Levels, Sources and Health Risk Assessment of Heavy Metals in Hair Dye Sold in Nigeria

Abstract

The presence of heavy metals in hair-dye products is a potential public health concern because repeated dermal exposure may result in cumulative toxicological effects. This study investigated the concentrations, distribution, statistical relationships, and potential health risks associated with selected heavy metals in commercially available hair dyes sold in Nigeria. Seven hair-dye samples were analysed for cobalt (Co), arsenic (As), manganese (Mn), copper (Cu), cadmium (Cd), chromium (Cr), nickel (Ni), and lead (Pb), followed by descriptive, correlation, principal component, hierarchical cluster, and health-risk assessments. Nickel recorded the highest mean concentration (0.04411 mg/kg), followed by Mn (0.02796 mg/kg), Pb (0.02544 mg/kg), and Co (0.02358 mg/kg), while As had the lowest mean concentration (0.00044 mg/kg). The coefficient of variation ranged from 10.78% for Pb to 102.88% for Cu, demonstrating substantial differences in metal concentrations among products. The total measured heavy-metal concentration ranged from 0.1002 mg/kg in HD1 to 0.1735 mg/kg in HD7. Spearman correlation indicated a strong inverse association between As and Cd (ρ = −0.847), while Pearson correlation identified significant negative relationships between As–Cd (r = −0.770, p = 0.043) and As–Ni (r = −0.789, p = 0.035). Principal component analysis showed that the first three components explained 88.27% of the total variance, indicating substantial multivariate differentiation among the products. Hierarchical clustering further identified similarities between selected samples, particularly HD6–HD7 and HD2–HD3. The findings demonstrate heterogeneous heavy-metal profiles among the investigated hair dyes and underscore the importance of continued monitoring, regulatory control, and improved quality assurance to minimize potential health risks associated with repeated exposure.