In vitro toxicity of indoor and outdoor PM10 from residential wood combustion

Cytotoxicity and Epithelial Barrier Toxicity of Fine Particles from Residential Biomass Pellet Burning

Rising environmental concerns associated with the domestic use of solid biofuels have driven the search for clean energy alternatives. This study investigated the in vitro toxicological characteristics of PM2.5 emissions from residential biomass pellet burning using the A549 epithelial cell line. The potential of modern pellet applications to reduce PM2.5 emissions was evaluated by considering both mass reduction and toxicity modification. PM2.5 emissions from raw and pelletized biomass combustion reduced cell viability, indicative of acute toxicity, and also protein expression associated with epithelial barrier integrity, implying further systemic toxicity, potentially via an oxidative stress mechanism. Toxicity varied between PM2.5 emissions from raw biomass and pellets, with pelletized straw and wood inducing cytotoxicity by factors of 0.54 and 1.30, and causing epithelial barrier damage by factors of 1.76 and 2.08, respectively, compared to their raw counterparts. Factoring in both mass reduction and toxicity modifications, PM2.5 emissions from pelletized straw and wood dropped to 1.83 and 5.07 g/kg, respectively, from 30.1 to 9.32 g/kg for raw biomass combustion. This study underscores the effectiveness of pelletized biomass, particularly straw pellets, as a sustainable alternative to traditional biofuels and highlights the necessity of considering changes in toxicity when assessing the potential of clean fuels to mitigate emissions of the PM2.5 complex.

Criteria, Greenhouse Gas, and Hazardous Air Pollutant Emissions Factors from Residential Cordwood and Pellet Stoves Using an Integrated Duty Cycle Test Protocol

Air pollution from residential wood heating (RWH) presents challenges at the intersection of climate and public health. With a revised National Ambient Air Quality Standard (NAAQS, at 9 μg/m3) for particulate matter (PM) in the United States (U.S.), the Environmental Protection Agency (EPA) will likely classify new non-attainment areas due primarily to emissions from RWH. Agencies will use emissions factors (EFs) to develop attainment strategies. Many will rely on EPA modeling platforms based on data from the National Emissions Inventory (NEI). The NEI uses RWH EFs based on data from mid-1990's in-situ studies and a speciation profile from a 2001 study of fireplace emissions. The NEI does not include greenhouse gas (GHG) emissions for this sector, which plays a key role when assessing climate reduction strategies for the buildings sector. Here, we tested seven wood stoves to determine EFs, representing various vintages and control technologies, using a novel test method that reflects in-use operational settings called the Integrated Duty Cycle. The study measured multiple pollutants concurrently: criteria pollutants (particulate matter [PM], CO, and NOx), nonmethane total hydrocarbons (NMTHCs), GHGs, black carbon (eBC), brown carbon (BrC), and multiple hazardous air pollutants (HAPs). We found no significant difference in PM EFs between uncertified and non-catalytic stove technologies. RWH EF results from this study exceeded 2020 NEI RWH EFs for NMTHC and multiple HAPs. Applying our study's EFs to the 2020 NEI suggests that RWH, compared to all other sources, ranks as the 2nd largest source category of formaldehyde; the 3rd largest of benzene, 1,3-butadiene, and acrolein; and the 4th largest of Pb emissions. RWH also emits more methane compared to natural gas or oil residential heating, raising questions about substitution of wood as a climate neutral heating fuel. However, compared to uncertified stoves, pellet stove EFs (except toxic metals) were significantly lower (p < 0.01). In summary, RWH appears to be an underestimated source of PM (non-catalytic technology), methane, NMTHC, toxic metals, and other HAPs, which has important implications for climate and public health policy in the U.S. and globally.

Determining the toxicological effects of indoor air pollution on both a healthy and an inflammatory-comprised model of the alveolar epithelial barrier in vitro

Exposure to indoor air pollutants (IAP) has increased recently, with people spending more time indoors (i.e. homes, offices, schools and transportation). Increased exposures of IAP on a healthy population are poorly understood, and those with allergic respiratory conditions even less so. The objective of this study, therefore, was to implement a well-characterised in vitro model of the human alveolar epithelial barrier (A549 + PMA differentiated THP-1 incubated with and without IL-13, IL-5 and IL-4) to determine the effects of a standardised indoor particulate (NIST 2583) on both a healthy lung model and one modelling a type-II (stimulated with IL-13, IL-5 and IL-4) inflammatory response (such as asthma).Using concentrations from the literature, and an environmentally appropriate exposure we investigated 232, 464 and 608ng/cm2 of NIST 2583 respectively. Membrane integrity (blue dextran), viability (trypan blue), genotoxicity (micronucleus (Mn) assay) and (pro-)/(anti-)inflammatory effects (IL-6, IL-8, IL-33, IL-10) were then assessed 24 h post exposure to both models. Models were exposed using a physiologically relevant aerosolisation method (VitroCell Cloud 12 exposure system).No changes in Mn frequency or membrane integrity in either model were noted when exposed to any of the tested concentrations of NIST 2583. A significant decrease (p < 0.05) in cell viability at the highest concentration was observed in the healthy model. Whilst cell viability in the "inflamed" model was decreased at the lower concentrations (significantly (p < 0.05) after 464ng/cm2). A significant reduction (p < 0.05) in IL-10 and a significant increase in IL-33 was seen after 24 h exposure to NIST 2583 (464, 608ng/cm2) in the "inflamed" model.Collectively, the results indicate the potential for IAP to cause the onset of a type II response as well as exacerbating pre-existing allergic conditions. Furthermore, the data imposes the importance of considering unhealthy individuals when investigating the potential health effects of IAP. It also highlights that even in a healthy population these particles have the potential to induce this type II response and initiate an immune response following exposure to IAP.

Indoor PM from residential coal combustion: Levels, chemical composition, and toxicity

Indoor air quality is crucial for human health due to the significant time people spend at home, and it is mainly affected by internal sources such as solid fuel combustion for heating. This study investigated the indoor air quality and health implications associated with residential coal burning covering gaseous pollutants (CO, CO2 and total volatile organic compounds), particulate matter, and toxicity. The PM10 chemical composition was obtained by ICP-MS/OES (elements), ion chromatography (water-soluble ions) and thermal-optical analysis (organic and elemental carbon). During coal combustion, PM10 levels were higher (up to 8.8 times) than background levels and the indoor-to-outdoor ratios were, on average, greater than unity, confirming the existence of a significant indoor source. The chemical characterisation of PM10 revealed increased concentrations of organic carbon and elemental carbon during coal combustion as well as arsenic, cadmium and lead. Carcinogenic risks associated with exposure to arsenic exceeded safety thresholds. Indoor air quality fluctuated during the study, with varying toxicity levels assessed using the Aliivibrio fischeri bioluminescence inhibition assay. These findings underscore the importance of mitigating indoor air pollution associated with coal burning and highlight the potential health risks from long-term exposure. Effective interventions are needed to improve indoor air quality and reduce health risks in coal-burning households.

Biological Impact of Organic Extracts from Urban-Air Particulate Matter: An In Vitro Study of Cytotoxic and Metabolic Effects in Lung Cells

Atmospheric particulate matter (PM) with diameters below 10 µm (PM10) may enter the lungs through inhalation and are linked to various negative health consequences. Emergent evidence emphasizes the significance of cell metabolism as a sensitive target of PM exposure. However, the current understanding of the relationship between PM composition, conventional toxicity measures, and the rewiring of intracellular metabolic processes remains limited. In this work, PM10 sampled at a residential area (urban background, UB) and a traffic-impacted location (roadside, RS) of a Portuguese city was comprehensively characterized in terms of polycyclic aromatic hydrocarbons and plasticizers. Epithelial lung cells (A549) were then exposed for 72 h to PM10 organic extracts and different biological outcomes were assessed. UB and RS PM10 extracts dose-dependently decreased cell viability, induced reactive oxygen species (ROS), decreased mitochondrial membrane potential, caused cell cycle arrest at the G0/G1 phase, and modulated the intracellular metabolic profile. Interestingly, the RS sample, richer in particularly toxic PAHs and plasticizers, had a greater metabolic impact than the UB extract. Changes comprised significant increases in glutathione, reflecting activation of antioxidant defences to counterbalance ROS production, together with increases in lactate, NAD+, and ATP, which suggest stimulation of glycolytic energy production, possibly to compensate for reduced mitochondrial activity. Furthermore, a number of other metabolic variations hinted at changes in membrane turnover and TCA cycle dynamics, which represent novel clues on potential PM10 biological effects.

Toxicological and Mutagenic Effects of Particulate Matter from Domestic Activities

People spend most of their time indoors, particularly in their houses where daily activities are carried out, enhancing particulate matter (PM) emissions with consequent adverse health impacts. This study intended to appraise the toxicological and mutagenic responses of particulate matter with a diameter less than 10 μm (PM₁₀) released from cooking and ironing activities under different conditions. The cytotoxicity of the PM₁₀ total organic extracts was tested in A549 cells using the WST-8 and the lactate dehydrogenase (LDH) assays, while the interference in cell cycle dynamics and reactive oxygen species (ROS) production was analysed by flow cytometry. The S. typhimurium TA98 and TA100 Ames tester strains with and without metabolic activation were employed to determine the mutagenic potential of the PM₁₀-bound polycyclic aromatic hydrocarbons (PAHs). PM₁₀ organic extracts decreased the metabolic activity of A549 cells; however, no effects in the LDH release were observed. An increase in ROS levels was registered only for cells treated with PM₁₀ at IC₂₀ from steam ironing, in low ventilation conditions, while cell cycle dynamics was only affected by exposure to PM₁₀ at IC₂₀ from frying horse mackerel and grilling boneless pork strips. No mutagenic effects were observed for all the PM₁₀-bound PAHs samples.

Ecotoxicity of PM10 emissions generated during controlled burning of waste PET

Domestic waste is often burned either as fuel for winter heating or in open areas, simply to get rid of waste. Polyethylene terephthalate (PET) represents an important component of plastics usage as well as of plastic waste produced. While most studies attempt to characterize environmental risk of open burning of mixed household waste, present work evaluates chemical and ecotoxicological parameters of particulate matter (PM) produced during controlled burning of PET samples. In the PM₁₀ samples, polycyclic aromatic hydrocarbon and heavy metal concentrations were measured, ecotoxicity was evaluated using the kinetic Vibrio fischeri bioassay. Both chemical composition and ecotoxicity of the 4 samples showed significant correlation, regardless of the colored or colorless nature of the original PET sample. Antimony was found in considerable concentrations, in the range of 6.93-16.9 mg/kg. PAHs profiles of the samples were very similar, showing the dominance of 4-and 5-ring PAHs, including carcinogenic benzo(a)pyrene.

Physicochemical and toxicological properties of wood smoke particulate matter as a function of wood species and combustion condition

Wood burning is a major source of ambient particulate matter (PM) and has been epidemiologically linked to adverse pulmonary health effects, however the impact of fuel and burning conditions on PM properties has not been investigated systematically. Here, we employed our recently developed integrated methodology to characterize the physicochemical and biological properties of emitted PM as a function of three common hardwoods (oak, cherry, mesquite) and three representative combustion conditions (flaming, smoldering, incomplete). Differences in PM and off-gas emissions (aerosol number/mass concentrations; carbon monoxide; volatile organic compounds) as well as inorganic elemental composition and organic carbon functional content of PM0.1 were noted between wood types and combustion conditions, although the combustion scenario exerted a stronger influence on the emission profile. More importantly, flaming combustion PM0.1 from all hardwoods significantly stimulated the promoter activity of Sterile Alpha Motif (SAM) pointed domain containing ETS (E-twenty-six) Transcription Factor (SPDEF) in human embryonic kidney 293 (HEK-293 T) cells, a biomarker for mucin gene expression associated with mucus production in pulmonary diseases. However, no bioactivity was observed for smoldering and incomplete combustion, which was likely driven by differences in the organic composition of PM0.1. Detailed chemical speciation of organic components of wood smoke is warranted to identify the individual compounds that drive specific biological responses.

Using low-cost sensors to assess real-time comfort and air quality patterns in indoor households

People spend most of their time in indoor environments without knowing about the air quality in these spaces. In this study, indoor low-cost sensors were used (for 5 months) to assess the comfort and air quality patterns in two indoor households. To strengthen the robustness of the considered approach and build confidence in the obtained comfort and indoor air quality (IAQ) levels, the sensor measurements were also compared against information from reference monitoring equipment; in which, high correlation coefficients were obtained (> 0.85) and also low errors (on average 22%). The IAQ results were strongly influenced by the residents' activity and behaviour, the outdoor weather conditions, and indoor/outdoor air pollution sources. Overall, the recommended values of temperature and relative humidity for the occupant's comfort in indoor environments were not fulfilled. The highest particulate matter (PM) levels were recorded at the weekend (on average +14% higher), while maximum CO₂ and CO levels were obtained on the weekdays (on average +9% higher). PM daily profiles followed the outdoor concentrations with the maximum levels at the end of the night and the lowest values in the early morning/mid-afternoon. The highest and lowest CO₂ concentrations were registered in the early morning (< 1536 ppm) and mid-afternoon (< 627 ppm), respectively, while the CO daily profiles showed a high impact of outdoor emissions, with the minimum concentrations up to 0.81 mg m^-3 (at 10 a.m. or 6 p.m.), and a maximum concentration of 1.87 mg m^-3 (at 10 p.m.). Real-time comfort conditions and IAQ levels are a powerful approach to providing fast decisions to minimise human exposure and prevent negative health impacts.

Heavy metal analysis in of indoor and outdoor dust extracts and cytotoxicity evaluation and inflammation factors on lung, gastric and skin cell lines

Dust particles (DPs) are one of the most important public health concerns in the urban environment. The presence of heavy metals (HMs) on the surface of DPs might increase the health risk of exposure to the DPs. Accordingly, The purpose of this study was to examine the content of HMs in the outdoor and indoor DPs in Neyshabur city and assess the cytotoxic effects of DPs exposure on lung, gastric, and skin cell lines. To this end, the city was divided into three areas, high-traffic, medium-traffic, and low-traffic (rural). The average concentration of the HMs in the indoor DPs were as follows, 655.5 μg g-1 for Zn, 114.6 μg g-1 for Cu, 77.7 μg g-1 for Cr, 108.6 μg g-1 for Ni, 52 μg g-1 for Pb, 12 μg g-1 for Co, and 3.3 μg g-1 for Cd, while the average concentration of Zn, Cu, Cr, Ni, Pb, Co, Cd in the outdoor DPs were 293.7 μg g-1, 200.6 μg g-1, 100.7 μg g-1, 68.4 μg g-1, 44.7 μg g-1, 18.6 μg g-1, 0.25 μg g-1, respectively. A higher concentration of HMs, as well as cytotoxicity, were revealed in the indoor samples compared to outdoor ones. The degree of cytotoxicity of DPs collected from high-traffic areas was higher than that of low and medium-traffic ones. In addition, treatment of AGS and L929 cells with indoor dust samples induced the expression level of inflammatory agents such as TNFα, IL6, and, CYP1A1 genes more than in outdoor dust samples (P < 0.05). Briefly, a higher level of HMs concentration and cytotoxicity effect on the given cell lines was observed in the samples taken from indoor environments and high-traffic areas.

Evaluation of flue gas emission factor and toxicity of the PM-bounded PAH from lab-scale waste combustion

Atmospheric particulate matter (PM) has a significant threat not only to human health but also to our environment. In Hungary, 54% of PM10 comes from residential combustion, which also includes the practice of household waste burning. Therefore, this work aims to investigate the quality of combustion through the flue gas concentrations (CO, CO₂, O₂) and to identify and evaluate the negative impacts of PM and PAHs generated during controlled lab-scale combustion of different mixed wastes (cardboard and glossy paper, polypropylene and polyethylene terephthalate, polyester and cotton). Mixed wastes were burnt in a lab-scale tubular furnace at different temperatures with 180 dm³/h air flow rate. Chemical analyses were coupled with ecotoxicological tests using the bioluminescent bacterium Vibrio fischeri. Ecotoxicity was expressed as toxic unit (TU) values, toxic equivalent factors (TEF) were also presented. During the combustion same amount of O₂ enters the reaction, but a different amount CO₂ is generated due to the C content of the sample. The waste with highest C-content related to the highest CO₂ emission. Increasing the combustion temperature produces more PM-bound PAHs, which remains the same composition in the case of plastic and textile groups. The TU of solid contaminants decreases with increasing combustion temperature and increases with the minerals which are left behind in the water from the solid contaminants.

Fabrication of a label-free electrochemical cell-based biosensor for toxicity assessment of thiram

Thiram has been widely used in agriculture and may invades the food chain, posing a threat to human health. In this research, a label-free electrochemical cell-based biosensor was presented for in vitro toxicity assessment of thiram. HepG2 cells were cultured on poly-l-lysine@gold nano-flowers functionalized indium tin oxide coated glass electrode (PLL@AuNFs/ITO) to serve as biorecognition elements. AuNFs were electrodeposited on ITO to provide an enlarged specific surface area and benefited the output signal amplification. PLL was selected as an effective biocompatible coating material to facilitate cell adhesion and proliferation, thereby realizing one-step recording of electrochemical signals from thiram-treated cells. With the aid of the differential pulse voltammetry method, the fabricated biosensor was applied to assess the cytotoxicity of thiram. Results showed that the cytotoxicity measured by the fabricated biosensor exhibited a linear relationship related to thiram concentration ranging from 5 to 50 μM with a detection limit of 2.23 μM. The IC₅₀ of thiram obtained by the biosensor was 29.5 μM, which was close to that of conventional MTT assay (30.8 μM). The effects of thiram on HepG2 cells were also investigated via SEM and flow cytometry. Meanwhile, the proposed biosensor was used to evaluate the toxicity of thiram in fruit samples. Results indicated that the toxicity of thiram cannot be ignored even at a low residual concentration in food (≤5 mg/kg). In conclusion, the developed sensor showed excellent sensitivity, stability, and reliability, which provided a great capacity for the convenient toxicity evaluation of thiram residue in food.

Development of an Integrated Platform to Assess the Physicochemical and Toxicological Properties of Wood Combustion Particulate Matter

Wood burning contributes to indoor and ambient particulate matter (PM) pollution and has been associated with increased morbidity and mortality. Here, we present an integrated methodology that allows to generate, sample, and characterize wood smoke derived from different moisture contents and representative combustion conditions using pine wood as a model. Flaming, smoldering, and incomplete combustion were assessed for low-moisture pine, whereas both low-moisture pine and high-moisture pine were investigated under flaming conditions. Real-time monitoring of carbon monoxide, volatile organic compounds, and aerosol number concentration/size in wood smoke was performed. The PM was size-fractionated, sampled, and characterized for elemental/organic carbon, organic functional groups, and inorganic elements. Bioactivity of PM was assessed by measuring the sterile alpha motif (SAM) pointed domain containing ETS (E-twenty-six) transcription factor (SPDEF) gene promoter activity in human embryonic kidney 293 (HEK-293T) cells, a biomarker for mucin gene expression. Findings showed that moisture content and combustion condition significantly affected the organic and inorganic elemental composition of PM0.1 as well as its bioactivity. Also, for a given moisture and combustion scenario, PM chemistry and bioactivity differed considerably with PM size. Importantly, PM0.1 from flaming combustion of low-moisture pine contained the highest abundance of the oxygenated saturated aliphatic functional group [H-C-O] and was also biologically most potent in stimulating SPDEF promoter activity, suggesting the role of organic compounds such as carbohydrates and sugar alcohols (that contain [H-C-O]) in driving mucus-related respiratory outcomes. Our platform enables further well-controlled parametric studies using a combination of in vitro and in vivo approaches to link wood burning parameters with acute and chronic inhalation health effects of wood smoke.

Indoor air pollution from solid fuel on children pneumonia in low- and middle-income countries: a systematic review and meta-analysis

An updated systematic review was conducted to assessing on the association between indoor air pollution caused by household energy consumption and childhood pneumonia in low- and middle-income countries. We performed a meta-analysis from the electronic databases of PubMed, Cochrane library, Web of Science, EMBASE. Studies were selected when they reported childhood pneumonia or ALRI in relation to indoor air pollution resulted from solid fuel. Studies must provide results on exposure prevalence of children aged below 5 years from Asia or Africa. We devoted ourselves to identifying randomized controlled experiments and observational epidemiological researches, which revealed the relation between household usage of solid fuel and childhood pneumonia. Among 1954 articles, 276 were reviewed thoroughly and 16 conduced to such a meta-analysis. It was found that there is a significant relationship between the solid fuel combustion and increasing risk of childhood pneumonia (OR = 1.66, 95%CI 1.36-2.02). The summary odds ratios from biomass use and mixed fuel use were, respectively, 1.86 (95%CI 1.15-3.02) and 1.58 (95%CI 1.38-1.81), with substantial between study heterogeneity (I² = 87.2% and 29.2%, respectively). According to the subgroup analysis along with the meta-regression analysis, the risk of using solid fuel in Asian regions is higher than that in African regions. Studies based on non-hospital participates (I² = 49.5%) may also a source of heterogeneity. We found that indoor air pollution generated by the usage of solid fuel might be a significant risk factor for pneumonia in children and suggested improving the indoor air quality by promoting cleaner fuel will be important in undeveloped countries.

Impact of different sources on the oxidative potential of ambient particulate matter PM10 in Riyadh, Saudi Arabia: A focus on dust emissions

In this study, we employed Principal Component Analysis (PCA) and Multi-Linear Regression (MLR) to identify the most significant sources contributing to the toxicity of PM10 in the city center of Riyadh. PM10 samples were collected using a medium-volume air sampler during cool (December 2019-March 2020) and warm (May 2020-August 2020) seasons, including dust and non-dust events. The collected filters were analyzed for their chemical components (i.e., water-soluble ions, metals, and trace elements) as well as oxidative potential and elemental and organic carbon (EC/OC) contents. Our measurements revealed comparable extrinsic oxidative potential (P-value = 0.30) during the warm (1.2 ± 0.1 nmol/min-m3) and cool (1.1 ± 0.1 nmol/min-m3) periods. Moreover, we observed higher extrinsic oxidative potential of PM10 samples collected during dust events (~30% increase) compared to non-dust samples. Our PCA-MLR analysis identified soil and resuspended dust, secondary aerosol (SA), local industrial activities and petroleum refineries, and traffic emissions as the four sources contributing to the ambient PM10 oxidative potential in central Riyadh. Soil and resuspended dust were the major source contributing to the oxidative potential of ambient PM10, accounting for 31% of the total oxidative potential. Secondary aerosols (SA) were the next important source of PM10 toxicity in the area as they contributed to about 20% of the PM10 oxidative potential. Results of this study revealed the major role of soil and resuspended road dust on PM10 toxicity and can be helpful in adopting targeted air quality policies to reduce the population exposure to PM10.