This study was conducted to investigate the protection of disposable filtering half-facepiece respirators of different grades against particles between 0.093 and 1.61 μm. A personal sampling system was used to particle size-selectively assess the protection of respirators. The results show that about 10.9% of FFP2 respirators and 28.2% of FFP3 respirators demonstrate assigned protection factors (APFs) below 10 and 20, which are the levels assigned for these respirators by the British Standard. On average, the protection factors of FFP respirators were 11.5 to 15.9 times greater than those of surgical masks. The minimum protection factors (PFs) were observed for particles between 0.263 and 0.384 μm. No significant difference in PF results was found among FFP respirator categories and particle size. A strong association between fit factors and protection factors was found. The study indicates that FFP respirators may not achieve the expected protection level and the APFs may need to be revised for these classes of respirators.

The depressions in RBC, WBC, and neutrophils observed in this study are not only exposure dependent, but also significantly different in the lowest exposed group (at or below 0.25 ppm) compared with unexposed subjects. The results of the present study appear to suggest that lymphocytes may not be more sensitive to chronic benzene exposure than neutrophils.

Background The present study was conducted among Chinese workers employed in glue‐ and shoe‐making factories who had an average daily personal benzene exposure of 31±26 ppm (mean±SD). The metabolites monitored were S‐phenylmercapturic acid (S‐PMA), trans, trans‐muconic acid (t,t‐MA), hydroquinone (HQ), catechol (CAT), 1,2,4‐trihydroxybenzene (benzene triol, BT), and phenol. Methods S‐PMA, t,t‐MA, HQ, CAT, and BT were quantified by HPLC‐tandem mass spectrometry. Phenol was measured by GC‐MS. Results Levels of benzene metabolites (except BT) measured in urine samples collected from exposed workers at the end of workshift were significantly higher than those measured in unexposed subjects (P < 0.0001). The large increases in urinary metabolites from before to after work strongly correlated with benzene exposure. Concentrations of these metabolites in urine samples collected from exposed workers before work were also significantly higher than those from unexposed subjects. The half‐lives of S‐PMA, t,t‐MA, HQ, CAT, and phenol were estimated from a time course study to be 12.8, 13.7, 12.7, 15.0, and 16.3 h, respectively. Conclusions All metabolites, except BT, are good markers for benzene exposure at the observed levels; however, due to their high background, HQ, CAT, and phenol may not distinguish unexposed subjects from workers exposed to benzene at low ambient levels. S‐PMA and t,t‐MA are the most sensitive markers for low level benzene exposure. Am. J. Ind. Med. 37:522–531, 2000. © 2000 Wiley‐Liss, Inc.