Overview
Bastos and colleagues formulated two therapeutic peloids from a Portuguese bentonite and two sulfurous spa waters, measured their total trace elements by XRF, and measured what dissolved into artificial perspiration by ICP-MS. Arsenic and cadmium were below XRF detection in all solids, lead rose from 2.7 ppm in the bentonite to 9.5 ppm in one peloid, and the bentonite held 2140 ppm chromium and 250 ppm nickel. Very little of any toxic element dissolved into sweat.
Key numbers
- Lead, total by XRF: bentonite “2.7”, CRO1 peloid “6.3”, CR1 peloid “9.5” ppm; arsenic and cadmium ”< d.l” (Table 9, p. 6633).
- Chromium “2140”, “1850”, “1760” ppm and nickel “250.0”, “75.3”, “69.4” ppm in BV3, CRO1 and CR1 (Table 9).
- Artificial perspiration extracts: lead “0.75 ± 0.02” to “0.99 ± 0.04” µg/L; cadmium only in CR1 at “0.20 ± 0.02” µg/L (Table 12, pp. 6634-6635).
Methods (brief)
Solids were dried at 50 °C and analyzed by XRF; extracts in a stabilized artificial perspiration solution were analyzed by ICP-MS with per-element detection limits (for example lead 0.70 µg/L). Replicate RSD was 10 percent or less, and the blank perspiration solution itself contained some elements (lead 1.93 µg/L).
Evidence Fitness
Laboratory formulations, one solid result per material and three extract replicates; not retail products. Extract values are per litre and cannot be compared with mg/kg contents, and blank correction is not described. Therapeutic peloid mud is a proxy for cosmetic-clay; no retail cosmetic clay was measured, and that page is not linked. The same bentonite is described again in Bastos and Rocha 2023 (Clays and Clay Minerals).