Impact of trash burning on air quality in Mexico City

Contribution of plastic solid components to volatile organic compounds formation during plastics combustion

The combustion of plastic waste releases volatile organic compounds (VOCs) that are harmful to human health. However, information on the micro-mechanisms of VOC formation remains lacking. Here, the study hypothesized and verified the relationship between VOC formation and solid component degradation during plastics combustion. The VOCs released during plastics combustion exhibit characteristics such as low carbon content (nc< 10), volatility (9 μg m-3 < log10C0 < 11 μg m-3), and medium oxidation degree (-1.5 < OSC¯ < -0.5). The dominant VOCs ketones/aldehydes/acids (33-43 %) may be attributed to the depolymerization of the polymer structure of plastics, the oxidation of C-O/CO groups, and the secondary cleavage of gaseous oxygen-containing macromolecules. The VOCs released from the combustion of polyethylene terephthalate (PET) and poly(butyleneadipate-co-terephthalate) (PBAT) contained more aromatics than polyethylene (PE) and polypropylene (PP). And the temperature response of aromatics released from PET and PBAT lagged other VOCs compared that of PP and PE. However, compared to biomass thermal conversion, combustion of plastics releases fewer aromatics and nitrogenous compounds. Collectively, this work shows that the formation mechanisms of VOCs contributed by the solid components during plastic combustion are similar for PET and PBAT due to their similar chemical structures. The proposed mechanism in this paper will provide insight into the control of contaminants during plastic combustion.

The crucial role of circular waste management systems in cutting waste leakage into aquatic environments

Waste leakage has become a major global concern owing to the negative impacts on aquatic ecosystems and human health. We combine spatial analysis with the Shared Socioeconomic Pathways to project future waste leakage under current conditions and develop mitigation strategies up to 2040. Here we show that the majority (70%) of potential leakage of municipal solid waste into aquatic environments occurs in China, South Asia, Africa, and India. We show the need for the adoption of active mitigation strategies, in particular circular waste management systems, that could stop waste from entering the aquatic ecosystems in the first place. However, even in a scenario representing a sustainable world in which technical, social, and financial barriers are overcome and public awareness and participation to rapidly increase waste collection rates, reduce, reuse and recycling waste exist, it would be impossible to entirely eliminate waste leakage before 2030, failing to meet the waste-related Sustainable Development Goals.

Household Air Pollution Interventions to Improve Health in Low- and Middle-Income Countries: An Official American Thoracic Society Research Statement

Background: An estimated 3 billion people, largely in low- and middle-income countries, rely on unclean fuels for cooking, heating, and lighting to meet household energy needs. The resulting exposure to household air pollution (HAP) is a leading cause of pneumonia, chronic lung disease, and other adverse health effects. In the last decade, randomized controlled trials of clean cooking interventions to reduce HAP have been conducted. We aim to provide guidance on how to interpret the findings of these trials and how they should inform policy makers and practitioners.Methods: We assembled a multidisciplinary working group of international researchers, public health practitioners, and policymakers with expertise in household air pollution from within academia, the American Thoracic Society, funders, nongovernmental organizations, and global organizations, including the World Bank and the World Health Organization. We performed a literature search, convened four sessions via web conference, and developed consensus conclusions and recommendations via the Delphi method.Results: The committee reached consensus on 14 conclusions and recommendations. Although some trials using cleaner-burning biomass stoves or cleaner-cooking fuels have reduced HAP exposure, the committee was divided (with 55% saying no and 45% saying yes) on whether the studied interventions improved measured health outcomes.Conclusions: HAP is associated with adverse health effects in observational studies. However, it remains unclear which household energy interventions reduce exposure, improve health, can be scaled, and are sustainable. Researchers should engage with policy makers and practitioners working to scale cleaner energy solutions to understand and address their information needs.

Wintertime Air Quality across the Kathmandu Valley, Nepal: Concentration, Composition, and Sources of Fine and Coarse Particulate Matter

The Kathmandu Valley in Nepal experiences poor air quality, especially in the dry winter season. In this study, we investigated the concentration, chemical composition, and sources of fine and coarse particulate matter (PM2.5, PM10, and PM10-2.5) at three sites within or near the Kathmandu Valley during the winter of 2018 as part of the second Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE 2). Daily PM2.5 concentrations were very high throughout the study period, ranging 72-149 μg m-3 at the urban Ratnapark site in Kathmandu, 88-161 μg m-3 at the suburban Lalitpur site, and 40-74 μg m-3 at rural Dhulikhel on the eastern rim of the Kathmandu Valley. Meanwhile, PM10 ranged 194-309, 174-377, and 64-131 μg m-3, respectively. At the Ratnapark site, crustal materials from resuspended soil contributed an average of 11% of PM2.5 and 34% of PM10. PM2.5 was largely comprised of organic carbon (OC, 28-30% by mass) and elemental carbon (EC, 10-14% by mass). As determined by chemical mass balance source apportionment modeling, major PM2.5 OC sources were garbage burning (15-21%), biomass burning (10-17%), and fossil fuel (14-26%). Secondary organic aerosol (SOA) contributions from aromatic volatile organic compounds (13-23% OC) were larger than those from isoprene (0.3-0.5%), monoterpenes (0.9-1.4%), and sesquiterpenes (3.6-4.4%). Nitro-monoaromatic compounds-of interest due to their light-absorbing properties and toxicity-indicate the presence of biomass burning-derived SOA. Knowledge of primary and secondary PM sources can facilitate air quality management in this region.

Plastic Burning Impacts on Atmospheric Fine Particulate Matter at Urban and Rural Sites in the USA and Bangladesh

To better understand the impact of plastic burning on atmospheric fine particulate matter (PM_2.5), we evaluated two methods for the quantification of 1,3,5-triphenylbenzene (TPB), a molecular tracer of plastic burning. Compared to traditional solvent-extraction gas chromatography mass spectrometry (GCMS) techniques, thermal-desorption (TD) GCMS provided higher throughput, lower limits of detection, more precise spike recoveries, a wider linear quantification range, and reduced solvent use. This method enabled quantification of TPB in fine particulate matter (PM_2.5) samples collected at rural and urban sites in the USA and Bangladesh. These analyses demonstrated a measurable impact of plastic burning at 5 of the 6 study locations, with the largest absolute and relative TPB concentrations occurring in Dhaka, Bangladesh, where plastic burning is expected to be a significant source of PM_2.5. Background-level contributions of plastic burning in the USA were estimated to be 0.004-0.03 μg m^-3 of PM_2.5 mass. Across the four sites in the USA, the lower estimate of plastic burning contributions to PM_2.5 ranged 0.04-0.8%, while the median estimate ranged 0.3-3% (save for Atlanta, Georgia, in the wintertime at 2-7%). The results demonstrate a consistent presence of plastic burning emissions in ambient PM_2.5 across urban and rural sites in the USA, with a relatively small impact in comparison to other anthropogenic combustion sources in most cases. Much higher TPB concentrations were observed in Dhaka, with estimated plastic burning impacts on PM_2.5 ranging from a lower estimate of 0.3-1.8 μg m^-3 (0.6-2% of PM_2.5) and the median estimate ranging 2-35 μg m^-3 (5-15% of PM_2.5). The methodological advances and new measurements presented herein help to assess the air quality impacts of burning plastic more broadly.

Compilation of a city-scale black carbon emission inventory: Challenges in developing countries based on a case study in Brazil

Black carbon (BC) inventories for cities are scarce, especially in developing countries, despite their importance to tackle climate change and local air pollution. Here, we draw on results from a case study in a Brazilian city to discuss the challenges of compiling a BC inventory for different activity sectors. We included traditionally inventoried sectors, such as industries and on-road transportation, other less reported sectors (food establishments and aviation), and open burning of household solid waste (HSW), typically found in developing countries. We present a machine-learning technique (Random Forest) as a novel approach to obtain HSW burning activity using a set of spatial predictors. The BC inventory was based on PM_2.5 emissions weighted by the fraction of PM_2.5 emitted as BC and developed for the year 2018. We also reported the disaggregated spatial PM_2.5 emissions for the same combustion sources, and documented the databases used for activity data and emission factors (EF). The total estimated BC and PM_2.5 emissions amounted to 57.88 and 234.75 tons, respectively, with on-road vehicle exhaust emissions and industrial combustion as the main BC sources (63 and 22%, respectively). For PM_2.5 emissions, on-road transportation (exhaust and non-exhaust) contributed 48%, followed by industrial combustion (21%) and food establishments (20%). Population density, number of vacant lots, and property tax values were identified as the most important features to predict the HSW fire activity. A comparison with other inventories revealed that the BC emission profile of Londrina is similar to the profile reported for Greater Mexico City, another Latin American city. Thus, the methodology used in this study could be extended to other cities with similar local BC sources. Finally, we highlight that the lack of local activity data, representative EF, and even methodology may undermine the development of reliable BC inventories, and intensive research should be conducted to characterize the emission sources.

Potential for future reductions of global GHG and air pollutants from circular waste management systems

The rapidly rising generation of municipal solid waste jeopardizes the environment and contributes to climate heating. Based on the Shared Socioeconomic Pathways, we here develop a global systematic approach for evaluating the potentials to reduce emissions of greenhouse gases and air pollutants from the implementation of circular municipal waste management systems. We contrast two sets of global scenarios until 2050, namely baseline and mitigation scenarios, and show that mitigation strategies in the sustainability-oriented scenario yields earlier, and major, co-benefits compared to scenarios in which inequalities are reduced but that are focused solely on technical solutions. The sustainability-oriented scenario leaves 386 Tg CO2eq/yr of GHG (CH4 and CO2) to be released while air pollutants from open burning can be eliminated, indicating that this source of ambient air pollution can be entirely eradicated before 2050.

Commodity plastic burning as a source of inhaled toxic aerosols

Commodity plastic is ubiquitous in daily life and commonly disposed of via unregulated burning, particularly in developing regions. We report here the much higher emission factors (13.1 ± 7.5 g/kg) and toxicities of inhalable aerosols emitted from the unregulated burning of plastic waste based on field measurements and cellular experiments, including oxidative stress and cytotoxic tests in A549 cells. Plastic foam burning emitted aerosols possesses the highest EFs (34.8 ± 4.5 g/kg) and toxicities, which are 4.2- to 13.4-fold and 1.1- to 2.7-fold higher than those emitted from the burning of other waste types. These quantified toxicities are mainly attributed to aerosols containing carbonaceous matter, especially persistent organic pollutants, including polycyclic aromatic hydrocarbons and dioxins, which originate from incomplete combustion processes. The aerosol emission amounts were estimated from the obtained experimental results. Approximately 70.2 million tons (29%) of plastic waste was burned without regulation worldwide in 2016, leading to 0.92 ± 0.53 million tons of toxic aerosols being released into the air, a majority of which occurred in developing regions. The results indicate improved combustion technology and control strategies are urgently needed in developing regions for discarded plastic -waste to mitigate toxic exposure risks and achieve sustainable development.

Dynamics of PM2.5 pollution in the vicinity of the old municipal solid waste dumpsite

The present study explored the effect of local meteorology on the dispersion of PM_2.5 from a 30-year open municipal solid waste (MSW) dumpsite in Chennai, India. The spatial monitoring was conducted in and around the dumpsite to understand the impacts of dumpsite activities on the nearby residential area. Results showed that dumpsite activities are responsible for deteriorating local air quality. The 24-h average PM_2.5 concentrations were 50, 43.7, and 34 µg m^-3 during stagnation, recirculation, and ventilation events, respectively. Spearman's correlation showed an inverse relationship between PM_2.5 and temperature; wind speed indicated dispersion of fine aerosols. The observed inverse relationship between PM_2.5 and relative humidity indicated the hygroscopic growth of fine aerosols in the study area. We used AERMOD to simulate the dispersion of 1-h, 8-h, and 24-h PM_2.5 emissions from open waste burning in the dumpsite. The 1-h, 8-h, and 24-h simulated results showed the maximum concentration of 247, 136, and 53.4 µg m^-3 in the dumpsite, and concentration levels ranged between 50-60, 30-50, and 10-20 µg m^-3 were observed in the nearby residential area. The AERMOD predictions indicated that open waste burning could be a significant contributor to high PM_2.5 concentration in an adjacent residential area of the dumpsite.

Garbage Burning in South Asia: How Important Is It to Regional Air Quality?

Increasing air pollution in South Asia has serious consequences for air quality and human/ecosystem health within the region. South Asia, including India and Nepal, suffers from severe air pollution, including high concentrations of aerosols, as well as gaseous pollutants. One of the often-neglected sources contributing to the regional air pollution is garbage burning. It is mostly related to numerous yet small, open, uncontrolled fires burning diverse fuels, making it difficult to quantify activity and emissions. In this study, we attempted to quantify the total emissions due to garbage burning and its contribution to regional air quality, using new observational data, a new inventory, and a regional chemical transport model. We implemented the newly available emission factors (EFs) from a recent field campaign, Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE), which took place in April 2015. Using a chemical transport model-Weather Research and Forecasting model coupled with Chemistry version 3.5 (WRF-Chem)-and three emission scenarios, we assessed the impact of open garbage burning emissions on regional air quality. Our results show that garbage burning emissions could increase PM_2.5 concentrations by nearly 30% in India and Nepal, and result in ∼300 000 premature deaths from chronic obstructive pulmonary disease in the two countries.

Understanding the emission pattern and source contribution of hazardous air pollutants from open burning of municipal solid waste in China

The open burning of municipal solid waste (MSW) is common in China. Therein, low-temperature anoxic combustion results in the emission of hazardous air pollutants. This study employed a dilution sampling system to conduct open burning testing on MSW samples from different functional urban areas. Additionally, modified combustion efficiency was used to distinguish smoldering and flaming combustion in two of the most common open burning practices in China: pile-up burning and barrel burning. The sampled pollutants included gaseous pollutants (e.g., CO₂, CO, SO₂, and NO_x) and fine particles (PM_2.5). This study also analyzed the carbonization compounds, 9 water-soluble ions, and 8 toxic heavy metals in PM_2.5. Emission factors of air pollutants from open burning of different MSW compositions and burning modes were determined. The composition of PM_2.5 from MSW open burning comprised average 43.9%, 22.5%, and 0.4% of organic carbon (OC), water-soluble ions, and toxic heavy metals (THMs), respectively. OC was found to be the primary component of PM_2.5. Based on localized emission factor database, the emissions and source contribution of open burning of MSW in China were quantified. The open burning of MSW can contribute averaged 8.7%, 16.7%, 3.8%, 1.3% of PM_2.5, OC, THMs, and gaseous air pollutants of reported emissions of anthropogenic sources, respectively. This work can complement current anthropogenic emission inventory and assist policy-making.

Exploring the Phenomenon of Zero Waste and Future Cities

The evolving phenomenon of zero waste encompasses the theory, practice, and learning of individuals, families, businesses, communities, and government organisations, responding to perceptions of crisis and failure around conventional waste management. The diverse and growing body of international zero waste experience, can be portrayed as both, an entirely new and alternative waste management paradigm, and or, interpreted as overlapping, extending, and synergetic with a general evolution towards more sustainable waste/resource management practices. Combining the terms zero and waste provokes creative, intellectual, and pragmatic tensions, which provide a contemporary axis for necessary debate and innovation in this sphere of resource management. This commentary draws on an interdisciplinary perspective and utilises some elements of the critique of zero waste, as a lens to examine and better understand this heterogeneous global community of practice. In particular, how the concept and implementation of a zero waste goal can increase community engagement and be a catalyst for the design and management of a more circular urban metabolism and hence, more adaptive, resilient, and sustainable future (zero waste) cities.

Estimating emissions from open burning of municipal solid waste in municipalities of Nepal

Open burning of municipal solid waste (MSW) is a poorly-characterized and frequently-underestimated source of air pollution in developing countries. This paper estimates the quantity of MSW that was burned in five erstwhile municipalities of the Kathmandu valley, Nepal. A household survey, a transect walk survey, an experiment to measure the fraction of waste that is combustible, a survey on fraction of population burning waste outside their houses, and a survey of the fraction of MSW burned at dump sites were performed in this study, whereas burning/oxidation efficiency, municipal populations, MSW generation rates, and emission factors were derived from the literature. The total mass of MSW burned during 2016 is estimated to be 7400 tons (i.e., 20 tons/day), which was of 3% of the total MSW generated in the valley municipalities that year. This exceeds Government estimates by a factor of three. Multiplying the burned MSW mass by emission factors, the air pollutant emissions are estimated as PM_2.5 55 tons (OC 42 tons and EC 1.4 tons), PM₁₀ 60 tons, BC 25 tons, CO₂ 11,900 tons, CH₄ 30 tons, SO₂ 5.0 tons, NO_x 19.2 tons, CO 630 tons, NMVOC 112 tons, and NH₃ 5.7 tons per year. Open burning of MSW can trigger health impacts such as acute and chronic respiratory disease, heart diseases, and allergic hypersensitivity, in addition to impacts on local climate. Improved waste-segregation practices at the source and waste-collection systems throughout the valley are needed to mitigate this pollution source and its effects.

Uncontrolled burning of solid waste by households in Mexico is a significant contributor to climate change in the country

Uncontrolled burning of municipal solid waste (MSW) is an important source of air pollution and is wide spread in many developing countries, but only limited data quantify the extent of domestic open burning of household waste. Here, we present some of the first field data to be reported on the uncontrolled domestic burning of waste. A representative community of Mexico (Huejutla de Reyes Municipality) was investigated and household surveys, interviews with waste operators and a waste characterisation analysis were completed to assess the extent of, and factors controlling, the open burning of waste. Waste collection provision to rural communities was very limited and, consequently 92% of households in rural areas reported that they disposed of waste by uncontrolled burning in backyards or unofficial dumps. Overall, 24% of the total MSW generated in the Municipality was disposed by uncontrolled burning. Urban and periurban areas received twice-weekly collections and the rate of uncontrolled burning was considerably smaller compared to rural households, corresponding to approximately 2% of total waste generation. Carbon equivalency calculations showed that burning waste in backyards represented approximately 6% of the total and 8.5% of fuel related CO₂Eq emissions by the municipality. Moreover, the equivalent carbon dioxide (CO₂Eq) from black carbon (BC) emitted by uncontrolled burning in backyards was over fifteen times larger compared to methane (CH₄) potentially released from equivalent amounts of combustible biodegradable waste disposal at the official dumpsite. An assessment of local respiratory health data showed the incidence of disease was higher in rural than in urban areas, when the opposite trend is typically observed in the international literature; given the high rate of burning activity found in rural areas we suggest that open burning of waste could be a major reason for the apparent poorer respiratory health status of the rural population and requires further investigation. The results emphasise the importance of including BC from uncontrolled burning of waste in international emission inventories of greenhouse gases and in the assessment of the health status of local communities in developing countries where this practice is prevalent.

Analysis of remotely sensed and surface data of aerosols and meteorology for the Mexico Megalopolis Area between 2003 and 2015

This paper presents an aerosol characterization study from 2003 to 2015 for the Mexico City Metropolitan Area using remotely sensed aerosol data, ground-based measurements, air mass trajectory modeling, aerosol chemical composition modeling, and reanalysis data for the broader Megalopolis of Central Mexico region. The most extensive biomass burning emissions occur between March and May concurrent with the highest aerosol optical depth, ultraviolet aerosol index, and surface particulate matter (PM) mass concentration values. A notable enhancement in coarse PM levels is observed during vehicular rush hour periods on weekdays versus weekends owing to nonengine-related emissions such as resuspended dust. Among wet deposition species measured, PM_2.5, PM₁₀, and PM_coarse (PM₁₀-PM_2.5) were best correlated with NH₄⁺, SO₄^2-, and Ca²⁺, suggesting that the latter three constituents are important components of the aerosol seeding raindrops that eventually deposit to the surface in the study region. Reductions in surface PM mass concentrations were observed in 2014-2015 owing to reduced regional biomass burning as compared to 2003-2013.

An emission processing system for air quality modelling in the Mexico City metropolitan area: Evaluation and comparison of the MOBILE6.2-Mexico and MOVES-Mexico traffic emissions

This article describes the High-Elective Resolution Modelling Emission System for Mexico (HERMES-Mex) model, an emission processing tool developed to transform the official Mexico City Metropolitan Area (MCMA) emission inventory into hourly, gridded (up to 1km²) and speciated emissions used to drive mesoscale air quality simulations with the Community Multi-scale Air Quality (CMAQ) model. The methods and ancillary information used for the spatial and temporal disaggregation and speciation of the emissions are presented and discussed. The resulting emission system is evaluated, and a case study on CO, NO₂, O₃, VOC and PM_2.5 concentrations is conducted to demonstrate its applicability. Moreover, resulting traffic emissions from the Mobile Source Emission Factor Model for Mexico (MOBILE6.2-Mexico) and the MOtor Vehicle Emission Simulator for Mexico (MOVES-Mexico) models are integrated in the tool to assess and compare their performance. NO_x and VOC total emissions modelled are reduced by 37% and 26% in the MCMA when replacing MOBILE6.2-Mexico for MOVES-Mexico traffic emissions. In terms of air quality, the system composed by the Weather Research and Forecasting model (WRF) coupled with the HERMES-Mex and CMAQ models properly reproduces the pollutant levels and patterns measured in the MCMA. The system's performance clearly improves in urban stations with a strong influence of traffic sources when applying MOVES-Mexico emissions. Despite reducing estimations of modelled precursor emissions, O₃ peak averages are increased in the MCMA core urban area (up to 30ppb) when using MOVES-Mexico mobile emissions due to its VOC-limited regime, while concentrations in the surrounding suburban/rural areas decrease or increase depending on the meteorological conditions of the day. The results obtained suggest that the HERMES-Mex model can be used to provide model-ready emissions for air quality modelling in the MCMA.

Exploring social and infrastructural factors affecting open burning of municipal solid waste (MSW) in Indian cities: A comparative case study of three neighborhoods of Delhi

Open municipal solid waste (MSW)-burning is a major source of particulate matter emissions in developing world cities. Despite a legal ban, MSW-burning is observed ubiquitously in Indian cities with little being known about the factors shaping it. This study seeks to uncover social and infrastructural factors that affect MSW-burning at the neighborhood level. We couple physical assessments of the infrastructure provision and the MSW-burning incidences in three different neighborhoods of varying socio-economic status in Delhi, with an accompanying study of the social actors (interviews of waste handlers and households) to explore the extent to which, and potential reasons why, MSW-burning occurs. The observed differences in MSW-burning incidences range from 130 km^-2 day^-1 in low-income to 30 km^-2 day^-1 in the high-income areas. However, two high-income areas neighborhoods with functional infrastructure service also showed statistical differences in MSW-burning incidences. Our interviews revealed that, while the waste handlers were aware of the health risks associated with MSW-burning, it was not a high priority in the context of the other difficulties they faced. The awareness of the legal ban on MSW-burning was low among both waste handlers and households. In addition to providing infrastructure for waste pickup, informal restrictions from residents and neighborhood associations can play a significant role in restricting MSW-burning at the neighborhood scale. A more efficient management of MSW requires a combined effort that involves interplay of both social and infrastructural systems.

Characterizing the Spatial and Temporal Patterns of Open Burning of Municipal Solid Waste (MSW) in Indian Cities

Open-burning of municipal solid waste (MSW) is a major source of PM emissions in developing world cities, but few studies have characterized this phenomenon at the city and intracity (neighborhood) scale relevant to human health impacts. This paper develops a consistent field method for measuring the spatial frequency of the incidence of MSW-burning and presents results in three neighborhoods of varying socioeconomic status (SES) in Delhi, India, observed in winter and summer over 2 years. Daily MSW-burning incidents ranged from 24 to 130/km2-day during winter and 5-87/km2-day during summer, with the highest intensity in low SES neighborhoods. Distinct seasonal and diurnal patterns are observed. The daily mass of MSW-burned was also estimated at 90-1170 kg/km2-day and 13-1100 kg/km2-day in highest to low SES neighborhoods, in winter and summer, respectively. The scaled-up estimate of total MSW-burned for Delhi city ranged from 190 to 246 tons/day, about 2%-3% of total generated MSW; morning-burning contributed >65% of the total. MSW composition varied systematically across neighborhoods and season. Agra had much higher MSW-burning (39-202 incidents/km2-day; 672-3485 kg/km2-day) in the summer. The field method thus captures differences in MSW-burning across cities, neighborhoods, diurnally and seasonally, important for more fine grained air pollution modeling, and for tracking/monitoring policy effectiveness on-ground.