Assessment of Spatio-Seasonal Variations in Heavy Metal Contamination and Associated Health Risks of Fumarolic Condensates in Mt. Suswa, Kajiado County, Kenya

Abstract

Abstract Geothermal resources in the East African Rift System provide renewable energy opportunities but also pose health and environmental risks through heavy metal emissions in fumarolic condensates. This study assessed the spatio-seasonal variations of arsenic (As), lead (Pb), mercury (Hg), and cadmium (Cd) in fumarolic condensates at Mt. Suswa, Kajiado County, Kenya, and evaluated associated human health risks. A mixed-methods design was adopted, triangulating quantitative laboratory and geospatial analyses with qualitative evidence from household surveys and key informant interviews. Condensate samples were collected from 19 fumarolic vents across the inner and outer caldera during the dry (January–March) and wet (May–July) seasons. Physico-chemical parameters were determined using APHA (2022) methods, while heavy elements were analysed using an Agilent 5110 ICP-OES. Data analysis included ANOVA, Pearson‘s correlation, and IDW interpolation, with human health risks quantified following USEPA (2011) ingestion and dermal exposure guidelines. Results demonstrated significant spatial heterogeneity (p < 0.001). The highest concentrations were observed at hotspot fumaroles: As (5.59 µgL-1 , F18), Pb (1.98 µgL-1 , F14), Cd (1.84 µgL-1 , F5), and F⁻ (3.84 mgL-1 , F13), while the lowest occurred at background vents such as Cd (0.37 µgL-1 , F2) and As (1.29 µgL-1 , F10). Carcinogenic risk (CR) values ranged from 3.36 × 10⁻⁵ in F2 (children, wet season) to 1.35 × 10⁻⁴ in F15 (adult females, dry season). A clear spatial divide was observed: outer caldera vents (F1, F2, F4, F7–F15) fell within the acceptable risk range (10⁻⁶–10⁻⁴), while inner caldera fumaroles (F5, F17, F18, F20) exceeded the 10⁻⁴ threshold, classifying them as persistent high-risk hotspots. Seasonal patterns indicated dilution during the wet season, but hotspot fumaroles remained consistently above the risk threshold. Qualitative evidence confirmed widespread community reliance on fumarolic condensates despite visible health outcomes such as dental fluorosis, with coping strategies like boiling and dilution proving ineffective. Fumarolic condensates in Mt. Suswa pose non-trivial and persistent carcinogenic risks, particularly in inner caldera hotspots, with children and adult females the most vulnerable. Recommendations include routine geochemical monitoring of vents, structured risk communication and health awareness programs, and the development of alternative safe water supplies to reduce dependence on contaminated condensates while enabling sustainable geothermal development.