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Making visible the invisible: Health risks from environmental exposures among socially deprived populations of Nairobi, Kenya
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Most countries of sub-Saharan Africa (SSA) are experiencing a high rate of ur­banization accompanied with unplanned development resulting into sprawl of slums. The weath­er patterns and air pollution sources in most urban areas are changing with significant effects on health. Studies have established a link between environmental exposures, such as weather variation and air pollution, and adverse health outcomes. However, little is known about this relationship in urban populations of SSA where more than half the population reside in slums, or slum like conditions. A major reason for this is the lack of systematic collection of data on exposure and health outcomes. High quality prospective data collection and census registers still remain a great challenge. However, within small and spatially defined areas, dynamic cohorts have been established with continuous monitoring of health outcomes. Collection of environmental exposure data can complement cohort studies to investigate health effects in relation to environmental exposures. The objective of this research was to study the health effects of selected environmental exposure among the urban poor population in Nairobi, Kenya.

Methods: We used the platform of the Nairobi Urban Health and Demographic Surveillance System (NUHDSS), including two nested research studies, to provide data on mortality and mor­bidity. The NUHDSS was established in two areas of Nairobi, Korogocho and Viwandani, in 2003 and provides a unique opportunity for access to longitudinal population data. In addition, we conducted real-time measurements of particulate matter (PM2.5) in the areas from February to October in 2013. We obtained meteorological measurements from the Moi Air Base and Nairobi airport weather stations for the study period. We also conducted a cross-sectional survey to estab­lish the communities’ perceptions about air pollution and its related health risks. Time series re­gression models with a distributed lag approach were used to model the relationship between weather and mortality. A semi-ecological study with group level exposure assignment to individuals was used to assess the relationship between child health (morbidity and mortality) and the extent of PM2.5 exposure.

Results: There was a significant association between daily mean temperature and all-cause mor­tality with minimum mortality temperature (MMT) in the range of 18 to 20 °C. Both mortality risk and years of life lost analysis showed risk increases in relation to cold temperatures, with pronounced effect among children under-five. Overall, mortality risks were found to be high during cold periods of the year, rising with lower temperature from MMT to about 40% in the 0–4 age group, and by about v 20% among all ages. The results from air pollution assessment showed high levels of PM2.5 concentration exceeding World Health Organization (WHO) guideline limits in the two study ar­eas. The air pollution concentration showed similar seasonal and diurnal variation in the two slums. The majority of community residents reported to be exposed to air pollution at work, with 66% reporting to be exposed to different sources of air pollution. Despite the observed high level of exposure, residents had poor perception of air pollution levels and associated health risks. Children in the high-pollution areas (PM2.5≥ 25 μg⁄m3) were at significantly higher risk for morbidity (OR = 1.30, 95% CI: 1.13-1.48) and cough as the only form of morbidity (OR = 1.33, 95% CI: 1.15-1.53) compared to those in low-pollution areas. In addition, exposure to high levels of pollution was associated with high child mortality from all-causes (IRR=1.15, 95% CI: 1.03-1.28), and indicated a positive association to respiratory related mortality (IRR=1.10, 95% CI: 0.91-1.33).

Conclusion: The study findings extend our knowledge on health impacts related to environmental exposure by providing novel evidence on the risks in disadvantaged urban populations in Af­rica. More specifically, the study illustrates the invisible health burden that the urban poor population are facing in relation to weather and air pollution exposures. The effect of cold on population is preventable. This is manifested by the effective adaptation to cold conditions in high-latitude Nordic countries by housing standards and clothing, as well as a well-functioning health system. Further, awareness and knowledge of consequences, and reductions in exposure to air pollution, are necessary to improve public health in the slum areas. In conclusion, adverse health impacts caused by environmental stressors are critical to assess further in disadvantaged populations, and should be followed by development of mitigation measures leading to improved health and well being in SSA.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2015. , 60 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1734
Keyword [en]
air pollution, urban health, temperature-related mortality, particulate matter, exposure assessment, child health
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Research subject
Epidemiology; Public health
Identifiers
URN: urn:nbn:se:umu:diva-106857ISBN: 978-91-7601-306-9 (print)OAI: oai:DiVA.org:umu-106857DiVA: diva2:846541
Public defence
2015-09-11, Sal 135, Allmänmedicin, Norrlands Universitetssjukhus, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2015-08-21 Created: 2015-08-11 Last updated: 2015-08-21Bibliographically approved
List of papers
1. Time-series analysis of weather and mortality patterns in Nairobi's informal settlements
Open this publication in new window or tab >>Time-series analysis of weather and mortality patterns in Nairobi's informal settlements
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2012 (English)In: Global Health Action, ISSN 1654-9716, E-ISSN 1654-9880, Vol. 5, 23-32 p.Article in journal (Refereed) Published
Abstract [en]

Background: Many studies have established a link between weather (primarily temperature) and daily mortality in developed countries. However, little is known about this relationship in urban populations in sub-Saharan Africa. Objectives: The objective of this study was to describe the relationship between daily weather and mortality in Nairobi, Kenya, and to evaluate this relationship with regard to cause of death, age, and sex. Methods: We utilized mortality data from the Nairobi Urban Health and Demographic Surveillance System and applied time-series models to study the relationship between daily weather and mortality for a population of approximately 60,000 during the period 2003-2008. We used a distributed lag approach to model the delayed effect of weather on mortality, stratified by cause of death, age, and sex. Results: Increasing temperatures (above 75th percentile) were significantly associated with mortality in children and non-communicable disease (NCD) deaths. We found all-cause mortality of shorter lag of same day and previous day to increase by 3.0% for a 1 degree decrease from the 25th percentile of 18 degrees C (not statistically significant). Mortality among people aged 50+ and children aged below 5 years appeared most susceptible to cold compared to other age groups. Rainfall, in the lag period of 0-29 days, increased all-cause mortality in general, but was found strongest related to mortality among females. Low temperatures were associated with deaths due to acute infections, whereas rainfall was associated with all-cause pneumonia and NCD deaths. Conclusions: Increases in mortality were associated with both hot and cold weather as well as rainfall in Nairobi, but the relationship differed with regard to age, sex, and cause of death. Our findings indicate that weather-related mortality is a public health concern for the population in the informal settlements of Nairobi, Kenya, especially if current trends in climate change continue.

Keyword
time-series, temperature, rainfall, mortality, climate, urban
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-63044 (URN)10.3402/gha.v5i0.19065 (DOI)000311724400001 ()
Available from: 2012-12-27 Created: 2012-12-27 Last updated: 2017-12-06Bibliographically approved
2. Temperature variation and heat wave and cold spell impacts on years of life lost among the urban poor population of Nairobi, Kenya
Open this publication in new window or tab >>Temperature variation and heat wave and cold spell impacts on years of life lost among the urban poor population of Nairobi, Kenya
2015 (English)In: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 12, no 3, 2735-2748 p.Article in journal (Refereed) Published
Abstract [en]

Weather extremes are associated with adverse health outcomes, including mortality. Studies have investigated the mortality risk of temperature in terms of excess mortality, however, this risk estimate may not be appealing to policy makers assessing the benefits expected for any interventions to be adopted. To provide further evidence of the burden of extreme temperatures, we analyzed the effect of temperature on years of life lost (YLL) due to all-cause mortality among the population in two urban informal settlements. YLL was generated based on the life expectancy of the population during the study period by applying a survival analysis approach. Association between daily maximum temperature and YLL was assessed using a distributed lag nonlinear model. In addition, cold spell and heat wave effects, as defined according to different percentiles, were investigated. The exposure-response curve between temperature and YLL was J-shaped, with the minimum mortality temperature (MMT) of 26 °C. An average temperature of 21 °C compared to the MMT was associated with an increase of 27.4 YLL per day (95% CI, 2.7-52.0 years). However, there was no additional effect for extended periods of cold spells, nor did we find significant associations between YLL to heat or heat waves. Overall, increased YLL from all-causes were associated with cold spells indicating the need for initiating measure for reducing health burdens.

Keyword
cold-related mortality, heat-related mortality, heat wave, cold spell, temperature
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-103391 (URN)10.3390/ijerph120302735 (DOI)000351929700026 ()25739007 (PubMedID)
Available from: 2015-05-21 Created: 2015-05-21 Last updated: 2017-12-04Bibliographically approved
3. Measuring exposure levels of inhalable airborne particles (PM2.5) in two socially deprived areas of Nairobi, Kenya
Open this publication in new window or tab >>Measuring exposure levels of inhalable airborne particles (PM2.5) in two socially deprived areas of Nairobi, Kenya
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2016 (English)In: Environmental Research, ISSN 0013-9351, E-ISSN 1096-0953, Vol. 148, 500-506 p.Article in journal (Refereed) Published
Abstract [en]

Introduction: Ambient air pollution is a growing global health concern tightly connected to the rapid global urbanization. Health impacts from outdoor air pollution exposure amounts to high burdens of deaths and disease worldwide. However, the lack of systematic collection of air pollution and health data in many low-and middle-income countries remains a challenge for epidemiological studies in the local environment. This study aimed to provide a description of the particulate matter (PM2.5) concentration in the poorest urban residential areas of Nairobi, Kenya. Methods: Real-time measurements of (PM2.5) were conducted in two urban informal settlements of Nairobi City, Kenya"s Capital, from February 2013 to October 2013. The measurements were conducted using DustTrak II 8532 hand-held samplers at a height of about 1.5 m above ground level with a resolution of 1-min logging. Sampling took place from early morning to evenings according to a fixed route of measurement within areas including fixed geographical checkpoints. Results: The study period average concentration of PM2.5 was 166 mu g/m(3) in the Korogocho area and 67 mu g/m(3) in the Viwandani area. The PM2.5 levels in both areas reached bimodal daily peaks in the morning and evening. The average peak value of morning concentration in Korogocho was 214 mu g/m(3), and 164 mu g/m(3) in the evening and in Viwandani was 76 mu g/m(3) and 82 mu g/m(3) respectively. The daily midday average low observed during was 146 mu g/m(3) in Korogocho and 59 mu g/m(3) in Viwandani. Conclusion: The results show that residents in both slums are continuously exposed to PM2.5 levels exceeding hazardous levels according to World Health Organization guidelines. The study showed a marked disparity between the two slum areas situated only 7 km apart indicating the local situation and sources to be very important for exposure to PM2.5.

Keyword
Particulate matter, Urban pollution, Exposure, Air pollution, Assessment, Slum; PM2.5, Low- and middle-income country
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-106854 (URN)10.1016/j.envres.2016.03.018 (DOI)000376712800054 ()27152713 (PubMedID)
External cooperation:
Available from: 2015-08-11 Created: 2015-08-11 Last updated: 2017-12-04Bibliographically approved
4. Child morbidity and mortality associated with exposure to inhalable particles (PM2.5) among the urban poor in Nairobi, Kenya
Open this publication in new window or tab >>Child morbidity and mortality associated with exposure to inhalable particles (PM2.5) among the urban poor in Nairobi, Kenya
(English)Article in journal (Refereed) Submitted
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-106856 (URN)
Available from: 2015-08-11 Created: 2015-08-11 Last updated: 2015-08-21Bibliographically approved
5. Community perceptions of air pollution and related health risks in Nairobi slums
Open this publication in new window or tab >>Community perceptions of air pollution and related health risks in Nairobi slums
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2013 (English)In: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 10, no 10, 4851-4868 p.Article in journal (Refereed) Published
Abstract [en]

Air pollution is among the leading global risks for mortality and responsible for increasing risk for chronic diseases. Community perceptions on exposure are critical in determining people's response and acceptance of related policies. Therefore, understanding people' perception is critical in informing the design of appropriate intervention measures. The aim of this paper was to establish levels and associations between perceived pollution and health risk perception among slum residents. A cross-sectional study of 5,317 individuals aged 35+ years was conducted in two slums of Nairobi. Association of perceived score and individual characteristics was assessed using linear regression. Spatial variation in the perceived levels was determined through hot spot analysis using ArcGIS. The average perceived air pollution level was higher among residents in Viwandani compared to those in Korogocho. Perceived air pollution level was positively associated with perceived health risks. The majority of respondents were exposed to air pollution in their place of work with 66% exposed to at least two sources of air pollution. Less than 20% of the respondents in both areas mentioned sources related to indoor pollution. The perceived air pollution level and related health risks in the study community were low among the residents indicating the need for promoting awareness on air pollution sources and related health risks.

Keyword
perceived air quality, air pollution, perceived health risk, urban slum
National Category
Environmental Health and Occupational Health Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-84022 (URN)10.3390/ijerph10104851 (DOI)000330520500020 ()24157509 (PubMedID)
Available from: 2013-12-12 Created: 2013-12-12 Last updated: 2017-12-06Bibliographically approved

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