A spatial approach to assessing PM2.5 exposure level of a brickmaking community in South Africa.

Globally, particulate matter with an aerodynamic diameter of 2.5 µm or less poses a significant threat to human health. The first step in quantifying human health impacts caused by exposure to PM2.5 pollution is exposure assessment. Population-weighted exposure level (PWEL) estimation is one of the methods that provides a more precise exposure assessment since it incorporates the spatiotemporal distribution of population with the pollution concentration estimate. In this study, PM2.5 exposure levels in the local communities around brickmaking industries were investigated, using the population census data of the study area and 1-year data from nine PM2.5 monitoring stations installed in and around the brickmaking industries. The observed PM2.5 data was spatially interpolated using inverse distance weight (IDW). Data on PM2.5 levels across the study area were classified based on the World Health Organization interim target (IT) guidelines and the South African National ambient air quality standard (NAAQS). An annual PM2.5 population weighted exposure level of 27.6 µg/m3 was estimated for the study area. However, seasonal exposure levels of 28.9, 37.6, 26.5, and 20.7 µg/m3 were estimated for the autumn, winter, spring, and summer seasons, respectively. This implies that local communities around the brick kiln in the Vhembe District are exposed to high levels of PM2.5, especially in winter. The PM2.5 levels in the brickmaking industries as well as its other sources in the Vhembe District, therefore, need to be lowered. Findings from population exposure level to pollutants can provide valuable data for formulating policies and recommendations on exposure reduction and public health protection.Implications: PM2.5 concentration in any given environment has high spatial and temporal variability due to the presence of diffused sources in the environment. Using ambient air concentrations to directly estimate population exposure without taking into consideration the disproportionate spatial and temporal distribution of the pollutant and the population may not yield accurate results on human exposure levels. It is, therefore, important to assess the aggregated PM2.5 exposure of a populace within a given area. This study therefore examines the PM2.5 population-weighted-exposure level of the host communities of the brickmaking industry in Vhembe District, South Africa.

Incidence and transmission of respiratory syncytial virus in urban and rural South Africa, 2017-2018.

Data on respiratory syncytial virus (RSV) incidence and household transmission are limited. To describe RSV incidence and transmission, we conducted a prospective cohort study in rural and urban communities in South Africa over two seasons during 2017-2018. Nasopharyngeal swabs were collected twice-weekly for 10 months annually and tested for RSV using PCR. We tested 81,430 samples from 1,116 participants in 225 households (follow-up 90%). 32% (359/1116) of individuals had ≥1 RSV infection; 10% (37/359) had repeat infection during the same season, 33% (132/396) of infections were symptomatic, and 2% (9/396) sought medical care. Incidence was 47.2 infections/100 person-years and highest in children <5 years (78.3). Symptoms were commonest in individuals aged <12 and ≥65 years. Individuals 1-12 years accounted for 55% (134/242) of index cases. Household cumulative infection risk was 11%. On multivariable analysis, index cases with ≥2 symptoms and shedding duration >10 days were more likely to transmit; household contacts aged 1-4 years vs. ≥65 years were more likely to acquire infection. Within two South African communities, RSV attack rate was high, and most infections asymptomatic. Young children were more likely to introduce RSV into the home, and to be infected. Future studies should examine whether vaccines targeting children aged <12 years could reduce community transmission.

Quantification of ambient PM2.5 concentrations adjacent to informal brick kilns in the Vhembe District using low-cost sensors.

The widespread exposure to ambient PM2.5 poses a substantial health risk globally, with a more pronounced impact on low- to medium-income nations. This study investigates the spatiotemporal distribution of PM2.5 in the communities hosting informal brickmaking industries in Vhembe District. Utilizing Dylos DC1700, continuous monitoring of PM2.5 was conducted at nine stations adjacent to informal brick kilns from March 2021 to February 2022. The study determined the correction factor for PM2.5 measurements obtained from the Dylos DC1700 when it was collocated with the GRIMM Environmental Dust Monitor 180. Additionally, the diurnal and seasonal variations across monitoring stations were assessed, and potential PM2.5 sources were identified. The study also evaluated the compliance of ambient PM2.5 concentrations across the stations with the South African National Ambient Air Quality Standard (NAAQS) limits. Annual PM2.5 concentrations for the stations ranged from 22.6 to 36.2 µgm-3. Diurnal patterns exhibited peak concentrations in the morning and evening, while seasonal variations showed higher concentrations in winter and lower concentrations in summer and spring. All monitoring stations reported the highest daily exceedance with respect to the daily NAAQS limit in the winter. Major PM2.5 sources included domestic biomass combustion, vehicular emissions, industrial emissions, and construction sites. Well-calibrated low-cost sensors could be employed in suburb regions with scarce air quality data. Findings from the study could be used for developing mitigation strategies to reduce health risks associated with PM2.5 exposure in the area.

Determinants of Solid Fuel Use and Emission Risks among Households: Insights from Limpopo, South Africa.

Emissions from residential solid fuels reduce ambient air quality and cause indoor air pollution resulting in adverse human health. The traditional solid fuels used for cooking include coal, straws, dung, and wood, with the latter identified as the prevalent energy source in developing countries. Emissions from such fuel sources appear to be significant hazards and risk factors for asthma and other respiratory diseases. This study aimed at reporting factors influencing the choice of dominant solid fuel for cooking and determine the emission risk from such solid fuel in three villages of Phalaborwa, Limpopo province, South Africa. The study used descriptive analysis to show the relationship between the socio-economic variables and the choice of cooking fuel at the household level. Multiple correspondence analysis (MCA) was used further to detect and represent underlying structures in the choice of dominant fuels. MCA shows the diversity and existing relationship of how variables are related analytically and graphically. Generalised linear logistic weight estimation procedure (WLS) was also used to investigate the factors influencing choice of fuel used and the inherent emission risks. In the three villages, wood was the prevalent cooking fuel with 76.8% of participant households using it during the summer and winter seasons. Variables such as low monthly income, level of education, and system of burning are revealed as strong predictors of wood fuel usage. Moreover, income, water heating energy, types of wood, and number of cooking hours are significant (p ≤ 0.05) in influencing emission from wood fuel in the community. A notable conclusion is that variables such as income, education status and system of burning are determinants of wood fuel usage in the three villages, while income, water heating energy, types of wood and number of hours influence vulnerability to household emission and possible health risks in the use of solid energy sources.

Housing Quality in a Rural and an Urban Settlement in South Africa.

During 2016 to 2018, a prospective household cohort study of influenza and respiratory syncytial virus community burden and transmission dynamics (the PHIRST study) was undertaken to examine the factors associated with influenza and other respiratory pathogen transmissions in South Africa. We collected information on housing conditions in the PHIRST study sites: Rural villages near Agincourt, Bushbuckridge Municipality, Mpumalanga Province, and urban Jouberton Township in North West Province. Survey data were collected from 159 and 167 study households in Agincourt and Jouberton, respectively. Multiple housing-related health hazards were identified in both sites, but particularly in Agincourt. In Agincourt, 75% (119/159) of households reported daily or weekly interruptions in water supply and 98% (154/159) stored drinking water in miscellaneous containers, compared to 1% (1/167) and 69% (115/167) of households in Jouberton. Fuels other than electricity (such as wood) were mainly used for cooking by 44% (70/159) and 7% (11/167) of Agincourt and Jouberton households, respectively; and 67% (106/159) of homes in Agincourt versus 47% (79/167) in Jouberton were located on unpaved roads, which is associated with the generation of dust and particulate matter. This study has highlighted housing conditions in Agincourt and Jouberton that are detrimental to health, and which may impact disease severity or transmission in South African communities.

Cohort profile: A Prospective Household cohort study of Influenza, Respiratory syncytial virus and other respiratory pathogens community burden and Transmission dynamics in South Africa, 2016-2018.

PURPOSE: The PHIRST study (Prospective Household cohort study of Influenza, Respiratory Syncytial virus, and other respiratory pathogens community burden and Transmission dynamics in South Africa) aimed to estimate the community burden of influenza and respiratory syncytial virus (RSV) including the incidence of infection, symptomatic fraction, and to assess household transmission. PARTICIPANTS: We enrolled 1684 individuals in 327 randomly selected households in a rural and an urban site over three consecutive influenza and two RSV seasons. A new cohort of households was enrolled each year. Participants were sampled with nasopharyngeal swabs twice-weekly during the RSV and influenza seasons of the year of enrolment. Serology samples were collected at enrolment and before and after the influenza season annually. FINDINGS TO DATE: There were 122 113 potential individual follow-up visits over the 3 years, and participants were interviewed for 105 783 (87%) of these. Out of 105 683 nasopharyngeal swabs, 1258 (1%) and 1026 (1%) tested positive on polymerase chain reaction (PCR) for influenza viruses and RSV, respectively. Over one third of individuals had PCR-confirmed influenza each year. Overall, there was influenza transmission to 10% of household contacts of an index case. FUTURE PLANS: Future planned analyses include analysis of influenza serology results and RSV burden and transmission. Households enrolled in the PHIRST study during 2016-2018 were eligible for inclusion in a study of SARS-CoV-2 transmission initiated in July 2020. This study uses similar testing frequency to assess the community burden of SARS-CoV-2 infection and the role of asymptomatic infection in virus transmission.

Asymptomatic transmission and high community burden of seasonal influenza in an urban and a rural community in South Africa, 2017-18 (PHIRST): a population cohort study.

BACKGROUND: Data on influenza community burden and transmission are important to plan interventions especially in resource-limited settings. However, data are limited, particularly from low-income and middle-income countries. We aimed to evaluate the community burden and transmission of influenza in a rural and an urban setting in South Africa. METHODS: In this prospective cohort study approximately 50 households were selected sequentially from both a rural setting (Agincourt, Mpumalanga Province, South Africa; with a health and sociodemographic surveillance system) and an urban setting (Klerksdorp, Northwest Province, South Africa; using global positioning system data), enrolled, and followed up for 10 months in 2017 and 2018. Different households were enrolled in each year. Households of more than two individuals in which 80% or more of the occupants agreed to participate were included in the study. Nasopharyngeal swabs were collected twice per week from participating household members irrespective of symptoms and tested for influenza using real-time RT-PCR. The primary outcome was the incidence of influenza infection, defined as the number of real-time RT-PCR-positive episodes divided by the person-time under observation. Household cumulative infection risk (HCIR) was defined as the number of subsequent infections within a household following influenza introduction. FINDINGS: 81 430 nasopharyngeal samples were collected from 1116 participants in 225 households (follow-up rate 88%). 917 (1%) tested positive for influenza; 178 (79%) of 225 households had one or more influenza-positive individual. The incidence of influenza infection was 43·6 (95% CI 39·8-47·7) per 100 person-seasons. 69 (17%) of 408 individuals who had one influenza infection had a repeat influenza infection during the same season. The incidence (67·4 per 100 person-seasons) and proportion with repeat infections (22 [23%] of 97 children) were highest in children younger than 5 years and decreased with increasing age (p<0·0001). Overall, 268 (56%) of 478 infections were symptomatic and 66 (14%) of 478 infections were medically attended. The overall HCIR was 10% (109 of 1088 exposed household members infected [95% CI 9-13%). Transmission (HCIR) from index cases was highest in participants aged 1-4 years (16%; 40 of 252 exposed household members) and individuals with two or more symptoms (17%; 68 of 396 exposed household members). Individuals with asymptomatic influenza transmitted infection to 29 (6%) of 509 household contacts. HIV infection, affecting 167 (16%) of 1075 individuals, was not associated with increased incidence or HCIR. INTERPRETATION: Approximately half of influenza infections were symptomatic, with asymptomatic individuals transmitting influenza to 6% of household contacts. This suggests that strategies, such as quarantine and isolation, might be ineffective to control influenza. Vaccination of children, with the aim of reducing influenza transmission might be effective in African settings given the young population and high influenza burden. FUNDING: US Centers for Disease Control and Prevention.

Concentrations, distributions and critical level exceedance assessment of SO2, NO2 and O3 in South Africa.

South Africa has been identified as a source of industrial pollution that is significant at a global scale. This study was designed to provide quantitative information, by direct measurement, across northeastern South Africa, which includes the highly industrialised Mpumalanga Highveld. The specific aim of the study was to evaluate whether or not acidic atmospheric pollution poses a threat to soils, plants and water bodies of South Africa. To address this aim, a network of 37 passive sampling sites was established to measure monthly mean concentrations of near-surface SO(2), NO(2) and ozone. The area covered extended over the northern and eastern interior of South Africa while avoiding sources of local emissions such as towns, mines and highways. The field campaign was conducted between August 2005 and September 2007. Spatial distributions and temporal trends for these pollutant gases were assessed. Critical levels analysis comparisons were made against applicable air quality standards, guidelines and limits to evaluate the potential for adverse atmospheric pollution impacts on regional environments. The assessment indicates that only in the central source area of the South African industrial Highveld are some levels exceeded. In remote areas, including the sensitive forested regions of the Drakensberg escarpment, pollutant concentrations are below the critical thresholds for environmental damage.

Global Statement on Air Pollution and Health: Opportunities for Africa.

The editorial speaks to the Global Statement on Air Pollution and Health and How it may assist African countries to eliminate air pollution-related health impacts.

Characteristics of columnar aerosol optical and microphysical properties retrieved from the sun photometer and its impact on radiative forcing over Skukuza (South Africa) during 1999-2010.

The detailed analysis of columnar optical and microphysical properties of aerosols obtained from the AErosol RObotic NETwork (AERONET) Cimel sun photometer operated at Skukuza (24.98° S, 31.60° E, 150 m above sea level), South Africa was carried out using the level 2.0 direct sun and inversion products measured during 1999-2010. The observed aerosol optical depth (AOD) was generally low over the region, with high values noted in late winter (August) and mid-spring (September and October) seasons. The major aerosol types found during the study period were made of 3.74, 69.63, 9.34, 8.83, and 8.41% for polluted dust (PD), polluted continental (PC), non-absorbing (NA), slightly absorbing (SA), and moderately absorbing (MA) aerosols, respectively. Much attention was given to the aerosol fine- and coarse-modes deduced from the particle volume concentration, effective radius, and fine-mode volume fraction. The aerosol volume size distribution pattern was found to be bimodal with the fine-mode showing predominance relative to coarse-mode during the winter and spring seasons, owing to the onset of the biomass burning season. The mean values of total, fine-, and coarse-mode volume particle concentrations were 0.07 ± 0.04, 0.03 ± 0.03, and 0.04 ± 0.02 µm3 µm-2, respectively, whereas the mean respective effective radii observed at Skukuza for the abovementioned modes were 0.35 ± 0.17, 0.14 ± 0.02, and 2.08 ± 0.02 µm. The averaged shortwave direct aerosol radiative forcing (ARF) observed within the atmosphere was found to be positive (absorption or heating effect), whereas the negative forcing in the surface and TOA depicted significant cooling effect due to more scattering type particles.

A web-based survey of horse owners' perceptions and network analysis of horse movements relating to African horse sickness distribution in Namibia and South Africa.

Africa horse sickness (AHS) is the most lethal infectious non-contagious horse disease and has accordingly been declared notifiable by the World Organisation for Animal Health. AHS is endemic to sub-Saharan Africa and causes considerable losses to the equestrian industry. The effect of diseases in livestock on socio-economic factors is well researched, but the effect of anthropogenic factors on the distribution of a disease is poorly understood. The purpose of the study was to assess Namibian and South African horse owners' perceptions and the effect of horse movement on AHS distribution. A cross-sectional study was conducted to collect information from horse owners in Namibia and South Africa. To that end 'Fluid survey' was used for survey development. The survey was launched on Facebook and the link shared to horse related focus groups in Namibia and South Africa. A total of 508 responses were collected during the survey period. Of the 417 completed questionnaires received, 22% were from Namibia and 78% from South Africa. The participants comprised of 71% social and 29% professional riders. The most popular precautionary measures used, in addition to vaccination, were chemical repellents (64%) and stabling of horses during dusk and dawn (59%). A network analysis was performed in Gephi 0.8.2.B to illustrate the movement of horses between countries and districts/provinces. Network analysis results indicate that areas with the highest movement of horses corresponded to the areas with a high occurrence of AHS. Although 93% of the participants were aware that AHS is a notifiable and controlled disease, the process and efficiency of reporting is mostly unknown. With this snapshot of horse owners' perceptions and the effect of horse movement on the distribution of AHS, it is clear that a more holistic approach is needed. To that end, all environmental and social factors must be taken into account in effective management strategies.

Culicoides species composition and environmental factors influencing African horse sickness distribution at three sites in Namibia.

African horse sickness (AHS) is one of the most lethal infectious, non-contagious, vector-borne disease of equids. The causative agent, African horse sickness virus (AHSV) is transmitted via Culicoides midges (Diptera: Ceratopogonidae). AHS is endemic to Namibia but detailed studies of Culicoides communities and influencing environmental parameters are limited. This study aims to determine the Culicoides species composition at three different sites and to assess environmental parameters influencing the geographical distribution of AHS in Namibia. Weekly collections of Culicoides were made during the AHS peak season from January to May for 2013 and 2014 using the Onderstepoort 220V UV-light trap. Out of 397 collections made, 124 collections (3287 Culicoides) were analysed for AHSV presence with RT-qPCR. A total of 295 collections were analysed for total Culicoides (all collected Culicoides individuals) and in 75% of these collections the Culicoides were identified to species level. C. imicola was the dominant species with proportional representation of 29.9%. C. subschultzei, C. exspectator and C. ravus each contribute more than 10% to the species composition. The lowest number of Culicoides was collected at Aus 9980, a total of 21819 at Windhoek and the highest number at Okahandja 47343. AHSV was present at all three sites during 2013 but only in Windhoek and Okahandja during 2014. Multivariate analyses of data from the two year survey indicate the environmental parameters in order of importance for the distribution of AHS in Namibia as precipitation>temperature>clay>relative humidity>NDVI. The implication of these findings is that any precipitation event increases Culicoides numbers significantly. Together with these results the high number of species found of which little is known regarding their vector competence, add to the complexity of the distribution of AHS in Namibia.

Comparing the effect of modeled climatic variables on the distribution of African horse sickness in South Africa and Namibia.

Africa horse sickness (AHS) is a lethal disease of horses with a seasonal occurrence that is influenced by environmental conditions that favor the development of Culicoides midges (Diptera: Ceratopogonidae). This study compared and evaluated the relationship of various modeled climatic variables with the distribution and abundance of AHS in South Africa and Namibia. A comprehensive literature review of the historical AHS reported data collected from the Windhoek archives as well as annual reports from the Directorate of Veterinary services in Namibia were conducted. South African AHS reported data were collected from the South African Department of Agriculture, Forestry, and Fisheries. Daily climatic data were extracted for the time period 1993-2011 from the ERA-interim re-analysis dataset. The principal component analysis of the complete dataset indicated a significant statistical difference between Namibia and South Africa for the various climate variables and the outbreaks of AHS. The most influential parameters in the distribution of AHS included humidity, precipitation, evaporation, and minimum temperature. In South Africa, temperature had the most significant effect on the outbreaks of AHS, whereas in Namibia, humidity and precipitation were the main drivers. The maximum AHS cases in South Africa occurred at temperatures of 20-22° C and relative humidity between 50-70%. Furthermore, anthropogenic effects must be taken into account when trying to understand the distribution of AHS.

Seasonal changes in organotin compounds in water and sediment samples from the semi-closed Port of Gdynia.

The effect of seasonal changes on the distribution of organotin compounds (OTC) in the sediments and seawater from the docks of the Port of Gdynia was investigated. Sediment and seawater samples were collected from four industrial docks in February (winter) and June (summer) in 2009. The samples were analyzed for butyltin, phenyltin, octyltin, and tricyclohexyltin (total of 9 OTC derivatives). The fine fraction (<0.063 mm) accumulated the highest concentration of OTC, although it was not the dominant fraction in the sediment samples from the Port of Gdynia. The average concentration of TBT, DBT and MBT in collected samples were as follows: 4400; 2188; 730 ng cation g⁻¹ d.w. (February) 3638; 1590; 474 ng cation g⁻¹ d.w. (June) in the fine sediment samples, 2805; 1266; 485 ng cation g⁻¹ d.w. (February) in <2.00 mm sediment fractions and 118.6; 39.2; 25.3 ng cation L⁻¹ (February) and 46.5; 12.6; 8.2 ng cation L⁻¹ (June) in the water samples. Higher concentrations of butyltin derivatives (BT) were observed in samples collected in February than in those collected in June. Seasonal changes in BT correlate well with changes in the water pH and concentrations of organic matter and can be attributed to sorption/desorption to sediments, photodegradation and biodegradation. Although the Port of Gdynia does not represent the natural features of a marine environment, seasonal variations recorded in the pH values as well as BT, organic carbon and biogenic element concentrations seem to be influenced by temperature and microbial activity.

Statistical evaluation of aerosol data from Ben Macdhui mountain, South Africa.

The aim of this study is re-evaluation of the data collected during Ben Macdhui High Altitude Trace Gas and Aerosols Transport Experiment (BHATTEX) to identify the dominant species of aerosols and their interactions in the atmosphere. Particularly, investigations of seasonal variations, the origin of sulphates and the formation of the ammonia sulphate were essential topics of this study. Such analyses were done by application of unique combination of supervised and unsupervised learning classification methods. Namely discriminant function analysis (DFA) for simple identification of parameters and principal component analysis (PCA) for the further investigations on hidden structure of data has been applied. The analysis shows that sulphate concentration and C,N isotopic ratios can classify winter and summer patterns of data. Differences between sulphate concentrations in summer and winter samples indicated by second PCA component were probably related to meteorological conditions over that region. The relations between anthropogenic compounds and ammonia or sulphate were much more stronger in summer samples than in winter ones, that is related with seasonal transport of that particles from industry to the investigated regions. The hypothesis of competitive reaction between sulphates, nitrates and ammonia ions has been also proven by application of simple regression analysis. Moreover the analysis of correlations coefficients shows that those relations are independent on seasons.