Table 1 Comparison of personal characteristics, work experience and health behaviour between 288 male restaurant workers Personal characteristics, mean (SD) Age (years) Height (cm) Weight (kg) Body mass index (kg/m2) Work experience, mean (SD) Working years Work days per week Work hours per day Cooking hours at work per day Main cooking methods at work, n (%) Deep frying Stir frying Grilling Steaming Stewing Health behaviour, n (%) or mean (SD) Smoking (>4 days per week) Number of cigarettes smoked per day Cooking at home (>4 days per week) Second-hand smoke exposure (>4 days per week) Service staff (n = 117) 35.6 (12.5) 167.8 (6.3) 69.7 (10.5) 24.8 (3.5) 12.2 (11.1) 5.3 (0.4) 8.5 (1.8) 0.0 (0.0) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 56 (47.9%) 5.5 (SD 7.4) 8 (6.8%) 45 (38.5%) Kitchen staff (n = 171) 39.3 (11.0){ 167.1 (6.5) 71.2 (11.6) 25.5 (3.6) 15.0 (9.9)* 5.4 (0.3)* 9.1 (2.5)* 4.1 (2.3) 97 (56.7%) 120 (70.2%) 73 (42.7%) 95 (55.36) 95 (55.36) 78 (45.6%) 6.3 (SD 9.6) 62 (36.3%){ 74 (43.3%) *Kitchen staff differ significantly from service staff at p,0.05 by Student’s t test; {kitchen staff differ significantly from service staff at p,0.01 by Student’s t test; {kitchen staff differ significantly from service staff at p,0.001 by x2 test. having to be present on at least 4 days each week. Subjects who reported smelling cigarette smoke at any time in any place were counted as having been exposed to second-hand smoke that day. Based on job titles, the 288 restaurant workers were divided into two groups. Kitchen staff included chefs, sous chefs, sauce chefs, executive chefs and assistant cooks, all of whom were relatively close to the sources of COFs in restaurants. Service staff included reception staff, cashiers, waiters and valets, who had relatively low COF exposure in restaurants. Spot urine samples were collected from all subjects during their 2005 annual physical examination. All participants were asked to wash their hands before urine collection to avoid contamina- tion. The Institute Review Board of the National Health Research Institutes in Taiwan approved this study. All subjects provided informed consent. Exposure measurement Daily area monitoring was conducted for particulate PAHs in kitchens and dining areas over two consecutive days in all 19 Chinese restaurants in this study. Particulate PAHs in the work place were sampled using IOM (Institute of Occupational Medicine, UK) samplers with glass fibre filters (diameter 25 mm, pore size 0.7 mm) at a flow rate of 2.0 l/min. The samplers were placed near the breathing zone of the workers and duplicate samples were obtained for each sampling location. Airborne particulate PAHs were measured for 12 h on each of two consecutive work days, and then analysed by high performance liquid chromatography (HPLC). Five PAH species (pyrene, benzo(k)fluroranhene, benzo(a)pyrene, benzo(ghi)per- ylene and dibenzo(a,e)pyrene) were quantified via HPLC. Each sample collected was extracted using 2 ml n-hexane in an ultrasonic bath for 20 min and 4 ml 5% NaOH was added before centrifuging at 3000 rpm for 20 min. Subsequently, Occup Environ Med 2008;65:732–735. doi:10.1136/oem.2007.036970 Original article dimethyl sulfate (DMS) was added to a 1.5-ml suspension solution and condensed via nitrogen gas (N2). PAH content in the final solution was determined by a Shimadzu HPLC system (Kyoto, Japan) with a system controller (SCL-10A) and a fluorescent detector (RF-10AXL) equipped with a semi-micro column (Kaseisorb LC ODS-60-5, 4.6 mm6250 mm). The mobile phase consisted of a CH3CN/H2O (9:1) solution with a flow rate of 1.0 ml/min. The detection limits were determined via seven repeated analyses of the lowest standards for each PAH species. The coefficient variation for these repeated analyses was less than 2% for all five PAHs. The detection limits were 0.28 pg for pyrene, 0.72 pg for benzo(k)fluroran- hene, 0.28 pg for benzo(a)pyrene, 0.63 pg for benzo(ghi)per- ylene and 0.43 pg for dibenzo(a,e)pyrene. Urinary 1-OHP and MDA Urinary 1-OHP was analysed via HPLC using a fluorescent detector.12 The detection limit was found to be approximately 0.1 mg/l based on seven repeated analyses of 1-OHP at 15.0 mg/l, and the variation in the coefficients of repeated analyses for urinary 1-OHP was less than 10%. Urinary MDA concentration was measured with an HPLC system (JASCO, Model 980-PU, Tokyo, Japan) using a C18 column and ultraviolet-visible detector at 532 nm (JASCO UV-975). The mobile phase comprised methanol/potassium phosphate (9:11) buffer and the flow rate was 1.2 ml/min. The within-run and run-to-run precisions of MDA in urine were assessed. The samples were analysed for MDA based on thiobarbituric acid (TBA) reaction, with HPLC separation of the MDA (TBA)2 adduct, using tetraethoxypropane as a standard. A detection limit of 0.06 mg/l was obtained from seven repeated analyses of deionised water and the coefficient variation in repeated analyses was less than 10%. The urinary 1-OHP and MDA levels of each individual were corrected according to urine creatinine values, which were measured using an automated method based on the Jaffe reaction.24 Statistical methods Student’s t and x2 statistics were used to compare personal covariates, urinary MDA and 1-OHP between kitchen and service staff. Furthermore, non-parametric tests with Mann– Whitney U test were used to compare differences in work place PAH levels between kitchen and service staff. Urinary MDA and 1-OHP concentrations were log-transformed to normalise their distributions prior to regression analysis. All data from 154 non- smoking restaurant workers were then included in multiple linear regression models to identify significant predictors of Table 2 Comparisons of particulate polycyclic aromatic hydrocarbon (PAH) levels (median, ng/m3) between kitchens and dining areas in 19 Chinese restaurants PAH Pyrene Benzo(k)fluroranhene Benzo(a)pyrene Benzo(ghi)perylene Dibenzo(a,e)pyrene Summed PAHs{ Dining areas (n = 76) 0.2 0.2 1.2 0.6 1.8 4.9 Kitchens (n = 76) 3.3* 1.4* 5.9* 5.2* 8.7* 23.9* *Kitchen staff differ significantly from service staff at p,0.001 by Mann–Whitney U test; {summed PAHs: sum of pyrene, benzo(k)fluroranhene, benzo(a)pyrene, benzo(ghi)perylene and dibenzo(a,e)pyrene. 733