Biomarker-Based Assessment of Aflatoxin B ₁ Exposure and Health Risk Among Smallholder Farmers in Baringo County, Kenya Using Deterministic and Probabilistic Modelling

Aflatoxin exposure studies in Kenya have focused mainly on risk-prone regions and food-based risk estimates, which may under- or overestimate internal dose. This study estimated the chronic health risks associated with AFB₁ exposure among smallholder farmers in Baringo County using urinary biomarker. Urinary AFM₁ (n = 72) was quantified using enzyme-linked immunosorbent assay and probable daily intake of AFB₁ derived, incorporating participant-specific urine volumes and AFM₁ excretion factors (1 - 2%). Deterministic and Monte Carlo modelling were used to assess risk. AFM₁ was detected in 61.1% of urine samples (LOD: 0.10 ng/mL), indicating recent AFB₁ exposure. The deterministic PDI range (86.236 - 260.976 ng/kg bw/day) yielded Margin of Exposure values (1.381 - 4.297), well below the European Food Safety Authority threshold (10,000), suggesting high public health concern. Monte Carlo simulation mean PDI was 149.349 ng/kg bw/day. Annual liver cancer risk exceeded the 1 case/100,000 person-years reference under national (HBV prevalence 3.0%; mean: 2.793; 95th percentile: 6.648) and county-level (HBV prevalence 11.9%; mean: 3.885; 95th percentile: 9.248) estimates. These results indicate ongoing aflatoxin exposure and elevated health risk among the smallholder farmers in Baringo County. There is an urgent need for targeted dietary, storage and community education interventions, and biomarker-integrated surveillance.