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A field study was conducted on 42 asphalt-roofing workers at 7 built-up roofing sites across the United States. Sixteen out of 42 samples show levels of exposure to asphalt fumes that exceed the current American Conference of Governmental In-dustrial Hygienists' (ACGIH R )-recommended threshold limit value of 0.5 mg/m 3 as benzene extractable inhalable particu-late. Statistically, the geometric mean of all 42 worker samples was 0.27 mg/m 3 (geometric standard deviation =3.40), the average was 0.70 mg/m 3 (standard deviation =1.69) and the median value was 0.24 mg/m 3 . The impact of work practices is discussed including the use of a novel product that uses a polymer skin to reduce fumes from built up roofing asphalt. Its use resulted in a reduction of benzene soluble matter (BSM) of >70%. Other testing measures utilized included total particu-late matter, total organic matter, simulated distillation, and fluorescence analysis. Additionally, a controlled pilot study using 16 kettle-area and 16 worker samples clearly showed that when the temperature of the kettle was reduced by 28C, there was a 38--59% reduction in fume exposure and a 54% reduction in fluorescence with standard asphalts. Reduction of BSM exposures using fuming-suppressed asphalt was also confirmed during this pilot plant study (81--92%), with fluo-rescence lowered by 88%. Confounding agents such as roof tear-off materials were also analyzed and their contribution to worker exposure is discussed. [ABSTRACT FROM AUTHOR]