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LEAD
CASRN: 7439921

Update: May 2004

Current Massachusetts Regulatory Limit
MMCL = Treatment Technique. Action Level = 0.015 mg/L. (ORS has adopted the Action Level published by the U.S. EPA.) (FR 6/7/91, 56 FR32112; 7-15-91)

The Treatment Technique for lead requires systems to control the corrosiveness of their water. If more than 10% of tap water samples exceed the lead Action Level of 0.015 mg/L, water systems must take additional steps (U.S. EPA, 2002).

Federal Regulatory Limit
The action level is not a health-based value. Instead, exceeding the action level triggers a series of treatment techniques including:

  1. replacement of lead-lined service pipes,
  2. corrosion control,
  3. source water reduction,
  4. public education

The U.S. EPA has decided that setting an MCL for lead is not feasible and the approach outlined in the regulations (56 FR 32112) will achieve the public health goals of the Safe Drinking Water Act.

Basis for Criteria
The MCLG for lead is zero based on (1) the occurrence of low level effects and difficulty in identifying clear threshold levels, (2) the goal of reducing the overall exposure to lead and (3) the classification of lead as a group B-2 carcinogen. The Action Level is based on treatment technique.

Critical Effects
The toxicology of lead is complicated. High blood lead concentrations (Hb-Pb) have been associated with mental retardation in children, neurological and nephrological adverse health effects in adults and children, and high blood pressure in adults. A threshold for effects has not been established.

Cancer Assessment: 
Likely to be Carcinogenic To Humans/B2

Lead is currently classified as a B2 carcinogen by U.S. EPA. There is sufficient animal evidence. Ten rat bioassays and one mouse bioassay have shown statistically significant increase in renal tumors with dietary and subcutaneous exposure to several soluble lead salts. Human evidence is inadequate (see IRIS for more details).

Class
naturally occurring heavy metal

Analytical Information
PQL
: Method dependent 

Analytical Methods
200.8; ICP/MS
200.9; AA/furnace

PQLs and analytical methods may have been updated since this guidance value was last revised. 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. Friday, June 7, 1991. Vol. 56, No. 110. Maximum Contaminant Level Goals and National Primary Drinking Water Regulations for Lead and Copper; Final Rule.

U.S. Environmental Protection Agency (U.S. EPA). July 2002. List of Contaminants and Their MCLs. U.S. EPA 816-F-02-013.