Method Development for Antimony Speciation Analysis and Assessment of Occupational Exposure to Antimony Trioxide

Antimony trioxide (Sb2O3) is a fire retardant with various applications widely used in industry. Animal studies have shown that antimony trioxide is a carcinogen associated with lung cancer and cardiopulmonary diseases in rats. Antimony hydride compounds of high concentrations may cause central nervous system damage and hemolysis. The American Conference of Governmental Industrial Hygienists (ACGIH), International Agency for Research on Cancer (IARC) and the European Union have classified the carcinogenesis of antimony trioxide at A2 level, 2B level and the third category, respectively. A convenient and robust analytical method is required for determining various antimony species.
This study attempted to develop an analytical method to simultaneously determine antimony species and to measure human exposure at industries, such as manufacturing or using chemicals containing antimony. For the on-site exposure assessment, we conducted “biological monitoring” at three plants: one antimony smelting plant A, and two engineering plastic plants B and C.
This study first developed and established an analytical protocol to simultaneously determine three antimony species in urine samples, including: inorganic trivalent antimony (Sb(III)), pentavalent antimony (Sb(V)) and organic trimethylantimony (TMSb), using HPLC-ICP-MS. We employed 20 mM EDTA, 10% methanol and de-ionized water as the elution buffer for the gradient elution. The results showed that Sb (III), Sb (V) and TMSb were appropriately separated with the retention times of 9.86, 6.20 and 2.40 min, and the detection limits of 0.79, 0.22 and 1.23 μg/L, respectively. We have obtained good chromatograms for these three species of antimony in urine, but there were two other unknown antimony species in the sample deserving determination.
For the on site survey, we collected air samples at work places and workers’ urine samples at Plant A for 5 week days by 5 subgroups: packaging group, oxidation furnace group, management group, quality control and analysis group, and accounting group. The convenient hair samples were also collected from workers. The results showed that the 5-day average antimony concentrations in the air (standard deviations) were: 3.36 (2.35), 1.86 (1.69), 0.12 (0.14), 0.03 (0.03) and 0.03 (0.02) mg/m3, respectively. The corresponding average concentrations (standard deviation) were 266.2 (88.4), 178.1 (72.1), 51.4 (40.5), 42.4 (33.2) and 28.8 (22.6) μg Sb/g cre in urine samples, and 12.52 (1.85), 1.44 (0.83), 0.41 (0.47), 0.07 (0.08) and 0.03 (0.005) mg Sb/g in hair samples. The mean concentrations of Sb among the 5 survey sites at the Plant A were significantly different for each type of sample (p < 0.001, by Kruskal-Wallis One Way Analysis of Variance by Ranks). The relationships between Sb concentrations in the air samples and Sb concentrations in the urine samples was in the function of Y = 42.76X + 67.31, r = 0.6377. The corresponding association for hair samples was Y = 2.011X - 0.0611, r = 0.6926. Both indicate a good relationship.
We also collected the air samples at the work place for one-day and urine samples from workers at the antimony trioxide plant (A), engineering plastics plant (B) and engineering plastics plant (C). The average concentrations (standard deviation) of antimony trioxide in the air samples were: 5.31 (5.88), 0.50 (0.31) and 0.45 (0.79) mg/m3, respectively. The average concentrations (standard deviation) in the urine samples collected from the respective plants on that single day were 313.7 (437.4), 40.1 (32.8) and 14.7 (7.3) μg Sb/g cre. The average Sb level in the air samples of Plant A was 10-fold greater than Taiwan’s standard for permissible exposure to Sb of 0.5 mg/m3. The average air concentrations of Sb at plants B and C were both near the permissible level. Air samples were also taken from Plant C for a short period during the operation of “feeding” antimony ore; and the overall average concentration (standard deviation) was 3.92 (4.40) mg/m3, which was 8-fold greater than the permissible level. This is another extreme high level for workers to expose to.
We have carried out a “biological monitoring” and analysis study on 3 workers who exposed to high levels of Sb at work except Saturdays & Sundays. The air samples at work were collected on a Friday and the following Monday. Each worker provided 8 urine samples starting from the Friday before work until Monday by the end of the daily duty. We monitor the change of antimony concentration in urine in order to calculate the half-life of metabolism of the antimony. The average (standard deviation) concentration of the airborne Sb the workers exposed to was 4.43 (3.37) mg/m3. Among the air samples, 5 samples greatly surpassed the “permissible exposur limits” and 1 sample exceeded the “action level”. The antimony species identified from the urine samples for the workers who exposed to antimony trioxide consisted of trimethyl antimony, trivalent antimony, pentavalent antimony and two unknown species. The half-life of antimony trioxide was 60hrs with a coefficient of variation of 14.8%. The analysis of the metabolites in the urine samples showed that the concentration of trimethyl antimony was much lower than other two species. On the other hand, the concentration of pentavalent antimony increased as the antimony trioxide exposure increased. The urinary concentration of trivalent antimony began to rise at the end of exposure and reached to a peak at 2400 min after the exposure. The concentrations of the two unknown species increased as the exposure duration increased; the increasing trends continuously proceeded for 1000 min after the exposure and then declined until another exposure occurred. In conclusion, we have established an analytical method to determine inorganic trivalent antimony, pentavalent antimony and organic trimethylantimony in environmental samples and urinary samples. Future study should emphasize exposure reduction at work place and identify the two unknown species.