Carcinogenic Effects of Benzene : An Update

By Environmental Protection Agency

Book Id: WPLBN0000035945
Format Type: PDF eBook
File Size: 0.3 MB
Reproduction Date: 2007

Title:	Carcinogenic Effects of Benzene : An Update
Author:	Environmental Protection Agency
Volume:
Language:	English
Subject:	Ecology, Natural resource issues, Environemtal protection
Collections:	Environmental Awareness Library Collection
Historic Publication Date:
Publisher:	United States Environmental Protection Agency


Citation APA MLA Chicago Agency, E. P. (n.d.). Carcinogenic Effects of Benzene : An Update. Retrieved from http://www.self.gutenberg.org/

Description
Excerpt: The major issue addressed in this document involves the nature and magnitude of the inhalation risk of cancer to humans exposed to low levels of benzene. Occupational studies continue to provide the bulk of evidence of benzene’s carcinogenicity. Workers are exposed at much higher levels than is the general public. This document reconfirms that benzene is a “known” human carcinogen by all routes of exposure. This finding is supported by evidence from human epidemiologic studies, animal data, and an improvement in understanding of mechanism(s) of action. Human epidemiologic studies of highly exposed occupational cohorts have demonstrated that inhalation exposure to benzene can cause acute nonlymphocytic leukemia and other blood disorders, that is, preleukemia and aplastic anemia. Additionally, changes in blood and bone marrow consistent with hematotoxicity are recognized in humans and experimental animals. Currently, there is insufficient evidence to deviate from using an assumption of a linear dose-response curve for benzene, hence, the Agency’s past approach of using a model with lowdose linearity is still recommended. Of the various approaches employing a linear assumption, utilizing the Pliofilm workers cohort, the inhalation risk at 1 ppm ranges from 7.1 × 10-3 to 2.5 × 10-2. This reflects a modest change from the EPA’s 1985 interim risk assessment which provided only a single estimate of risk (i.e., 2.6 × 10-2).

Table of Contents
CONTENTS LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v AUTHORS, CONTRIBUTORS, AND REVIEWERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi GLOSSARY OF ACRONYMS AND ABBREVIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . vii EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii 1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1. HISTORY OF THE 1985 INTERIM DOCUMENT . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2. PROPOSED 1996 GUIDELINES FOR CARCINOGEN RISK ASSESSMENT . . 2 2. HAZARD ASSESSMENT AND CHARACTERIZATION . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. HUMAN DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. LABORATORY ANIMAL DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.3. MODE-OF-ACTION INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.3.1. Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.3.2. Mutagenicity and Genotoxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.3.3. Epigenetic Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.3.4. Pathogenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 2.3.5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 2.4. HAZARD CHARACTERIZATION SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . 28 3. DOSE-RESPONSE ASSESSMENT AND CHARACTERIZATION . . . . . . . . . . . . . . . . . 30 3.1. DESCRIPTION OF DIFFERENT RISK ASSESSMENTS . . . . . . . . . . . . . . . . . 32 3.2. SHAPE OF THE DOSE-RESPONSE FUNCTION AT LOW DOSES . . . . . . . . . 34 3.3. DOSE-RESPONSE CHARACTERIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 4. CHILDREN’S RISK CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 5. FUTURE RESEARCH NEEDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 6. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45