RESPIRATORY EFFECTS AND SERUM TYPE-III PROCOLLAGEN IN POTATO SORTERS EXPOSED TO DIATOMACEOUS-EARTH

Exposure to diatomaceous earth with low crystalline silica content (< 1%) is rarely reported to cause pneumoconiotic disease, whereas airway obstruction and bronchitis are more frequently reported. We investiga ted the occurrence of pneumoconiosis and airflow limitation in 172 mal e workers from 5 potato sorting plants (55 controls, 29 salesmen, 72 c urrently exposed, and 16 retired exposed) exposed to inorganic dust fr om former sea terraces (7.7-15.4 mg/m(3)), high in diatomaceous earth. The presence of fibrosis was evaluated by chest radiographs (exposed only) and serum levels of type III procollagen (P-III-P) were measured as an estimate of fibrogenetic activity. Lung function was assessed b y flow volume curves and impedance measurements. A validated questionn aire was used to record respiratory symptoms. No pneumoconiotic abnorm alities were demonstrated by chest radiographs. In line with this find ing, serum P-III-P levels were not elevated in exposed workers as comp ared to controls, suggesting no differences in fibrogenetic activity. In fact, serum P-III-P levels decreased significantly (P < 0.03) with increasing cumulative exposure. Flow volume parameters indicated airfl ow obstruction, dose-related to (cumulative) dust exposure; the annual decline in forced expiratory flow volume (FEV,) was estimated at 10.5 ml/year (P < 0.05). Airway obstruction was confirmed by impedance ana lysis: In the retired group impedance changes were compatible with air way obstruction extending into the peripheral airways. We conclude tha t this exposure to quartz during potato sorting does not result in an increased risk for pneumoconiosis, but that (prolonged) surveillance i n this group is desirable in order to detect early indications of airf low obstruction.