Benzene carcinogenic effect

Table 8.4 provides a few examples of these various protective limits. Recall that RfD is for non-carcinogenic effects only benzene is regulated as a carcinogen (see later). 

Levels of exposure associated with the carcinogenic effects (Cancer Effect Levels, CELs) of benzene are indicated in Figures 2-1 and 2-2. Because cancer effects could occur at lower exposure levels, the figures also show a range for the upper bound of estimated excess risks, ranging from a risk of 1 in 10,000 to 1 in 10,000,000 (10 4 to 10 7), as developed by EPA. 

Estimates of exposure levels posing minimal risk to humans (Minimal Risk Levels or MRLs) have been made for benzene. An MRL is defined as an estimate of daily human exposure to a substance that is likely to be without an appreciable risk of adverse effects (noncarcinogenic) over a specified duration of exposure. MRLs are derived when reliable and sufficient data exist to identify the target organ(s) of effect or the most sensitive health effect(s) for a specific duration within a given route of exposure. MRLs are based on noncancerous health effects only and do not consider carcinogenic effects. MRLs can be derived for acute, intermediate, and chronic duration exposures for inhalation and oral routes. Appropriate methodology does not exist to develop MRLs for dermal exposure. 

Carcinogenic Effects. Specific petroleum hydrocarbon indicator compounds that have EPA cancer potency factors are assessed these are benzene and benzo(a)pyrene. EPA relative potency factors can be used for benz(a)anthracene, indeno(l,2,3-cd)pyrene, dibenz(a,h)anthracene, chrysene, benzo(b)fluoranthene, and benzo(k)fluoranthene. 

Carcinogenic Effects. Specific petroleum hydrocarbon indicator compounds that have EPA cancer potency factors are assessed (i.e., benzene and benzo(a)pyrene). 

Polyhalogenated aromatic hydrocarbons TCDD (2,3,7,8-tetrachlorodibenzo p dioxin), PBB (polybromated biphenyls), PCDF (polychlorinated dibenzofuran), PCBs (polychlorinated biphenyls), hexachloro benzene, 2,4- dichlorophenol Appears to correlate with carcinogenic effect. Case studies for PCB and organochlorine pesticides resulted infections associated with immunosuppression... 

IChemE metrics of sustainability consist of 49 indicators classified into three main categories economic, environmental and social. The environmental indicators within the IChemE metrics are similar to those in the CWRT metrics. However, there are some differences. The IChemE metrics include the area of land as an environmental indicator. The actual indicators are (i) the sum of directly occupied and affected land per value added and (ii) the rate of land restoration. Other differences relate to the assessment of the relative impacts of pollutants on the environment and human health. The IChemE indicators do not take into account the life-time of chemicals in various media of the environment. The human health indicator is limited to carcinogenic effects and is normalized to benzene. 

EPA (1998). Carcinogenic Effects of Benzene An Update. National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, Washington, D.C., EPA/600/P-97/001F. Accessed at http //www.epa.gov/ncea/pdfs/benzenef.pdf. 

Toluene is metabolized to benzoic acid and finally, to hippuric acid and benzoylglu-curonide. The latter two are excreted in urine along with small amounts of cresols, formed by direct hydroxylation of toluene. Chronic exposure may cause some accumulation of toluene in fatty tissues, which may be eliminated over a period of time. The chronic effects of toluene are much less severe to benzene. It is not known to cause bone marrow depression or anemia. Animal tests showed no carcinogenic effects. 

Aksoy, M. 1989. Leukemogenic and carcinogenic effects of benzene. Adv. Mod. Environ. Toxicol. 16 87-98 cited in Chem. Abstr. CA 113(2) 11293a. 

Relative to other carcinogens, the hazard of alkenyl-benzenes is small yet present. One study compared the number of liver tumors (hepatomas) induced in mice by a set of compounds with well known carcinogenic effects. Diethylnitrosamine and aflatoxin B1 respectively induced... 

In addition to carcinogenic effects, animal studies have shown the effects of benzene exposure on the immune system. Reid et al. showed a significant decrease in splenic cell proliferation in mice exposed to benzene for 14 days. Experimental animal studies also reported reduced circulating white blood cells, as well as changes in spleen morphology and weight in various experimental animal studies. These experimental animal studies further support the observation from 1913 by Wintemits and Hirschfelder that rabbits exposed to... 

USEPA, Attachment to IRIS file for benzene, 10/14/98, Response to the Peer-Review Draft Carcinogenic Effects of Benzene An Update, EPA/600/P-97/001A, June 1997... 

The use of benzene as the desorption solvent in-aeases the hazards of analysis because of the potential carcinogenic effects of benzene. 

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