US EPA

63722 

Technical Report 

EPA Report 

Health effects assessment for hexavalent chromium 

U.S. Environmental Protection Agency :: U.S. EPA 

1984 

U.S. Environmental Protection Agency 

Cincinnati, OH 

EPA 540/1-86-019 

EPA 

1984 

1-86 

English 

http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=2000FDCU.txt 

In order to place to risk assessment evaluation in proper context, refer to the preface of this document. The preface outlines limitations applicable to all documents of this series as well as the appropriate interpretation and use of the quantitative estimates presented. Chromium exposure has been shown to contribute to increased incidence of respiratory cancers in occupationally exposed workers. The particular form(s) of chromium responsible is not clear. Increases in cancer incidence in experimental animals following chromium inhalation has not been demonstrated. However, intrapleural and intrabronchial implantation of hexavalent chromium compounds has resulted in tumors at the site of implantation. Hexavalent chromium has been shown to be mutagenic in bacterial systems. Using human epidemiological data, a unit risk of 41 (mg/kg/day) has been estimated for inhalation exposure. Data are not available to assess the potential carcinogenicity of hexavalant chromium following oral exposure. Data are inadequate to consider chromium as a carcinogen by the oral route. Using data from a 1-year rat drinking water exposure study, an oral AIC of 0.35 mg/day is estimated. Environmental chemistry and fate. In the hexavalent state, chromium exists as oxo species that are strongly oxidizing. In solution, hexavalent chromium exists as hydrochromate, chromate and dichromate ionic species. The proportion of each ion in solution is pH dependent. In basic and neutral pH, the chromate form predominate. As the pH is lowered (6.0 to 6.2), the hydrochromate concentration increases. At very low pH, the dichromate species predominate. The primary sources of hexavalent chromium in the atmosphere probably are chromate chemicals used as rust inhibitors in cooling towers and emitted as mists, particulate matter emitted during manufacture and use of metal chromates, and chromic acid mist from the plating industry. Both hexavalent and trivalent chromium are removed from air by atmospheric fallout and precipitation. The atmospheric half-life for the physical removal mechanism is expected to depend on the particle size and particle density. Chromium particles of small aerodynamic diameter (<10 um) may remain airborne for a long period. Hexavalent chromium may exist in aquatic media as water soluble complex anions and may persist in water for a long time. Hexavalent chromium is a moderately strong oxidizing agent and may react with organic matter or other reducing agents to form trivalent chromium. The trivalent chromium will eventually be precipitated as CrO3 x xH2O. Therefore, in surface water rich in organic content, hexavalent chromium will exhibit a much shorter lifetime. Any hexavalent chromium in soil is expected to be reduced to trivalent chromium by the organic matter in soil. The primary processes by which the converted trivalent chromium is lost from soil are aerial transport through aerosol formation and surface water transport through runoff. Very little chromium is leached from soil because it is present as insoluble CrO3 x xH2O. The BCF for hexavalent chromium in fish muscle appears to be <1.0, but values of 125 and 192 were obtained for oyster and blue mussel, respectively. 

ANIMAL; HUMAN; carcinogenicity; Carcinogens; genetic toxicity; Mutagens; occupational exposure; Chronic toxicity; risk assessment; ENVIRONMENT; BIOACCUMULATION; aquatic; MOBILITY; soil/sediment