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Download Tulane ELC Crude oil is a complex mixture of organic and some
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Patricia M Williams PhD, DABT Associate Professor Coordinator, Toxicology Research Laboratories Pontchartrain Institute for Environmental Sciences University of New Orleans Cell: 504-915-1817 Crude oil is a complex mixture varying with its geologic origin. Crude oil contains hundreds, perhaps even thousands of hydrocarbons ranging from C1 to greater than C50. (Patty’s Toxicology, 2001). Benzene is a naturally occurring component of crude oil, wand may be listed on MSDS sheets at concentrations up to 2% of benzene in this complex mixture. Benzene is a confirmed Human Carcinogen (International Agency for Research on Cancer; Occupational Safety and Health Act, National Institute for Occupational Safety and Health). This 2% benzene is equal to 2 parts per hundred or 20,000 parts per million in concentration. The OSHA permissible exposure level for workers is 1 ppm of benzene in an eight hour work day (OSHA 1910.1028) and the ATSDR Minimal Risk Level of benzene for residents is 0.003 ppm for chronic exposure (365 or longer); 0.006 ppm for intermediate exposure (15-364 days); and 0.009 ppm for acute exposure to benzene (1-14 days) (Agency for Toxic Substances and Disease Registry, December 2010). Benzene is a DNA-reactive carcinogen that binds to the DNA of a cell and damages its structure resulting in adduct formation (insertion of the benzene metabolite into the DNA) and chromosome breakage. These damaged portions of the DNA may remain as lesions in the parental DNA strand and induce alteration or mutations in the daughter strand of DNA during replication. The mutation may ultimately be expressed as damaged genes that express mutant proteins that reprogram cells for multiplication. When such cells undergo cell division, their descendants also carry the damaged DNA and as a result have the propensity for enhanced proliferation which is a characteristic of malignant transformation. These damaged reprogrammed cells will continue increased proliferation with a growth advantage over normal cells. The final outcome of the DNA damage is a tumor consisting of transformed rapidly proliferating cells that have undergone a malignant transformation due to the original DNA damage produced by the benzene toxicant. (Casarett and Doull, 2001)