Arsenic Contamination in Water from Selected Boreholes in Nairobi City County, Kenya

Arsenic is a metalloid, which may be found in surface water, ground plants and rocks. In high concentrations, its compounds are considered to genotoxic carcinogenic. Its levels drinking water must regularly monitored controlled. The objective of study was determine the concentration arsenic with reference WHO limits from selected boreholes Nairobi County, Kenya. Water randomly sampled total 63 five zones (Central, Eastern, Northern, Western Southern) during dry wet season. analyzed by Hydride Generation Atomic Absorption Spectrometer (HG-AAS). results showed that content borehole season ranged between 0.00455±0.0022 0.01007±0.006 range 0.002057±0.0008 - 0.00744±0.0051 mg/L There significant difference (P˂0.05) samples Central zone compared other zones. During season, ten (16%) four (6%) above recommended limit 0.01 mg/L. calculated contamination factor for slightly contaminated very all were arsenic. pollution index both seasons not polluted Steps should taken monitor treat domestic purposes order mitigate effect on human health due contamination.