Follow-up study of chrysotile textile workers: cohort mortality and exposure-response

Abstract

Objectives: This report provides an update of the mortality experience of a cohort of South Carolina asbestos textile workers. Methods: A cohort of 3072 workers exposed to chrysotile in a South Carolina asbestos textile plant (1916-77) was followed up for mortality through 2001. Standardised mortality ratios (SMRs) were computed using US and South Carolina mortality rates. A job exposure matrix provided calendar time dependent estimates of chrysotile exposure concentrations. Poisson regression models were fitted for lung cancer and asbestosis. Covariates considered included sex, race, age, calendar time, birth cohort and time since first exposure. Cumulative exposure lags of 5 and 10 years were considered by disregarding exposure in the most recent 5 and 10 years, respectively. Results: A majority of the cohort was deceased (64%) and 702 of the 1961 deaths occurred since the previous update. Mortality was elevated based on US referent rates for a priori causes of interest including all causes combined (SMR 1.33, 95% CI 1.28 to 1.39); all cancers (SMR 1.27, 95% CI 1.16 to 1.39); oesophageal cancer (SMR 1.87, 95% CI 1.09 to 2.99); lung cancer (SMR 1.95, 95% CI 1.68 to 2.24); ischaemic heart disease (SMR 1.20, 95% CI 1.10 to 1.32); and pneumoconiosis and other respiratory diseases (SMR 4.81, 95% CI 3.84 to 5.94). Mortality remained elevated for these causes when South Carolina referent rates were used. Three cases of mesothelioma were observed among cohort members. Exposure-response modelling for lung cancer, using a linear relative risk model, produced a slope coefficient of 0.0198 (fibre-years/ml) (standard error 0.00496), when cumulative exposure was lagged 10 years. Poisson regression modelling confirmed significant positive relations between estimated chrysotile exposure and lung cancer and asbestosis mortality observed in previous updates of this cohort. Conclusions: This study confirms the findings from previous investigations of excess mortality from lung cancer and asbestosis and a strong exposure-response relation between estimated exposure to chrysotile and mortality from lung cancer and asbestosis.

Update of Potency Factors for Asbestos-Related Lung Cancer and Mesothelioma

“…The estimate of K L with α = 1 is 0.030 (f-yr/ml) −1 , 90% CI: (0.023, 0.037), and the estimate with α variable (α = 1.35) is K L = 0.018 (f-yr/ml) −1 , 90% CI: (0.011, 0.027). Hein et al (2007) reported three deaths from mesothelioma, and Hein graciously identified these for us in the data files. Applying the method described in the main article for calculating K M from raw data, the following estimate was obtained:…”

“…For studies conducted at the same facility (generally among highly overlapping cohorts), a single study was selected for presentation in Figure 11. Thus, for South Carolina, the Hein et al (2007) study was selected because this study includes the most recent follow-up and because of access to the raw data for this study. Similarly, the Sullivan (2007) study was selected to represent the Libby vermiculite site over the other studies at this facility (McDonald et al, 1986;.…”

“…As in Figure 11, data from the Hein et al (2007) study are used to represent the South Carolina textile cohort. Also, the estimate of K M for the Quebec miners is based on the combined data from the Asbestos and Thetford Mines.…”

Peritoneal Mesothelioma and Asbestos: Clarifying the Relationship by Epidemiology

“…The authors noted there were several other death certificates which mentioned 'cancer of the abdomen' however, no autopsy or other confirmatory data were available. Further description and follow-up of this South Carolina chrysotile asbestos textile worker cohort [40] expanded the numbers of workers to 3072 and found three cases of mesothelioma including the specification that the one peritoneal case was a female case.…”

Collegium Ramazzini response to ‘Asbestos, asbestosis, and cancer, the Helsinki criteria for diagnosis and attribution 2014: recommendations’

“…The 2014 Helsinki report (1) states on pages 6 and 7: "Using an estimate of 4% increase of risk for each fibres per cubic centimeter per year (fibre year) of cumulative exposure: 'A cumulative exposure of 25 fibre-years is estimated to increase the risk of lung cancer 2-fold, clinical cases of asbestosis may occur at comparable cumulative exposures." Setting aside the fact that published studies support a linear dose-response relationship without a threshold (24)(25)(26)(27), the 2014 consensus statement ignores its previously acknowledged range of risk estimates and chooses the upper end of the range without comment or explanation. This compounds the error of its failure to acknowledge and reference studies indicating a linear dose-response relationship and instead embraces a statement that implicates a specific threshold.…”