Levels, Human Exposure and Health Risk Assessment of Heavy Metals in Indoor and Outdoor Dust from Basra, Iraq

This study determined the levels and distribution patterns of Pb, Cd, Co, Cu, Ni, and Zn in indoor (n = 22) and outdoor (n = 22) dust from Basra, Iraq, and evaluated the associated human health risks. The total mean concentration of ∑ 6HMs was 247 mg/kg in the indoor dust and 285 mg/kg in the outdoor dust. Zn was the dominant metal in both environments, with mean concentrations of 155 and 161 mg/kg, contributing 63% and 56% of the total metal burden, respectively. Pb, Cd, Co, and Ni concentrations were significantly higher (p < 0.05) in outdoor dust, indicating the influence of outdoor emission sources. Human exposure assessment showed that the average daily doses (ADD) for children through ingestion, inhalation, and dermal contact were approximately 9.3-fold higher than those for adults across all metals. Zn exposure reached 1.99 × 10-3 and 2.13 × 10-4 mg kg-1 day-1 for children and adults, respectively. The non-carcinogenic hazard index (HI) for all metals remained below the acceptable threshold (HI < 1), while carcinogenic risks (CR) for Pb, Cd, and Ni were within the acceptable range (10-6–10-4). Nevertheless, Ni in outdoor dust exhibited comparatively higher carcinogenic risk values (4.03 × 10-5 for children and 1.73 × 10-5 for adults), highlighting the importance of continued environmental monitoring. These findings provide a comprehensive baseline for assessing human exposure to heavy metals in indoor and outdoor dust in Basra, Iraq.