Assessment Methods

Material flow analysis (MFA) is a quantitative method to determine the flow of materials and energy through an economy. It works by capturing the mass balance in an economy, where extraction and imports are considered inputs and consumption and exports as outputs. The mass balance of inputs should be equal to outputs, which is useful in determining the efficiency of the use of material resources.

From the perspective of waste in general, MFA is required to develop a standard tool of waste statistics between countries. However, for plastic waste thiscan be difficult to implement because many plastic materials, such as polyethylene and polypropylene, are used for many different products (Moriguchi and Hashimoto, 2016).

MFA of Plastics in Thailand

Bureecaam, Chaisomphob, and Sungsomboon (2018) demonstrate the MFA for plastic waste and plastic waste management in Thailand. They use primary and secondary sources to obtain the data from 11 provinces.

Figure 1. MFA of Plastic in Thailand in 2013 

(Source: Bureecaam et al., 2018).

Figure 1 shows petrochemical industries in Thailand produced 7,827,481 tonnes of raw materials in 2013, around 1,101,329 tonnes of which were derived from recycled materials. After 2,732,675 tonnes was consumed, 3,560,595 tonnes of plastic waste was generated. Some of the plastic waste was then collected and disposed of by the local government, while 499,295 tonnes remained uncollected. The collected waste went to different treatment facilities, 765,883 tonnes of which was recycled while 220,949 tonnes was incinerated to generate energy. The remaining 1,986,648 tonnes was disposed of to a landfill site. Unfortunately, 597,115 tonnes of plastic waste was improperly managed in the collection and transportation process. The waste was then mixed with the uncollected waste in the previous process, resulting in 1,076,410 tonnes ending up in the open environment, which potentially leaked into the oceans.

The Philippines

MFA for plastic scraps in the Philippines is shown in Figure 2.

Figure 2. MFA of Plastic Scraps in the Philippines (Source: Japan International Cooperation Agency, 2008).

The Philippines produces 1,013,242 tonnes of plastic per year derived from three sources: imported resins (581,639 tonnes/year) and imported plastic waste (14,841 tonnes/year), local supply of recycled plastic (288,000 tonnes/year), and from local production of virgin raw materials (128,762 tonnes/year). The total number of plastic products is then calculated by adding total plastic production and imports of plastic finished products (344,493 tonnes/year) or 1,357,735 tonnes/year. To obtain the total local consumption, this number is deducted from the number of exported plastic finished products (96,330 tonnes/year), for a total of 1,261,405 tonnes/year.

Local plastic consumption is processed in several phases: recycled, kept (still being used), and disposed of to a landfill. Recycled plastic accounts for 243,267 tonnes/year. Those still being used and those disposed of to a landfill account for 574,309 tonnes/year and 399,096 tonnes/year, respectively (Japan International Cooperation Agency, 2008). Unfortunately, the study of MFA in the Philippines does not calculate the amount of unmanaged plastic waste that ends up in the open environment and could leak into oceans.

Malaysia

Malaysia’s plastic inventory was calculated based on a survey study which showed local production of 587,062 tonnes of plastic products which, added to the 170,248 tonnes of imported plastic products, totalled 733,828 tonnes of plastic products. Local consumption of plastics was 511,697 tonnes, whilst exports were 222,131 tonnes. Of local plastic consumption, 47,843 tonnes was recycled and the rest (463,854 tonnes) went to final disposal. This study does not cover the amount of plastic waste that ended up in the open environment. Details of MFA plastics in Malaysia are shown in Figure 3.

Figure 3. MFA of Plastics in Malaysia (Source: National Solid Waste Management Department Ministry of Housing and Local Government, 2011).

Viet Nam

Plastic material in Viet Nam are derived from two sources: domestic resin (1,000 Ktonnes) and imported resin (5,900 Ktonnes). Plastic (semi) products are used for export and domestic purposes. Exports of plastic (semi) products stood at 3,803 Ktonnes, whilst plastic (semi) products for domestic purposes were 3,690 Ktonnes. Domestic use of the products was by consumers such as the food processing, beverage, textile, and electronics industries; and by end-users such as households, markets, hospitals, and schools. Unfortunately, the process generated 730 Ktonnes of uncollected plastic waste that was disposed of into the oceans. The 2,815–3,115 Ktonnes of remaining plastic waste was collected and transported to the next process. Some 807 Ktonnes of resin was exported, while the remaining waste and scraps were recycled. The waste generated from recycling, collection, and transportation was eventually disposed of in landfills – 1,308 Ktonnes of waste went to landfills.

Figure 4. MFA of Plastics in Viet Nam (Vietnam Business Council for Sustainable Development and United States Business Council for Sustainable Development, 2019).

In summary, some plastic waste continues to be uncollected or improperly managed, when looking at the MFA of plastic-related products in Southeast Asian countries, thus ending up in the open environment and oceans, as in the Philippines and Viet Nam. In general, countries in this region have huge amounts of plastic waste going to landfills instead of being recycled or used to generate energy. Uncontrolled landfills can lead to the leakage of plastic waste into oceans.

Estimates on capturing plastic leakage in the marine environment can differ depending on the scope and methodologies applied by field researchers.

Land to Ocean Leakage

Jambeck et al. (2015) estimated plastic leakage in 2010 by calculating the amount of annually mismanaged plastic waste generated by populations in 192 countries living within 50 kilometres of a coast. The estimation framework calculated: annual waste generation per capita, percentage of plastic waste, and percentage of mismanaged plastic waste. The amount of mismanaged plastic waste was then converted to the amount of marine plastic debris by applying a range of conversion rates.

Table 1 lists countries who contributed the most leakage in 2010. Six ASEAN members (Indonesia, the Philippines, Viet Nam, Thailand, Malaysia, and Myanmar) were included in the top 20 countries, while China topped the list. The global leakage estimate was 4.8 million–12.7 million metric tonnes/year (equivalent to 1.7%–4.6% of total plastic waste generated in those countries).

Table 1. Estimated Marine Plastic Debris Leakage in 2010

Source: Jambeck et al. (2015).

Land to River, Lake, and Ocean Leakage

Borrelle et al. (2020) compiled the annual amount of mismanaged plastic waste entering aquatic ecosystems (covering oceans, rivers, and lakes) in 173 countries from 2016 to 2030. Applying a methodology similar to that of Jambeck et al. (2015), the estimation integrates expected population growth, annual waste generation per capita, and proportion of plastic waste and mismanaged waste. Those variables were integrated using a distance-based probability function, considering the spatially explicit waste generation and downhill flow accumulation.

The leakage in 2016 is the baseline estimation (Table 2), while the 2030 leakage is estimated for three scenarios: business as usual, where waste generation and plastic production follow current trajectories; ambitious, which draws upon existing global commitments in leakage reduction; and target (<8 million metric tonnes), estimated in 2010 by Jambeck et al. (2015). Russia tops the list, while two East Asia countries (China and Japan) and five ASEAN countries (Indonesia, Thailand, the Philippines, Myanmar, and Viet Nam) are included in the top 20. Under the business-as-usual scenario, global estimated leakage will reach up to 90 million metric tonnes/year by 2030.

Table 2. Estimated Aquatic Ecosystem Plastic Waste Leakage in 2016 and 2030

Source: Borrelle et al. (2020).

River to Ocean Leakage

More than 1,500 rivers account for 80% of global plastic waste leakage from 31,904 rivers in 163 countries, Meijer et al. (2021) estimated. The estimated global leakage of 0.8 million–2.7 million metric tonnes/year by Meijer et al. (2021) is far below the estimate by Jambeck et al. (2015) in 2010. However, the lower estimate is due to the estimation methodologies, not the reduction of single-use plastics or the improvement of waste management systems. In addition to common variables, such as population, waste generation per capita, and proportion of mismanaged waste, Meijer et al. (2021) utilised a probabilistic model that considered additional variables, including land use, terrain slope, wind, and precipitation. The model was then calibrated and validated against field observations from 2017 to 2020. Despite the difference, the results show ASEAN countries remain the main contributors.

Table 3 lists five ASEAN countries in the top 10 contributors, ranking the Philippines as the largest with seven rivers in the top 10 plastic-emitting rivers (Table 4), followed by Malaysia (ranked 3), Indonesia (5), Myanmar (6), Viet Nam (8), and Thailand (10).

Table 3. Recent Estimated Marine Plastic Leakage

Source: Meijer et al. (2021).

Table 4. Predicted Top 10 Plastic-Emitting Rivers

Source: Meijer et al. (2021).

The results are consistent with Lebreton et al. (2017) and Schmidt et al. (2017), who found 1.15 million–2.41 million metric tonnes and 0.41 million–4 million metric tonnes, respectively, of plastic annually flowing from rivers to oceans. The top 20 polluting rivers were mostly in Asia (Table 5) and accounted for more than two-thirds (67%) of the global leakage (Lebreton et al., 2017). Seven rivers in the top 20 were in ASEAN countries: Brantas (ranked 6), Pasig (8), Irrawaddy (9), Solo (10), Mekong (11), Serayu (14), and Progo River (19).

Table 5. Predicted Top 20 Polluting Rivers

Source: Lebreton et al. (2017).

Using underlying mismanaged plastic waste data similar to that used by Lebreton et al. (2017), Schmidt et al. (2017) Eight out of the 10 rivers are in Asia, including the Mekong (10), which flows through five ASEAN countries. The estimated leakage is higher because Schmidt et al. (2017) compiled a larger data set and treated microplastic and macroplastic separately. Reducing plastic leakage by 50% in the 10 top-ranked rivers would reduce total river-based leakage by 45%.

Table 6. Predicted Top 10 Polluting Rivers

Source: Schmidt et al. (2017).

An estimation by Meijer et al. (2021) shows a significant leakage increase from several rivers in the Philippines, in comparison with the estimation by Lebreton et al. (2017).The amount of leakage from the Pasig River increased more than 60%, from 0.039 million metric tonnes/year in 2017 (Table 5). Rivers in ASEAN countries, especially in the Philippines, toppled rivers in China from the top spot as emitters of plastic to oceans, as Meijer et al. (2021) considered the spatial variability of the amount of mismanaged plastic waste within a river basin and utilised climate and terrain characteristics to differentiate the probability of leakage. With these assumptions, relatively small river basins, including those in ASEAN countries (eg the rivers in the Philippines), contribute proportionally more leakage than larger river basins, where the amount of mismanaged plastic waste is similar but located further upstream. Meijer et al. (2021) answer the limitation on Lebreton et al. (2017) and Schmidt et al. (2017), who overestimated the leakage from large rivers and underestimated the leakage from smaller rivers due to the exclusion of those important assumptions. The trend is a backstep and a warning the region must reduce marine plastic debris.

Harmonised Methodology to Support Effective Countermeasures

Although several estimations have been undertaken to capture plastic leakage into the marine environment, more data is needed more often. The estimations differ from one another depending on the scope and methodology applied. To avoid any underestimation, harmonising the methodologies is important. With a harmonised methodology, data can be compared and validated against each other. Using a larger set of data, as done by Schmidt et al. (2017) and Borrelle et al. (2020), will further increase the accuracy of estimations. However, some countries may not have country-specific data, so data estimated using a proxy value with assumptions and a level of uncertainties may lead to underestimation.

For instance, Schmidt et al. (2017) extended by 41 countries the estimation of Jambeck et al. (2015) of the mismanaged plastic waste generation rate from 192 coastal countries. The waste generation rate and plastic composition for these 41 countries were taken from Hoornweg and Bhada-Tata (2012) based on past regional estimations, while the mismanaged plastic waste was calculated based on average values for each World Bank economic classification (high income, upper middle income, lower middle income, or low income). In most developing countries, including India (Nandy et al., 2015), where plastic waste is mostly recovered by the informal sector, a significant amount is excluded from the estimation.

To address this issue, governments should support such research by monitoring leakage in rivers and regularly provide valid waste management data. The lack of actual waste management data, especially in ASEAN countries, might lead to lower or higher leakage estimations, depending on the proxy data. The lower estimation by Meijer et al. (2021) does not necessarily mean the reduction of leakage. By utilising the appropriate harmonised methodology, and supported by valid government data, policies can be formulated and/or evaluated to create effective countermeasures against marine plastic leakage.

An increase in global plastic production to 322 million metric tonnes in 2015, due its lightness, durability, and flexibility, combined with a low production cost, has triggered rising concerns about the effects on the marine environment due to its long-term chemical stability in the oceans (Andrady and Rajapakse, 2017).

Ocean plastic is fragmented into smaller pieces by UV radiation, which, in turn, are ingested by marine organisms, causing wounds, ulcerating sores, digestive system blockages, and in extreme circumstances, ruptured bladders in marine species such as turtles. Ingestion of large amounts of plastic can also create a false sense of fullness while slowing the rate of digestion (Ryan, 2016).

Three types of plastic toxicity threaten the environment: additives mixed during product processing and fabrication, residual monomers or catalysts trapped in the resin, and chemicals picked up by plastics from the environment. Additives in plastic products have the highest concentrations of the three, including fillers, plasticisers, flame retardants, colourants, UV stabilisers, thermal stabilisers, and processing aids (Table 1).

Table 1. Types of Additives in Common Plastic

Source: Andrady and Rajapakse (2017).

Ocean plastics retain additives which are then directly transferred to marine organisms through prey ingestion. Indirect toxicity results when additives not chemically bound to the plastic are released into the environment and become available to organisms (Hermabessiere et al, 2017).

The most common additives found in marine debris are brominated flame retardants (BFRs), phthalates, nonylphenols, bisphenol A (BPA), and antioxidants.

1. BFRs

Generally, BFRs are potential endocrine disruptors. Organisms exposed to endocrine disruptors will suffer in multiple developmental, reproductive, neurological, immune, and metabolic diseases (Ingre-Khans, Ågerstrand, and Rudén, 2017). They are used to reduce flammability in plastic products such as electronic devices and insulation foams. The additives cover a range of chemicals, including the most commonly used additives in the plastic industry, such as polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane, and tetrabromobisphenol A. Research shows some types of BFRs are not chemically bound to a polymer matrix, causing them to leach into the environment. Some commercial formulations of BFRs, such as penta-, octa-, and deca-brominated diphenyl ethers (BDEs), are ubiquitous, harmful, stable, and bioaccumulate in the environment, with detrimental impacts on human health. Penta- and octa-BDEs were banned in the European Union (EU) in 2004, and the EU also banned deca-BDE for electronic and electrical applications in 2009 (European Commission, 2003; European Council Decision, 2009). Japan banned production and importation of tetra- and hepta-BDEs in 1995 (Covaci et al, 2008).

Several BDEs have also been controlled by the Stockholm Convention since 2004, which prohibits persistent organic pollutants, including deca-, hexa-, hepta-, tetra-, and penta-BDEs.  Southeast Asia and East Asia countries have ratified the convention, including Japan, China, the Republic of Korea, Cambodia, Indonesia, the Lao People’s Democratic Republic, Myanmar, the Philippines, Singapore, and Thailand (Stockholm Convention, 2019a).

Under the regulation, deca-BDEs in plastic housing and parts used for heating home appliances are allowed at concentrations lower than 10% by weight (Stockholm Convention, 2019b). Although it does not set allowances for hexa-, hepta-, tetra-, and penta-BDEs, they have to be recycled through an environmentally sound mechanism, are not allowed to be exported if their concentrations exceed the standard in the territory of the involved party, and their use must be under the control of relevant stakeholders (Stockholm Convention, 2019c; Stockholm Convention, 2019d).

The EU adopted the Restriction of Hazardous Substances (RoHS) Directive 2002/95/EC, in 2003, which restricts the use of hazardous substances in electrical and electronic equipment, including PBDEs. PBDEs can only be used at 0.1% concentration by weight as they affect the endocrine system (RoHS Guide, 2020). Some Southeast Asian and East Asian countries have adopted a similar approach to PBDEs.

China’s Requirements for Concentration Limits for Certain Restricted Substances in Electrical and Electronic Products SJ/T 11363-2006 states PBDE concentration (deca-BDE not included) in products should not surpass 0.1% by weight. China also has PBDE regulations, such as the Ordinance on Management of Pollution and Control of Pollution from Electronic Information Products in 2007, and the Administrative Measures on Pollution Prevention of Waste from Electrical and Electronic Equipment in 2008 (revised in 2016) (Ni et al., 2012; Chem Safety Pro, 2019).

Weak enforcement of those regulations, however, remains an issue (Ni et al., 2012). Viet Nam and Singapore allow the use of PBDEs with as much as 0.1% concentration by weight in electric or electronic products (Government of Viet Nam, 2011; Government of Singapore, 2020). As Thailand has no strong legal frameworks controlling the use of PBDEs, they are found in products such as electronics, furniture, and car seats. However, some types of BDEs (47, 99, 153, 175, and 183) will be added to the Thailand Hazardous Substances List, which is annexed to the Notification of Ministry of Industry on List of Hazardous Substances (No 4) (Muenhor and Harrad, 2018).

Malaysia also prohibits the use of PBDEs in lighting equipment parts based on MS 2237:2009, which restricts certain hazardous substances in electrical and electronic devices (SCP Malaysia, 2014). In Indonesia, a recommendation on industrial waste management is being formulated by the Ministry of Industry and the United Nations Development Programme, to reduce or eliminate substances, including PBDEs, which can endanger the environment (Pusat Penelitian Kimia LIPI, 2017).

2. Phthalates or phthalic acid esters (PAEs), found mostly in polyvinyl chloride (PVC), are plasticisers that can take 10%–60% concentration by weight of PVC. As these additives are not bound to a polymer matrix, they can easily leach into the environment during their manufacture, use, and disposal. A big concern is phthalates can serve as endocrine disruptors even in small concentrations (Hermabessiere et al, 2017).

3. Bisphenol A (BPA), as one of the most commonly and globally produced chemicals, is primarily used as monomer of the main component of the lining of aluminium cans. Humans are exposed to BPA once it is released from food and drink packaging. Like phthalates, BPA is a significant endocrine disruptor. Other types of bisphenol, including bisphenol B, F, and S, may also pose threats to the environment (Hermabessiere et al, 2017).

4. Nonylphenols (NPs) are widely used as antioxidants and plasticisers in plastic production and leach out of plastic bottles. Effluent from wastewater treatment plants is also a major source of NPs. These additives disrupt the endocrine system and can have an adverse impact on human health and the environment. NPs are banned in the EU, and  can be found in seafood, including oysters, mussels, and fish (Hermabessiere et al, 2017).

5. Antioxidants help prevent plastic ageing and delay oxidation, but can leach out of plastic packaging and into food. The use of antioxidants in plastic can be harmful because they are oestrogen mimics (Hermabessiere et al, 2017). An oestrogen mimic, an endocrine disruptor, is an artificial hormone that biologically behaves as oestrogen but has a different chemical structure. Excessive amounts of oestrogen in the marine environment can delay the sexual maturity of marine animals, decreasing the size of male reproductive anatomy, and making eggs thinner (UWEC, 2020).

These additives can be found in marine water, sediment, and microplastics. As the final stop of all wastewater, marine water receives huge amounts of additives. PBDEs, di (2-ethylexyl) phthalate (DEHP), and NPs are all detected in marine water. Additives can also be found in sediment affected by anthropogenic discharge through wastewater, atmospheric deposition, and sewage sludge. Plastic additives are found in microplastics as they are added in the manufacture of polyethylene and polypropylene (Hermabessiere et al, 2017).

Several studies on the chemical impacts of plastic have been conducted in Southeast Asian and East Asian countries. A study in the Mekong River Delta in Viet Nam revealed PBDE contamination in catfish, posing risks to people who eat them. The study showed runoffs from dumping sites during floods and rains are possible drivers that bring additives to surrounding areas, and municipal waste in dumping sites, consisting of household goods and electrical equipment, might contain PBDEs. Research in informal e-waste recycling sites in Viet Nam found high PBDE contamination in surrounding sediment and in fish, particularly mud carp. This was attributed to the high level of PBDEs in plastic parts in obsolete electronic equipment in e-waste recycling sites. 

Liu et al (2011) discovered PBDE contamination in marine fish tissue from the South China Sea, the Bohai Sea, the East China Sea, and the Yellow Sea, while Ilyas et al. (2013) indicated that a high level of PBDEs was observed in municipal dumpsites. Seabirds are also vulnerable to the impacts of chemicals in plastic. A study in the northern Pacific Ocean found oceanic seabirds ingesting plastic debris due to the growing amount of plastic in the ocean. PBDEs were found in the abdominal adipose tissue of the species.