State of California
AIR RESOURCES BOARD






Staff Report:  Initial Statement of Reasons
                   for Proposed Rulemaking








Public Hearing to Consider the Adoption of a Regulatory
Amendment Identifying Hexavalent Chromium as a
Toxic Air Contaminant







Agenda Item No.:  86-1-3
Scheduled for Consideration:  January 23, 1986
Release Date:  December 9, 1985








(This report has been reviewed by the staffs of the California Air Resources Board and the California Department of Health Services and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Air Resources Board or the Department of Health Services, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.)


OVERVIEW AND RECOMMENDATION


I.        INTRODUCTION

II.      REGULATORY BACKGROUND AND PROCEDURES






*    See Section II.

**  Health and Safety Code section 39655; all statutory references are to the Health and
      Safety Code, except as otherwise stated.

III.     EVALUATION OF CHROMIUM


TABLE 1

SUMMARY OF DATA IN PART A

Emissions

 

 

 

 

Inventory Year

Chromium Measured

Estimated Statewide
Emissions, tons

Stationary Sources

 

 

 

Chrome plating

1983

Hexavalent

0.77-16

Cooling towers

1979/81

Hexavalent

0.23-9.2

Oil combustion

1983

Total

13.2-28.1

Coal combustion

1981

Total

0.02

Cement production

1981

Total

0.9

Waste incineration

1981

Total

0.02-0.16

Refractory Production

1984

Hexavalent

<0.01

Fate in the atmosphere:  The half-life and reactions of chromium (VI) are unknown; chromium particulate is removed from the atmosphere through physical processes, mainly by wet disposition.










Ambient Concentrations

   


Location (year)


Form

Concentration
nanogram/cubic meter
(ng/m3)

San Francisco Bay Area
Air Basin (partial) (1977)
Total chromium, annual average

10.8

South Coast Air Basin (1977) Total chromium, annual average

16.9

Fresno Area (1977) Total chromium, annual average

12.3

San Diego Area (1977) Total chromium, annual average

11.7

San Jose Area (1977) Total chromium, annual average

14.3

El Monte (1985)1 Total chromium
(average of four samples)

13.2

El Monte (1985)1 Hexavalent chromium
(average of four samples)

0.5

1 Samples taken during the last week of August 1985.



Figure A Diagram Goes Here

IV.     ENVIRONMENTAL IMPACTS

V.      RECOMMENDATION

UNIVERSITY OF CALIFORNIA, DAVIS


BERKLEYoDAVISoIRVINEoLOS ANGELESoRIVERSIDEoSAN DIEGOoSAN FRANCISCOoSANTA BARBARAoSANTA CRUZ

DAVID PIERPONT GARDNER                                                                                                                UNIVERSITY HOUSE
President of the University                                                                                                                          DAVIS, CALIFORNIA  95616

EMIL M. MRAK
Chancellor Emeritus

November 21, 1985

Mr. James D. Boyd, Executive Officer
State Air Resources Board
P. O. Box 2815
Sacramento, CA 95812

Dear Mr. Boyd:

         The Sclentific Revlew Panel on Toxic Alr Contaminants has reviewed the Report to the Scientific Review Panel on Chromium, and has formulated Its findings regarding the report. With this letter, I am formally submitting the Sclentific Revlew Panel's written findings to the Air Resources Board.


Enclosure

cc:  Scientific Revlew Panel
      Dr. John Holmes
      Mr. Richard Bode








Flndings of the Scientific Review Panel

Regarding the Report on Chromium


       In accordance with the provisions of the Health and Safety Code Section 39661, the Scientific Review Panel (SRP) has reviewed the September 1985 Report to the Scientific Review Panel on Chromium, and has reviewed the pubilc comments received regarding this report. The SRP finds the Report on Chromium to be adequate and sufficient.

       Specifically, the SRP finds each of the following propositions to be prudent interpretations of the available evidence:

       For these reasons, we agree that hexavalent chromium CCr(VI) should be listed by the Air Resources Board as a toxic air contaminant, but we are unable to recommend an exposure level below which carcinogenic effects would not have some probability of occurring.

COMMENTS

       Using extrapolation procedures recommended by the EPA and Interagency advisory groups, DHS has estimated that the added lifetime cancer risk from a 70-year exposure to 1 nanogram per cubic meter (ng/m3) of atmospheric hexavalent chromium ranges from 12 to 146 cases per million people exposed. The SRP concurs with DHS's evaluation, but wishes to clarify several points: