Environmental Radiation Exposure and Lifetime Cancer Risk at Lumoru Dumpsite, Western Kenya

Abstract

This study quantified the activity concentrations of natural radionuclides 238U, 232Th, and 40K in soils from the Lumoru Dumpsite, Bungoma County, Kenya, using a NaI (Tl) gamma spectrometer. The mean concentrations were 7 ± 0.4 Bq/kg for 238U, 57 ± 2.0 Bq/kg for 232Th, and 25 ± 1.3 Bq/kg for 40K. From these values, the absorbed dose rate was estimated at 39 ± 3.4 nGy/h, the outdoor annual effective dose equivalent at 0.09 ± 0.01 mSv/y, and the radium equivalent activity at 91 ± 3.4 Bq/kg. The hazard indices (Hex = 0.25 ± 0.01; Hin = 0.28 ± 0.01) were all within international safety limits, while the mean excess lifetime cancer risk was 0.30 ± 0.03 × 10−3. Compared with similar dumpsites in Kenya and across Africa, Lumoru exhibited lower activity concentrations and radiological risks than Machinjoni, Nigerian, and Ukrainian landfills, though its risks remain comparable to food-chain pathways in Bungoma. These findings establish Lumoru as a moderately impacted site and provide a critical baseline for monitoring cumulative exposures from environmental and household sources in Western Kenya.