Malignant mesotheliomas in former miners and millers of crocidolite at Wittenoom (Western Australia) after more than 50 years follow-up

Abstract

Background:To report the number of malignant pleural and peritoneal mesotheliomas that have occurred in former Wittenoom crocidolite workers to the end of 2008, to compare this with earlier predictions, and to relate the mesothelioma rate to amount of exposure.Methods:A group of 6489 men and 419 women who had worked for the company operating the former Wittenoom crocidolite mine and mill at some time between 1943 and 1966 have been followed up throughout Australia and Italy to the end of 2008.Results:The cumulative number of mesotheliomas up to 2008 was 316 in men (268 pleural, 48 peritoneal) and 13 (all pleural) in women. There had been 302 deaths with mesothelioma in men and 13 in women, which was almost 10% of all known deaths. Mesothelioma rate, both pleural and peritoneal, increased with time since first exposure and appeared to reach a plateau after about 40 to 50 years. The mesothelioma rate increased with amount of exposure and the peritoneal mesotheliomas occurred preferentially in the highest exposure group, 37% compared with 15% overall.Conclusion:By the end of 2008, the number of mesothelioma deaths had reached 4.7% for all the male workers and 3.1% for the females. Over the past 8 years the numbers were higher than expected. It is predicted that about another 60 to 70 deaths with mesothelioma may occur in men by 2020.

Mesothelioma risk after 40 years since first exposure to asbestos: a pooled analysis

“…Lower asbestos exposure has been shown elsewhere to be associated with a longer latency period 25. Among the Wittenoom women, those who worked for the asbestos company had a shorter latency period than those who obtained similar cumulative exposure through their residence at Wittenoom26 although the Wittenoom workers’ latency was shown to be independent of degree of exposure 6…”

“…A clearance term (as used in Berry 20126) was included in the models to examine changes in the time exponent (power of time since first exposure). The time exponent was also examined by duration of exposure.…”

“…Among Turin textile workers a reduction of the MM rate was observed 4. Similarly, the overall rate of MM appeared to level off after 50 years following first exposure in the Wittenoom workers,5 and this was in pleural and peritoneal MM 6…”

Prognostic factors influencing survival in 35 patients with malignant peritoneal mesothelioma

“…High cumulative asbestos exposure is a major risk factor for both pleural and peritoneal mesothelioma [3]. However, asbestos-induced MPM usually requires a higher cumulative dose than its pleural counterpart [13]. It is well known that people have been exposed to environmental asbestos in some rural areas of the Southeast Anatolia Region of Turkey due to its geographical structure [14].…”

Asbestos-Related Research: First Objectivity then Conclusions

“…The evidence in favor of crocidolite toxicity based e.g. on the Wittenoom cohort studies seems to be compelling [81][82][83], although the number of deaths with mesothelioma in men in the period 1987 to 2008 remained similar to the lowest predictions (the number of Mt in the past 8 years was higher than predicted -74 vs. 63) [83], while genetic predisposition was discussed along with asbestos as an etiologic factor of Mt [84]. There is considerable evidence that the risk of Mt is enhanced after exposure to chrysotile without amphibole admixture [46,48,[72][73][74][75][76]85].…”