The age-mortality curve of endemic pleural mesothelioma in Karain, Central Turkey

The presence of erionite in North American geologies and the estimated mesothelioma potency by region

OBJECTIVE

Erionite is a naturally occurring fibrous mineral found in soils in some geographical regions. Known for its potency for causing mesothelioma in the Cappadocia region of Turkey, the erionite fiber has attracted interest in the United States due to its presence in a band of rock that extends from Mexico to Montana. There are few toxicology studies of erionite, but all show it to have unusually high chronic toxicity. Despite its high potency compared to asbestos fibers, erionite has no occupational or environmental exposure limits. This paper takes what has been learned about the chemical and physical characteristics of the various forms of asbestos (chrysotile, amosite, anthophyllite, and crocidolite) and predicts the potency of North American erionite fibers.

MATERIALS AND METHODS

Based on the fiber potency model in Korchevskiy et al. (2019) and the available published information on erionite, the estimated mesothelioma potency factors (the proportion of mesothelioma mortality per unit cumulative exposure (f/cc-year)) for erionites in the western United States were determined.

RESULTS AND DISCUSSION

The model predicted potency factors ranged from 0.19 to 11.25 (average ∼3.5), depending on the region. For reference, crocidolite (the most potent commercial form of asbestos) is assigned a potency factor ∼0.5.

CONCLUSION

The model predicted mesothelioma potency of Turkish erionite (4.53) falls in this same range of potencies as erionite found in North America. Although it can vary by region, a reasonable ratio of average mesothelioma potency based on this model is 3,000:500:100:1 comparing North American erionite, crocidolite, amosite, and chrysotile (from most potent to least potent).

Age Characteristics of Mesothelioma Incidence in the General Population of the Province of Padova, 1965–1976

Twenty-four incidental cases of mesothelioma, diagnosed in the province of Padova during the period 1965–1976, were analyzed according to age characteristics. The results show that the incidence rate increases in the general population under study at the same rate as in other populations occupationally and non-occupationally exposed to carcinogenic fibers according to the time since first exposure. This finding suggests a similar neoplastic process independent of age, in different environmental situations.

The Cappadocia mesothelioma epidemic: its influence in Turkey and abroad

The epidemic of mesothelioma in Cappadocia, Turkey, is unprecedented in medical history. In three Cappadocian villages, Karain, Tuzkoy and "old" Sarihidir, about 50% of all deaths (including neonatal deaths and traffic fatalities) have been caused by mesothelioma. No other epidemic in medical history has caused such a high incidence of death. This is even more unusual when considering that (I) epidemics are caused by infectious agents, not cancer, and (II) mesothelioma is a rare cancer. World-wide mesothelioma incidence varies between 1/10⁶ in areas with no asbestos industry to about 10-30/10⁶ in areas with asbestos industry. This article reviews how the mesothelioma epidemic was discovered in Cappadocia by Dr. Baris (my mentor), how we initially linked the epidemic to erionite exposure, and later (with Dr. Carbone) to the interaction between genetic predisposition and environmental exposure. Our team's work had an important positive impact on the lives of those living in Cappadocia and also in many genetically predisposed families living around the world. I will discuss how the work that started in three remote Cappadocian villages led to the award of a NCI P01 grant to support our studies. Our studies proved that genetics modulates mineral fiber carcinogenesis and led to the discovery that carriers of germline BAP1 mutations have a very high risk of developing mesothelioma and other malignancies. A new, very active field of research developed following our discoveries to elucidate the mechanism by which BAP1 modulates mineral fiber carcinogenesis as well as to identify additional genes that when mutated increase the risk of mesothelioma and other environmentally related cancers. I am the only surviving member of this research team who saw all the phases of this research and I believe it is important to provide an accurate report, which hopefully will inspire others.

Ultrasound bioeffects and safety

The main mechanisms by which ultrasound can induce biological effects as it passes through the body are thermal and mechanical in nature. The mechanical effects are primarily related to the presence of gas, whether drawn out of solution by the negative going ultrasound pressure wave (acoustic cavitation), a naturally occurring gas body (such as lung alveoli), or deliberately introduced into the blood stream to increase imaging contrast (microbubble contrast agents). Observed biological effects are discussed in the context of these mechanisms and their relevance to ultrasound safety is discussed.

Ultrasound-induced cavitation: applications in drug and gene delivery

Ultrasound, which has been conventionally used for diagnostics until recently, is now being extensively used for drug and gene delivery. This transformation has come about primarily due to ultrasound-mediated acoustic cavitation - particularly transient cavitation. Acoustic cavitation has been used to facilitate the delivery of small molecules, as well as macromolecules, including proteins and DNA. Controlled generation of cavitation has also been used for targeting drugs to diseased tissues, including skin, brain, eyes and endothelium. Ultrasound has also been employed for the treatment of several diseases, including thromboembolism, arteriosclerosis and cancer. This review provides a detailed account of mechanisms, current status and future prospects of ultrasonic cavitation in drug and gene delivery applications.

Epidemiology of peritoneal mesothelioma: a review

The epidemiology of peritoneal mesothelioma is complicated by possible geographic and temporal variations in diagnostic practices. The incidence rates in industrialized countries range between 0.5 and three cases per million in men and between 0.2 and two cases per million in women. Exposure to asbestos is the main known cause of peritoneal mesothelioma. Results on peritoneal mesothelioma have been reported for 34 cohorts exposed to asbestos, among which a strong correlation was present between the percentages of deaths from pleural and peritoneal mesothelioma (correlation coefficient 0.8, P < 0.0001). Studies of workers exposed only or predominantly to chrysotile asbestos resulted in a lower proportion of total deaths from peritoneal mesothelioma than studies of workers exposed to amphibole or mixed type of asbestos. Cases of peritoneal mesothelioma have also been reported following exposure to erionite and Thorotrast, providing further evidence of common etiological factors with the pleural form of the disease. The role of other suspected risk factors, such as simian virus 40 infection and genetic predisposition, is unclear at present. Control of asbestos exposure remains the main approach to prevent peritoneal mesothelioma.

Targeted disruption of the blood-brain barrier with focused ultrasound: association with cavitation activity

Acoustic emission was monitored during focused ultrasound exposures in conjunction with an ultrasound contrast agent (Optison) in order to determine if cavitation activity is associated with the induction of blood-brain barrier disruption (BBBD). Thirty-four locations were sonicated (frequency: 260 kHz) at targets 10 mm deep in rabbit brain (N = 9). The sonications were applied at peak pressure amplitudes ranging from 0.11 to 0.57 MPa (burst length: 10 ms; repetition frequency of 1 Hz; duration: 20 s). Acoustic emission was recorded with a focused passive cavitation detector. This emission was recorded at each location during sonications with and without Optison. Detectable wideband acoustic emission was observed only at 0.40 and 0.57 MPa. BBBD was observed in contrast MRI after sonication at 0.29-0.57 MPa. The appearance of small regions of extravasated erythrocytes appeared to be associated with this wideband emission signal. The results thus suggest that BBBD resulting from focused ultrasound pulses in the presence of Optison can occur without indicators for inertial cavitation in vivo, wideband emission and extravasation. If inertial cavitation is not responsible for the BBBD, other ultrasound/microbubble interactions are likely the source. A significant increase in the emission signal due to Optison at the second and third harmonics of the ultrasound driving frequency was found to correlate with BBBD and might be useful as an online method to indicate when the disruption occurs.

The relationship of scattered subharmonic, 3.3-MHz fundamental and second harmonic signals to damage of monolayer cells by ultrasonically activated Albunex

Cultured Chinese hamster ovary cells attached to thin Mylar sheets were exposed to 3.3-MHz ultrasound in the presence of Albunex ultrasound contrast agent. The ultrasound beam was directed upward at the exposure chamber with the monolayer on the inside of the upper acoustic window. Cell membrane damage was detected by the firefly enzyme assay for released ATP and the subharmonic, fundamental, and second harmonic scattered signals were recorded. ATP release increased monotonically with increasing pressure amplitude above apparent thresholds of 0.28 MPa for 1-s continuous and 0.56 MPa for 100-s pulsed (10-microseconds pulses, 1-ms PRP) exposures with 5% Albunex. The subharmonic signal and, to a lesser extent, the second harmonic signal both increased with the cell membrane damage, which suggests that these signals have predictive value for bioeffects. If the monolayer was positioned on the front window of the exposure chamber, cell membrane damage was greatly reduced, which confirms the protective influence of this configuration of monolayers reported in the literature. The effect decreased both at high (50%) or low (0.5%) concentrations of Albunex. The strong nonlinear scattering of ultrasound by contrast agent gas bodies appears to provide useful indicators of gas body activity including cavitational bioeffects.

Epidemiological and environmental evidence of the health effects of exposure to erionite fibres: a four-year study in the Cappadocian region of Turkey

An environmental and epidemiological study has been carried out in Central Cappadocia, Turkey, aiming at investigating the relationship between exposure to naturally occurring erionite fibres and the reported high incidence of malignant mesotheliomas. Airborne fibre levels are generally low but show a higher proportion of erionite fibres in the villages affected by malignant disease than in a control village. The same pattern is confirmed by analysis of the fibre content in lung tissues of sheep from several villages, both affected and unaffected by malignant disease. The 3 villages with the highest proportion of erionite fibres have high rates of malignant pleural mesothelioma, malignant peritoneal mesothelioma and lung cancer. No case of malignancy for the same sites has been reported during the study period from the control village. The relationships between these findings and their consistency with the results from experimental studies indicate erionite fibres as a carcinogenic agent, although some aspects of the exposure are not fully clarified.

The in vitro genetic effects of fibrous erionite and crocidolite asbestos

Epidemiologic evidence has recently identified an association between an endemic outbreak of pleural and peritoneal mesothelioma in the Urgup region of Turkey and exposure to zeolite fibres. This malignancy is usually associated with exposure to asbestos dusts whose mineralogical characteristics differ from those of zeolites. The present study further defines the in vitro biologic activity of erionite, a common zeolite fibre found in the Urgup region of Turkey. Both erionite and crocidolite asbestos fibres were clastogenic in synchronous Chinese hamster ovary (CHO) fibroblasts. Both fibres also altered CHO ploidy. Erionite, unlike crocidolite or Min-U-Sil quartz, caused a slight increase in sister chromatid exchanges in synchronous CHO cells. Neither erionite nor crocidolite was mutagenic in a human lymphoblastoid cell line. Erionite fibres thus produced in vitro cytogenic changes similar to those caused by asbestiform mineral dusts and, like asbestos fibres, did not induce mutations in human lymphoblastoid cells.

Features of asbestos-exposed and unexposed mesothelioma

Thirty-six histologically confirmed cases of pleural and peritoneal mesothelioma have been observed in a chest unit over a period of 53 months. The past asbestos exposure was assessed by a standardized questionnaire in all cases and the asbestos lung burden was determined by means of mineralogical analysis of lung-related biological specimens (sputum, bronchoalveolar lavage fluid, lung tissues) in 28 cases. The results of these two methods were found in good agreement. Past asbestos exposure has been definitely implicated in 17 cases and definitely eliminated in 10 cases. The results were inconclusive in other cases. The group with definite past asbestos exposure was different from the nonasbestos-exposed group by clinical, biological, pathological, and prognosis features that were analyzed. In cases without past asbestos exposure there were no other possible causative agents. Younger age and similar incidence in men and women suggest an environmental or natural disease.