Yang Qi Shi

Twenty-two batches of Yangqishi and Yinqishi were characterised by morphological examination, conventional physicochemical analysis and X-ray diffraction Fourier patterns. The mineral origin of Yangqishi was established as tremolite and actinolite, and that of Yinqishi as talc schist. The authors note that the two drugs differ in properties, actions, indications and composition and warn against confusing them, and recommend XRD as a rapid and accurate identification method. This is the direct evidence that the drug in this entry is amphibole material, not a generic silicate.

Actinolite asbestos, previously the least thermally characterised of the asbestos minerals, was studied by thermogravimetry and differential scanning calorimetry with X-ray diffraction of the heated products. Decomposition occurs at about 1030 degrees C, with dehydroxylation preceding recrystallisation into stable phases, and complete transformation requires roughly 1000 to 1200 degrees C. Critically, the recrystallised product retains fibrous morphology by pseudomorphosis. This is the reason traditional calcination cannot be assumed to detoxify the drug: the temperature is lower than required, and even at sufficient temperature the fibre shape persists.

Tremolite asbestos from Val d'Ala, Italy and UICC standard anthophyllite asbestos were dry-ground in eccentric vibration mills for 30 seconds, 5 minutes and 10 minutes. Grinding lowered dehydroxylation and breakdown temperatures through increased lattice strain and reduced crystallinity, and after 10 minutes all fibres fell below the dimensions defining a WHO countable fibre. The paper opens by restating that all six commercial asbestos minerals, fibrous tremolite and fibrous actinolite included, are IARC Group 1 human carcinogens. The result should not be read as a licence to grind medicinal amphibole: it describes industrial inertisation, the shortened particles remain amphibole, and the grinding itself is a dust-generating operation.

A systematic review of 17 human studies plus critical review of animal and in vitro evidence, followed by a weight-of-evidence integration. Confidence was very low or evidence insufficient for cancers in 15 organ systems and for three non-cancer endpoints; eight studies reported possible associations with stomach cancer in men but few were high quality, and good animal studies did not support increased risk. The authors conclude the evidence is insufficient to establish a link and call for more research, noting the absence of a validated kinetic model for ingested asbestos. For an orally administered mineral this is the most relevant evidence base, and it is genuinely equivocal on the swallowed route. It says nothing about the inhalation exposure that grinding and dispensing create, where the evidence is not equivocal at all.

A cohort of 726 Norwegian lighthouse keepers first employed between 1917 and 1967 was followed for cancer incidence from 1960 to 2002. Stomach cancer incidence was raised overall (SIR 1.6, 95% CI 1.0 to 2.3), in the definitely exposed subgroup (SIR 2.5, 95% CI 0.9 to 5.5) and at 20 or more years after first possible exposure (SIR 1.7, 95% CI 1.1 to 2.7); colon cancer results were less consistent. The authors read this as supporting an association between ingested asbestos and gastrointestinal, particularly stomach, cancer risk. It is one of the better individual-level studies on the ingestion route, though the confidence interval for the exposed subgroup includes unity.

Ten asbestos samples, six chrysotile, two crocidolite, one amosite and one tremolite, were studied to establish the thermal treatment needed to destroy fibre structure and convert the minerals to non-hazardous phases. Amphibole asbestos converts to pyroxene phases in roughly the 800 to 1000 degrees C range, with tremolite fired at 1100 degrees C yielding diopside and enstatite. The practical implication for this drug is that the temperatures required lie at or above the top of what a traditional charcoal calcination reaches.