Evaluation of Heavy Metals Level in Hair Dyes and their Potential Health Risk

Overview

Yashim and colleagues measured lead (Pb), total chromium (Cr), cadmium (Cd), nickel (Ni), and Cu in hair-dye products sold at Samaru market in Zaria, Nigeria. The paper reports mg/kg concentrations for four product-form composites: pure mineral dye, henna dye, black shampoo oil, and black shampoo jelly. The study is useful as C-tier finished-product occurrence evidence because the sampling frame is small and composited, no DOI is printed, and the source contains several figure/prose inconsistencies.

Key numbers

• Article identity: Nigerian Research Journal of Chemical Sciences 8(2):241-251; no DOI printed in extracted text.
• Sample frame: 25 samples of each hair-dye product form were purchased from different locations in Samaru market, Zaria, Nigeria. Solid pure mineral dye and henna samples were separately mixed/ground into composites; viscous black shampoo oil and black shampoo jelly samples were separately drained/mixed into composites.
• Analytical concentration basis: all occurrence values below are source-reported mg/kg; no conversion to ppm was performed even though the paper compares its values with ppm limits and literature.

Abstract concentration summary (mean ± reported error, mg/kg):

• Lead, Results/Figure 1: the narrative gives pure mineral dye 97.1 ± 0.013 mg/kg, henna dye 19.50±0.003 mg/kg, black shampoo oil 5.52±0.007 mg/kg, and black shampoo jelly 6.67±0.007 mg/kg; the abstract gives black shampoo oil 5.52±0.003 mg/kg and black shampoo jelly 6.76±0.007 mg/kg.
• Chromium, Results/Figure 3: pure mineral dye has the highest total-Cr value 42.45±0.001 mg/kg, followed by black shampoo jelly 7.36±0.004 mg/kg, henna dye 7.20±0.000 mg/kg, and black shampoo oil 3.92±0.004 mg/kg. The abstract gives pure mineral total Cr as 42.45±0.002 mg/kg.
• Nickel, Results/Figure 4: pure mineral dye 7.40±0.008 mg/kg, henna dye 6.60±0.005 mg/kg, black shampoo jelly 5.76±0.004 mg/kg, and black shampoo oil 5.68±0.010 mg/kg.
• Cadmium, Results/Figure 5: henna dye 5.40±0.002 mg/kg, pure mineral dye 3.80±0.005 mg/kg, black shampoo oil 1.50±0.013 mg/kg, and black shampoo jelly 1.20±0.002 mg/kg.
• Copper, Results/Figure 2: pure mineral dye 65.10±0.003 mg/kg, black shampoo oil 33.60±0.001 mg/kg, black shampoo jelly 30.50±0.029 mg/kg, and henna dye 22.00±0.001 mg/kg; the abstract instead prints black shampoo jelly Cu as 3.50±0.029 mg/kg.
• Statistical test: the paper reports one-way ANOVA with Tukey post hoc comparison at 95% confidence and states that metal levels differed significantly across studied samples (p < 0.05).

Methods (brief)

The authors bought hair-dye samples from different locations in Samaru market in Zaria, Nigeria. A total of 25 samples was collected for each of four product forms. The solid pure mineral dye and henna dye samples were separately mixed and ground to form composite powdered samples; the viscous black shampoo oil and black shampoo jelly products were separately drained into a 150 cm3 beaker and mixed to form composite samples.

For the solid products, 1 g of powdered hair dye was digested with 20 cm3 of concentrated HNO3 and HCl in a 3:1 ratio. For viscous products, 1 g was digested with 15 cm3 of concentrated H2SO4 and H2O2 in a 2:1 ratio. Digests were cooled, filtered through ashless Whatman No. 42 paper into 100 cm3 volumetric flasks, and diluted to volume with distilled water. Pb, Cd, total Cr, Ni, and Cu were measured by atomic absorption spectrophotometry using a model AAS-HP MY14470001; analysis was done in triplicate.

Speciation: the paper reports elemental Pb, Cd, Ni, Cu, and total Cr only. It discusses Cr(VI) toxicity in background text, but the analytical results are total Cr and should not be interpreted as Cr(VI).

Related evidence

• Permanent hair dyes/tints (remain in hair after application)
• Hair dye/color rinses (rinse-off after processing)
• Shampoo (general adult)
• Lead
• Chromium
• Cadmium
• Nickel
• Copper

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git.