In this re-analysis, the association with lung cancer was consistent for silicotics, but the data were limited for non silicotic subjects and not easily explained for undefined silicosis status workers. This leaves open the issue of dose-risk relation and pathogenic mechanisms and supports the conclusion that the carcinogenic role of silica per se in absence of silicosis is still unclear.

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Objectives-To study the role of dust exposure on incidence of respiratory symptoms and decline of lung function in young coal miners. Methods-The loss of lung function (forced vital capacity (FVC), forced expiratory volume in one second (FEV,), forced expiratory flow (MEF), carbon monoxide transfer factor (TLCO)) with time and the incidence of respiratory symptoms in 909 Sardinian coal miners (followed up between 1983 and 1993 with seven separate surveys) has been compared with the past and current individual exposures to respirable mixed coal dust. Multiple linear and logistic regression models were used simultaneously controlling for age, smoking, past occupational exposures, and other relevant covariates. Results-According to the relatively low dust exposures experienced during the follow up few abnormal chest x ray films were detected. In the cross sectional analysis ofinitial data, significant associations between individual cumulative exposure to dust, decrements in FEV, and MEFs, and increasing prevalence of respiratory symptoms were detected after allowing for the covariates included in the model.The yearly decline of FVC, FEV,, and single breath carbon monoxide transfer factor (TLCOIVA) was still significantly related to the individual exposure to dust experienced during the follow up, even after allowing for age, smoking, initial cumulative exposure to dust, and initial level ofeach functional variable. In logistic models, dust exposure was a significant predictor of the onset of respiratory symptoms besides age and smoking. Conclusions-The results show that even moderate exposures to mixed coal dust, as in our study, significantly affect lung function and incidence of symptoms of underground miners. Although the frequency of chest x ray examination might be fixed at every three or four years, yearly measurements of lung function (spirometry, MEFs, and TLCo) are recommended for evaluation of the respiratory risk from the coal mine environment to assess the need for further preventive interventions.(Occup Environ Med 1996;53:312-319)

We determined the tracheo-bronchial mucociliary clearance (MCC) in order to evaluate a possible impairment of this function in patients affected by Sjögren's syndrome (SS) with or without overt clinical symptoms of xerotrachea. The MCC was expressed as flow rate (mm/min) and studied in 22 non-smoking SS patients (10 pSS and 12 sSS) and in 8 control subjects by specifically adapted ventilation lung scintigraphy (VLS). The MCC in the control group was 5.9 +/- 1.1 mm/min. No values were produced for MCC in 16 SS patients (8 pSS and 8 sSS) in the time interval considered and were reduced in the remaining 6 SS patients (3.3 +/- 1.2 mm/min). In all nine cases with clinical evidence of xerotrachea no values for MCC were obtained. A significant correlation was found between the MCC values and the rate of stimulated salivary excretion determined by dynamic scialoscintigraphy in the same patients (p < 0.001). These preliminary data show that the majority of SS patients studied presented with MCC impairment, always found when clinical symptoms of xerotrachea were present.

Starting from a cross-sectional survey in 1973, the mortality of two cohorts of Sardinian metal miners was followed through December 31, 1988. In mine A, the quartz concentration in respirable dust ranged between 0.2% and 2.0% and the exposure to radon daughters averaged 0.13 working level (WL), with the highest estimated cumulative exposure around 80-120 WLM. In mine B, the silica content was much higher (6.5-29%), but exposure to radon daughters was significantly lower than in mine A. More than 98% of the overall work force in 1973 (1,741 miners) entered the cohort, providing 25,842.5 person-years. Smoking, occupational history, chest radiographs, and lung function tests were available for the cohort members at admission. Mortality for all causes was slightly lower than expected. A significant excess for nonmalignant chronic respiratory diseases was noticed in both mines. Twenty-four subjects died of lung cancer, 17 from mine A (SMR: 128; 95% confidence interval [CI]: 75-205) and 7 from mine B (SMR: 85; 95% CI: 34-175). The SMR for lung cancer was highest among the underground workers from mine A (SMR: 148; 95% CI: 74-265), with a significant upward trend by duration of employment in underground jobs. Mine B underground miners showed lung cancer SMRs close to 100 without a significant trend by duration of employment. Among underground miners with spirometric airways obstruction in 1973, those from mine A showed the highest risk (SMR: 316; 95% CI: 116-687). The relationship did not change after adjusting for age and smoking. Based on the present findings, crystalline silica per se does not appear to affect lung cancer mortality. A slight association between lung cancer mortality and exposure to radon daughters, though within relatively low levels, may be considered for underground miners from mine A. Impaired pulmonary function may be an independent predictor of lung cancer and an important risk factor enhancing the residence time of inhaled carcinogens, i.e., alpha particles or PAHs, by impairing their bronchial and alveolar clearance.