Inhalation of sulfuric acid mist by human subjects.

Abstract

Retention of inhaled mist (as measured by inhalation--exhalation determinations of concentration by electrostatic precipitation or filter paper) averaged 77% (range 50 to 87%) for exposures of 0.4 to 1 mg/m/sup 3/. Mist particle size average was 1 ..mu..m, which could reach alveoli. Threshold of detection was 1 to 3 mg/m/sup 3/. Average respiration rate of 15 volunteers breathing 0.35, 0.4, or 0.5 mg/m/sup 3/ via mask increased sharply to a plateau of about 35% above control within 5 min and dropped to within 13% of control within 3 min after 15-min exposure. Maximum inspiration and expiration flow rates fell to about 20% below control and returned to near normal after termination of exposure. Tidal volume dropped from about 900 ml to 650 ml within 3 to 4 min, and returned to normal during recovery in 4 min (after initial increase at start of recovery). Rapid, shallow breathing may be a protective reflex (less retention). Higher concentrations of 5 mg/m/sup 3/ could be detected, and response was influenced by this. There was varied response but mainly a decrease in minute volume.