Non-Substantive Reference Change for the December 2010 Draft Public Health Goal for Hexavalent Chromium

Jan 25, 2011

The current draft of the proposed PHG for Chromium VI, posted on December 31, 2010, referenced an internal working draft document on drinking water consumption values, cited as OEHHA, 2010. Since the OEHHA document is still in draft and not yet publically available, OEHHA has determined it would be more appropriate to cite comparable published studies as a basis for calculation of the non-cancer health-protective value and the draft PHG, found on pages 92-94 of the draft PHG document.

The relevant published materials to be referenced for the drinking water consumption values are:

U.S. EPA (2008). Child-Specific Exposure Factors Handbook. U.S. Environmental Protection Agency, Washington, DC. EPA/600/R-06/096F. Accessed at: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=199243.

Kahn HD, Stralka K (2009). Estimated daily average per capita water ingestion by child and adult age categories based on USDA's 1994-1996 and 1998 continuing survey of food intakes by individuals. J Expo Sci Environ Epidemiol 19(4):396-404.

Use of these two reference documents, rather than the draft OEHHA document, results in minor changes to the drinking water consumption estimates used for the calculation of the non-cancer health-protective value on page 92 of the December 31, 2010 document, but does not change the proposed PHG of 0.02 parts per billion (ppb). To be more consistent with the exposure periods reported in the above-cited U.S. EPA Exposure Factors Handbook, the child-exposure period used in the document will change from 1 to 10 years of age to 0 to 11 years in Table 16 on page 92. The proposed non-cancer health-protective concentration derived from this child-exposure calculation rounds to 3 ppb instead of 2 ppb.

For the cancer exposure calculations, we have summed the consumer-only consumption values in U.S. EPA (2008) for the age ranges for the cancer potency calculation on pages 93-94 of the draft PHG document. These drinking water consumption values are then 0.114, 0.041, and 0.038 L/kg-day for infancy, childhood and adult life stages (minor differences from the values used in the December 2010 draft PHG document). These adjustments result in minor changes to the oral exposure values in the life-stage adjusted calculations presented in Table 17 on page 94, and to the calculation of the health-protective value, C, on the same page. This value still rounds off to the same number, 0.02 µg/L or ppb proposed in the December 31, 2010 PHG document.

While the replacement of the reference materials is important for purposes of transparency in our process, it represents a non-substantive change to the document itself. We apologize for any confusion that may have resulted from our citation to the OEHHA draft document. In making these non-substantive changes, OEHHA has amended pages 1, 91-94, 96, 106 and 115 of the December 2010 PHG document. The attached pdf file contains these amended pages, with new text shown in italics.

For questions concerning these changes, please contact:
Hermelinda Jimenez (Hermelinda.Jimenez@oehha.ca.gov)
Pesticide and Environmental Toxicology Branch
Office of Environmental Health Hazard Assessment
California Environmental Protection Agency
1515 Clay St., 16th floor
Oakland, California 94612

Attn: PHG project.

The public comment period remains open until 5 p.m. on February 15, 2011, and comments can be sent to the address above.