Benzene

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Summary

TBD.

Studies and Reports

• Swaen G et al., Low level occupational benzene exposure and hematological parameters, Chem Biol Interact. 2010 Mar 19;184(1-2):94-100. Epub 2010 Jan 13.
  • Abstract. At high and prolonged exposure levels (e.g. >30 ppm), benzene can cause hematological effects. However, there is conflicting evidence on potential hematological effects at lower concentrations. We conducted a study to examine hematological effects at low benzene exposure levels in an occupational setting. Extensive exposure data and data from routine hematology examinations were available for Dow employees at the Terneuzen site in the Netherlands. We compared 8532 blood samples of Dow employees with low benzene exposure to 12,173 samples of employees with no benzene exposure that were available for the period between 1981 and 2007. Based on 21,584 benzene air measurements, a Job Exposure Matrix (JEM) was constructed for all employees with exposure. The JEM was used to estimate benzene exposure in the year in which each blood sample was collected. The average lymphocyte counts for the exposed and non-exposed group were similar. By means of mixed model regression adjustments were made for smoking, age and month of blood sample. These adjustments did not change the results and there was no indication for an adverse effect on any of the hematological parameters under investigation. A further stratification of the exposed population into three subgroups (<0.5 ppm, 0.5-1 ppm and >1 ppm) showed no significant differences for any of the hematological parameters between the three exposure categories or compared with the non-exposed group. The analysis modeling the continuous exposure effect relationship showed similar findings. This study does not indicate that workers exposed to low benzene concentrations are at an increased risk for hematological effects."
• Haws L et al., Assessment of potential human health risks posed by benzene in beverages, J Food Sci. 73(4):T33-41. May 2008.
  • Abstract. "A recent study by the U.S. Food and Drug Administration (FDA) indicated that some beverages contained benzene at levels above the federal drinking water standard of 5 parts per billion (ppb). In tests conducted by the FDA, Crystal Light Sunrise Classic Orange (CLSCO) was reported to contain benzene levels as high as 87.9 ppb. The purpose of the present study was to better characterize benzene concentrations in CLSCO and to quantify potential human health risks. Twenty-eight samples of CLSCO were obtained from retail stores in Houston, Tex., U.S.A. The mean benzene concentrations in 16 oz original and new formulation bottles were 90 and 0.18 ppb, respectively, while 64-oz bottles contained an average of 3.38 ppb. A variety of exposure scenarios were evaluated to determine potential health risks using both deterministic and probabilistic techniques. In the deterministic analyses, upper bound point estimate cancer risks ranged from 5.4E-6 to 8.7E-8, while hazard indices (HI) ranged from 0.28 to 0.00104. Probabilistic analyses were conducted to develop more realistic cancer risk estimates. In these analyses, the 50th and 95th percentile cancer risk estimates were 3.7E-6 and 8.0E-6, and the 50th and 95th percentile hazard indices were 0.19 and 0.42, respectively. In conclusion, all cancer risk estimates and noncancer hazards met the typical health risk benchmarks established by the U.S. regulatory agencies (1E-4 to 1E-6 for cancer and hazard indices less than 1.0)."
• Modl A and Paustenbach D, Airborne concentrations of benzene due to diesel locomotive exhaust in a roundhouse, J Toxicol Environ Health A. 13;65(23):1945-64, December 2002.
  • Abstract. "Concentrations of airborne benzene due to diesel exhaust from a locomotive were measured during a worst-case exposure scenario in a roundhouse. To understand the upper bound human health risk due to benzene, an electromotive diesel and a General Electric four-cycle turbo locomotive were allowed to run for four 30-min intervals during an 8-h workshift in a roundhouse. Full-shift and 1-h airborne concentrations of benzene were measured in the breathing zone of surrogate locomotive repairmen over the 8-h workshift on 2 consecutive days. In addition, carbon monoxide was measured continuously; elemental carbon (surrogate for diesel exhaust) was sampled with full-shift area samples; and nitrogen dioxide/nitric oxide was sampled using full-shift and 15-min (nitrogen dioxide only) area samples. Peak concentrations of carbon monoxide ranged from 22.5 to 93 ppm. The average concentration of elemental carbon for each day of the roundhouse study was 0.0543 and 0.0552 microg/m(3 )for an 8-h workshift. These were considered "worst-case" conditions since the work environment was intolerably irritating to the eyes, nose, and throat. Short-term nitrogen dioxide concentrations ranged from 0.81 to 2.63 ppm during the diesel emission events with the doors closed. One-hour airborne benzene concentrations ranged from 0.001 to 0.015 ppm with 45% of the measurements below the detection limit of 0.002-0.004 ppm. Results indicated that the 8-h time-weighted average for benzene in the roundhouse was approximately 100-fold less than the current threshold limit value (TLV) of 0.5 ppm. These data are consistent with other studies, which have indicated that benzene concentrations due to diesel emissions, even in a confined environment, are quite low."
• Paustenbach D et al., Benzene toxicity and risk assessment, 1972-1992: implications for future regulation, Environ Health Perspect. 101 Suppl 6:177-200, December 1993.
  • Abstract. "Acute and chronic exposure to benzene vapors poses a number of health hazards to humans. To evaluate the probability that a specific degree of exposure will produce an adverse effect, risk assessment methods must be used. This paper reviews much of the published information and evaluates the various risk assessments for benzene that have been conducted over the past 20 years. There is sufficient evidence that chronic exposure to relatively high concentrations of benzene can produce an increased incidence of acute myelogenous leukemia (AML). Some studies have indicated that benzene may cause other leukemias, but due to the inconsistency of results, the evidence is not conclusive. To predict the leukemogenic risk for humans exposed to much lower doses of benzene than those observed in most epidemiology studies, a model must be used. Although several models could yield plausible results, to date most risk assessments have used the linear-quadratic or conditional logistic models. These appear to be the most appropriate ones for providing the cancer risk for airborne concentrations of 1 ppb to 10 ppm, the range most often observed in the community and workplace. Of the seven major epidemiology studies that have been conducted, there is a consensus that the Pliofilm cohort (rubber workers) is the best one for estimating the cancer potency because it is the only one with good exposure and incidence of disease data. The current EPA, OSHA, and ACGIH cancer potency estimates for benzene are based largely on this cohort. A retrospective exposure assessment and an analysis of the incidence of disease in these workers were completed in 1991. All of these issues are discussed and the implications evaluated in this paper. The range of benzene exposures to which Americans are commonly exposed and the current regulatory criteria are also presented."
• Paustenbach D et al., Reevaluation of benzene exposure for the Pliofilm (rubberworker) cohort (1936-1976), J Toxicol Environ Health. 36(3):177-231, July 1992.
  • Abstract. "The Pliofilm cohort is the most intensely studied group of workers chronically exposed to benzene. Information on this cohort has been the basis for regulations and/or guidelines for occupational and environmental exposure to benzene. Rinsky et al. (1986, 1987) and Crump and Allen (1984) developed different approaches for reconstructing the exposure history of each member of the group. The predicted levels of exposure, combined with the data on the incidence of disease, have been used to estimate benzene's carcinogenic potency. In this paper, recent information from worker interviews and historical records from the National Archives and elsewhere were used to evaluate the accuracy of prior exposure estimates and to develop better ones for the cohort. The following factors were accounted for: (1) uptake of benzene due to short-term, high-level exposure to vapors, (2) uptake due to background concentrations in the manufacturing building, (3) uptake due to contact with the skin, (4) morbidity and mortality data on workers in the Pliofilm process, (5) the installation of industrial hygiene engineering controls, (6) extraordinarily long work weeks during the 1940s, (7) data indicating that airborne concentrations of benzene were underestimated due to inaccurate monitoring devices and the lack of adequate field calibration mated due to inaccurate monitoring devices and the lack of adequate field calibration of these devices, and (8) likely effectiveness of respirators and gloves. Our estimates suggest that Crump and Allen (1984) overestimated the exposure of workers in some job classifications and underestimated others, and that Rinsky et al. (1981, 1986) almost certainly underestimated the exposure of nearly all workers. Airborne concentrations of benzene at the St. Marys facility during the years of its operation were found (on average) to be about half those of the two Akron facilities. Our analysis indicates that short-term, high-level exposure to benzene vapors and dermal exposure significantly increased (by about 25-50%) the total absorbed dose of benzene for some workers. One of the key findings was that, unlike prior analyses, the three facilities probably had significantly different airborne concentrations of benzene, especially during the 1940s and 1950s."

Additional Resources

• Whelan E, Mother Nature's Chemical Bounty, New York Post, November 22, 2007.
• Kava R, Benzene Redux: This Time It's Soda, American Council on Science and Health, March 3, 2006.