Physicochemical and mineralogical characterization of test materials used in 28-day and 90-day intratracheal instillation toxicology studies in rats

Mineralogical, thermal and rheological characterization of some Tunisian green commercial clays and possible application as peloids with thermal and sea waters

Many of therapeutic treatments in spas are concentrated on mud therapy. Clays are included in the formulation of thermal mud as vehicles of the mineral medicinal water. To be suitable for therapeutic use, some mineralogical, rheological and thermal properties should be respected in order to be topically applied. Our objective is to explore the suitability of three Tunisian commercial green clays traditionally used as facial and body masks by women in the region of Douiret (CD), Tozeur (CT) and Korbous (CK) in terms of their physicochemical structure chemical composition, heavy metals risk assessment, thermal properties, plasticity, rheology and their potential application as peloid with distilled and sodium chloride-rich sulfated thermal waters from hot spring in the region of hammam Lif and Korbous and sea waters. The mineralogy of samples (clay fraction and associated minerals) was determined by X-ray powder diffraction and FT-IR analysis, and the chemical composition was obtained by ICP. The main clay fraction of the samples was smectite and illite with significant amount of kaolinite. Regarding their mineralogical properties, the samples with a high amount of smectite fraction are more suitable for use in Tunisian spas and for the application as peloids. The thermal analyses of clay powders shows a specific heat value comparable to those use used in spas. Also the muds showed a low cooling rate which is necessary for therapeutic use. Rheological properties of peloids prove their thixotropic characteristics.

An updated review of the genotoxicity of respirable crystalline silica

Human exposure to (certain forms of) crystalline silica (CS) potentially results in adverse effects on human health. Since 1997 IARC has classified CS as a Group 1 carcinogen [1], which was confirmed in a later review in 2012 [2]. The genotoxic potential and mode of genotoxic action of CS was not conclusive in either of the IARC reviews, although a proposal for mode of actions was made in an extensive review of the genotoxicity of CS by Borm, Tran and Donaldson in 2011 [3]. The present study identified 141 new papers from search strings related to genotoxicity of respirable CS (RCS) since 2011 and, of these, 17 relevant publications with genotoxicity data were included in this detailed review.

Studies on in vitro genotoxic endpoints primarily included micronucleus (MN) frequency and % fragmented DNA as measured in the comet assay, and were mostly negative, apart from two studies using primary or cultured macrophages. In vivo studies confirmed the role of persistent inflammation due to quartz surface toxicity leading to anti-oxidant responses in mice and rats, but DNA damage was only seen in rats. The role of surface characteristics was strengthened by in vitro and in vivo studies using aluminium or hydrophobic treatment to quench the silanol groups on the CS surface.

In conclusion, the different modes of action of RCS-induced genotoxicity have been evaluated in a series of independent, adequate studies since 2011. Earlier conclusions on the role of inflammation driven by quartz surface in genotoxic and carcinogenic effects after inhalation are confirmed and findings support a practical threshold. Whereas classic in vitro genotoxicity studies confirm an earlier no-observed effect level (NOEL) in cell cultures of 60-70 μg/cm², transformation frequency in SHE cells suggests a lower threshold around 5 μg/cm². Both levels are only achieved in vivo at doses (2–4 mg) beyond in vivo doses (> 200 μg) that cause persistent inflammation and tissue remodelling in the rat lung.

Folk pharmaceutical formulations in western Mediterranean: identification and safety of clays used in pelotherapy

ETHNOPHARMACOLOGICAL RELEVANCE

Clays are naturally occurring ingredients of many natural health products, being included in most of ancient Mediterranean/European medical texts and currently used to prepare therapeutic hot-muds (peloids) in several thermal stations of the Mediterranean region. Clays are included in the formulation of peloids as vehicles of the mineral-medicinal water, to obtain inorganic gels with rheological and thermal properties suitable to be topically applied. Knowledge about formulations and preparation procedures of these traditional medicines has been orally transmitted since ancient times. Increasing recognition of the therapeutic utility of these traditional and natural health care substances make necessary a full ethnopharmaceutic research to ascertain those compositional characters that allow to establish quality attributes and corresponding requirements for these materials and products, including identity, purity, richness and safety.

MATERIALS AND METHODS

Five clay samples (A, B, C, D and E) currently used in various spa centers of southern European/Mediterranean countries were studied. X-Ray diffraction (XRD) and X-ray fluorescence (XRF) data were used to asses sample identity and richness. Elemental impurities and microbiological contaminants were also determined and compared to normative limits. Particle size distribution was related to their safety as powder materials.

RESULTS

Samples A, C, D and E were identified as "high purity clay", while sample B was identified as a mix of clay minerals and carbonates. The presence of carbonates in this sample could compromise its suitability for pelotherapy. The studied clays meet the main normative limits for metals impurities, with the exception of arsenic in sample A and nickel in sample B. The samples comply with the microbiological limits proposed by European legislation for medicinal products. According to the particle size of the studied samples, prevention and control of dust exposure must be considered.

CONCLUSIONS

Despite their demonstrated longevity, the use of clays in traditional medicine formulations as peloids greatly requires comprehension of their identity and safety attributes. Continuity of these mineral substances as recognized health care ingredients oblige to conduct interdisciplinary research to know the features that sustain their traditional use in the preparation of medicines (ethnopharmaceutics).