Crocidolite and mesothelioma

Our plain-English summary of Crocidolite and mesothelioma, by F. Schneider, T.A. Sporn, V.L. Roggli (Ultrastructural Pathology, 2008).

The study

• Authors: F. Schneider, T.A. Sporn, V.L. Roggli
• Journal: Ultrastructural Pathology
• Published: 2008;32(5):171-7
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This study reports changes in the frequency of detection of various asbestos fiber types between 1982 and 2005. Crocidolite is increasingly detected in U.S. mesothelioma patients. The percentage of crocidolite fibers detected in lung tissue has risen from 4 to 10%, and the percentage of cases in which crocidolite was detected increased from 19 to 37%. Meanwhile, the frequency of detection of amosite and chrysotile has decreased. The authors performed a detailed analysis of cases in which crocidolite was identified in the absence of amosite. Most of such cases were identified in recent years, a finding of concern since crocidolite is considered the most potent fiber type with respect to the pathogenesis of mesothelioma.

In plain English

The authors examined lung-tissue fiber analyses from 398 people with mesothelioma in one author's database at Duke University Medical Center. The cases included medico-legal consultations and Duke cancer patients. They identified fiber types by electron microscopy and compared 136 cases from before 1994 with 262 cases from 1994 to 2005. Crocidolite was found in 98 of 262 later cases (37%), compared with 26 of 136 earlier cases (19%), and its share of all fibers counted rose from 4% to 10%. Amosite was found in 70% of later cases versus 74% earlier, and its share of fibers fell from 54% to 35%. Crocidolite usually appeared alongside amosite. In 15 cases it was the only commercial amphibole; 13 of these were from the 2000s, and in most the source was not obvious. The authors concluded that crocidolite detection appears to be rising in U.S. mesothelioma patients while amosite and chrysotile detection is decreasing. They noted they could not say for certain whether this was a true increase or a relative shift.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory case series: retrospective review of lung fiber burden analyses in mesothelioma cases, comparing fiber types over time, with a more detailed review of cases showing crocidolite but no amosite
• Who was studied: 398 mesothelioma cases with fiber-type analysis in the database of one author (VLR), from medico-legal consultations and patients in the Duke University Medical Center thoracic oncology program, USA. Cases were split into 136 through 1993 and 262 from 1994 to 2005. Median age was 63 years (range 25 to 94; age not recorded for 11), and 87% were men.
• Exposure: Asbestos and non-asbestos mineral fibers in lung tissue, measured by scanning electron microscopy and energy dispersive X-ray analysis. Fibers 5 micrometres or longer were classified as amosite, crocidolite, tremolite, anthophyllite, actinolite or chrysotile. Occupational and other exposure histories were reviewed for selected cases.
• Main results:
  • Tumor site: pleura in 366 cases, peritoneum in 28, testicular tunica vaginalis in 1; site not documented in 3.
  • Crocidolite was detected in 98 of 262 cases (37%) from 1994 to 2005, compared with 26 of 136 cases (19%) before 1994.
  • Amosite was detected in 183 of 262 cases (70%) from 1994 to 2005, compared with 101 of 136 cases (74%) before 1994.
  • Crocidolite made up 10% of all fibers identified from 1994 to 2005, compared with 4% through 1993.
  • Amosite made up 35% of all fibers from 1994 to 2005, down from 54% through 1993.
  • Median crocidolite concentration was 3270 fibers per gram of wet lung tissue from 1994 to 2005, compared with 4610 through 1993.
  • Median amosite concentration fell from 18,000 to 6670 fibers per gram of wet lung tissue. Median chrysotile concentration was 1270 fibers per gram from 1994 to 2005, compared with 1960 through 1993.
  • Among the 299 cases with at least one amosite or crocidolite fiber, amosite levels accounted for 37% of the variability in crocidolite levels. The association was statistically significant (R = .61, p less than .001).
  • Crocidolite was found together with amosite in 109 of 124 cases (88%) in which crocidolite was found.
  • Crocidolite was the asbestos fiber in highest concentration in 30 cases (7%). It was the only commercial amphibole in 15 cases (3.5%) and the only asbestos fiber in 4 cases (1%).
  • Of the 15 patients with crocidolite but no amosite, 9 had been exposed to asbestos-containing industrial products, 5 had indirect environmental or household contact exposures, and 1 denied asbestos exposure.
  • Of those 15 patients, 2 had peritoneal mesothelioma and the rest had pleural mesothelioma.
  • Of those 15 patients, 13 presented in the decade of publication (the 2000s) and only 1 before 1994.
• The authors' conclusion: The authors concluded that detection of crocidolite appears to be rising in U.S. mesothelioma patients, while detection of amosite and chrysotile is decreasing. They called this a concern because crocidolite is considered the most potent fiber type for mesothelioma. They said further studies are needed to identify the origin of crocidolite in cases without amosite.
• Limitations the authors state:
  • The authors could not say for certain whether the rise reflects a true increase in crocidolite or a relative shift, although they felt falling or stable median concentrations of other fibers supported a true increase.
  • Detection limits for each fiber type varied from case to case.
  • For 1% of all fibers analyzed, amosite and crocidolite could not be told apart; this affected 30 cases.
  • Chrysotile exposure may be underestimated by this method, because chrysotile splits and clears from the lung faster than other asbestos fibers.
  • In several cases only one crocidolite fiber was found, and such a finding might be coincidental.
  • In most cases with crocidolite but no amosite, the source of the crocidolite could not be identified.
  • Many cases were medico-legal referrals; the authors suggested the cases may nonetheless be representative of the United States.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Amosite, Crocidolite, Mesothelioma, Peritoneal mesothelioma.

Medical terms in this study, explained in our Lexicon: Crocidolite, Mesothelioma, Amosite, Chrysotile.

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