Loomis, et al. (2009) described the incidence of mesothelioma and lung cancer in four North Carolina textile plants. In the plants denoted as plant 1 and plant 2, there were no mesotheliomas or pleural cancers. There were three pleural cancers in plant 3. In plant 4, the authors reported four mesotheliomas and one pleural cancer among the workers.
With regard to the nature of the exposure at the plants, the authors reported: “According to available records, only chrysotile was used except for a separate operation in plant 3, where a limited amount of amosite was carded, twisted and woven between approximately 1963 and 1976.” Thus, the pleural cancers in plant 3 workers cannot be attributed to chrysotile.
But this paper also has been cited as proof that chrysotile caused the mesotheliomas in plant 4. Available evidence rebuts that argument.
Plant 4 was owned by Johns Manville during the 1960s. Our research at the Manville document repository revealed evidence that UNARCO previously owned plant 4 and that it made amosite blankets for the Navy as well as crocidolite valve packing. Our deposition of a co-author of the article confirmed that the authors had not checked the repository for information about the products made in plant 4 before publishing their article.
The authors and others have published follow-up papers on these textile plants. Elliot, et al. (2012) estimated the mean cumulative exposure for three of the plants. The authors’ mean cumulative exposure estimate for the plant 4 cohort was 147.5 fiber-years.
Loomis, et al. (2019) pooled the data from plants 1, 3, and 4 and quantified the risk of pleural cancer and mesothelioma. Figure 2 of the study indicates that a substantial portion of the workers experienced more than 1,000 fiber-yrs of exposure, and many experienced more than 4,000 fiber-yrs of exposure. Adjusting for age, race, and year of follow-up, the authors reported no statistically significant increased risk of pleural cancer or mesothelioma at 100 fiber-yrs of exposure with a 10-year lag. Adjusting only for race and length of follow-up, the authors were able to calculate a slight increased and significant risk of pleural cancer (1.15) for 100 fiber-yrs of exposure, but the risk was not doubled until after 500 fiber-yrs of exposure.
– Erin Therrian, Cary Schachter, Ray Harris