Mortality and Silicosis Morbidity - Update of the German Porcelain Workers Study

Status:

ongoing

Aims:

The morbidity and mortality risk with crystalline silica exposure in the low-dosage range will be determined using a cohort of workers in the German porcelain industry. The focus is the morbidity and mortality from silicosis, lung cancer mortality, and morbidity and mortality from kidney disease. The aim is to derive a threshold for an increased risk of silicosis and lung cancer.

Main Study Results: The mortality analysis provided no evidence of increased risk for lung cancer, kidney cancer, and other kidney diseases in the cohort. An increased risk for silicosis (mortality) -based on a small number of cases- was observed. The dose-response analysis suggests an increased risk of silicosis starting at an average exposure concentration of 0.15 mg/m³ respirable crystalline silica and a exposure of 4,0 mg/m³ x years cumulative (threshold). A threshold for lung cancer could not be determined.

With the update of the study, the observation period for about 15,000 workers (cohort members still alive at the cut-off date of December 31, 2005) will be extended by another 15 years until the end of 2020. Hereby the statistical power is increased, especially in regard to the latency period for cancer (in the most recent 10-15 years) and the occurrence of new silicosis cases given the relatively young average age of the cohort. The follow up does not include updating the exposure assessment.

Activities/Methods:

We conducted an epidemiological cohort study of approximately 18,000 workers who took part in a preventive medical surveillance program for early identification of silicotic signs between 1985 and 1987 (main study 2005 - 2009). In the main study, the employment history was reconstructed for each person using files from the German Berufsgenossenschaft der keramischen und Glas-Industrie and similar exposure groups (SEG) were defined. More than 8,000 combined static and personal monitoring samples were available for total dust, respirable dust, and respirable crystalline silica dust (for the period from 1954 and 2006). These data-sets were combined into SEGs. In a Job Exposure Matrix (JEM), the SEGs determined from the work history records and the SEGs from the industrial hygiene measurement data were individually assigned to each cohort member.The cohort will be monitored concerning mortality and silicosis morbidity until December 31, 2020. For this purpose, the radiographs will be re-read by two independent radiologists (ILO 2000). Causes of death (COD) from the official death certificates will be coded by a nosologist (ICD-10). Analyses of standardized mortality rates (SMR) are performed as a reference using the German population. Cox proportional hazard models will be used to estimate the risk for silicosis incidence and lung cancer mortality by cumulative and average exposure concentration (threshold) based on individual exposure estimates.

Last Update: