An assessment of the spatio-temporal dynamics of Landsat-derived aerosol concentration in relation with land cover and road networks in the Lagos megacity.

The interrelationships between air quality, land cover change, and road networks in the Lagos megacity have not been explored. Globally, there are knowledge gaps in understanding these dynamics, especially using remote sensing data. This study used multi-temporal and multi-spectral Landsat imageries at four epochs (2002, 2013, 2015, and 2020) to evaluate the aerosol optical thickness (AOT) levels in relation to land cover and road networks in the Lagos megacity. A look-up table (LUT) was generated using Py6S, a python-based 6S module, to simulate the AOT using land surface reflectance and top of atmosphere reflectance. A comparative assessment of the method against in situ measurements of particulate matter (PM) at different locations shows a strong positive correlation between the imagery-derived AOT values and the PMs. The AOT concentration across the land cover and road networks showed an increasing trend from 2002 to 2020, which could be explained by urbanization in the megacity. The higher concentration of AOT along the major roads is attributed to the high air pollutants released from vehicles, including home/office generators and industries along the road corridors. The continuous rise in pollutant values requires urgent intervention and mitigation efforts. Remote sensing-based AOT monitoring is a possible solution.

The Exposure of Workers at a Busy Road Node to PM2.5: Occupational Risk Characterisation and Mitigation Measures.

The link between air pollution and health burden in urban areas has been well researched. This has led to a plethora of effective policy-induced monitoring and interventions in the global south. However, the implication of pollutant species like PM2.5 in low middle income countries (LMIC) still remains a concern. By adopting a positivist philosophy and deductive reasoning, this research addresses the question, to what extent can we deliver effective interventions to improve air quality at a building structure located at a busy road node in a LMIC? This study assessed the temporal variability of pollutants around the university environment to provide a novel comparative evaluation of occupational shift patterns and the use of facemasks as risk control interventions. The findings indicate that the concentration of PM2.5, which can be as high as 300% compared to the WHO reference, was exacerbated by episodic events. With a notable decay period of approximately one-week, adequate protection and/or avoidance of hotspots are required for at-risk individuals within a busy road node. The use of masks with 80% efficiency provides sufficient mitigation against exposure risks to elevated PM2.5 concentrations without occupational shift, and 50% efficiency with at least '2 h ON, 2 h OFF' occupational shift scenario.

A Systematic Review Protocol of Opportunities for Noncommunicable Disease Prevention via Public Space Initiatives in African Cities.

Public spaces have the potential to produce equitable improvements in population health. This mixed-methods systematic review aims to understand the components of, determinants, risks, and outcomes associated with public space initiatives in African cities. This study will include quantitative and qualitative study designs that describe public space initiatives in African cities with implications for promoting health and wellbeing, particularly through the prevention of noncommunicable diseases. Only studies published after 1990 and that contain primary or secondary data will be included in the review. Literature search strategies will be developed with a medical librarian. We will search PubMed, using both text words and medical subject headings. We will adapt this search to Scopus, Global Health, and Web of Science. This systematic review will adopt a mixed methods analytical approach. Mixing will occur in extracting both qualitative and quantitative findings; in synthesizing findings; and in the analysis where we will integrate the qualitative and quantitative strands. The learnings from this study will contribute to advancing knowledge on noncommunicable disease prevention through public space initiatives in African cities.

Atmospheric concentrations of polychlorinated biphenyls, brominated flame retardants, and novel flame retardants in Lagos, Nigeria indicate substantial local sources.

Polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs) like polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD), and novel flame retardants (NFRs) like decabromodiphenyl ethane (DBDPE) are ubiquitous environmental pollutants. Despite this, little is known about their concentrations in outdoor air in the African continent. To address this knowledge gap, concentrations of BFRs, NFRs, and PCBs were measured in outdoor air at 8 sites located within the metropolitan area of Lagos, Nigeria. Concentrations of ∑8BDEs, ∑HBCDD, ∑7NFRs and ∑8PCBs were: 21-750 (median = 100) pg/m3, <12-180 (median = < 12) pg/m3, 34-900 (median = 300) pg/m3 and 85-460 (median = 300) pg/m3, respectively. Decabromodiphenyl ether (BDE-209, range: <16-620 pg/m3, median = 71 pg/m3) and DBDPE (range: <37-890 pg/m3, median = 280 pg/m3) were the dominant BFRs detected, while the non-Arochlor PCB 11 (range: 49-220 pg/m3, median = 100 pg/m3) was the dominant PCB. To the authors' knowledge, these are the first data on the non-Arochlor PCB 11 in outdoor air in Africa. In general, concentrations of all target contaminants in this study were within the range reported elsewhere in Africa and worldwide. Likely due to the tropical climate of Lagos, no seasonal variation in concentrations was discernible for any of the target contaminants. While concentrations of PBDEs and some NFRs were correlated with population density, concentrations of PCBs appear more impacted by leaks from electrical transformers and for PCB 11 to proximity to activities like textile factories that produce and use dyes.

Concentrations of halogenated flame retardants and polychlorinated biphenyls in house dust from Lagos, Nigeria.

Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecane (HBCDD) are regulated under the Stockholm Convention of the United Nations' Environment Programme; with similar concerns emerging about alternative halogenated flame retardants (alt-HFRs), the use of which is increasing as replacements for PBDEs and HBCDD. While the presence in indoor dust of PCBs, PBDEs, and HBCDDs has been reported previously in a few African locations including Lagos, Nigeria, we are unaware of similar data for alt-HFRs. The present study thus aimed to provide the first information on alt-HFRs in indoor dust in sub-Saharan Africa, and to evaluate the impact of restrictions on the use of PBDEs, HBCDD, and PCBs on their concentrations in house dust in Lagos, Nigeria. Concentrations of ∑8PBDEs, ∑HBCDDs, ∑7alt-HFRs, and ∑8PCBs in 15 samples of dust from homes in Lagos, Nigeria were found to be: 43-810 (median = 300) ng g-1,

GAPS-megacities: A new global platform for investigating persistent organic pollutants and chemicals of emerging concern in urban air.

A pilot study was initiated in 2018 under the Global Atmospheric Passive Sampling (GAPS) Network named GAPS-Megacities. This study included 20 megacities/major cities across the globe with the goal of better understanding and comparing ambient air levels of persistent organic pollutants and other chemicals of emerging concern, to which humans residing in large cities are exposed. The first results from the initial period of sampling are reported for 19 cities for several classes of flame retardants (FRs) including organophosphate esters (OPEs), polybrominated diphenyl ethers (PBDEs), and halogenated flame retardants (HFRs) including new flame retardants (NFRs), tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCDD). The two cities, New York (USA) and London (UK) stood out with ∼3.5 to 30 times higher total FR concentrations as compared to other major cities, with total concentrations of OPEs of 15,100 and 14,100 pg/m3, respectively. Atmospheric concentrations of OPEs significantly dominated the FR profile at all sites, with total concentrations in air that were 2-5 orders of magnitude higher compared to other targeted chemical classes. A moderately strong and significant correlation (r = 0.625, p < 0.001) was observed for Gross Domestic Product index of the cities with total OPEs levels. Although large differences in FR levels were observed between some cities, when averaged across the five United Nations regions, the FR classes were more evenly distributed and varied by less than a factor of five. Results for Toronto, which is a 'reference city' for this study, agreed well with a more in-depth investigation of the level of FRs over different seasons and across eight sites representing different urban source sectors (e.g. traffic, industrial, residential and background). Future sampling periods under this project will investigate trace metals and other contaminant classes, linkages to toxicology, non-targeted analysis, and eventually temporal trends. The study provides a unique urban platform for evaluating global exposome.

Impact of gas flaring on surface and underground water: a case study of Anieze and Okwuibome areas of Delta State, Nigeria.

Gas flaring is a major activity in oil exploration processes in Nigeria with concerns on its effects on the oil communities. This study investigated the contribution of flare gases to pollution burden of Anieze and Okwuibome communities. Water samples were displayed at 10-m, 50-m, and 100-m locations from gas-flaring stations, and control samples were taken in another location. After a month, the water samples were examined for heavy metals, polycyclic aromatic hydrocarbons, and physico-chemical parameters. Pb was found only in the 50-m location and above the WHO standard. Fe, Zn, and Cr were detected in the order 10 m > 50 m > 100 m > control whereas Cd was detected in the order 100 m > 50 m > 10 m > control. Fe, Zn, Cr, and Cd were linked to gas-flaring activities. The total PAHs were found in the order 10 m (1929.43 µg/L) > 100 m (1759.64 µg/L) > 50 m (620.27 µg/L) > control (389.37 µg/L). The signature ratio related the PAH sources to combination of petroleum and combustion sources. The sources of the PAHs were linked to the flare gas. The study implicates gas-flaring activities for the increased pollution burden in the communities and suggests policies that guide its reduction in petroleum explorations.