Assessment of butadiene exposure in synthetic rubber manufacturing workers in Texas using frequencies of hprt mutant lymphocytes as a biomarker.
1,3-Butadiene (BD), which is used to manufacture synthetic rubber, is a mutagen and carcinogen. Because past occupational exposures have been associated with an increased risk of leukemia, there has been a dramatic reduction in workplace exposure standards. The health benefits of these reduced levels of occupational exposure to BD will be difficult to evaluate using relatively insensitive traditional epidemiological studies; however, biomarkers can be used to determine whether there are genotoxic effects associated with recent exposures to BD. In past studies of BD-exposed workers in Southeast Texas, we observed an increase in the frequency of lymphocytes with mutations in a reporter gene, hprt. Frequencies of hprt mutant cells correlated with air levels of BD and with the concentration of a BD metabolite in urine. Average exposures to 1-3 parts per million (p.p.m.) of BD were associated with a threefold increase in hprt variant (mutant) frequencies (Vfs). We now report results from a follow-up study of workers in a synthetic rubber plant in Southeast Texas. Thirty-seven workers were evaluated on three occasions over a 2-week period for exposure to BD by the use of personal organic vapor monitors and by determining the concentration of a BD metabolite in urine. The frequency of hprt mutants was determined, by autoradiography, with lymphocyte samples collected 2 weeks after the final exposure measurement. Based on their work locations, the study participants were assigned to high-exposure (N=22) or low-exposure (N=15) groups. The BD exposure, +/-standard error, of the workers in the high-exposure group (1.65+/-0.52 p.p.m.) was significantly greater than the low-exposure group (0.07+/-0.03 p.p.m.; P<0.01). The frequency of hprt mutant lymphocytes was also significantly different in the two groups (high, 10.67+/-1.5 x 10(-6); low, 3.54+/-0.6 x 10(-6); P<0.001). The concentration of the urine metabolite was greater in the high-exposure group, but the difference was not significant. The correlation coefficient between hprt Vf and BD exposure levels was r=0.44 (CI(95), 0.11-0.69; P=0.011). This study reproduced the findings from a previous study at this plant. Although studies of butadiene-exposed workers in other countries have not detected an effect of exposure on frequencies of hprt mutant lymphocytes, we have repeatedly observed this result in our studies in Texas.
Ward
J B
JB
Division of Environmental Toxicology, Department of Preventive Medicine and Community Health, 2.102 Ewing Hall, University of Texas Medical Branch, Galveston, TX 77555-1110, USA. jward@utmb.edu
Abdel-Rahman
S Z
SZ
Henderson
R F
RF
Stock
T H
TH
Morandi
M
M
Rosenblatt
J I
JI
Ammenheuser
M M
MM
D000395:Air Pollutants, Occupational / Q000032:analysis / Q000633:toxicity; D015415:Biomarkers; D002070:Butadienes / Q000032:analysis / Q000633:toxicity*; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D008214:Lymphocytes / Q000187:drug effects / Q000201:enzymology; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity; D009154:Mutation; D016273:Occupational Exposure; D011110:Polymorphism, Genetic; D012408:Rubber / Q000138:chemical synthesis*; D013781:Texas
D000395:Air Pollutants, Occupational; D015415:Biomarkers; D002070:Butadienes; D009153:Mutagens; D012408:Rubber; D007041:Hypoxanthine Phosphoribosyltransferase; C031763:1,3-butadiene