Census-independent population mapping in northern Nigeria.

Although remote sensing has long been used to aid in the estimation of population, it has usually been in the context of spatial disaggregation of national census data, with the census counts serving both as observational data for specifying models and as constraints on model outputs. Here we present a framework for estimating populations from the bottom up, entirely independently of national census data, a critical need in areas without recent and reliable census data. To make observations of population density, we replace national census data with a microcensus, in which we enumerate population for a sample of small areas within the states of Kano and Kaduna in northern Nigeria. Using supervised texture-based classifiers with very high resolution satellite imagery, we produce a binary map of human settlement at 8-meter resolution across the two states and then a more refined classification consisting of 7 residential types and 1 non-residential type. Using the residential types and a model linking them to the population density observations, we produce population estimates across the two states in a gridded raster format, at approximately 90-meter resolution. We also demonstrate a simulation framework for capturing uncertainty and presenting estimates as prediction intervals for any region of interest of any size and composition within the study region. Used in concert with previously published demographic estimates, our population estimates allowed for predictions of the population under 5 in ten administrative wards that fit strongly with reference data collected during polio vaccination campaigns.

Mapping for Health in Cameroon: Polio Legacy and Beyond.

During the poliovirus outbreak in Cameroon from October 2013 to April 2015, the Ministry of Public Health's Expanded Program on Immunization requested technical support to improve mapping of health district boundaries and health facility locations for more effective planning and analysis of polio program data. In December 2015, teams collected data on settlements, health facilities, and other features using smartphones. These data, combined with high-resolution satellite imagery, were used to create new health area and health district boundaries, providing the most accurate health sector administrative boundaries to date for Cameroon. The new maps are useful to and used by the polio program as well as other public health programs within Cameroon such as the District Health Information System and the Emergency Operations Center, demonstrating the value of the Global Polio Eradication Initiative's legacy.

Improving polio vaccination coverage in Nigeria through the use of geographic information system technology.

BACKGROUND: Historically, microplanning for polio vaccination campaigns in Nigeria relied on inaccurate and incomplete hand-drawn maps, resulting in the exclusion of entire settlements and missed children. The goal of this work was to create accurate, coordinate-based maps for 8 polio-endemic states in northern Nigeria to improve microplanning and support tracking of vaccination teams, thereby enhancing coverage, supervision, and accountability. METHODS: Settlement features were identified in the target states, using high-resolution satellite imagery. Field teams collected names and geocoordinates for each settlement feature, with the help of local guides. Global position system (GPS) tracking of vaccination teams was conducted in selected areas and daily feedback provided to supervisors. RESULTS: Geographic information system (GIS)-based maps were created for 2238 wards in the 8 target states. The resulting microplans included all settlements and more-efficient team assignments, owing to the improved spatial reference. GPS tracking was conducted in 111 high-risk local government areas, resulting in improved team performance and the identification of missed/poorly covered settlements. CONCLUSIONS: Accurate and complete maps are a necessary part of an effective polio microplan, and tracking vaccinators gives supervisors a tool to ensure that all settlements are visited.

Lessons learned from the Global Polio Eradication Initiative: A roadmap for the international COVID-19 vaccination campaign.

The COVID-19 vaccine is lauded by many as one of the greatest accomplishments in modern medicine, with the potential to definitively contain the deadliest pandemic of the last century. With the vaccine rollout now underway in the developing world, a robust, methodical, and swift global distribution effort is required to ensure that it will be done in an equitable manner. Taking into account the vast geographic, socioeconomic, cultural, and political diversity of countries around the world, global vaccination efforts have historically required multifaceted, time consuming, and labor-intensive approaches to be effective. However, with over 33 years of experience from the Global Polio Eradication Initiative - an international health initiative aimed at eradicating poliomyelitis - the COVID-19 vaccination campaign does not have to be approached blindly. Using lessons learned from the Global Polio Eradication Initiative, this paper aims to identify the supply- and demand-side barriers to the success of the international COVID-19 vaccination effort, and ways each can be overcome. Most notably, health systems shortcomings, political and cultural messaging, and civil unrest and violent conflict serve as daunting obstacles to the success of the COVID-19 vaccination campaign. The Global Polio Eradication Initiative has been able to overcome many of these same obstacles with innovative strategies such as context-specific microplanning, robust health surveillance systems, and community-centered education and advocacy programs. Ultimately, while the Global Polio Eradication Initiative is still fighting the battle of polio eradication, it has provided a roadmap for the COVID-19 vaccination campaign to be executed in a more swift and equitable manner.

Development and application of a sensitive method to determine concentrations of acrolein and other carbonyls in ambient air.

Acrolein, an unsaturated aldehyde, has been identified as one of the most important toxic air pollutants in recent assessments of ambient air quality. Current methods for determining acrolein concentrations, however, suffer from poor sensitivity, selectivity, and reproducibility. The collection and analysis of unsaturated carbonyls, and acrolein in particular, is complicated by unstable derivatives, coelution of similar compounds, and ozone interference. The primary objective of this research was to develop an analytical method to measure acrolein and other volatile carbonyls present in low part-per-trillion concentrations in ambient air samples obtained over short sampling periods. The method we devised uses a mist chamber in which carbonyls from air samples form water-soluble adducts with bisulfite in the chamber solution, effectively trapping the carbonyls in the solution. The mist chamber methodology proved effective, with collection efficiency for acrolein of at least 70% for each mist chamber at a flow rate of approximately 17 L/min. After the sample collection, the carbonyls are liberated from the bisulfite adducts through the addition of hydrogen peroxide, which converts the bisulfite to sulfate, reversing the bisulfite addition reaction. The free carbonyls are then derivatized by o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA*), which stabilizes the analytes and makes them easier to detect by electron-capture negative ionization mass spectrometry (ECNI-MS). The derivatives are then extracted and analyzed by gas chromatography-mass spectrometry (GC-MS). The mist chamber method was applied in a field test to determine the extent of acrolein in ambient air near the Peace Bridge plaza in Buffalo, New York, an area of heavy traffic near a major border crossing between the United States and Canada. In addition, XAD-2 adsorbent cartridges coated with 2-(hydroxymethyl)piperidine (2-HMP) according to Occupational Safety and Health Administration (OSHA) Method 52 and passive samplers based on the use of dansylhydrazine (DNSH) were deployed at this location at the same time, which provided the opportunity to compare methods. The mist chamber results showed that the Peace Bridge traffic was clearly a source of acrolein, with an average concentration of 0.26 microg/m3 at a site 152.4 m downwind (northeast) of the plaza. The OSHA cartridges proved to be too insensitive to determine ambient acrolein concentrations. The DNSH passive samplers returned concentrations near the limit of detection; hence the values were a little higher and less consistent than those in the mist chamber results. The optimized mist chamber method was then applied to determine atmospheric acrolein concentrations at three sites in northern California: a site chosen to reflect the hemispheric background, a region dominated by biogenic sources, and an urban environment. The resulting average acrolein concentrations were 0.056, 0.089, and 0.290 microg/m3, respectively, and the limit of detection was 0.012 microg/m3 The consistency of the replicate samples obtained in the field was good, with the relative standard deviations (RSDs) ranging from 19% at the hemispheric background site to 3% at the urban site. The advantage of the current mist chamber method is that it can determine ambient acrolein concentrations over short time periods with enough sensitivity to be effective even in relatively "clean" environments. This allows for the determination of temporal patterns related to acrolein concentrations, such as diurnal cycles of reaction kinetics. The main disadvantages of the method are that it is laborious and time-consuming and requires specialized equipment that makes it difficult to utilize for routine monitoring of acrolein.

Advancing digital methods in the fight against communicable diseases.

Important advances are being made in the fight against communicable diseases by using new digital tools. While they can be a challenge to deploy at-scale, GPS-enabled smartphones, electronic dashboards and computer models have multiple benefits. They can facilitate program operations, lead to new insights about the disease transmission and support strategic planning. Today, tools such as these are used to vaccinate more children against polio in Nigeria, reduce the malaria burden in Zambia and help predict the spread of the Ebola epidemic in West Africa.

Origin, occurrence, and source emission rate of acrolein in residential indoor air.

Acrolein, a volatile, unsaturated aldehyde, is a known respiratory toxicant and one of the 188 most hazardous air pollutants identified by the U.S. EPA. A newly developed analytical method was used to determine residential indoor air concentrations of acrolein and other volatile aldehydes in nine homes located in three California counties (Los Angeles, Placer, Yolo). Average indoor air concentrations of acrolein were an order of magnitude higher than outdoor concentrations at the same time. All homes showed similar diurnal patterns in indoor air concentrations, with acrolein levels in evening samples up to 2.5 times higherthan morning samples. These increases were strongly correlated with temperature and cooking events, and homes with frequent, regular cooking activity had the highest baseline (morning) acrolein levels. High acrolein concentrations were also found in newly built, uninhabited homes and in emissions from lumber commonly used in home construction, suggesting indoor contributions from off-gassing and/or secondary formation. The results provide strong evidence that human exposure to acrolein is dominated by indoor air with little contribution from ambient outdoor air.

A sensitive method for the quantification of acrolein and other volatile carbonyls in ambient air.

Acrolein, an unsaturated aldehyde found in both indoor and outdoor air, is considered one of the greatest noncancer health risks of all organic air pollutants. Current methods for determining acrolein often employ sorbent-filled cartridges containing a carbonyl derivatizing agent (e.g., dinitrophenylhydrazine). These methods are of limited use for unsaturated compounds due to the formation of unstable derivatives, coelution of similar compounds, long sample collection times, and ozone interferences that result in poor sensitivity, selectivity, and reproducibility. The goal of this research was to develop an analytical method for determining ppt concentrations of acrolein and other carbonyls in air with short sampling times (10 min). The method uses a mist chamber to collect carbonyls by forming water-soluble carbonyl-bisulfite adducts. The carbonyls are then liberated from the bisulfite, derivatized, and quantified by gas chromatography/electron capture negative ionization mass spectrometry. The method was applied to determine atmospheric acrolein concentrations at three sites in northern California reflecting hemispheric background concentrations, biogenic-dominated regions, and urban environments. The resulting acrolein concentrations were 0.056, 0.089, and 0.29 microg/m3, respectively, which are all above the EPA Reference Concentration of 0.02 microg/m3. The minimum detection limit of 0.012 microg/m3 is below that of other published methods. Methacrolein, methyl vinyl ketone, crotonaldehyde, glyoxal, methyl glyoxal, and benzaldehyde were also quantified.