Applicability of selected Brighton Collaboration case definitions in low-resource settings: A prospective hospital-based active surveillance in Addis Ababa, Ethiopia.

INTRODUCTION: Standardizing case definitions for priority vaccine safety conditions facilitates uniform evaluation and consolidation of data obtained from different settings. The Brighton Collaboration case definitions (BCCD) were created to support this harmonization and enable classification from level 1 (most certain) to level 5 (not a case) of certainty. Assessing the performance of BCCD in practice is critical, particularly in resource-limited settings, where many new vaccines may be introduced without prior monitoring in high-income countries. We assessed the performance of BCCD in Addis Ababa, Ethiopia, as applicable to COVID-19 and other vaccines. METHODS: Active surveillance was conducted at Tikur Anbessa Specialized Hospital, the largest referral hospital in Ethiopia. During June 1, 2022-May 31, 2023, three trained physicians prospectively identified patients eligible for COVID-19 vaccination (regardless of vaccine receipt) who presented with one or more of eleven pre-specified adverse events of special interest (AESI) from the emergency department and inpatient wards. Standardized data collection forms were used to capture patient information and assign level of certainty (LOC), regardless of vaccination status for COVID-19. We conducted descriptive analysis to characterize cases and the LOCs reached for each AESI. RESULTS: We detected 203 AESI cases. The most detected conditions were thrombosis and thromboembolism (n = 100, 49 %) and generalized convulsions (n = 38, 19 %). Ninety-six percent of the cases were confirmed at levels 1-3 (n = 187) or level 5 (n = 9) LOC. Non-classifiable (level 4) cases were observed for pericarditis (n = 2), encephalitis (n = 2), myelitis (n = 2), and generalized convulsion (n = 1). CONCLUSION: The BCCD were successfully applied in > 95 % of cases in a large referral hospital in Ethiopia, with generalized convulsion, pericarditis, and encephalomyelitis as the exceptions. We recommend further evaluation in other low-resource settings, particularly in rural or non-referral hospitals, to gain additional insights into performance of these definitions for revision or adaptation, as needed.

Residual hydrocarbons in long-term contaminated soils: implications to risk-based management.

Petroleum hydrocarbon (PHC) contamination is a widespread and severe environmental issue affecting many countries' resource sectors. PHCs are mixtures of hydrocarbon compounds with varying molar masses that naturally attenuate at different rates. Lighter fractions attenuate first, followed by medium-molar-mass constituents, while larger molecules remain for longer periods. This results in significant regulatory challenges concerning residual hydrocarbons in long-term contaminated soils. This study examined the potential risks associated with residual PHC and its implications for risk-based management of heavily contaminated soils (23,000-26,000 mg PHC/kg). Ecotoxicological properties, such as seedling emergence and growth of two native plant species-small Flinders grass (Iseilema membranaceum) and ruby saltbush (Enchylaena tomentosa)-and earthworm survival tests in PHC-contaminated soils, were assessed. Additionally, the effects of aging on the attenuation of PHC in contaminated soils were evaluated. Toxicity responses of plant growth parameters were determined as no-observed-effect concentrations: 75%-100% for seedling emergence, < 25%-75% for plant shoot height, and 75%-100% for earthworm survival. After 42 weeks of aging, the total PHC levels in weathered soils decreased by 14% to 30% and by 67% in diesel-spiked soil due to natural attenuation. Dehydrogenase enzyme activity in soils increased during the initial aging period. Furthermore, a clear shift of bacterial communities was observed in the soils following aging, including enrichment of PHC-resistant and -utilizing bacteria-for example, Nocardia sp. This study underscores the potential of natural attenuation for eco-friendly and cost-effective soil management, underlining that its success depends on site-specific factors like water content and nutrient availability. Therefore, we recommend detailed soil assessments to evaluate these conditions prior to adopting a risk-based management approach.

Two-dimensional chlorinated vapour intrusion model involving advective transport of vapours with a highly permeable granular layer in the vadose zone serving as the preferential pathway.

Vapour intrusion (VI) is the process through which volatile organic compounds migrate from the subsurface source to the soil predominantly by diffusion, entering the overlying buildings through joints, cracks or other openings. This activity poses potentially serious health hazards for the occupants. Because of these health risks, recommendations for site closure are often made by quantifying the VI risks using mathematical models known as 'vapour intrusion models' (VIM). Most of these VIMs seem to overlook the role of preferred pathways like utility lines, high conductivity zones of soil or rocks, etc., which act as the path of least resistance for vapour transport thereby increasing vapour intrusion risks. This study presents a two-dimensional (2-D) chlorinated vapour intrusion (CVI) model which seeks to estimate the source-to-indoor air concentration attenuation. It takes into account the effects of a highly permeable utility line embedment as a preferential pathway. The transport of 2-D soil gas is described using the finite difference method where advection serves as the dominant transport mechanism in the preferential pathway layer, while diffusion applies to the rest of the vadose zone. The model returned results comparable with other models for the same input parameters, and was found to closely replicate the results of 3-D models. The simulations indicate that the presence of highly permeable utility line embedment and backfill layers do trigger a higher indoor air concentration compared to a no preferential pathway scenario.

Chemicals of concern in construction and demolition waste fine residues: A systematic literature review.

Despite the increasing use of chemical additives in construction and their potential threat to the environment and human health, many C&DW studies lack a comprehensive view of chemicals of concern (COC) in C&DW. This study systematically reviewed published studies from 2010 to August 2021 using a keyword search methodology to explore COC in C&DW fine residues based on 73 articles identified from 5 prominent databases. Results show that trace/heavy metals (As, Cr, Cu, Cd, and Pb) as well as high concentrations of toxic gasses (methane, hydrogen sulphide and mercury vapour) have been reported in landfills. Besides, organic chemicals such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and brominated flame retardants have been found in landfill leachates in the Netherlands and widely detected in landfill leachates in Sweden, Japan, and Canada. The potential of these contaminants to cause health complications has also been reported. Carcinogenicity, liver and kidney damage, cumulative damage, neurological disorders and foetal damage were reported as associated health implications of exposure to COC from C&DW. A waste disposal lens was used to explore the factors that influence the environment and human health impacts (pH, gypsum and organic content, size fraction, atmospheric exposure and liquid infiltration rate). Despite environmental and health issues relating to C&DW fine residues, the ultimate destination for C&DW fine residues remains in general landfills. Although significant efforts in managing C&DW have been implemented at various levels, those specifically targeting C&DW fine residues remain sparse.

Insights into vapour intrusion phenomena: Current outlook and preferential pathway scenario.

Vapour intrusion (VI) is the phenomenon by which volatile organic compounds (VOCs) migrate from the subsurface source through the soil and enter into the overlying buildings, affecting the indoor air quality and ultimately causing health hazards to the occupants. Health risk assessments associated with hydrocarbon contaminated sites and recommendations of site closure are often made by quantifying the VI risks using mathematical models known as 'vapour intrusion models' (VIM). In order to predict the health risk, various factors such as the lithological and geochemical conditions of the subsurface, environmental conditions, building operational conditions etc. are commonly evaluated using VIMs. Use of these models can overlook the role of preferential pathways like highly permeable subsurface layers and utility lines which act as the path of least resistance for vapour transport, which can increase the VI risks. The extensive networks of utility lines and sanitary sewer systems in urban areas can significantly exacerbate the uncertainty of VI investigations. The backfill materials like sand and gravel surrounding the utility lines can allow the vapours to easily pass through due to their high porosity as compared to natural formations. Hence, failure to understand the role of preferential pathways on the fate and transport of VOC in the vadose zone can result in more conservative predictions of indoor air vapour concentrations and wrong clean up approaches. This comprehensive review outlines the vapour transport mechanisms, factors influencing VI, VIMs and the role of preferential pathways in predicting indoor air vapour concentrations.

A review of electrokinetically enhanced bioremediation technologies for PHs.

Since the early 1980's there have been several different strategies designed and applied to the remediation of subsurface environment including physical, chemical and biological approaches. They have had varying degrees of success in remediating contaminants from subsurface soils and groundwater. The objective of this review is to examine the range of technologies for the remediation of contaminants, particularly petroleum hydrocarbons, in subsurfaces with a specific focus on bioremediation and electrokinetic remediation. Further, this review examines the efficiency of remediation carried out by combining bioremediation and electrokinetic remediation. Surfactants, which are slowly becoming the selected chemicals for mobilizing contaminants, are also considered in this review. The current knowledge gaps of these technologies and techniques identified which could lead to development of more efficient ways of utilizing these technologies or development of a completely new technology.

Incorporating perfluoroalkyl acids (PFAA) into a geochemical index for improved delineation of legacy landfill impacts on groundwater.

Historical, or 'legacy' landfills are commonly unlined and can therefore pose risks to human health and the environment via the discharge of leachate to sensitive groundwater and surface waters. Characterising the impacts on groundwater from legacy landfills located within urban re-development precincts is therefore of growing importance worldwide and is difficult using conventional indicators. At Australia's largest urban re-development precinct, Fishermans Bend, seven known legacy landfills exist, as well as numerous other contamination sources (e.g. historical industrial spillages). Conventional landfill leachate indicators (e.g. ammonia-N and bicarbonate) and perfluoroalkyl acids (PFAA) were measured in 36 bores to distinguish leachate-impacted groundwater from non-impacted areas. Whilst eleven bores showed clear leachate impacts based on conventional indicators, others did not show clearly identifiable leachate signals, particularly those installed near landfills thought to have accepted a larger component of non-putrescible waste (e.g. industrial, construction and/or demolition waste). A new index for detection of legacy landfill leachate impact on groundwater was therefore developed, incorporating perfluorooctanoate (PFOA) as a proportion of PFAA (PFOA/∑PFAA) into an existing method based on leachate to native cation ratios, ('L/N ratios'). Significant differences between the means of the leachate-impacted versus non-impacted bores were found using the 'modified L/N ratio' (p = .006), whereas no significant differences were found between the means of the two groups using the standard L/N ratio (p = .063). The modified L/N ratios also showed a statistically significant difference between the means of the bores impacted by municipal waste versus those impacted by non-putrescible waste (p = .003), indicating they are a much more sensitive indicator of both the existence and type of landfill leachate impact on groundwater than previously reported. This new index may prove particularly useful in complex urban areas where multiple potential contamination sources exist, and land use histories are either unknown or complicated. CAPSULE: Conventional methods for leachate detection in groundwater surrounding legacy landfills have been analysed and further developed via the inclusion of perfluoroalkyl acids, to better understand contaminant sources, fate and transport.

A method for separation of heavy metal sources in urban groundwater using multiple lines of evidence.

Determining sources of heavy metals in soils, sediments and groundwater is important for understanding their fate and transport and mitigating human and environmental exposures. Artificially imported fill, natural sediments and groundwater from 240 ha of reclaimed land at Fishermans Bend in Australia, were analysed for heavy metals and other parameters to determine the relative contributions from different possible sources. Fishermans Bend is Australia's largest urban re-development project, however, complicated land-use history, geology, and multiple contamination sources pose challenges to successful re-development. We developed a method for heavy metal source separation in groundwater using statistical categorisation of the data, analysis of soil leaching values and fill/sediment XRF profiling. The method identified two major sources of heavy metals in groundwater: 1. Point sources from local or up-gradient groundwater contaminated by industrial activities and/or legacy landfills; and 2. contaminated fill, where leaching of Cu, Mn, Pb and Zn was observed. Across the precinct, metals were most commonly sourced from a combination of these sources; however, eight locations indicated at least one metal sourced solely from fill leaching, and 23 locations indicated at least one metal sourced solely from impacted groundwater. Concentrations of heavy metals in groundwater ranged from 0.0001 to 0.003 mg/L (Cd), 0.001-0.1 mg/L (Cr), 0.001-0.2 mg/L (Cu), 0.001-0.5 mg/L (Ni), 0.001-0.01 mg/L (Pb), and 0.005-1.2 mg/L (Zn). Our method can determine the likely contribution of different metal sources to groundwater, helping inform more detailed contamination assessments and precinct-wide management and remediation strategies.

Development of a modular vapor intrusion model with variably saturated and non-isothermal vadose zone.

Human health risk assessment at hydrocarbon-contaminated sites requires a critical evaluation of the exposure pathways of volatile organic compounds including assessments of vapor exposure in indoor air. Although there are a number of vapor intrusion models (VIM) currently available, they rarely reproduce actual properties of soils in the vadose zone. At best, users of such models assume averaged parameters for the vadose zone based on information generated elsewhere. The objective of this study was to develop a one-dimensional steady-state VIM, indoorCARE™ model, that considers vertical spatial variations of the degree of saturation (or effective air-filled porosity) and temperature of the vadose zone. The indoorCARE™ model was developed using a quasi-analytical equation that (1) solves the coupled equations governing soil-water movement driven by pressure head and a soil heat transport module describing conduction of heat and (2) provides a VIM that accommodates various types of conceptual site model (CSM) scenarios. The indoorCARE™ model is applicable to both chlorinated hydrocarbon and petroleum hydrocarbon (PHC) contaminated sites. The model incorporates biodegradations of PHCs at a range of CSM scenarios. The results demonstrate that predictions of indoor vapor concentrations made with the indoorCARE™ model are close to those of the J&E and BioVapor models under homogeneous vadose zone conditions. The newly developed model under heterogeneous vadose zone conditions demonstrated improved predictions of indoor vapor concentrations. The research study presented a more accurate and more realistic way to evaluate potential human health risks associated with the soil-vapor-to-indoor-air pathways.

Influence of soil properties on vapor-phase sorption of trichloroethylene.

Current practices in health risk assessment from vapor intrusion (VI) using mathematical models are based on assumptions that the subsurface sorption equilibrium is attained. The time required for sorption to reach near-steady-state conditions at sites may take months or years to achieve. This study investigated the vapor phase attenuation of trichloroethylene (TCE) in five soils varying widely in clay and organic matter content using repacked columns. The primary indicators of TCE sorption were vapor retardation rate (Rt), the time required for the TCE vapor to pass through the soil column, and specific volume of retention (VR), and total volume of TCE retained in soil. Results show TCE vapor retardation is mainly due to the rapid partitioning of the compound to SOM. However, the specific volume of retention of clayey soils with secondary mineral particles was higher. Linear regression analyses of the SOM and clay fraction with VR show that a unit increase in clay fraction results in higher sorption of TCE (VR) than the SOM. However, partitioning of TCE vapor was not consistent with the samples' surface areas but was mainly a function of the type of secondary minerals present in soils.

Novel methodologies for automatically and simultaneously determining BTEX components using FTIR spectra.

This study introduced a patented novel methodological system for automatically analysis of Fourier Transform Infrared Spectrometer (FTIR) spectrum data located at 'fingerprint' region (wavenumber 670-800 cm(-1)), to simultaneously determinate multiple petroleum hydrocarbons (PHs) in real mixture samples. This system includes: an object oriented baseline correction; Band decomposition (curve fitting) method with mathematical optimization; and Artificial Neural Network (ANN) for determination, which is suitable for the characteristics of this IR regions, where the spectra are normally with low signal to noise ratio and high density of peaks. BTEX components are potentially lethal carcinogens and contained in many petroleum products. As a case study, six BTEX components were determinate automatically and simultaneously in mixture vapor samples. The robustness of the BTEX determination was validated using real petroleum samples, and the prediction results were compared with gas chromatography-mass spectrometry (GC-MS).

Uncertainties in human health risk assessment of environmental contaminants: A review and perspective.

Addressing uncertainties in human health risk assessment is a critical issue when evaluating the effects of contaminants on public health. A range of uncertainties exist through the source-to-outcome continuum, including exposure assessment, hazard and risk characterisation. While various strategies have been applied to characterising uncertainty, classical approaches largely rely on how to maximise the available resources. Expert judgement, defaults and tools for characterising quantitative uncertainty attempt to fill the gap between data and regulation requirements. The experiences of researching 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) illustrated uncertainty sources and how to maximise available information to determine uncertainties, and thereby provide an 'adequate' protection to contaminant exposure. As regulatory requirements and recurring issues increase, the assessment of complex scenarios involving a large number of chemicals requires more sophisticated tools. Recent advances in exposure and toxicology science provide a large data set for environmental contaminants and public health. In particular, biomonitoring information, in vitro data streams and computational toxicology are the crucial factors in the NexGen risk assessment, as well as uncertainties minimisation. Although in this review we cannot yet predict how the exposure science and modern toxicology will develop in the long-term, current techniques from emerging science can be integrated to improve decision-making.