Int Arch Occup Environ Health (1992) 64:325-327
InternationalArchivesof
O Ce Upatioald
Environmental Health © Springer-Verlag 1992
Urinary excretion of 3,4-dimethylhippuric acid in workers exposed to 1,2,4-trimethylbenzene Masayoshi Ichibal, Hidemi Hama 2 , Shiro Yukitake2 , Masaki Kubota2 , Seiji Kawasaki 3 , and Katsumaro Tomokunil 'Department of Community Health Science, Saga Medical School, Nabeshima, Saga 849, Japan Saga Association of Industrial Medicine, 2-8 Sakae, Saga 840, Japan 3 Department of Laboratory Medicine, Saga Medical School, Nabeshima, Saga 849, Japan 2
Received April 16 / Accepted August 8, 1992
Summary The urinary excretion of 3,4-dimethylhippuric acid ( 34DMHA), a 1,2,4-trimethylbenzene ( 124 TMB) metabolite, was investigated in workers exposed to 124TMB vapor The time-weighted average of exposure to 124 TMB was determined with a diffusive sampler For biological monitoring of exposure, urine samples were collected from individual workers and analyzed for metabolites by high-pressure liquid chromatography The concentration of urinary 34 DMHA had a positive correlation with the level of exposure to 124TMB (r = 0 72) The data suggest that 34 DMHA is one of the useful indicators for biological monitoring of 124TMB exposure. Urinary metabolite Key words: Trimethylbenzene Dimethylhippuric acid Biological monitoring
Introduction Trimethylbenzene (TMB) is used in industry as solvents and paint thinners The threshold limit value (TLV) has been set at 25 ppm (American Conference of Governmental Industrial Hygienists 1987 ; Japan Association of Industrial Health 1991). There is some published information with regard to the metabolism of TMB (Mikulski and Wiglusz 1975 ; Cerf et al 1980 ; Huo et al 1989) Huo et al found that 124TMB, one of the 3 isomers of TMB ( 1,2,3-, 1,2,4-, and 1,3,5-trimethylbenzene), was metabolized mainly to 3,4-dimethylhippuric acid ( 34DMHA) in rats after oral administration However, there is no report on workers with occupational exposure to trimethylbenzene. In the present study, we examined the urinary excretion of 34 DMHA in workers exposed occupationally to 124 TMB and evaluated whether it is useful as a biological indicator of 124 TMB exposure. Correspondenceto: M Ichiba
Subjects and methods Subjects Seven exposed workers were employed in the plant to make printing transfer paper for ceramics They were exposed to thinner (screen printing oil) vapor This thinner is imported from Germany They did not wear a protective mask. Exposure monitoring The time-weighted average (TWA) vapor concentration in the breathing zone of individual workers was measured using a diffusive sampler (3500 Organic Vapor Monitor, 3 M, USA) The exposure monitoring was performed twice except in one worker (n = 13) It was performed from 8:30 to 12:00 a m. at first try (n = 6) and from 8:30 a m to 5:00 p m at second (n = 7) The exposed carbon cloth was extracted with carbon disulfide We used 26 3 cm 3 /min for sampling rate and 1 06 for desorption rate (3 M technical data, for 135TMB). The extract was injected on the GC column (PEG-20 M) for the gas chromatographic analysis (GC-7 AG, Shimadzu, Kyoto, Japan). The oven and injected port were heated at 85 °C and 150 °C, respectively The peaks were identified by GC/MS (GCMS-QP 2000, Shimadzu, Kyoto, Japan) Figure 1 shows a GC chromatogram of air from the working area obtained with a diffusive sampler. Urine collection and analysis for 34DMHA Urine samples were collected from two workers during the working time and from other workers at the end of shift (12:00 a m and 5:00 p m ). After measuring urinary creatinine (Cr) concentration, the urine samples were stored at -20°C until analysis. As authentic chemicals, 34DMHA and TMB were purchased from Tokyo Kasei Chemicals (Tokyo, Japan) and Wako Pure Chemicals (Osaka, Japan), respectively. Urine sample was diluted ten times with distilled water Ten microliters of the sample was injected on the high-pressure liquid chromatography (HPLC) column (STR-OD 52, 4 6 x 150 mm, Shimadzu Techno-Research, Kyoto, Japan) The instrument used was a Shimadzu HPLC Model LC9 A, connected with a controller (SCL-6B), autoinjector (SIL-6 B), column oven (CTO-6B), UV detector (SPD-6 AV), and data processor (CR-4 A) The mobile phase was 10% isopropanol containing 20m M phosphate buffer (pH 2 6) at flow rate of 1 Oml/min The wavelength was set at 240 nm and the column temperature at 400 C Figure 2 shows a metabolite separation pattern of an urine sample from a worker. Several peaks appeared and urinary 34DMHA appeared at 19 min. The relationship between the 34DMHA concentration and the peak area of its chromatogram was linear up to 100 mg/l The relative standard deviation was 1 5 %, and detection limit was 0 5 mg/l.
326
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Time Fig 3 Changes in the concentration of urinary 34DMHA during and after the exposure for each of two workers Exposure time was from 8:30 a m to 12:00 a m and from 1:00 p m to 5:00 p m. or Co 12
100
10 (min)
5
0
Fig 1 GC chromatogram of air from working area obtained with a diffusive sampler
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InternationalArchivesof
O Ce Upatioald
Environmental Health © Springer-Verlag 1992
Urinary excretion of 3,4-dimethylhippuric acid in workers exposed to 1,2,4-trimethylbenzene Masayoshi Ichibal, Hidemi Hama 2 , Shiro Yukitake2 , Masaki Kubota2 , Seiji Kawasaki 3 , and Katsumaro Tomokunil 'Department of Community Health Science, Saga Medical School, Nabeshima, Saga 849, Japan Saga Association of Industrial Medicine, 2-8 Sakae, Saga 840, Japan 3 Department of Laboratory Medicine, Saga Medical School, Nabeshima, Saga 849, Japan 2
Received April 16 / Accepted August 8, 1992
Summary The urinary excretion of 3,4-dimethylhippuric acid ( 34DMHA), a 1,2,4-trimethylbenzene ( 124 TMB) metabolite, was investigated in workers exposed to 124TMB vapor The time-weighted average of exposure to 124 TMB was determined with a diffusive sampler For biological monitoring of exposure, urine samples were collected from individual workers and analyzed for metabolites by high-pressure liquid chromatography The concentration of urinary 34 DMHA had a positive correlation with the level of exposure to 124TMB (r = 0 72) The data suggest that 34 DMHA is one of the useful indicators for biological monitoring of 124TMB exposure. Urinary metabolite Key words: Trimethylbenzene Dimethylhippuric acid Biological monitoring
Introduction Trimethylbenzene (TMB) is used in industry as solvents and paint thinners The threshold limit value (TLV) has been set at 25 ppm (American Conference of Governmental Industrial Hygienists 1987 ; Japan Association of Industrial Health 1991). There is some published information with regard to the metabolism of TMB (Mikulski and Wiglusz 1975 ; Cerf et al 1980 ; Huo et al 1989) Huo et al found that 124TMB, one of the 3 isomers of TMB ( 1,2,3-, 1,2,4-, and 1,3,5-trimethylbenzene), was metabolized mainly to 3,4-dimethylhippuric acid ( 34DMHA) in rats after oral administration However, there is no report on workers with occupational exposure to trimethylbenzene. In the present study, we examined the urinary excretion of 34 DMHA in workers exposed occupationally to 124 TMB and evaluated whether it is useful as a biological indicator of 124 TMB exposure. Correspondenceto: M Ichiba
Subjects and methods Subjects Seven exposed workers were employed in the plant to make printing transfer paper for ceramics They were exposed to thinner (screen printing oil) vapor This thinner is imported from Germany They did not wear a protective mask. Exposure monitoring The time-weighted average (TWA) vapor concentration in the breathing zone of individual workers was measured using a diffusive sampler (3500 Organic Vapor Monitor, 3 M, USA) The exposure monitoring was performed twice except in one worker (n = 13) It was performed from 8:30 to 12:00 a m. at first try (n = 6) and from 8:30 a m to 5:00 p m at second (n = 7) The exposed carbon cloth was extracted with carbon disulfide We used 26 3 cm 3 /min for sampling rate and 1 06 for desorption rate (3 M technical data, for 135TMB). The extract was injected on the GC column (PEG-20 M) for the gas chromatographic analysis (GC-7 AG, Shimadzu, Kyoto, Japan). The oven and injected port were heated at 85 °C and 150 °C, respectively The peaks were identified by GC/MS (GCMS-QP 2000, Shimadzu, Kyoto, Japan) Figure 1 shows a GC chromatogram of air from the working area obtained with a diffusive sampler. Urine collection and analysis for 34DMHA Urine samples were collected from two workers during the working time and from other workers at the end of shift (12:00 a m and 5:00 p m ). After measuring urinary creatinine (Cr) concentration, the urine samples were stored at -20°C until analysis. As authentic chemicals, 34DMHA and TMB were purchased from Tokyo Kasei Chemicals (Tokyo, Japan) and Wako Pure Chemicals (Osaka, Japan), respectively. Urine sample was diluted ten times with distilled water Ten microliters of the sample was injected on the high-pressure liquid chromatography (HPLC) column (STR-OD 52, 4 6 x 150 mm, Shimadzu Techno-Research, Kyoto, Japan) The instrument used was a Shimadzu HPLC Model LC9 A, connected with a controller (SCL-6B), autoinjector (SIL-6 B), column oven (CTO-6B), UV detector (SPD-6 AV), and data processor (CR-4 A) The mobile phase was 10% isopropanol containing 20m M phosphate buffer (pH 2 6) at flow rate of 1 Oml/min The wavelength was set at 240 nm and the column temperature at 400 C Figure 2 shows a metabolite separation pattern of an urine sample from a worker. Several peaks appeared and urinary 34DMHA appeared at 19 min. The relationship between the 34DMHA concentration and the peak area of its chromatogram was linear up to 100 mg/l The relative standard deviation was 1 5 %, and detection limit was 0 5 mg/l.
326
70 60
0 50
E 40
G)
Q 0 C' .0:
I
30
c
20
a. EI m H l
0. aQ
r a
-o 0
N
8
12
10
14
0 E
16
18
20
22
24
Time Fig 3 Changes in the concentration of urinary 34DMHA during and after the exposure for each of two workers Exposure time was from 8:30 a m to 12:00 a m and from 1:00 p m to 5:00 p m. or Co 12
100
10 (min)
5
0
Fig 1 GC chromatogram of air from working area obtained with a diffusive sampler
I
r=0 72
o
3 80 a
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0)
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