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Massachusetts Water Resources Authority

Date: June 20, 2005

Contact: Ria Convery, (617) 788-1105, <>



Good News on Lead Levels

The most recent sampling round, once again, meets the Lead Action Level.  Results from lead and copper samples collected in March and April 2005 show that ninety-one percent of the targeted high-risk homes had lead levels equal to or below the Lead Action Level (AL) of 15 parts per billion (ppb), meeting the requirement of at least 90 percent.  The 90th percent value was 13.2 ppb.  MWRA, as a system, has met three straight rounds and 6 of the last 8 sampling rounds.


MWRA source waters contain virtually no lead, but lead can leach from lead service pipes connecting homes to water mains and from lead solder and brass fixtures in homes.  In 1991, EPA issued the Lead & Copper Rule which set action levels of 15 ppb for lead and 1,300 ppb for copper, and required that 90 percent or more of targeted high-risk homes be below that level.  The samples must be first flush samples taken at homes and locations most likely to have high levels of lead after the water has sat stagnant overnight.

In 1996, MWRA began to add sodium carbonate and carbon dioxide to the water to make it less corrosive.   Lead levels dropped significantly after this change in treatment, but still did not consistently meet the standard.  Therefore, in 2002 and 2003, MWRA adjusted the corrosion control process by fine-tuning the pH and alkalinity levels.  Six of the last eight rounds of lead sampling have now been below the 15 ppb Action Level, and MWRA continues to work so that the MWRA service area will consistently be below the 15-ppb Action Level.  Further optimization may be possible when the new ozone plant goes on-line in July 2005. 

Current Results

The March-June 2005 data showed that 91 percent of the targeted high-risk homes had lead levels below the Action Level, meeting the target of 90 percent. The 90th percentile of lead results was 13.2 ppb, compared to the 15-ppb standard.  Figure 1 shows the over 80% reduction in lead levels since 1992.

90% Lead Levels
in MWRA System of Fully-Supplied Communities

Chart of 90% Lead Levels in MWRA Fully Supplied Communities

(larger image)


Updated April 27, 2006