Abstract

Highlights

• Concentrations of 23 elements were established in urine of Ethiopian Rift populations.
• As, F^–,B, Mo, Mn, Tl, Li, and Zn in urine were higher than in the reference populations.
• Elevated levels of elements such as As call for speciation and health studies.
• The study highlights the need for more biomonitoring studies in African nations to protect public health.

Biomonitoring of chemical concentrations in humans is important for detecting, monitoring, and addressing a wide range of health threats. However, it is virtually absent across many African nations, including Ethiopia. This study aims to determine urinary concentrations for metals and trace elements in populations living in the central Ethiopian Rift Valley. The region is unindustralized, rural, and characterized by unique geologic rifting and volcanic activities that have produced vast pyroclastic materials, forming its aquifer and fertile agricultural soils. Millions of people in the region rely on wells for drinking water and are engaged in cereal-based subsistence agriculture. We enrolled a total of 386 residents aged 10-50 years old (201 females and 185 males). The levels of 23 elements except F^– were quantified in water and urine samples by ICP-MS. Mean concentrations of B, F^–, Ca, and Mg were measured in mg/L levels, while concentrations of Mo, Zn, Sr, Rb, and Li ranged between 100 and 700 ug/L. Mean concentrations between 5 and 15 ug/L were found for Ni, Cu, and Mn, while Ag, Be, Cd, Co, Pb, Sb, Th, TI, and U were all below 5 ug/L. Arsenic and Al had mean concentrations between 30 and 50 ug/L. Mean urinary concentrations of Ca, Cu, Mg, Pb, Sr, and Zn were significantly higher in males than females, whereas Co and Mn were higher in females. Finally, younger individuals (10-30 years) had significantly higher mean concentrations of B, Cd, Co, Mg, Mo, and Pb than those between 31 and 50 years, whereas only Ca was higher in the older age group. The concentration ranges of B, Mo, Mn, TI, Li, Zn, and in particular F^– (0.44-44.6 mg/L) and As (2.2-164 ug/L) in urine were higher than the reference ranges reported in healthy unexposed North American and European populations, while those for the remaining 16 elements were comparable to published reference ranges from such settings. The established concentration ranges are important to monitor future changes in exposure, and risk factors for disease, that might stem from the economic growth and industrialization that is currently underway in the region.

*Free full-text study online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6440854/

Excerpt:

2.1. Study population

A total of 386 individuals (10 to 50 years old) were enrolled from 27 rural communities during two sampling periods (June 2015 and May 2016) (Figure 1). Based on extensive prior work conducted to characterize the range of F^– levels in community water sources in the Ethiopian Rift Valley region, communities covering the range of F^– exposures were selected for the study. Given the high correlation in F^– and other exposures in this location (Rango et al., 2009; 2014), it likely represents most of the range of potential exposures in the Rift population…

3.3. Distribution of metals and trace elements in urine

Fluoride concentrations fell between 0.44 and 44.6mg/L (mean:10.1±7.1 mg/L). More than 96% of the urine samples contained F^– at levels higher than the Biological Exposure Index (BEI) value of 2mg/L established by industrial hygienists as a guideline for occupational exposure (ACGIH, 2012). The maximum of 44.6mg/L is much higher than reported levels seen in other studies including from endemic areas (e.g., Susheela et al., 2002). We also compared our data with Biomonitoring Equivalents (BEs), which refer to the concentration or range of concentrations of chemicals in a biological medium that is consistent with an existing health-based exposure guideline. The F^– range we have obtained in our study is far beyond the established range for BEs (1.1-2.1mg/L) (Aylward et al., 2015), indicating high potential health risks to the Rift population.

 

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