Environmental Sustainability Impacts of Solid Waste Management Practices in the Global South

Many problems in the cities of the global South are often associated with a weak or inadequate SWM system, which leads to severe direct and indirect environmental and public health issues at every stage of waste collection, handling, treatment, and disposal [30,31,32,33,34]. Inadequate and weak SWM results in indiscriminate dumping of waste on the streets, open spaces, and water bodies. Such practices were observed in, for example, Pakistan [35,36], India [37], Nepal [38], Peru [39], Guatemala [40], Brazil [41], Kenya [42], Rwanda [43], South Africa [44,45], Nigeria [46], Zimbabwe [47], etc.

The problems associated with such practices are GHG emissions [37,48], leachates [40,44,49], the spread of diseases such as malaria and dengue [36], odor [35,38,50,51], blocking of drains and sewers and subsequent flooding [52], suffocation of animals in plastic bags [52], and indiscriminate littering [38,39,53].

Uncollected and untreated waste has socioeconomic and environmental costs extending beyond city boundaries. Environmental sustainability impacts of this practice include methane (CH4) emissions, foul odor, air pollution, land and water contamination, and the breeding of rodents, insects, and flies that transmit diseases to humans. Decomposition of biodegradable waste under anaerobic conditions contributes to about 18% and 2.9% of global methane and GHG emissions, respectively [54], with the global warming effect of about 25 times higher than carbon dioxide (CO2) emissions [55]. Methane also causes fires and explosions [56]. Emissions from SWM in developing countries are increasing due to rapid economic growth and improved living standards [57].

Irregular waste collection also contributes to marine pollution. In 2010, 192 coastal countries generated 275 million metric tons of plastic waste out of which up to 12.7 million metric tons (4.4%) entered ocean ecosystems [58]. Moreover, plastic waste collects and stagnates water, proving a mosquito breeding habitat and raising the risks of dengue, malaria, and West Nile fever [56]. In addition, uncollected waste creates serious safety, health, and environmental consequences such as promoting urban violence and supporting breeding and feeding grounds for flies, mosquitoes, rodents, dogs, and cats, which carry diseases to nearby homesteads [4,19,59,60].

In the global South, scavengers often throw the remaining unwanted garbage on the street. Waste collectors are rarely protected from direct contact and injury, thereby facing serious health threats. Because garbage trucks are often derelict and uncovered, exhaust fumes and dust stemming from waste collection and transportation contribute to environmental pollution and widespread health problems [61]. In India’s megacities, for example, irregular MSW management is one of the major problems affecting air and marine quality [62]. Thus, irregular waste collection and handling contribute to public health hazards and environmental degradation [63].

Most municipal solid waste in the Global South goes into unsanitary landfills or open dumps. Even during the economic downturn during the COVID-19 pandemic, the amount of waste heading to landfill sites in Brazil, for example, increased due to lower recycling rates [64]. In Johor, Malaysia, landfilling destroys natural habitats and depletes the flora and fauna [65]. Moreover, landfilling with untreated, unsorted waste led to severe public health issues in South America [66]. Based on a study on 30 Brazilian cities, Urban and Nakada [64] report that 35% of medical waste was not properly treated before disposal, which poses a threat to public health, including the spread of COVID-19. Landfills and open dumps are also associated with high emissions of methane (CH4), a major GHG [67,68]. Landfills and wastewater release 17% of the global methane emission [25]. About 29 metric tons of methane are emitted annually from landfills globally, accounting for about 8% of estimated global emissions, with 1.3 metric tons released from landfills in Africa [7]. The rate of landfill gas production steadily rises while MSW accumulates in the landfill emissions. Released methane and ammonia gases can cause health hazards such as respiratory diseases [37,69,70,71]. Since methane is highly combustible, it can cause fire and explosion hazards [72].

Open dumping sites with organic waste create the environment for the breeding of disease-carrying vectors, including rodents, flies, and mosquitoes [40,45,51,73,74,75,76,77,78,79]. Associated vector-borne diseases include zika virus, dengue, and malaria fever [70,71,72,73,74,75,76,77,78,79,80]. In addition, there are risks of water-borne illnesses such as leptospirosis, intestinal worms, diarrhea, and hepatitis A [80,81].

Odors from landfill sites, and their physical appearance, affect the lives of nearby residents by threatening their health and undermining their livelihoods, lowering their property values [37,38,68,82,83,84]. Moreover, the emission of ammonia (NH3) from landfill sites can damage species’ composition and plant leaves [85]. In addition, the pollutants from landfill sites damage soil quality [73,84]. Landfill sites also generate dust and are sources of noise pollution [86].

Air and water pollution are intense in the hot and rainy seasons due to the emission of offensive odor, disease-carrying leachates, and runoff. Considerable amounts of methane and CO2 from landfill sites produce adverse health effects such as skin, eyes, nose, and respiratory diseases [69,87,88]. The emission of ammonia can lead to similar problems and even blindness [85,89]. Other toxic gaseous pollutants from landfill sites include Sulphur oxides [89]. While less than 20% of methane is recovered from landfills in China, Western nations recover up to 60% [90].

Several studies report leachate from landfill sites contaminating water sources used for drinking and other household applications, which pose significant risks to public health [36,43,53,72,75,83,91,92,93,94,95]. For example, Hong et al. [95] estimated that, in 2006, the amount of leachates escaping from landfill sites in Pudong (China) was 160–180 m3 per day. On the other hand, a properly engineered facility for waste disposal can protect public health, preserve important environmental resources, prevent clogging of drainages, and prevent the migration of leachates to contaminate ground and surface water, farmlands, animals, and air from which they enter the human body [61,96]. Moreover, heat in summer can speed up the rate of bacterial action on biodegradable organic material and produce a pungent odor [60,97,98]. In China, for example, leachates were not treated in 47% of landfills [99].

Co-mingled disposal of industrial and medical waste alongside municipal waste endangers people with chemical and radioactive hazards, Hepatitis B and C, tetanus, human immune deficiency, HIV infections, and other related diseases [59,60,100]. Moreover, indiscriminate disposal of solid waste can cause infectious diseases such as gastrointestinal, dermatological, respiratory, and genetic diseases, chest pains, diarrhea, cholera, psychological disorders, skin, eyes, and nose irritations, and allergies [10,36,60,61].

Open burning of MSW is a main cause of smog and respiratory diseases, including nose, throat, chest infections and inflammation, breathing difficulty, anemia, low immunity, allergies, and asthma. Similar health effects were reported from Nepal [101], India [87], Mexico, [69], Pakistan [52,73,84], Indonesia [88], Liberia [50], and Chile [102]. In Mumbai, for example, open incineration emits about 22,000 tons of pollutants annually [56]. Mongkolchaiarunya [103] reported air pollution and odors from burning waste in Thailand. In addition, plastic waste incineration produces hydrochloric acid and dioxins in quantities that are detrimental to human health and may cause allergies, hemoglobin deficiency, and cancer [95,104]. In addition, smoke from open incineration and dumpsites is a significant contributor to air pollution even for persons staying far from dumpsites.

Composting is a biological method of waste disposal that entails the decomposing or breaking down of organic wastes into simpler forms by naturally occurring microorganisms, such as bacteria and fungi. However, despite its advantage of reducing organic waste by at least half and using compost in agriculture, the composting method has much higher CO2 emissions than other disposal approaches. In Korea, for example, composting has the highest environmental impact than incineration and anaerobic digestion methods [105]. The authors found that the environmental impact of composting was found to be 2.4 times higher than that of incineration [105]. Some reviews linked composting with several health issues, including congested nose, sore throat and dry cough, bronchial asthma, allergic rhinitis, and extrinsic allergic alveolitis [36,106].