Benzene in blood

Popp W, Rauscher D, Muller G et al. 1994. Concentrations of benzene in blood and S-phenylmercapturic acid and l, /-muconic acid in urine in car mechanics. Int Arch Occup Environ Health 66 1-6. 

Several tests can show if you have been exposed to benzene. Some of these tests may be available at your doctor s office. All of these tests are limited in what they can tell you. The test for measuring benzene in your breath must be done shortly after exposure. This test is not very helpful for detecting very low levels of benzene in your body. Benzene can be measured in your blood. However, since benzene disappears rapidly from the blood, measurements may be accurate only for recent exposures. In the body, benzene is converted to products called metabolites. Certain metabolites of benzene, such as phenol, muconic acid, and S-phenyl-N-acetyl cysteine (PhAC) can be measured in the urine. The amount of phenol in urine has been used to check for benzene exposure in workers. The test is useful only when you are exposed to benzene in air at levels of 10 ppm or greater. However, this test must also be done shortly after exposure, and it is not a reliable indicator of how much benzene you have been exposed to, since phenol is present in the urine from other sources (diet, environment). Measurement of muconic acid or PhAC in the urine is a more sensitive and reliable indicator of benzene exposure. The measurement of benzene in blood or of metabolites in urine cannot be used for making predictions about whether you will experience any harmful health effects. Measurement of all parts of the blood and measurement of bone marrow are used to find benzene exposure and its health effects. 

Benzene was rapidly distributed throughout the bodies of dogs exposed via inhalation to concentrations of 800 ppm for up to 8 hours per day for 8-22 days (Schrenk et al. 1941). Fat, bone marrow, and urine contained about 20 times the concentration of benzene in blood benzene levels in muscles and organs were 1-3 times that in blood and erythrocytes contained about twice the amount of benzene found in plasma. During inhalation exposure of rats to 1,000 ppm (2 hours per/day, for 12 weeks), benzene was stored longer (and eliminated more slowly) in female and male rats with higher body fat content than in leaner animals (Sato et al. 1975). 

Jirka AM, Bourne S. 1982. Gas-chromatographic analysis for benzene in blood. Clin Chem 28 1492-1494. 

Extraction Method for Determination of Benzene in Blood by Gas Chromatography... 

Fig. 39. Apparatus for determination of benzene in blood and in urine. (A) Reservoir of water (B) source of air (D) nitration mixture (E) water (F) 20 per cent solution of sodium hydroxide (K) manometer (G) sample of blood or urine according to S. Skramovsk and J. Teisinger.

The identification of benzene is most easily carried out by gas chromatography (83). Gas chromatographic analysis of benzene is the method of choice for determining benzene concentrations in many diverse media such as petroleum products or reformate, water, sod, air, or blood. Benzene in air can be measured by injection of a sample obtained from a syringe directiy into a gas chromatograph (84). 

Aplastic anemia and leukemia are not the only health effects ascribed to benzene exposure. A number of recent studies have associated benzene exposure with chromosomal changes (aberrations) (118). Other studies have shown abnormalities in porphyrin metabolism and decrease in leucocyte alkaline phosphatase activity in apparendy healthy workers exposed to 10—20 ppm benzene (119,120). Increases in leukoagglutinins, as well as increases in blood fibrinolytic activity, have also been reported and are believed to be responsible for the persistent hemorrhages in chronic benzene poisoning (121,122). 

Benzene zero 0.005 Anemia decrease in blood platelets increased risk of cancer Discharge from factories leaching from gas storage tanks and landfills... 

Some authorities suggest that still another condition can be found in some persons. This is a form of cancer of the white blood cells known as leukemia. Leukemia, which can occur in various forms depending on the cells involved, is an excessive overdevelopment of white blood cells. It is as though, while preventing the manufacture of red cells, the benzene in the bone marrow actually stimulates the manufacture of white cells to grossly excessive amounts, which will ultimately kill the person exposed. 

Target tissues. The target tissues were blood and bone marrow. The expected levels of phenol in blood and bone marrow, and total hydroquinone were substantially higher after phenol administration than after benzene administration. 

The level of phenol detected in blood or urine may not accurately reflect actual phenol exposure because phenol may also appear as a metabolite of benzene or other drugs. It has been shown that under certain acidic conditions used for the hydrolysis of conjugated phenols, acetyl salicylic acid (aspirin) may produce phenol (Baldwin et al. 1981) and yield spuriously higher values for phenol in blood and urine. 

Methods for Determining Biomarkers of Exposure and Effect. Exposure to 1,4-dichloro-benzene may be evaluated by measuring the levels of this compound in blood, breath, milk, and adipose tissue, and by measuring the level of 2,5-dichlorophenol, a metabolite of 1,4-dichlorobenzene, in urine (Bristol et al. 1982 Erickson et al. 1980 Jan 1983 Langhorst and Nestrick 1979 Pellizzari et al. 1985). Sensitive analytical methods are available for measurements in blood. Development of methods with improved specificity and sensitivity for other tissues and breath would be valuable in identifying individuals with low-level exposure. Development of standardized procedures would permit comparison of data and facilitate the study of correlations between exposure and measured levels biological samples. Interlaboratory studies are also needed to provide better performance data for methods currently in use. 

Tardif et al. (1992, 1993 a, 1997) have developed a physiologically based toxicokinetic model for toluene in rats (and humans—see Section 4.1.1). They determined the conditions under which interaction between toluene and xylene(s) occurred during inhalation exposure, leading to increased blood concentrations of these solvents, and decreased levels of the hippurates in urine. Similar metabolic interactions have been observed for toluene and benzene in rats (Purcell et al., 1990) toluene inhibited benzene metabolism more effectively than the reverse. Tardif et al. (1997) also studied the exposure of rats (and humans) to mixtures of toluene, we/a-xylene and ethylbenzene, using their physiologically based pharmacokinetic model the mutual inhibition constants for their metabolism were used for simulation of the human situation. 

Indoor and ambient air samples were measured from December 1992 to February 1993 by the Alaska Department of Environmental Conservation (Gordian and Guay 1995). Concentration levels for methyl tertiary butyl ether (MTBE), benzene, and formaldehyde were measured in ambient and indoor air samples. Blood samples were also taken from service station workers at the same time period. Blood samples from workers showed an increase of 300% in blood benzene concentrations after MTBE reformulated fuel was discontinued. Gasoline in Alaska has a benzene concentration of 5% (average U.S. national concentration is 1.5%). 

Animal data confirm that benzene is rapidly absorbed through the lungs. Inhalation studies with laboratory dogs indicate that distribution of benzene throughout the animal s body is rapid, with tissue values dependent on blood supply. A linear relationship existed between the concentration of benzene in air (200-1,300 ppm) and the equilibrium concentration in blood (Schrenk et al. 1941). At these exposures, the concentrations of benzene in the blood of dogs exposed to benzene reached a steady state within 30 minutes. 

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