Urinary fluoride as an exposure index in aluminum smelting

Urinary fluoride was Evaluated as an exposure index for a prospective study of asthma in an aluminum smelter, Two studies were conducted to evaluate t he relationship between airborne exposure and urinary excretion over a work week, and to describe exposures among jobs and over time. Thirty-two subjec ts were evaluated on Days 1 and 3 of a 3-day workweek. On each day, spot ur ine samples were collected prior to the start of work and again at the end of the shift. Samples were analyzed for fluoride and expressed as milligram s fluoride per gram of creatinine. Airborne exposures to total particulate, fluoride particulate, and hydrogen fluoride (HF; using a 37-mm filter cass ette containing a filter and treated back-up pad) were also evaluated on ea ch subject, In the second study, postshift urine samples were collected fro m asthma study volunteers in three surveys extending over 1.5 years and ana lyzed for fluoride, Average airborne exposures were 15.7, 4.1, and 0.7 mg/m (3) for particulates, particulate fluorides and HF, respectively, and were substantially higher among carbon setters than other workers, However, aver age urine fluorides among the same workers were reasonably low, 1.3 and 3.0 mg/g creatinine in pre- and postshift urine samples, respectively. Carbon setters, who routinely wore respiratory protection during high exposure per iods, had urinary fluoride levels similar to those of other potroom personn el, A significant variation in dose, as expressed by postshift urinary fluo ride levels, was observed between potroom and nonpotroom jobs and over thre e survey periods, These results suggest that postshift urinary fluorides pr ovide a reasonable exposure index for surveillance of exposure levels for a n epidemiologic study, and that a substantial variation of exposure occurs between jobs and over time, Although urinary fluorides may be used for expo sure surveillance, additional details on individual exposure agents and pat terns of exposure over time are required for complete assessment.