Plastic pollution is a major global challenge. Currently, an estimated 30 million tons of plastic waste lie in seas and oceans, and a further 109 million tons have accumulated in rivers [1]. Other quantities are found in terrestrial environments such as urban areas, landfills, and agricultural land. Plastics’ inherent resistance to biodegradation¹ leads to their growing build-up in the environment [2]. The accumulated plastic waste generates significant negative impacts on ecosystems, the economy, and people’s health. A recent study estimated the minimum lifetime cost of the plastic waste produced in 2019 at about USD3.7 trillion – more than India’s gross domestic product [3]. Moreover, the COVID-19 crisis led to a rise in littering, food takeaway packaging, and plastic medical equipment, such as masks².

The problem of plastic pollution is at the forefront of the environmental agendas of many governments and international organizations, such as the World Bank and the United Nations Environment Programme (UNEP). To date, most efforts to understand the magnitude of damages caused by plastic have focused on marine environments. Studies have estimated the economic damages due to marine plastic pollution at different levels: global level, e.g. [3] [4]; regional level, e.g. [5] [6] [7]; the coastal areas of individual countries, such as the United Kingdom [8], Norway [9], the Galapagos Islands [10], Indonesia [11]; and specific economic sectors, such as fisheries in Thailand [12] and tourism in South Africa [13].

Far less is known about the effects of plastic waste in inland environments. Although the presence of plastics has been documented at specific terrestrial sites, e.g., home gardens, urban agglomerations, and agricultural land [14] [15] [16] [17], there has been little analysis of the type and extent of impacts caused by plastic waste in such areas. This paper contributes to addressing this gap by estimating the economic damages caused by the inappropriate disposal of plastic waste in an urban area of a developing country—N’Djamena, the capital of Chad. The valuation is particularly important, given the serious problem of plastic waste management faced by the city: in 2010, N’Djamena banned the import, marketing, and use of plastic bags³. While this reduced plastic pollution for a short time—only during the mandate of the city’s mayor at the time - the trend has reversed in recent years, with increasing amounts of plastic waste blocking waterways and damaging the environment⁴.

To the authors’ knowledge, this is the first study that estimated in monetary terms the damages caused by plastic pollution in an inland setting. It is based on the data collected in the context of the World Bank’s Country Environmental Analysis for Chad [18].

The study area is located along the Canal des Jardiniers, which crosses the city center from the south to the north. The canal is primarily used for rainwater drainage. The study area stretches along the canal and covers about 25 ha (Map 1, red contour). It is home to 380 households, which include about 3540 residents. It covers a mix of residential and commercial buildings, with shops and markets. Most structures are mud houses (maisons en terre battue). Its socio-economic characteristics (income levels, poverty rate, education levels, etc.) are believed to reflect the city’s average (Table 1). However, the household size is slightly larger in the study area than the average of N’Djamena (9 vs. 6).

There are no formal waste collection or transfer centers in the vicinity of the canal. Therefore, the waste originating from this area and other upstream areas is usually dumped into the canal. The canal is cleaned every few years, but in the intervening years, waste accumulates rapidly in the canal; a large proportion of this waste consists of plastics. Local authorities estimated that the portion of the canal located in the study area held about 300 tons of solid waste in 2020, a third of which consisted of plastic waste, such as bottles, bags, and other packaging.

Sources: Population from [20]; remaining data from [21]. Note: * Based on the households’ own perception of their poverty level [21].

The waste obstructs many sections of the canal and contributes to several negative externalities: 1) health impacts, such as malaria, due to bites of mosquitoes that reproduce in the stagnant water created by the clogged canal; diarrhea and dysentery due to contamination of household water by polluted water from the canal⁵; 2) reduction in house value due to bad odor and aesthetic nuisance; 3) flood damages during rainy years, such as 2020, when torrential rains caused the flooding of a significant area around the canal.

Valuation techniques. A wide range of valuation techniques has been developed in environmental literature to estimate damages to natural resources [22] [23] [24]. Environmental damages can be valued either through exchange value-based approaches (i.e., techniques based on observed or imputed prices, replacement costs, treatment costs) or welfare-based approaches (i.e., techniques that seek the willingness to pay for a good, or to accept compensation for a loss) [25] [26]. Estimating different types of damages via comparable measures of value is essential to obtaining meaningful results. In this paper, we use exchange value-based approaches to estimate the damages caused by the solid waste accumulated in the canal, due to the lack of information related to welfare-based measures:

 Health impacts. The costs related to the morbidity associated with malaria, diarrhea, and dysentery are estimated based on the actual treatment costs, costs of caring for sick children, and income losses among sick adults.

 House devaluation. This loss is estimated based on hedonic prices, through the difference between the average value of houses located in close proximity to the canal and that of very similar houses located further away.

 Flood damages. These are estimated based on the actual repair cost of houses, income losses to businesses during the flood days, and other costs related to the temporary transfer of certain households.

Data collection. A primary survey was conducted among all 380 households of the study area. It was carried out through personal interviews based on a structured questionnaire. Due to time and resource constraints, the survey did not seek to collect a comprehensive range of data; rather, it focused on the essential information needed for the economic valuation: a few household characteristics (e.g., income, distance from the canal), types of solid waste in the canal (e.g., plastics, household waste), diseases (frequency, costs), flood impacts (types of damages, costs of repair) and households’ perceptions regarding the contribution of waste disposal to the damages incurred. Moreover, to improve the understanding of the overall situation, personal interviews were also conducted with local authorities (chefs de carré) to collect information related to the overall surface affected by floods, flood frequency, and house prices in different locations of the study area.

Data analysis. The data collected through the survey were analyzed for the entire study area. However, plastic pollution affects households differently, depending on their distance to the canal, construction material, livelihoods, etc. Because of these differences, the study area has been divided into three zones, based on their distance from the canal (Table 2).

Source: Household survey.

This section describes the valuation of the three types of damages due to inappropriate disposal of solid waste in the study area (Sections 4.1-4.3), based on the approaches mentioned previously. It then estimates the damages due to plastic waste for the study area and for the three zones (Section 4.4). All the estimates refer to the year 2020.

Although the study benefitted from valuable primary information, it is important to note that the valuation was subject to several limitations, mostly related to attribution challenges:

Þ The contribution of solid waste to the burden of disease. Ideally, a comparison between the prevalence of disease in the study area and that in an identical area, but subject to appropriate solid waste disposal would have been useful for the valuation. In its absence, we used as a proxy the difference between the prevalence of each disease locally and nationally. This may understate the difference because the national average also includes areas with poor waste management.

Þ The contribution of solid waste to flood damages. Sufficiently intense rain can cause flooding even if the canal is clear, but any obstruction in the canal will increase the likelihood and severity of flooding. It is not known how much the likelihood and severity of flooding increases as a result of obstructions, and whether the composition of that obstruction (e.g., the share of plastics, shape) affects it.

Þ The contribution of plastic waste to total damages. Plastics encompass a large range of materials (e.g., polyethylene, polyamides, etc.) and sizes (e.g., macro-plastics, micro-plastics, nano-plastics) which may contribute differently to economic damages. For example, macro-plastics might be more likely to obstruct the canal because they bind materials together, while micro-plastics, if ingested, are believed to cause other problems such as exposure to contaminants, internal injuries, or reduced nutrition [2]. In the absence of cause and effect relationships between the different types of plastics and their possible effects, this paper focuses only on macro-plastics, and estimates their contribution to the total damage based on their proportion in the total volume of solid waste dumped in the canal.

These considerations suggest that the study’s results underestimate several damages, by not capturing the cost related to the potential ingestion of micro-plastics, injuries due to floods, carbon emissions, etc. At the same time, they might overestimate certain effects, by failing to exclude factors other than solid waste which could potentially contribute to flooding damages; however, the degree of overestimation is believed to be low. Due to the above limitations, the results should be regarded as orders of magnitude of the impacts of plastic waste in the study area. In addition, as the results represent first-time estimates of damages in a specific context (urban inland environment in a Sahelian country during a rainy year), they should not be generalized to areas characterized by different conditions.

This paper demonstrated that plastic pollution could have a large economic impact on Chad’s urban areas. Key messages include:

Þ Damages due to plastic pollution reach over USD3000/ton in the study area in 2020. The lack of studies conducted in other inland environments makes it impossible to compare these results with plastic damages in other areas¹⁷. However, the estimated damage is substantially higher than the average impact of solid waste estimated for N’Djamena at USD60/ton per year by a different study [18].

Þ The most affected zone is located within 20 meters of the canal and bears more than 75 percent of the total plastic damage. The close proximity to the obstructed canal is the major reason for the decline in house values, the high occurrence of disease, and the intense flood damages in this zone.

Þ There are large differences in damages across the three zones. The average damage per household in zone A is more than seven times higher than that inflicted on the zones located further away¹⁸; similarly, the damage per hectare in zone A is more than six times higher than those in the other two zones¹⁹.

These results point out to several priority areas for future work in N’Djamena and other urban areas:

Þ identify hotspot areas of solid waste (including plastic), determine possible actions to reduce the damage (e.g., clean-up, recycling, reuse), and carry out cost-benefit analyses to identify the most socially attractive solutions to reduce damages.

Þ strengthen the collection of plastic waste data (e.g., systematic assessment of quantities generated and disposed of in areas of interest) and health information (e.g., prevalence of different diseases at the city level), and deepen the knowledge of the cause-and-effect relationships between the exposure to different types of plastic and possible health outcomes.

Þ identify practical ways to reinforce the municipal decree prohibiting the use of plastic bags; support waste recycling and promote the reuse of recycled products, e.g., by supporting partnerships between the Société Tchadienne d’Industrie et de Plastique, which is currently the only plastic recycling firm in Chad, and agencies such as the International Finance Corporation (IFC); invest in more solid waste collection points and sanitary landfills [18].

Þ conduct new studies to estimate the damages due to plastic waste in inland urban environments. Their results should provide damage estimates for a wider range of contexts, which will further improve the understanding of the range of possible costs and how they vary according to local conditions.

This paper is based on a survey conducted in the context of the Chad Country Environmental Analysis by the World Bank. The authors gratefully acknowledge the financial support provided by the World Bank’s Global Program of Sustainability. Special thanks are given to Mr. Seidou Mahamat Ahmat Seidou (Environmental Specialist), Mr. Stefano Pagiola (Sr. Environment Economist), and Ms. Maria Sarraf (Practice Manager, West Africa) for their continuous support.

The authors declare no conflicts of interest regarding the publication of this paper.

Croitoru, L., Singambaye, A. and Rossignol, A. (2022) The Cost of Plastic Pollution in N’Djamena: A Case Study. Journal of Environmental Protection, 13, 575-588. https://doi.org/10.4236/jep.2022.138036