Assessing the health effects of naturally-occurring groundwater contamination in the Rift Valley, Ethiopia

Many of the health impacts of climate change in the developing world are likely to be mediated through connections to water resources via shifting accessibility to safe drinking water and to a sustainable water supply for food production. This interdisciplinary project aims to study the specific linkages between climate change, water resources, population, and health in one such drought-sensitive region, the central Rift Valley of Ethiopia. The research aims to inform how adaptation to climate impacts on water and health might be enhanced in this and other similar locations, such that societal resilience and welfare can be improved. Also see related work on social capital here.

RiftValley well Figure 2

Rift Valley well

Main research collaborators:

RiftValley survey team

Rift Valley survey team

  • Tewodros Rango; Avner Vengosh; Chris Paul; Erika Weinthal; Julia Krauchanka; Wenhong Li; Brittany Merola (Duke)
  • Peter McCornick (IWMI)

Related Publications:

Li, L.; W. Li.; T. Ballard; G. Sun; and M. Jeuland (2015). “CMIP5 model simulations of Ethiopian Kiremt-season precipitation: current climate and future changes.” Climate Dynamics (Accepted).

Abstract: Kiremt-season (June–September) precipitation provides a significant water supply for Ethiopia, particularly in the central and northern regions. The response of Kiremt-season precipitation to climate change is thus of great concern to water resource managers. However, the complex processes that control Kiremt-season precipitation challenge the capability of general circulation models (GCMs) to accurately simulate precipitation amount and variability. This in turn raises questions about their utility for predicting future changes. This study assesses the impact of climate change on Kiremt-season precipitation using state-of-the-art GCMs participating in the Coupled Model Intercomparison Project Phase 5. Compared to models with a coarse resolution, high-resolution models (horizontal resolution <2°) can more accurately simulate precipitation, most likely due to their ability to capture precipitation induced by topography. Under the Representative Concentration Pathway (RCP) 4.5 scenario, these high-resolution models project an increase in precipitation over central Highlands and northern Great Rift Valley in Ethiopia, but a decrease in precipitation over the southern part of the country. Such a dipole pattern is attributable to the intensification of the North Atlantic subtropical high (NASH) in a warmer climate, which influences Ethiopian Kiremt-season precipitation mainly by modulating atmospheric vertical motion. Diagnosis of the omega equation demonstrates that an intensified NASH increases (decreases) the advection of warm air and positive vorticity into the central Highlands and northern Great Rift Valley (southern part of the country), enhancing upward motion over the northern Rift Valley but decreasing elsewhere. Under the RCP 4.5 scenario, the high-resolution models project an intensification of the NASH by 15 (3 × 105 m2 s −2 ) geopotential meters (stream function) at the 850-hPa level, contributing to the projected precipitation change over Ethiopia. The influence of the NASH on Kiremtseason precipitation becomes more evident in the future due to the offsetting effects of two other major circulation systems: the East African Low-level Jet (EALLJ) and the Tropical Easterly Jet (TEJ). The high-resolution models project a strengthening of the EALLJ, but a weakening of the TEJ. Future changes in the EALLJ and TEJ will drive this precipitation system in opposite directions, leading to small or no net changes in precipitation in Ethiopia.

Rango, T.; A. Vengosh; M. Jeuland; R. Tekle-Haimanot, E. Weinthal, J. Kravchenko, C. Paul, P. McCornick (2014). “Fluoride exposure from groundwater as reflected by urinary fluoride and children’s dental fluorosis in the Main Ethiopian Rift Valley.” Science of the Total Environment 496: 188-197.

AbstractBackground: Chronic exposure to excessive amounts of fluoride (F─) during tooth development can cause dental fluorosis (DF). While most previous DF studies have been limited to narrow ranges of F─ exposures, this study investigated adverse DF effects coupled with urinary F─ concentrations in children exposed to a wide range of water F─ concentrations within a specific homogeneous population in the Main Ethiopian Rift (MER).
Objectives: The study aims to explore the relationships between F─ exposure in drinking groundwater, urinary F─ concentrations, and DF development in children with stable and consistent F─ exposure during the critical period of enamel development as well as formation of permanent teeth.
Methods: A cross-sectional study was conducted between 2010 and 2012 that examined DF status among 491 children (10 to 15 years old) in 33 communities with groundwater F─ concentrations that ranged between 1.1 to 18 mg/L. A subset of 156 children was selected for urinary F─ measurements. We applied field and analytical methods to quantify F─ and other chemical parameters in groundwater and urine, and statistical methods to analyze health outcomes.
Results: The mean F─ concentrations in groundwater and urine were 8.5±4.1 (range: 1.1-18 mg/L) and 12.1±7.3 mg/L (range: 1.1-39.8 mg/L), respectively. The prevalence of mild, moderate, and severe DF in children’s teeth was 17%, 29%, and 45%, respectively. The exposure response relationship between F─ and DF was non-linear, with DF severity tending to level off above a F─ threshold of ~6 mg/L, most likely due to the fact that at ~6 mg/L the enamel is damaged as much as it can be clinically observed in most of the children. We also observed differential prevalence (and severity) of DF across children exposed to similar F─ concentrations in water. The majority (90%; n=140) of
children’s urinary F─ concentrations exceeded 3 mg/L, a level below which most of the teeth showed mild forms of DF.
Conclusion: The results highlight the non-linear and positive relationship between F─ concentrations in drinking water and the severity of DF in children with exceptionally high levels of F─ in urine. The study also suggests the importance of better understanding individual specific factors other than exposures through drinking water to explain inter-individual DF variation in this population.

Krauchanka, J.; T. Rango; I. Akushevich; B. Atlaw; P.G. McCornick; B.R. Merola; C. Paul; E. Weinthal; A. Vengosh; M. Jeuland (2014). “The effect of non-fluoride factors on risk of dental fluorosis: Evidence from rural populations of the Main Ethiopian Rift.” Science of the Total Environment 488-489: 595-606.

Abstract: Elevated level of fluoride (F−) in drinking water is a well-recognized risk factor of dental fluorosis (DF). While considering optimization of region-specific standards for F−, it is reasonable, however, to consider how local diet, water sourcing practices, and non-F− elements in water may be related to health outcomes. In this study, we hypothesized that non-F− elements in groundwater and lifestyle and demographic characteristics may be independent predictors or modifiers of the effects of F− on teeth.
Dental examinations were conducted among 1094 inhabitants from 399 randomly-selected households of 20 rural communities of the Ziway–Shala lake basin of the Main Ethiopian Rift. DF severity was evaluated using the Thylstrup-Fejerskov Index (TFI). Household surveys were performed and water samples were collected from community water sources. To consider interrelations between the teeth within individual (in terms of DF severity) and between F− and non-F− elements in groundwater, the statistical methods of regression analysis, mixed models, and principal component analysis were used.
About 90% of study participants consumed water fromwells with F− levels above theWHO recommended standard of 1.5 mg/l. More than 62% of the study population had DF. F− levels were amajor factor associatedwith DF. Age, sex, andmilk consumption (both cow’s and breastfed)were also statistically significantly (p b 0.05) associated with DF severity; these associations appear both independently and as modifiers of those identified between F− concentration and DF severity. Among 35 examined elements in groundwater, Ca, Al, Cu, and Rb were found to be significantly correlated with dental health outcomes among the residents exposed to waterwith excessive F− concentrations.
Quantitative estimates obtained in our study can be used to explore new water treatment strategies, water safety and quality regulations, and lifestyle recommendations which may be more appropriate for this highly populated region.

Rango, T.; J. Kravchenko; A. Vengosh; P. McCornick; B. Atlaw; M. Jeuland & B. Merola (2012). “Groundwater quality and its health impact: an assessment of dental fluorosis in rural inhabitants of the Main Ethiopian Rift.” Environment International 43: 37-47; doi:10.1016/j.envint.2012.03.002.

Abstract: This study aims to assess the link between fluoride content in groundwater and its impact on dental health in rural communities of the Ethiopian Rift. A total of 148 water samples were collected from two drainage basins within the Main Ethiopian Rift (MER). In the Ziway–Shala basin in particular, wells had high fluoride levels (mean: 9.4±10.5 mg/L; range: 1.1 to 68 mg/L), with 48 of 50 exceeding the WHO drinking water guideline limit of 1.5 mg/L. Total average daily intake of fluoride from drinking groundwater (calculated per weight unit) was also found to be six times higher than the No-Observed-Adverse-Effects-Level (NOAEL) value of 0.06 mg/kg/day. The highest fluoride levels were found in highly-alkaline (pH of 7 to 8.9) groundwater characterized by high salinity; high concentrations of sodium (Na+), bicarbonate (HCO3−), and silica (SiO2); and low concentrations of calcium (Ca2+). A progressive Ca2+ decrease along the groundwater flow path is associated with an increase of fluoride in the groundwater. The groundwater quality problem is also coupled with the presence of other toxic elements, such as arsenic (As) and uranium (U). The health impact of fluoride was evaluated based on clinical examination of dental fluorosis (DF) among local residents using the Thylstrup and Fejerskov index (TFI). In total, 200 rural inhabitants between the ages of 7 and 40 years old using water from 12 wells of fluoride range of 7.8–18 mg/L were examined. Signs of DF (TF score of ≥1) were observed in all individuals. Most of the teeth (52%) recorded TF scores of 5 and 6, followed by TF scores of 3 and 4 (30%), and 8.4% had TF scores of 7 or higher. Sixty percent of the teeth exhibited loss of the outermost enamel. Within the range of fluoride contents, we did not find any correlation between fluoride content and DF. Finally, preliminary data suggest that milk intake has contributed to reducing the severity of DF. The study highlights the apparent positive role of milk on DF, and emphasizes the importance of nutrition in management efforts to mitigate DF in the MER and other parts of the world.


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