Umeå University's logo

Around one-fourth of the global population lacks access to clean fuels and technologies for cooking, most of them living in low- and middle-income countries. Reliance on rudimentary and inefficient biomass cookstoves results in high pollutant concentrations that adversely affect the health of those exposed to indoor air pollution, the environment, and the climate. In this study, we systematically reviewed the literature on aerosol and particle properties from biomass cookstoves of relevance to health, climate and the environment. We identified 187 articles reporting aerosol characterization (i.e. particulate mass or number concentrations, or particle size distributions). Of these, 82 presented detailed particle characterization (e.g. chemical composition), thus selected for further analysis. Articles were classified based on the reported particle properties and the study type and location, which allowed mapping research efforts to date and identifying major knowledge gaps. Most reviewed studies (39 articles) on particle properties reported particulate organic and elemental carbon composition. Despite considerable variability, the EC/TC ratio generally varied in the range of 0.1-0.4 for all cookstove technologies, indicating that organic carbon is the dominating PM fraction in biomass cookstove emissions. Findings from this systematic review highlight the need for further studies on particle properties from biomass cookstoves that use a multidimensional approach simultaneously combining several properties and different cookstove-fuel combinations. We also assessed the policy landscape, including the three main global policies concerning biomass cookstove emissions, and evaluated whether those policies included the state of the knowledge on particle properties and their adverse effects on human health, climate, and the environment. We finally identify key aspects that future policies should integrate, and critical knowledge gaps that must be filled to advance the overall development of the field. Notable was that field studies consistently report particle emission factors (PM_2.5) higher than the ones determined under laboratory conditions, for example, an average of 8.9 g/kg_fuel (field) compared to 5.2 g/kg_fuel (lab) for traditional cookstoves and 4.0 g/kg_fuel (field) compared to 1.3 g/kg_fuel (lab) for advanced cookstoves. Cookstove manufacturers, practitioners, policymakers, and society in general will benefit from a solid knowledge base regarding particle properties from biomass cookstoves and their related adverse effects on human health, climate, and the environment.

Globally, 3 billion people rely on solid biomass fuel for their everyday cooking, most often using inefficient cooking practices, leading to high exposure levels of household air pollution. This is subsequently associated with negative health and climate impact. Further, the inefficient use of biomass fuels applies pressure on natural forests, resulting in deforestation, loss of biodiversity, and soil degradation. Improved cookstove technologies and biomass fuels are being promoted to mitigate these issues. However, limited knowledge exists about how the interaction between stove technology and new fuels affects the physical and chemical properties of particulate emissions. In this study, the emission performance of four cookstove technologies in combination with five fuels was evaluated in a laboratory setup, applying a modified water boiling test with a hood dilution system for flue gas sampling. Filter sampling was applied to determine the emissions of fine particulate matter (PM₁) and for subsequent analysis of polycyclic aromatic compounds (PAC), organic- and elemental carbon, and inorganic composition. Particle mass size distribution was determined by using a 13-stage low-pressure cascade impactor. Online instruments were used to determine gaseous emissions (e.g., CO, CH₄, and BTX) as well as particle number size distribution. The results show that both the stove design and fuel properties influence the total emissions as well as the physiochemical PM characteristics. It was further seen that the impact of fuel on the PM properties did not translate linearly among the different stove technologies. This implies that each stove should be tested with various fuels to determine both the total emissions and fuel suitability.

Background: Exposure to standard petrodiesel exhaust is linked to adverse health effects. Moreover, there is a mounting request to replace fossil-based fuels with renewable and sustainable alternatives and, therefore, rapeseed methyl ester (RME) and other biofuels have been introduced. However, recent toxicological research has indicated that biodiesel exhaust may also induce adverse health-related events.

Aim: To determine whether exposure to 100% RME biodiesel (BD100) exhaust would cause an acute airway neutrophilic recruitment in humans.

Methods: Fourteen healthy subjects underwent exposure to diluted BD100 exhaust and filtered air for 1-h, in a blinded, random fashion. Bronchoscopy with endobronchial mucosal biopsies, bronchial wash (BW) and bronchoalveolar lavage (BAL) was performed six hours after exposure. Differential cell counts and inflammatory markers were determined in the supernatant and biopsies were stained immunohistochemically.

Results: Compared with filtered air, BD100 exhaust exposure increased bronchial mucosal endothelial P-selectin adhesion molecule expression, as well as neutrophil, mast cell and CD68 + macrophage numbers. An increased influx of neutrophils and machrophages was also seen in BW.

Conclusion: Exposure to biodiesel exhaust was associated with an acute airway inflammation that appeared similar to preceding petrodiesel exposure studies. The present findings, together with the recently reported adverse cardiovascular effects after similar biodiesel exposure, indicate that biodiesel is not free of toxicity and may affect human health.

Most people in rural sub-Saharan Africa lack access to electricity and rely on traditional, inefficient, and polluting cooking solutions that have adverse impacts on both human health and the environment. Here, we propose a novel integrated agroforestry-bioenergy system that combines sustainable biomass production in sequential agroforestry systems with biomass-based cleaner cooking solutions and rural electricity production in small-scale combined heat and power plants and estimate the biophysical system outcomes. Despite conservative assumptions, we demonstrate that on-farm biomass production can cover the household’s fuelwood demand for cooking and still generate a surplus of woody biomass for electricity production via gasification. Agroforestry and biochar soil amendments should increase agricultural productivity and food security. In addition to enhanced energy security, the proposed system should also contribute to improving cooking conditions and health, enhancing soil fertility and food security, climate change mitigation, gender equality, and rural poverty reduction.

In urban areas, inhalation of fine particles from combustion sources such as diesel engines causes adverse health effects. For toxicity testing, a substantial amount of particulate matter (PM) is needed. Conventional sampling involves collection of PM onto substrates by filtration or inertial impaction. A major drawback to those methodologies is that the extraction process can modify the collected particles and alter their chemical composition. Moreover, prior to toxicity testing, PM samples need to be resuspended, which can alter the PM sample even further. Lastly, the choice of the resuspension medium may also impact the detected toxicological responses. In this study, we compared the toxicity profile of PM obtained from two alternative sampling systems, using in vitro toxicity assays. One system makes use of condensational growth before collection in water in an impinger – BioSampler (CG-BioSampler), and the other, a Dekati® Gravimetric Impactor (DGI), is based on inertial impaction. In addition, various methods for resuspension of DGI collected PM were compared. Tested endpoints included cytotoxicity, formation of cellular reactive oxygen species, and genotoxicity. The alternative collection and suspension methods affected different toxicological endpoints. The water/dimethyl sulfoxide mixture and cell culture medium resuspended particles, along with the CG-BioSampler sample, produced the strongest responses. The water resuspended sample from the DGI appeared least toxic. CG-BioSampler collected PM caused a clear increased response in apoptotic cell death. We conclude that the CG-BioSampler PM sampler is a promising alternative to inertial impaction sampling.

The use of alternative diesel fuels has increased due to the demand for renewable energy sources. There is limited knowledge regarding the potential health effects caused by exhaust emissions from biodiesel- and renewable diesel-fueled engines. This study investigates the toxic effects of particulate matter (PM) emissions from a diesel engine powered by conventional petroleum diesel fuel (SD10) and two biodiesel and renewable diesel fuels in vitro. The fuels used were rapeseed methyl ester (RME), soy methyl ester (SME), and Hydrogenated Vegetable Oil (HVO), either pure or as 50% blends with SD10. Additionally, a 5% RME blend was also used. The highest concentration of polycyclic aromatic hydrocarbon emissions and elemental carbon (EC) was found in conventional diesel and the 5% RME blend. HVO PM samples also exhibited a high amount of EC. A dose-dependent genotoxic response was detected with PM from SD10, pure SME, and RME as well as their blends. Reactive oxygen species levels were several times higher in cells exposed to PM from SD10, pure HVO, and especially the 5% RME blend. Apoptotic cell death was observed in cells exposed to PM from SD10, 5% RME blend, the 50% SME blend, and HVO samples. In conclusion, all diesel PM samples, including biodiesel and renewable diesel fuels, exhibited toxicity.

Biodiesel is considered to be a sustainable alternative for fossil fuels such as petroleum-based diesel. However, we still lack knowledge about the impact of biodiesel emissions on humans, as airways and lungs are the primary target organs of inhaled toxicants. This study investigated the effect of exhaust particles from well-characterized rapeseed methyl ester (RME) biodiesel exhaust particles (BDEP) and petro-diesel exhaust particles (DEP) on primary bronchial epithelial cells (PBEC) and macrophages (MQ). The advanced multicellular physiologically relevant bronchial mucosa models were developed using human primary bronchial epithelial cells (PBEC) cultured at air–liquid interface (ALI) in the presence or absence of THP-1 cell-derived macrophages (MQ). The experimental set-up used for BDEP and DEP exposures (18 µg/cm2 and 36 µg/cm2) as well as the corresponding control exposures were PBEC-ALI, MQ-ALI, and PBEC co-cultured with MQ (PBEC-ALI/MQ). Following exposure to both BDEP and DEP, reactive oxygen species as well as the stress protein heat shock protein 60 were upregulated in PBEC-ALI and MQ-ALI. Expression of both pro-inflammatory (M1: CD86) and repair (M2: CD206) macrophage polarization markers was increased in MQ-ALI after both BDEP and DEP exposures. Phagocytosis activity of MQ and the phagocytosis receptors CD35 and CD64 were downregulated, whereas CD36 was upregulated in MQ-ALI. Increased transcript and secreted protein levels of CXCL8, as well as IL-6 and TNF-α, were detected following both BDEP and DEP exposure at both doses in PBEC-ALI. Furthermore, the cyclooxygenase-2 (COX-2) pathway, COX-2-mediated histone phosphorylation and DNA damage were all increased in PBEC-ALI following exposure to both doses of BDEP and DEP. Valdecoxib, a COX-2 inhibitor, reduced the level of prostaglandin E2, histone phosphorylation, and DNA damage in PBEC-ALI following exposure to both concentrations of BDEP and DEP. Using physiologically relevant multicellular human lung mucosa models with human primary bronchial epithelial cells and macrophages, we found BDEP and DEP to induce comparable levels of oxidative stress, inflammatory response, and impairment of phagocytosis. The use of a renewable carbon-neutral biodiesel fuel does not appear to be more favorable than conventional petroleum-based alternative, as regards of its potential for adverse health effects.

Background: Exposure to wood smoke has been shown to contribute to adverse respiratory health effects including airway infections, but the underlying mechanisms are unclear. A preceding study failed to confirm any acute inflammation or cell influx in bronchial wash (BW) or bronchoalveolar lavage (BAL) 24 h after wood smoke exposure but showed unexpected reductions in leukocyte numbers. The present study was performed to investigate responses at an earlier phase, regarding potential development of acute inflammation, as well as indications of cytotoxicity.

Methods: In a double-blind, randomised crossover study, 14 healthy participants were exposed for 2 h to filtered air and diluted wood smoke from incomplete wood log combustion in a common wood stove with a mean particulate matter concentration of 409 µg/m3. Bronchoscopy with BW and BAL was performed 6 h after exposure. Differential cell counts, assessment of DNA-damage and ex vivo analysis of phagocytic function of phagocytosing BAL cells were performed. Wood smoke particles were also collected for in vitro toxicological analyses using bronchial epithelial cells (BEAS-2B) and alveolar type II-like cells (A549).

Results: Exposure to wood smoke increased BAL lactate dehydrogenase (LDH) (p = 0.04) and reduced the ex vivo alveolar macrophage phagocytic capacity (p = 0.03) and viability (p = 0.02) vs. filtered air. BAL eosinophil numbers were increased after wood smoke (p = 0.02), while other cell types were unaffected in BW and BAL. In vitro exposure to wood smoke particles confirmed increased DNA-damage, decreased metabolic activity and cell cycle disturbances.

Conclusions: Exposure to wood smoke from incomplete combustion did not induce any acute airway inflammatory cell influx at 6 h, apart from eosinophils. However, there were indications of a cytotoxic reaction with increased LDH, reduced cell viability and impaired alveolar macrophage phagocytic capacity. These findings are in accordance with earlier bronchoscopy findings at 24 h and may provide evidence for the increased susceptibility to infections by biomass smoke exposure, reported in population-based studies.

Adequate treatment of wastewater to remove micropollutants constitutes a major concern globally. Despite this, large volumes of untreated wastewater are released into the environment, mainly due to the cost involved. Biochars have been suggested to have the potential to remove pharmaceuticals and personal care products (PPCP) from wastewater, but, adsorption potential needs to be investigated further. Production of biochars should also preferably be sustainable and based on low-cost materials. This study investigated the ability of nine biochars produced in three cookstoves and from three feedstocks. All biochars were characterized and then applied in adsorption experiments, based on authentic hospital effluent. Our analytical method included 32 pharmaceuticals and personal care products, and 28 of these were detected and quantified in hospital wastewater effluent samples. Some PPCP were present in relatively high concentrations (more than 24 µg/L). Adsorption experiments showed that the biochars used in the investigation had average removal rates (RR) ranging from 14.2% to 65.5%. Removal rates also varied between and within cookstoves and feedstock. Although cookstove biochars with a low surface area in this study generally showed lower removal rates, results from surface characterization were not detailed enough to correlate the physicochemical properties of the pollutants with the adsorption. Further characterizations are therefore needed to point out the most important parameters involved in PPCP adsorption on cookstove biochars.