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 Asbestos as a
Toxic Air Contaminant






Agenda Item No.:  86 -
Scheduled for Consideration:  March 27, 1986
Release Date:  February 10, 1986










(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.  EVALUATION OF ASBESTOS


TABLE I
Summary of Data for Asbestos
Emissions

Source Source Type Statewide
(Ton Per Year)
Inventory Year
Mining Point 120 1984
Milling Point 340 1984
Manufacturing

    Primary

Point 4 1982 & 1984

    Secondary

Point 2 1982 & 1984
Automobile Brakes Mobile 0.8 1984
Quarrying Point 0.5 1981

    Total*

470

 Atmospheric Fate
Asbestos can be readily subdivided into fibers of submicron diameter, which can remain airborne for long periods of time. In addition, asbestos is exceptionally resistant to thermal degradation and chemical attack, therefore settled fibers are persistent in the environment and subject to re-entrainment into the atmosphere.

 Ambient Concentrations

Range of Total Asbestos Fibers Measured at Ten Sampling Locations (average of all samples analyzed by transmission electron microscopy and converted to PCM fiber concentrations).

      Averaged asbestos concentrations range from 8 to 80 PCM fibers per cubic meter at Sonora to 50 to 500 PCM fibers per cubic meter at South Gate. Generally, the highest concentrations were measured at sampling locations influenced by localized and industrial sources; the lowest concentrations were found at sites isolated from asbestos emission sources.


* The total emission estimate has been rounded off to one significant figure.


TABLE II
Estimated Lifetime Excess Risks of Lung Cancer and Mesothelioma Due to
Continuous Exposure to 100 Fiber/m3 of Asbestos
"Expressed as Cases per Million Population)l/

Exposure Group Lung Cancer Mesothelioma
Male Smokers 11 (110) 24 (120)
Female Smokers 5 (50) 32 (160)
Male Nonsmokers 2 (15) 32 (160)
Female Nonsmokers 1 (6) 38 (190)





1/ Numbers in parentheses represent approximate upper confidence limits. The analysis corrected for competing causes of death using life tables constructed from recent California vital statistics. Since risks for lung cancer and for other causes of death are dependent on smoking status, the life tables were modified to account for age- and gender-specific smoking prevalence. Thus, risks are presented by gender and smoking status.


















TABLE III
Estimated Lifetime Excess Lung Cancer Risk Due to
Continuous Exposure to Asbestos
(Expressed as Cases per Million Population)*
Exposure Level (fibers/m3)

Exposure Group 8 50 80 500 2000
Male Smokers

1(0-9)**

6(0-55)

9(0-88)

55(0-550)

221(0-2,210)

Female Smokers

1(0-5)

2(0-25)

5(0-41)

25(0-250)

101(0-1,010)

Male Nonsmokers

1(0-1)

1(0-8)

1(0-11)

8(0-75)

29(0-290)

Female Nonsmokers

1(0-1)

1(0-3)

1(0-5)

3(0-28)

11(0-110)


* Calculated with C1 = 0.01. Ranges in parentheses were estimated with a lower limit of zero and an upper limit calculated with C1 = 0.1. This upper bound is an approximate upper confidence limit.

** Sample Calculation For Excess Lung Cancer Risk - Male Smokers
 Conversion from TEM = (7,700 TEM fibers) (1 PCM fiber)
 to PCM concentrations m3 (1000 TEM fibers)
 = 7.7 or 8 fibers/m3

Estimated lifetime excess  = (PCM concentration) x (Lung cancer estimated
lung cancer risk-lower  (Estimated lifetime  lifetime risk)
confidence limit  risk exposure
 concentration)
 = (8 fibers/m3) x 11
(100 fibers/m3)
 = 0.88 or 1

Estimated lifetime  = (8 fibers/m3) x 110
excess lung cancer  (100 fibers m3)
risk - higher confidence
limit= 8.8 or 9

TABLE IV

Estimated Lifetime Excess Mesothelioma Risk Due to
Continuous Exposure to Asbestos
(Expressed as Cases per Million Population)*

Exposure Level (fibers/m3)

Exposure Group 8 50 80 500 2000
Male Smokers 2(0-9)* 11(0-59) 19(0-95) 120(0-590) 470(0-2,400)
Female Smokers 2(0-12) 16(0-81) 26(0-120) 160(0-810) 640(0-3,300)
Male Nonsmokers 2(0-12) 16(0-79) 25(0-120) 160(0-790) 630(0-3,200)
Female Nonsmokers 3(0-16) 19(0-97) 31(0-160) 190(0-970) 780(0-3,800)





* Calculated with Cm = 2.4 x 10-8, P = 3.0, 20-year lag. Ranges in parentheses were estimated with a lower limit of zero and an upper limit calculated with Cm = 1.2 x 10-7, which is the highest estimated value for the proportionality constant Cm (from Finkelstein, 1983).
















* Amphibole asbestos is a general term for all varieties other than chrysotile.

III.  REGULATORY BACKGROUND AND PROCEDURES

IV. ENVIRONMENTAL EFFECTS

V.  RECOMMENDATION