015 [3] (kg/ppd)	Rank According to the Study from 2015 [3]	Rank According to the Study from 2021 [24] Based on Country Coefficient in the Model
South Africa	2.00	3	1
Taiwan	N/A	N/A	2
Vietnam	0.79	10	3
Kenya	N/A	N/A	4
Mainland China	1.10	8	5
Sri Lanka	5.10	1	6
South Korea	N/A	N/A	7

).

Surveys conducted in selected sites in Sri Lanka [7,20,22] reveal that the contamination of marine debris is dominated by plastics mainly from packaging materials. Different methodologies and analysis techniques in individual studies make it difficult to compare abundance levels; hence, site-specific debris amounts can be understood. Anthropogenic activities, increasing population densities, river discharges, coastal winds, the tendency to retain plastics in coastal habitats, ocean currents and tides, beach typology, monsoonal conditions, meteorological conditions, and turbulence are highlighted as factors affecting debris accumulation in Sri Lanka.

4. Discussion

Several studies have estimated the global inputs of plastic into the environment, relying on worldwide data, national statistics, and modeling approaches [3,24,25]. However, these estimates exhibit uncertainty, driven by limited collected MSW management data [30]. The ranking of Jambeck et al. was primarily based on four factors; coastal population, waste generation rate, percentage of plastic waste, and percentage of mismanaged waste [3]. Coastal population data was based upon a 50 km coastal buffer, created in GIS with global population densities. The waste generation rate and percentage of plastic waste data were taken directly from the World Bank estimates [25]. The percentage of mismanaged waste data was calculated using values in the model.

The waste generation rate of 5.1 (kg/ppd) for Sri Lanka is the highest value in the world. The United States was listed second, with 2.58 (kg/ppd), South Africa third, with 2.0 (kg/ppd), and the rest of the top twenty countries were listed as having < 2 (kg/ppd); this indicates that Sri Lanka has extremely high estimates. The World Bank report refers to [31,32] as sources for waste generation rate data. One of the studies, ref. [31] is an article published in a conference proceeding, not peer-reviewed, and provides basic information on solid waste based on interviews, gray literature, and site visits to two major housing schemes in the Colombo suburbs. The second reference, [32], summarizes the quantities of waste and its composition for some Asian countries, indicating that the waste generation for Sri Lanka is 0.2–0.9 (kg/ppd); meanwhile, the waste compositions (% wet weight) are given as follows: biodegradable: 76.4, plastic: 5.7, paper: 10.6, glass 1.3: metal 1.3, inert and other: 4.7. Therefore, it is not clear how the waste generation rate of 5.1 (kg/ppd) was estimated in the World Bank report [25], and how a seven percent plastic waste generation value was taken in the model prediction [3] for the global ranking.

According to Jambeck and colleagues [3], the total annual waste generation is mostly a function of population size, where countries with large coastal populations produce top-waste loads. However, Sri Lanka has the second smallest coastal population size, with a population of 14.6 million, among the top twenty countries that have the world’s highest waste generation rate. By contrast, the study by Schuyler and team [24], noted that the relationship between population and mismanaged waste was not necessarily linear, although a significant positive relationship was exhibited between population density alone and total debris.

Most debris data collection efforts around the world are based on beach surveys that are biased toward hotspots. However, naturally, marine debris is not only beach-based or ocean-based. Significant amounts of debris are carried to the coast from inland areas via rivers and streams [33]. According to CSIRO research, drivers for the distribution of inland debris were not consistent among countries [24]. The best models for the individual countries had their variables included, and the directions (i.e., negative or positive correlations) of those variables differed. Factors such as land use, local site-level variables (i.e., site type, visible humans, etc.), and infrastructure and socioeconomics were more strongly correlated with plastic in the environment than population density estimates. It was revealed that population density alone does not explain the distribution of debris, and such estimations would be potentially inaccurate. Though it is suggested that the top waste-producing countries have some of the largest coastal/urban populations [3], countries with significantly fewer coastal/urban populations have reported larger amounts of waste (i.e., Egypt: coastal population—21.8 million; MPW—0.97 MMT/year, Thailand: coastal population—26.0 million; MPW—1.03 MMT/year), while countries with significantly higher coastal/urban populations have reported the least amounts of waste (i.e., The U.S.: coastal population—112.9 million; MPW—0.28 MMT/year, India: coastal population—187.5 million; MPW—0.60 MMT/year). Therefore, the relationship between waste production and the country’s coastal/urban population is not always linear [3,24,25].

According to the World Bank report [25], the South Asian region reported a comparatively lower annual solid waste amount (70 million tons/year). Lower middle-income countries reported an average per capita waste generation rate of 0.79 kg/person/day. Therefore, as per the region or the country’s economic status, Sri Lanka’s record high waste generation rate may not be accurate.

Further, the top ten plastic offenders listed by Jambeck and colleagues [3] belong to upper-middle-income, lower-middle-income, and lower-income categories, questioning the relationship between waste generation and country income level. Decreased amounts of plastic debris from higher-income level countries are considered to be an advantage of improved waste management infrastructures. However, the World Bank report [25] reveals a linear relationship between a country’s income level and average per capita waste generation rate.

Present municipal solid waste generation in Sri Lanka is reported as being 6500–7000 metric tons per day, which varies from 0.4 to 1 kg/capita/day based on living standards [19]. According to local authorities, less than 59% of the waste generated within the country is properly collected and discarded. The municipal solid waste collection rate is 3500 metric tons per day [19], which represents almost 50% of the waste generated. This implies that approximately 50% of the waste generated at the municipal level becomes mismanaged. This is a significant deviation from the assumption that 84% of the waste generated in Sri Lanka is mismanaged [3]. Mismanaged debris density and socioeconomic status show a negative relationship, explaining the tendency of richer countries to report fewer instances of mismanaged waste as a result of better waste management systems [24]. Therefore, the importance of establishing baselines and monitoring programs on a local or regional scale was highlighted, rather than solely predicting or projecting large-scale estimations based on global proxies.

Concerning the government involvement in solid waste management in Sri Lanka, the National Strategy for Solid Waste Management (NSSWM) was formulated in 2000, and the national policy on solid waste management was formulated in 2007 [34]. Consequently, the Central Environmental Authority (CEA), under the Ministry of Environment, launched “Pilisaru project–2008” under the theme of, “Year 2018–Waste Free Sri Lanka”. The main objectives of this project were as follows: (1) the preparation of a national policy and strategy on solid waste management, (2) the provision of training on effective solid waste management, including education and awareness of relevant officers, (3) the provision of the necessary facilities for the implementation of solid waste management projects and programs, and (4) strengthening the legal framework for solid waste management. However, marine debris is treated under solid waste and is not recognized as a separate entity that needs to be rectified immediately in the national policy developments and waste management approaches. Strengthening a national policy on solid waste management will provide systemized, sustainable pathway-generating solutions to issues arising from waste collection and disposal. Facilitating scientific research and development will provide upgraded technical assistance by improving existing methodologies, and implementing novel technologies. Steps such as introducing the smart disposal of personal e-waste, and incentivizing the proper disposal of garbage, would arrest the attention of future generations.

5. Conclusions

The generation of waste by countries around the world is estimated, enumerated, or projected using globally available proxy data, and/or empirical data derived via surveys. The reported amounts are mostly compared against region, country income level, coastal or urban population, etc., and regional and global rankings for waste generation are developed from this desktop information. Therefore, establishing baselines via empirical studies and continuous monitoring is of high importance, since the unavailability of updated information makes it difficult to develop projection models, study the sources and trends, and initiate proper mitigation plans to curb the global menace of mismanaged plastics. Referring to unbiased, scientifically generated, critically reviewed sources and information is of equal importance in reporting. Therefore, Sri Lanka is one of the countries that may be a victim of limited data on mismanaged waste in the environment, and its position in the global ranking deserves reconsideration. Our heavy reliance on model predictions using globally available data layers, without actual on-ground information, needs to be rectified.