Exposure to soda-lime dust in closed and semi-closed diving apparatus

Chronic exposure to hyperbaric hyperoxia and venous gas microembolism have been shown to contribute to the long term health effects of diving, especially diver's lung function. Factors related to special diving equipment may add to these effects. This study was conducted to evaluate possible additional hazards for respiratory function of divers employing closed and semi-closed diving apparatus.

We analyzed soda-lime dust found in the air-intake loop of a closed-circuit oxygen rebreathing diving apparatus which had passed through the filter screen of the diving apparatus's soda-lime cartridge. The geometrical characteristics were evaluated by scanning electron microscopy. The amount of dust that passed through the screen during a normal dive profile was measured by an artificial airflow through a filter membrane. After dives by subjects using these devices, the pH-value of water condensate in the air-intake hose was measured.

There was a relevant amount of residual soda-lime dust found in the air-intake loop. The dust particles showed diameters down to 1 micron and a rounded structure. The total amount of dust averaged 9.6 mg.m-3 of breathing mixture. During diving, the mean pH-value of condensate in the hose is estimated at 8.87 (+/- 0.12).

There is a relevant exposure to soda-lime dust in divers using closed-circuit rebreathing apparatus. This occupational exposure may contribute to chronic airway inflammation and subsequent development of small airway disease in divers.