Benzene intake

The odor perception threshold for benzene in water is 2 ing/L. The benzene drinking water unit risk is 8.3 x lO L/pg. Calculate the potential benzene intake rate (mg benzene/kg-d) and the cumulative cancer risk from drinking water with benzene concentrations at half of its odor threshold for a 30 year exposure duration. 

The following benzene intake rate is determined using the ingestion rate equation given in the problem statement... 

C57BL/6 male mice were given benzene at concentration levels of 200 and 1,000 mg/L (assumed benzene intake of 27 and 154 mg/kg/day) in drinking water for 28 days (Fan 1992). Control groups were given... 

In comparison with other possible sources of exposure (emissions from motor vehicles, evaporation losses during handling, storage and distribution of gasohne) the benzene intake via soft drinks is negligible. Nevertheless, in order to reduce benzene intake by the body, soft drink recipes should be formulated to avoid benzene formation, which means that the simultaneous presence... 

What are the maximum number of excess lifetime cancer cases expected for a population of 5,000 adults with a daily intake of O.lOing of benzene The slope factor for benzene may be assumed to be 0.029 (mgAcg-day)". ... 

Determine the action level in pg/iiv for an 80 kg person with a life expectancy of 70 years exposed to benzene over a 15-year period. The "acceptable risk is one incident of cancer per 1 million persons or lO ". Assume a breathing (intake) rate of 15 m /d and an absorption factor of 75%. The potency factor for benzene is 1.80 (mg/kg-d)." ... 

Estimates of daily exposure to benzene from urban or suburban air range from 180 to 1300 /ig/person/day.1112 Urban air concentrations of the other aromatic hydrocarbons are similar to those of benzene and the vast majority of exposure of the general population to these other aromatic hydrocarbons will be due to road transport or solvent-containing products rather than food. A 1995 survey of these compounds in samples from the UK Total Diet Study showed that average dietary exposures to benzene and related compounds from food in the UK are low, and very much lower than estimated exposure from active smoking of tobacco or intakes from air by urban dwellers.13 The mean dietary exposure to benzene was estimated to be in the range 0.9-2.4 /ig/person/day. 

After that the solvents are distilled in apparatus 9. In the system of solvent condensation (cooler 10 and receptacle 11) a vacuum is created (66.6-93.3 GPa). Cooler 10 is filled with cooled water. The solvents (benzene and methanol mixture) are distilled at agitation and a temperature in apparatus 9 not exceeding 45 °C. The solvent vapours are condensed in cooler 10 and collected in receptacle 11. The process of distillation is monitored through a run-down box on the solvent intake line. After the solvents are no longer released, the vacuum is released by nitrogen in cooler 10 and the product is sampled to check its appearance. 

All outdoor sources, including automobile exhaust and stationary source emissions, account for only about 20% of the total population exposure to benzene (Wallace 1989b). The main outdoor source is likely to be automobile exhaust (Wallace 1995). Average air intake of benzene for urban/suburban residents (assuming atypical concentration range of 2.8-20 ppb and an intake of 20 m3 air/day) is 180-1,300 pg/day. 

Average water intake of benzene (assuming a typical drinking water concentration of 0.1 ppb and a consumption of 2 L/day) is 0.2 pg/day (HSDB 1996). According to another estimate, the daily intakes of benzene for a non-smoking individual (not exposed to secondary smoke) are 1-550 pg (Fishbein 1992). 

The Occupational Safety and Health Administration permissible exposure limit is 100 ppm (435 mg m ) (8h time-weighted average), based on irritation. The National Institute for Occupational Safety and Health short-term exposure limit (15 min exposure limit) is 125 ppm (543mgm ), based on irritation. The odor threshold is 8.7 ppm. Hazardous waste number F003. The acceptable daily intake (US Environmental Protection Agency (EPA)) is 1.6 mg day The EPA oral reference dose (Rfd) for ethyl benzene is 0.1 mg kg day The oral Rfd... 

ICH Q3C guides in determining, on a safety basis, acceptable residual solvent levels for intake by use of the term permitted daily exposure (PDE). This Guidance classifies residual solvents used in the synthesis and processing into four categories. The Guidance recommends that Class I solvents be avoided. These include benzene, carbon tetrachloride, 1,2-dichloromethane, 1,1-dichloroethane, and 1,1,1-trichloroethane. Table 2 is an example from the list of Class II solvents that should be limited because of their inherent toxicity either by calculation of concentration (PPM) or by PDE. 

For higher organisms, e.g., mammals, phenylalanine and tryptophan are so-called essential amino acids, i.e., they cannot be synthesized by the animal and must be supplied in the diet (for man, see 728, 729). Tyrosine is derived, as we shall see later, from phenylalanine, and is not therefore itself an essential amino acid as long as the phenylalanine intake is adequate (726, 950) if the conversion of phenylalanine to tyrosine is inhibited, as in phenylketonuria, tyrosine can become essential (65). The essential nature of the aromatic amino acids is a reflection of the general inability of higher organisms to synthesize the benzene ring. 

Benzene-soluble fractions coal tar pitch volatiles (pg/m ), 8-h average Benzo[a]pyrene Daily intake (tig/m )... 

The use of supercritical fluid extraction (SEE) as an extraction technique is related to the unique properties of the supercritical fluid. These fluids have a low viscosity, high diffusion coefficients, low toxicity, and low flammability, all clearly superior to the organic solvents used in SPE extraction. The most common fluid used is carbon dioxide. SEE extractions of sediment samples have shown recoveries of >95% for all the individual PCBs. The separation of PCDDs from PCBs and chlorinated benzenes is difficult because of their similar solubility. An interesting development is the use of fat retainers. Samples, mixed in different weight ratios with, e.g., silica/silver nitrate 10% or basic alumina, can be placed in 7 ml extraction cells. The analytes are recovered by elution with 1.5-1.8 ml of hexane. With the correct fat-silica ratios and SEE conditions, no additional cleanup procedure is necessary for GC with an electron-capture detector (ECD). One drawback of SEE may be that the methods developed are valid for a specific matrix, but as soon as, e.g., the fat content of a biota sample or the type of lipids changes, the method has to be adapted. SEE is relatively complicated compared to other extraction techniques. In addition, the cell volumes are small, which limits the sample intake, and, with that, the detection limits. Einally, some reliable types of SEE equipment have recently been withdrawn from the market. This will have a substantial negative effect on the use of SEE in the near future. 

These gases may carry volatile wastes, such as benzene and chlorinated hydrocarbons, from the disposal site into the atmosphere and cause air pollution problems or pose health hazards near the site. In some cases, it may be necessary to collect the gases and treat them as discussed in Section 16.24. Filtration over activated carbon can be employed, and in some cases the gases have been pumped with intake air into internal combustion engines where they are destroyed by combustion. 

Another important pathway leading to PAHs is the thermal elimination reaction of benzene derivatives (Figure 12.22). For example, the elimination of water from phenolic compounds (X = OH) yields, via 1,2-didehydrobenzene (often incorrectly called ben-zyn), another reactive intermediate benzobicyclo[2,2,2]triene and naphthalene as a final product. The contribution of endogenously generated compounds to the total dietary intake of PAHs is not too significant as the contamination of food is largely exogenous. 

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