Heavy metal contamination in cosmetic hair dyes, dermal health risk assessment, and in vivo toxicological implications among exposed women in Khartoum, Sudan

Cosmetic hair dyes can expose users to heavy metals, but integrated evidence combining product contamination, biomonitoring, and dermal risk assessment remains limited in Sudan. We quantified Cu, Cd, Hg, Pb, Mn, and Ni in eleven commercial black hair dyes using validated flame atomic absorption spectrometry. Blood samples from a pilot group of 19 women were analysed for selected metals, and a validated Arabic questionnaire assessed exposure practices and self-reported effects among 312 respondents. Consumer and occupational dermal risks were estimated using the estimated daily intake, hazard quotient, hazard index, and lifetime cancer risk. Manganese and lead were the predominant contaminants. Non-carcinogenic risk remained below the conventional threshold for individual products, but occupational exposure approached this threshold for high-lead products. Cadmium produced the clearest risk signal, with lifetime cancer risk above the commonly accepted range for occupational workers under the modelled assumptions. In the GFAAS pilot subset, detectable blood Pb occurred only among participants with at least 20 years of occupational exposure; this finding is exploratory and requires confirmation in a larger study. The results support mandatory pre-market metal screening, occupational biomonitoring, improved ventilation and personal protective equipment, and stronger surveillance of powdered and stone-based dyes in Sudan.