Fine particulate matter constituents and infant mortality in Africa: A multicountry study

Low-Cost Hourly Ambient Black Carbon Measurements at Multiple Cities in Africa

There is a notable lack of continuous monitoring of air pollutants in the Global South, especially for measuring chemical composition, due to the high cost of regulatory monitors. Using our previously developed low-cost method to quantify black carbon (BC) in fine particulate matter (PM2.5) by analyzing reflected red light from ambient particle deposits on glass fiber filters, we estimated hourly ambient BC concentrations with filter tapes from beta attenuation monitors (BAMs). BC measurements obtained through this method were validated against a reference aethalometer between August 2 and 23, 2023 in Addis Ababa, Ethiopia, demonstrating a very strong agreement (R2 = 0.95 and slope = 0.97). We present hourly BC for three cities in sub-Saharan Africa (SSA) and one in North America: Abidjan (Côte d'Ivoire), Accra (Ghana), Addis Ababa (Ethiopia), and Pittsburgh (USA). The average BC concentrations for the measurement period at the Abidjan, Accra, Addis Ababa Central summer, Addis Ababa Central winter, Addis Ababa Jacros winter, and Pittsburgh sites were 3.85 μg/m3, 5.33 μg/m3, 5.63 μg/m3, 3.89 μg/m3, 9.14 μg/m3, and 0.52 μg/m3, respectively. BC made up 14-20% of PM2.5 mass in the SSA cities compared to only 5.6% in Pittsburgh. The hourly BC data at all sites (SSA and North America) show a pronounced diurnal pattern with prominent peaks during the morning and evening rush hours on workdays. A comparison between our measurements and the Goddard Earth Observing System Composition Forecast (GEOS-CF) estimates shows that the model performs well in predicting PM2.5 for most sites but struggles to predict BC at an hourly resolution. Adding more ground measurements could help evaluate and improve the performance of chemical transport models. Our method can potentially use existing BAM networks, such as BAMs at U.S. Embassies around the globe, to measure hourly BC concentrations. The PM2.5 composition data, thus acquired, can be crucial in identifying emission sources and help in effective policymaking in SSA.

Long- and Intermediate-Term Ambient Particulate Pollution Is Associated with Increased Osteoarthritis Risk: A Population-Based Prospective Analysis

Recent studies found the intrusion and retention of exogenous fine particles into joints, but epidemiological data for long- and intermediate-term exposure associations are scare. Here, all urban working, retired employee, and rural residents (16.78 million) in Beijing from January 1, 2011 to December 31, 2019 were included to investigate the effects of long- and intermediate-term ambient particulate exposure on development of osteoarthritis. We identified 1,742,067 participants as first-visit patients with osteoarthritis. For each interquartile range increase in annual PM2.5 (23.32 μg/m3) and PM10 (23.92 μg/m3) exposure concentration, the pooled hazard ratios were respectively 1.238 (95% CI: 1.228, 1.249) and 1.178 (95% CI: 1.168, 1.189) for first osteoarthritis outpatient visits. Moreover, age at first osteoarthritis outpatient visits significantly decreased by 4.52 (95% CI: 3.45 to 5.40) days per μg/m3 for annual PM2.5 exposure at below 67.85 μg/m3. Finally, among the six constituents analyzed, black carbon appears to be the most important component associated with the association between PM2.5 exposure and the three osteoarthritis-related outcomes.

Long-term exposure to major constituents of fine particulate matter and neurodegenerative diseases: A population-based survey in the Pearl River Delta Region, China

BACKGROUND

Exposure to PM2.5 has been linked to neurodegenerative diseases, with limited understanding of constituent-specific contributions.

OBJECTIVES

To explore the associations between long-term exposure to PM2.5 constituents and neurodegenerative diseases.

METHODS

We recruited 148,274 individuals aged ≥ 60 from four cities in the Pearl River Delta region, China (2020 to 2021). We calculated twenty-year average air pollutant concentrations (PM2.5 mass, black carbon (BC), organic matter (OM), ammonium (NH4+), nitrate (NO3-) and sulfate (SO42-)) at the individuals' home addresses. Neurodegenerative diseases were determined by self-reported doctor-diagnosed Alzheimer's disease (AD) and Parkinson's disease (PD). Generalized linear mixed models were employed to explore associations between pollutants and neurodegenerative disease prevalence.

RESULTS

PM2.5 and all five constituents were significantly associated with a higher prevalence of AD and PD. The observed associations generally exhibited a non-linear pattern. For example, compared with the lowest quartile, higher quartiles of BC were associated with greater odds for AD prevalence (i.e., the adjusted odds ratios were 1.81; 95% CI, 1.45-2.27; 1.78; 95% CI, 1.37-2.32; and 1.99; 95% CI, 1.54-2.57 for the second, third, and fourth quartiles, respectively).

CONCLUSIONS

Long-term exposure to PM2.5 and its constituents, particularly combustion-related BC, OM, and SO42-, was significantly associated with higher prevalence of AD and PD in Chinese individuals.

ENVIRONMENTAL IMPLICATION

PM2.5 is a routinely regulated mixture of multiple hazardous constituents that can lead to diverse adverse health outcomes. However, current evidence on the specific contributions of PM2.5 constituents to health effects is scarce. This study firstly investigated the association between PM2.5 constituents and neurodegenerative diseases in the moderately to highly polluted Pearl River Delta region in China, and identified hazardous constituents within PM2.5 that have significant impacts. This study provides important implications for the development of targeted PM2.5 prevention and control policies to reduce specific hazardous PM2.5 constituents.

Case-crossover study for the association between increased hospital admissions for respiratory diseases and the increase in atmospheric PM2.5 and PM2.5-bound trace elements in Pretoria, South Africa

Outdoor PM2.5 was sampled in Pretoria, 18 April 2017 to 28 February 2020. A case-crossover epidemiology study was associated for increased PM2.5 and trace elements with increased hospital admissions for respiratory disorders (J00-J99). The results included a significant increase in hospital admissions, with total PM2.5 of 2.7% (95% CI: 0.6, 4.9) per 10 µg·m-3 increase. For the trace elements, Ca of 4.0% (95% CI: 1.4%-6.8%), Cl of 0.7% (95% CI: 0.0%-1.4%), Fe of 3.3% (95% CI: 0.5%-6.1%), K of 1.8% (95% CI: 0.2-3.5) and Si of 1.3% (95% CI: 0.1%-2.5%). When controlling for PM2.5, only Ca of 3.2% (95% CI: 0.3, 6.1) and within the 0-14 age group by 5.2% (95% CI: 1.5, 9.1). Controlling for a co-pollutant that is highly correlated with PM2.5 does reduce overestimation, but further studies should include deposition rates and parallel sampling analysis.

Factors associated with infant mortality in Nigeria: A scoping review

BACKGROUND

Infant mortality persists as a global public health concern, particularly in lower-middle-income countries (LIMCs) such as Nigeria. The risk of an infant dying before one year of age is estimated to be six times higher in Africa than in Europe. Nigeria recorded an infant mortality rate of 72.2 deaths per 1,000 live births in 2020, in contrast to the global estimate of 27.4 per 1,000 live births. Several studies have been undertaken to determine the factors influencing infant mortality.

OBJECTIVE

This scoping review sought to identify and summarise the breadth of evidence available on factors associated with infant mortality in Nigeria.

METHODS

This review followed the five-stage principles of Arksey and O'Malley's framework. Four electronic databases were searched with no limit to publication date or study type: Ovid MEDLINE, PubMed, CINAHL Complete, and Web of Science. Selected studies were imported into Endnote software and then exported to Rayyan software where duplicates were removed. Included articles were thematically analysed and synthesised using the socioecological model.

RESULTS

A total of 8,139 references were compiled and screened. Forty-eight articles were included in the final review. At the individual level, maternal- and child-related factors were revealed to influence infant mortality; socioeconomic and sociocultural factors at the interpersonal level; provision and utilisation of health services, health workforce, hospital resources and access to health services at the organisational level; housing/neighbourhood and environmental factors at the community level; and lastly, governmental factors were found to affect infant mortality at the public policy level.

CONCLUSION

Factors related to the individual, interpersonal, organisational, community and public policy levels were associated with infant mortality in Nigeria.

Association of Fine Particulate Matter Constituents with the Predicted 10-Year Atherosclerotic Cardiovascular Disease Risk: Evidence from a Large-Scale Cross-Sectional Study

Little is known concerning the associations of fine particulate matter (PM2.5) and its constituents with atherosclerotic cardiovascular disease (ASCVD). A total of 31,162 participants enrolled from the Henan Rural Cohort were used to specify associations of PM2.5 and its constituents with ASCVD. Hybrid machine learning was utilized to estimate the 3-year average concentration of PM2.5 and its constituents (black carbon [BC], nitrate [NO3-], ammonium [NH4+], inorganic sulfate [SO42-], organic matter [OM], and soil particles [SOIL]). Constituent concentration, proportion, and residual models were utilized to examine the associations of PM2.5 constituents with 10-year ASCVD risk and to identify the most hazardous constituent. The isochronous substitution model (ISM) was employed to analyze the substitution effect between PM2.5 constituents. We found that each 1 μg/m3 increase in PM2.5, BC, NH4+, NO3-, OM, SO42-, and SOIL was associated with a 3.5%, 49.3%, 19.4%, 10.5%, 21.4%, 14%, and 28.5% higher 10-year ASCVD risk, respectively (all p < 0.05). Comparable results were observed in proportion and residual models. The ISM found that replacing BC with other constituents will generate the greatest health benefits. The results indicated that long-term exposure to PM2.5 and its constituents were associated with increased risks of ASCVD, with BC being the most attributable constituent.

Fine particulate matter air pollution and the mortality of children under five: a multilevel analysis of the Ethiopian Demographic and Health Survey of 2016

Background

Every year, polluted air is costing the globe 543,000 deaths of children under five. The particulate matter below 2.5 μm diameter (PM_2.5) is a part of air pollution that has adverse effects on children's health. In Ethiopia, the effect of ambient PM_2.5 is least explored. This study aimed to assess the association between PM_2.5 and under-five mortality in Ethiopia.

Methods

The study used the data from the Ethiopian Demographic Health Surveys conducted in 2016, collected between January 18 and June 27. All children under five who had data on child mortality and location coordinates were included in the study. Exposure to ambient PM_2.5 concentration was a satellite-based estimate by the Atmospheric Composition Analysis Group at Washington and Dalhousie University, in the United States and Canada, respectively. Annual mean pollution levels and mortality datasets were matched by children's geographical location and dates of birth, death, and interview. The relationship between ambient PM_2.5 and under-five mortality was determined by a multilevel multivariable logistic regression on R software. The statistical analyses were two-sided at a 95% confidence interval.

Results

The study addressed 10,452 children with the proportion of under-five mortality being 5.4% (95% CI 5.0-6.8%). The estimated lifetime annual mean exposure of ambient total PM_2.5 was 20.1 ± 3.3 μgm^-3. A 10-unit increase in the lifetime annual mean ambient total PM_2.5 was associated with 2.29 [95% CI 1.44, 3.65] times more odds of under-five mortality after adjusting for other variables.

Conclusion

Children under five are exposed to higher levels of ambient PM_2.5 concentration, exceeding the limit set by the World Health Organization. Ambient PM_2.5 is significantly associated with under-five mortality, adjusting for other variables. Strong measures need to be taken to reduce air pollution.

Ambient air pollution and infant health: a narrative review

The extensive evidence regarding the effects of ambient air pollution on child health is well documented, but limited review summarized their health effects during infancy. Symptoms or health conditions attributed to ambient air pollution in infancy could result in the progression of severe diseases during childhood. Here, we reviewed previous empirical epidemiological studies and/or reviews for evaluating the linkages between ambient air pollution and various infant outcomes including adverse birth outcomes, infant morbidity and mortality, early respiratory health, early allergic symptoms, early neurodevelopment, early infant growth and other relevant outcomes. Patterns of the associations varied by different pollutants (i.e., particles and gaseous pollutants), exposure periods (i.e., pregnancy and postpartum) and exposure lengths (i.e., long-term and short-term). Protection of infant health requires that paediatricians, researchers, and policy makers understand to what extent infants are affected by ambient air pollution, and a call for action is still necessary to reduce ambient air pollution.

Maternal exposure to extreme high-temperature, particulate air pollution and macrosomia in 14 countries of Africa

BACKGROUND

Macrosomia has increased rapidly worldwide in the past few decades, with a huge impact on health. However, the effect of PM_2.5 and extreme high-temperature (EHT) on macrosomia has been ignored.

OBJECTIVE

This study aimed to explore the association between maternal exposure to EHT, PM_2.5 and macrosomia based on the Seventh Demographic and Health Survey (DHS) in 14 countries of Africa.

METHODS

The study included detailed demographic information on 106 382 births and maternal. Satellite inversion models estimated monthly mean PM_2.5 and mean surface temperature of 2 m (SMT_2m ). Macrosomia was defined as the birth weight ≥ 4000 g. We used a Cox proportional risk regression model to estimate the association between PM_2.5 , EHT and macrosomia. We further explored the susceptibility of exposure to EHT and PM_2.5 at different pregnancy periods to macrosomia, and plotted the expose-response curve between PM_2.5 and macrosomia risk using a restricted cubic spline function. In addition, the Interplot model was used to investigate the interaction between EHT and PM_2.5 on macrosomia. Finally, some potential confounding factors were analysed by stratification.

RESULTS

There was the positive association between EHT, PM_2.5 and macrosomia, and the risk of macrosomia with the increase in concentrations of PM_2.5 without clear threshold. Meanwhile, EHT and PM_2.5 had a higher effect on macrosomia in middle/later and early/middle stages of pregnancy, respectively. There was a significant interaction between EHT and PM_2.5 on macrosomia.

CONCLUSIONS

Maternal exposure to EHT, PM_2.5 during pregnancy was associated with an increased risk of macrosomia in Africa.

Health risk assessment of PM2.5 and PM2.5-bound trace elements in Pretoria, South Africa

Exposure to outdoor air pollutants poses a risk for both non-carcinogenic and carcinogenic respiratory disease outcomes. A standardized health risk assessment (US EPA) utilizes air quality data, body mass and breathing rates to determine potential risk. This health risk assessment study assesses the hazard quotient (HQ) for total PM_2.5 and trace elemental constituents (Br, Cl, K, Ni, S, Si, Ti and U) exposure in Pretoria, South Africa. The World Health Organization (WHO) air quality guideline (5 µg m^-3) and the yearly South African National Ambient Air Quality Standard (NAAQS) (20 µg m^-3) were the references dosages for total PM_2.5. A total of 350 days was sampled in Pretoria, South Africa. The mean total PM_2.5 concentration during the 34-month study period was 23.2 µg m^-3 (0.7-139 µg m^-3). The HQ for total PM_2.5 was 1.17, 3.47 and 3.78 for adults, children and infants. Non-carcinogenic risks for trace elements K, Cl, S and Si were above 1 for adults. Seasonally, Si was the highest during autumn for adults (1.9) and during spring for S (5.5). The HQ values for K and Cl were highest during winter. The exposure to Ni posed a risk for cancer throughout the year and for As during winters.

Effect of biomass burning on premature mortality associated with long-term exposure to PM2.5 in Equatorial Asia

The health burden from exposure to ambient fine particulates (PM_2.5) in Equatorial Asia is substantially affected by the peatland fires in Indonesia, but the long-term health effect of the fires on local inhabitants is unclear. In this study, PM_2.5-associated excess mortality in Equatorial Asia over the past 30 years (1990-2019) was estimated and then the health effect of biomass burning was identified. The PM_2.5-related death in Equatorial Asia almost tripled from 113 (95% confidence interval, 100-125) thousand in 1990 to 337 (300-373) thousand in 2019, with a rate of increase of 6.4 (6.2-6.9) thousand/yr. The intense biomass burning between 1990 and 2019 was estimated to have induced 317 (282-348) thousand excess deaths in the study regions, with excess deaths mainly occurring in the El Niño years, such as in 1997, 2006, 2015 and 2019. Although the remote sensing data and emission inventories both reveal that the effective control measures have reduced biomass burning intensity in Equatorial Asia (especially in Sumatra and Borneo), the corresponding health benefit has been offset by variations in demographic factors, i.e., population and age structure. Over the same period, fossil fuel emissions continued to increase rapidly. Thus, more stringent and ambitious policies are required to reduce the health burden from biomass burning and anthropogenic emissions simultaneously to maximize the health benefits from government measures and policies.

Association between Long-Term Ambient PM2.5 Exposure and under-5 Mortality: A Scoping Review

Studies have established a link between exposure to fine particles (PM2.5) and mortality in infants and children. However, few studies have explored the association between post-birth exposure to PM2.5 and under-5 mortality. We conducted a scoping review to identify relevant epidemiological evidence on the association between post-birth ambient PM2.5 exposure and under-5 mortality. We searched PubMed and Web of Science for articles published between 1970 and the end of January 2022 that explicitly linked ambient PM2.5 and under-5 mortality by considering the study area, study design, exposure window, and child age. Information was extracted on the study characteristics, exposure assessment and duration, outcomes, and effect estimates/findings. Ultimately, 13 studies on infant and child mortality were selected. Only four studies measured the effect of post-birth exposure to PM2.5 on under-5 mortality. Only one cohort study mentioned a positive association between post-birth ambient PM2.5 exposure and under-5 mortality. The results of this scoping review highlight the need for extensive research in this field, given that long-term exposure to ambient PM2.5 is a major global health risk and child mortality remains high in some countries.

Source sectors underlying PM2.5-related deaths among children under 5 years of age in 17 low- and middle-income countries

BACKGROUND

Fine particulate matter (PM_2.5) from different source sectors might differ in toxicity. However, data from large-scale studies on vulnerable children in low- and middle-income countries (LMICs) are insufficient.

OBJECTIVE

To analyze the association of under-five death (U5D) with long-term exposure to PM_2.5 from different sources.

METHOD

We evaluated demographic and health survey data for 79,995 babies born in 2017 in 16 Asian and African LMICs (AA-LMICs) and a Latin America low-income country (i.e., Haiti). Long-term exposure to PM_2.5 was assessed by a well-established product that attributed the annual concentration to 20 source sectors in 2017. The associations of survival during < 5-year periods with each source-specific concentration of PM_2.5 were analyzed by Cox regression with multiple adjustments. We derived a multiple-pollutant ridge regression model to estimate the joint exposure-response function (JERF) between U5D and PM_2.5 mixtures. To evaluate how sources affected PM_2.5 toxicity, we evaluated the number of U5Ds attributable to PM_2.5 based on the source profiles for 88 AA-LMICs.

RESULTS

According to the single-pollutant model, the risk of U5D increased by 7% (95% confidence interval [CI]: 5%, 9%) for each 10 μg/m³ increment in total PM_2.5 concentration. The model performance was lower than that of the multiple-pollutant ridge regression model. For each 10 μg/m³ increment in PM_2.5, the excess risk of U5D ranged from 6% (95% CI: 4%, 9%) in Nepal to 10% (95% CI: 6%, 14%) in Mauritania. Based on the JERF, PM_2.5 contributed to 817,647 (95% CI: 585,729, 1,050,439), i.e., 28.0% (95% CI: 20.1%, 35.8%), of all U5Ds across the 88 AA-LMICs. The PM_2.5-related U5Ds were mostly attributable to PM_2.5 produced by desert dust, followed by solid biofuel combustion and open fires.

CONCLUSION

The average toxicity of PM_2.5 varied by source profile, which should be taken into consideration when planning public health interventions. For some AA LMICs, natural sources of PM_2.5 had the most significant health effects, and should not be ignored to ensure the protection of child health.

Spatiotemporal variation of PM2.5-related preterm birth in China and India during 1990-2019 and implications for emission controls

Preterm birth is the leading threat to neonatal health. The variation of PM_2.5-associated preterm birth in China and India from 1990 through 2019 was estimated in this study. Meanwhile, four mitigation scenarios were proposed, and the corresponding PM_2.5-related preterm birth was projected for 2030. Owing to differences in emission control policies and the effects of various factors (e.g., differences in population-control policies), the PM_2.5 concentration and PM_2.5-associated preterm birth in the two countries presented disparate spatiotemporal characteristics and variation trends during 1990-2019. The 30-year average of annual PM_2.5-associated preterm birth in India was 1018 (95% confidence interval, 718-1289) thousand, which was much larger than in China (280 [196-358] thousand). To fight air pollution, China launched several control strategies in the past two decades, and the nationwide maternal exposure risk dramatically decreased after 2010. In contrast, India's air-pollution control measures and policies have not effectively mitigated the nationwide PM_2.5 pollution. Under current mitigation measures and policies, the projected decrease in maternal exposure risk by 2030 is greater for China than India, and the scope for controlling air pollutant emissions and reducing maternal exposure risk is much large for India. The results of all four scenarios revealed that the annual PM_2.5-associated preterm birth in the two countries is likely to decrease in the future. In particular, if China and India implement more robust emission control strategies than those currently, the number of associated preterm birth is projected to be more than 50% lower in 2030 compared with 2019 rates.

Decadal changes in premature mortality associated with exposure to outdoor PM2.5 in mainland Southeast Asia and the impacts of biomass burning and anthropogenic emissions

In mainland Southeast Asia (SEA), a rapid increase of fossil fuel consumption and massive particulate matter emissions from biomass burning (BB) are severely threatening the health of local inhabitants. In this study, surface PM2.5 data, satellite fire observations and emission inventories were integrated with the Global Exposure Mortality Model (GEMM) to estimate premature mortality attributable to PM2.5 exposure from 1990 through 2019 and to explore and quantify the health burden associated with BB and anthropogenic emissions in mainland SEA. BB in mainland SEA has remained intense over the past decades. Owing to a lack of effective control measures, emission inventory and satellite-observed data both showed that BB has markedly intensified in several regions, including northern Cambodia and northern Laos. The multiannual average (1997-2015) BB PM2.5 emission was 1.6 × 106 t/yr, which is much higher than that of anthropogenic (fossil fuel combustion) PM2.5 emission. GEMM results indicated that PM2.5-related premature mortality in mainland SEA more than doubled from 100 (95 % confidence interval [CI], 88-112) thousand in 1990 to 257 (95 % CI, 228-286) thousand in 2019. Decomposition analysis revealed that variations in population size and age structure also promoted this increase of PM2.5-related deaths. Given that mainland SEA is a rapidly developing region, it is expected that local public health will face increasing challenges due to population growth, population ageing, and increased anthropogenic emissions. Therefore, it is imperative for policymakers to consider these influential factors, set practical mitigation targets, and explore how to effectively and systematically combine BB with anthropogenic emission controls to maximize the health benefits.

Fine particulate matter air pollution and under-5 children mortality in China: A national time-stratified case-crossover study

BACKGROUND

Under-5 mortality rate is an important indicator in Millennium Development Goals and Sustainable Development Goals. To date, no nationally representative studies have examined the effects of fine particulate matter (PM_2.5) air pollution on under-5 mortality.

OBJECTIVE

To investigate the association of short-term exposure to PM_2.5 with under-5 mortality from total and specific causes in China.

METHODS

We used the national Maternal and Child Health Surveillance System to identify under-5 mortality cases during the study period of 2009 to 2019. We adopted a time-stratified case-crossover study design at the individual level to capture the effect of short-term exposure to daily PM_2.5 on under-5 mortality, using conditional logistic regression models.

RESULTS

A total of 61,464 under-5 mortality cases were included. A 10 μg/m³ increase in concentrations of PM_2.5 on lag 0-1 d was significantly associated with a 1.15% (95%confidence interval: 0.65%, 1.65%) increase in under-5 mortality. Mortality from diarrhea, pneumonia, digestive diseases, and preterm birth were significantly associated with exposure to PM_2.5. The effect estimates were larger for neonatal mortality (<28 days), female children, and in warm seasons. We observed steeper slopes in lower ranges (<50 μg/m³) of the concentration-response curve between PM_2.5 and under-5 mortality, and positive associations remained below the 24-h PM_2.5 concentration limit recommended by WHO Air Quality Guidelines and China Air Quality Standards.

CONCLUSIONS

This nationwide case-crossover study in China demonstrated that acute exposure to PM_2.5 may significantly increase the risk of under-5 mortality, with larger effects for neonates, female children, and during warm seasons. Relevant control strategies are needed to remove this roadblock to achieving under-5 mortality targets in developing countries.