TOXICOLOGICAL PROFILE FOR CHROMIUM - Davidborowski.com

CHROMIUM 2855. POTENTIAL FOR HUMAN EXPOSURE5.2 RELEASES TO THE ENVIRONMENTAccording to the Toxics Release Inventory (TRI), in 1997 a total of 32,811,382 pounds (14,883,243 kg)of chromium was released to the environment from 3,391 large processing facilities (TRI97 1999).Table 5-1 lists estimated amounts released from specific anthropogenic sources during an unspecifiedtime prior to 1990, including the percentage which were in the hexavalent state (EPA 1990b). Inaddition, an estimated 272,732 pounds (123,711 kg) were released by manufacturing and processingfacilities to publicly owned treatment works (POTWs) and an estimated 5,788,705 pounds(2,625,757 kg) were transferred offsite (TRI97 1999). The TRI data should be used with caution becauseonly certain types of facilities are required to report. This is not an exhaustive list.5.2.1 AirAccording to the Toxics Release Inventory, in 1997 the estimated releases of chromium of706,204 pounds (320,334 kg) to the air from 3,391 large processing facilities accounted for about 2.2% oftotal environmental releases (TRI97 1999). Table 5-2 lists amounts released from facilities. The TRIdata should be used with caution, however, since only certain types of facilities are required to report.This is not an exhaustive list.Total chromium has been identified in 45 air samples collected from 1,036 NPL hazardous waste siteswhere it was detected in some environmental media (HazDat 2000). Chromium(VI) has been identifiedin 4 air samples collected from 120 NPL hazardous waste sites where it was detected in someenvironmental media (HazDat 2000).Continental dust flux is the main natural source of chromium in the atmosphere; volcanic dust and gasflux are minor natural sources of chromium in the atmosphere (Fishbein 1981). Chromium is releasedinto the atmosphere mainly by anthropogenic stationary point sources, including industrial, commercial,and residential fuel combustion, via the combustion of natural gas, oil, and coal. Other importantanthropogenic stationary point sources of chromium emission to the atmosphere are metal industries. Ithas been estimated that .16,000 metric tons of chromium were emitted into the atmosphere from U.S.anthropogenic sources in 1970 (EPA 1984a). These older estimates indicated that emissions from themetal industry ranged from 35% to 86% of the total, and emissions from fuel combustion ranged from11% to 65% of the total (EPA 1978). More recent estimates of atmospheric chromium emission in 1976and 1980 in the Los Angeles, California, and Houston, Texas, areas indicate that emissions from