Heavy Metal Index
Ask the IndexAboutIndex Pro

Assessment of Heavy Metals and pH Levels in Commercial Blonde Hair Dyes Marketed in Benghazi, Libya: Human Dermal Exposure and Health Risk Assessment

Cite this pageVersion history

Ten blonde hair dyes bought in Benghazi pharmacies were digested in nitric and hydrochloric acid and measured by flame atomic absorption for seven metals. Every product had lead between 0.058 and 0.095 mg/kg, and eight of ten had cadmium. The authors’ dermal model put hazard quotients below 1. The paper states no detection or quantification limits and reports no reference material, so its sub-0.1 mg/kg values are hard to judge.

Key numbers

  • Lead: 0.058 to 0.095 mg/kg across the ten products; mean 0.076 ± 0.013 mg/kg (Table 2, p. 3421).
  • Cadmium: not detected in two products; 0.011 to 0.093 mg/kg in the other eight; mean 0.026 mg/kg across all ten, which counts the two non-detects as zero (Table 2, p. 3421).
  • Chromium: not detected in three products; 1.226 to 2.233 mg/kg in seven; mean 1.335 mg/kg. Nickel: 0.276 to 1.782 mg/kg, mean 0.921 mg/kg (Table 2, p. 3421).
  • Iron 10.0 to 25.1 mg/kg, zinc 2.3 to 9.0 mg/kg, manganese not detected to 1.543 mg/kg (Table 2, p. 3421).
  • Most dyes had pH between 10.0 and 11.5 (Abstract, p. 3416).
  • The authors compare lead with the US FDA’s 10 mg/kg recommended maximum for externally applied cosmetics; all ten products were far below it (p. 3421).

Methods (brief)

0.5 g of each dye, 6 mL 65% HNO3 plus 4 mL HCl on a hot plate, filtered and made up to 50 mL; flame AAS (Thermo iCE 3000) with deuterium background correction (pp. 3418-3419). Calibration used a commercial 1000 mg/L stock. The paper names a hydride generator for arsenic and mercury but reports no arsenic or mercury results.

Limitations: no detection or quantification limits, blanks, recoveries or reference material are reported. After a 100-fold dilution, 0.06 mg/kg lead in the dye is under 1 µg/L in solution, which is normally below what flame AAS can quantify, so the lead and cadmium values should be treated as indicative. Non-detects are counted as zero in the reported means. One sample per product.

Implications

Certification: Gives a small retail data point for lead and cadmium in permanent blonde dyes that is consistent with low single-digit µg/g levels or less. It does not support any brand-level comparison, and the missing detection limits keep it from serving as a reference level.

Courses: Shows why a detection limit must be reported with any low cosmetic metal result.

App: Treat as low-confidence context for the hair dye page.

Microbiome: Not applicable.

Update history

No substantive edit history is available in this build. The full commit record is available in git.

Referenced by