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ARSENIC (INORGANIC)
CASRN: 7440382

Update: February 2006

Current Massachusetts Regulatory Limit
MMCL = 0.010 mg/L. ORS has adopted the MCL published by U.S. EPA. 

Federal Regulatory Limit
The U.S. EPA conducted an extensive reevaluation of arsenic and published its results in the January 22, 2001 Federal Register (Volume 66, Number 14). The MCLG is equal to zero based on the fact that arsenic is a carcinogen. A proposed revised MCL was identified using the Agency's benefit/cost provisions of the Safe Drinking Water Act (SDWA). U.S. EPA proposed 0.003 mg/L as the feasible MCL, after considering treatment costs and efficiency under field conditions as well as considering the appropriate analytical methods. U.S. EPA determined that the benefits of regulating arsenic at the feasible level would not justify the costs. The promulgated MCL of 0.010 mg/L (based on the discussion below) went into effect on January 23, 2006. 

Basis for Criteria
The promulgated MCL of 0.010 mg/L was derived based on the RfD presented below and assuming a 70 kg adult drinks 2 L water per day.

RfD oral = 3 x 10-4 mg/kg/day (U.S EPA 02/01/93)

UF: 3 (for the uncertainty as to whether the NOAEL accounts for all sensitive individuals and to preclude reproductive toxicity as a critical effect)

MF: 1

Oral Cancer Potency Factor = 1.5 (mg/kg/day)-1

Critical Effects
Hyper-pigmentation, keratosis and possible vascular effects were reported. The RfD is based on an adjusted NOAEL of 0.0008 mg/kg/d derived from a chronic exposure study done in humans (Tseng et al., 1968). 

Cancer Assessment Carcinogenic to Humans/A.
The cancer classification is based on observations of increased lung cancer mortality in multiple human populations exposed primarily via inhalation and also increased skin cancer incidence from ingestion in several human populations comparing drinking water with high levels of arsenic (Tseng, 1977).

Class
Heavy metal

Analytical Information
PQL
: The PQL considered in setting the MCL is 0.003 mg/L.

Analytical Methods
206.2 AA - Furnace
206.3 AA - Gaseous Hydride
ASTMD - 2972-78 B " "
200.9 ICP

Updated analytical methods for drinking water and their associated PQLs may be found at http://www.epa.gov/safewater/methods/methods.html

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 http://www.epa.gov/waterscience/drinking/standards/dwstandards.pdf

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 http://www.epa.gov/iris/. Please note that the information in IRIS may differ from that used in the derivation process as published in the Federal Register notice.

References
Federal Register. January 22, 2001. Part VIII. Environmental Protection Agency. 40 CFR Parts 9, 141 and 142. National Primary Drinking Water Regulations; Arsenic and Clarifications to Compliance and New Source Contaminants Monitoring; Final Rule. (66 FR 6976).

Tseng, W.P., H.M. Chu, S.W. How, J.M. Fong, C.S. Lin and S. Weh. 1968. Prevalence of Skin Cancer in an endemic area of chronic arsenism in Taiwan. J. Natl. Cancer Inst. 40(3):453-463.

Tseng, W.P. 1977. Effects and dose response relationships of skin cancer and Blackfoot disease with arsenic. Environ. Health Perspect. 10:109-119.

U.S. EPA (U.S. Environmental Protection Agency). February 1, 1993. Integrated Risk information System (IRIA). U.S. Environmental Protection Agency. Washington, D.C. http://cfpub.epa.gov/ncea/iris/index.cfm