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CASRN: 1332214

Update: August 1993

Current Massachusetts Regulatory Limit
MMCL = 7 million fibers per liter. ORS has adopted the MCL published by U.S. EPA under the Phase II rule. (56 FR 3526; 1-30-91). 

Federal Regulatory Limit
The MCL is 7 million fibers per liter based on its potential to produce cancer. 

Basis for Criteria
The MCL is based on the observation that benign polyps in male rats were statistically elevated from controls when the animals were exposed to fibers greater than ten (10) microns. The Science Advisory Board found it difficult to dismiss the possibility of increased gastric tumors given historical inhalation data and the rat ingestion data. There are insufficient data upon which to base a non-cancer risk assessment.

Critical Effects
Increased cancer rates 

Cancer Assessment A
Observations of increased mortality and incidence of lung cancer, mesotheliomas and gastrointestinal cancer in occupationally exposed individuals.

Animal studies by inhalation in two strains of rats showed similar findings for lung cancer and mesotheliomas. Animal evidence for carcinogenicity via ingestion is limited (male rats fed intermediate range chrysotile fibers, i.e. > 10 um length, developed benign polyps), and epidemiological data in this regard are inadequate. (Unit risk for Inhalation: 2.3 x 10-1 per (fibers/ml).)

Asbestos drinking water concentration at an Excess Lifetime Cancer Risk (ELCR) of
1 x 10-4 = 700 million fibers per liter
1 x 10-5 = 70 million fibers per liter
1 x 10-6 = 7 million fibers per liter 


Analytical Information

Analytical Methods
TEM (transmission electron microcopy)

Updated analytical methods for drinking water and their associated PQLs may be found at

Other Regulatory Data
Any Health Advisories, Reference Doses (RfDs), cancer assessments or Cancer Potency Factors (CPFs) referenced in this document pertain to the derivation of the current guidance value. Updated information may be obtained from the following sources:

Health Advisories - The U.S. EPA provides guidance for shorter-term exposures for chemicals based on their non-cancer effects. Current health advisories may be more current than those used to derive MCLs and may be found at

RfDs, cancer assessments and CPFs - For specific information pertaining to derivation of drinking water criteria, consult the Federal Register notice that announces the availability of the most current guidance for that chemical. In addition, information on other current RfDs and CPFs as well as cancer assessments for specific chemicals may be found in the U.S. EPA Integrated Risk Information System (IRIS) at Please note that the information in IRIS may differ from that used in the derivation process as published in the Federal Register notice.

Elmes, P.C. and M.J. Simpson. 1971. Insulation workers in Belfast. III. Mortality 1940-AGG. Br. J. Ind. Med. 28:226-236.

Federal Register. November 13, 1985. Part IV. Environmental Protection Agency. 40 CFR Part 141. National Primary Drinking Water Regulations; Synthetic Organic Chemicals, Inorganic Chemicals and Microorganisms; Proposed Rule. (50 FR 46936).

Federal Register. January 30, 1991. Part II. Environmental Protection Agency. 40 CFR Parts 141, 142, and 143. National Primary Drinking Water Regulations; Final Rule.(56 FR 3526)

Selikoff, I.J. 1976. Lung cancer and mesothelioma during prospective surveillance of 1249 asbestos insulation workers, 1963-1974. Ann. N.Y. Acad. Sci. 271:448-456.

[2] For fibers longer than 10 microns.