A statistical analysis of data on exposure to xylene at selected workplaces in the U.K

The results of sampling surveys carried out by the Health and Safety Executive (HSE) during 1987-1988 at a random selection of 49 premises, where xylene was used, are reported. A total of 465 personal exposure samples were collected, from which 369 8-h time weighted average (TWA) exposures were calculated. These had a geometric mean (GM) of 2.2 ppm (GSD, +/- 2.9; range, < 1-202 ppm). At that time HSE already had data for personal exposure to xylene in 122 premises collected between 1980 and 1987. These data yielded 511 8-h TWA personal exposures to xylene with a GM of 7.5 ppm (GSD, +/- 4.3; range, < 1-610 ppm). These GMs are significantly different (P < 0.01), suggesting that the pre-existing data were somewhat biased. This is discussed in the context of the use of these data in setting the Occupational Exposure Limits for xylene and the significance to standard setting of any bias in HSE data.