1. EWG Drinking Water Quality Commentary
Water Issues Committee
May 15, 2019

2. Who is the Environmental Working Group (EWG)?
Non-profit 501(c)(3), based in Washington, DC
Maintain affiliated 501(c)(4) lobbying organization
Publish articles, guides, and “studies” on many topics:
Pesticide residues (i.e., the “Dirty Dozen”)
Cosmetics and sunscreens
Energy and Farm Policy
Tap water quality

3. EWG “Commentary” on Tap Water in CA
Published in journal Environmental Health on April 30th, 2019
Not subject to traditional scientific peer-review process
Analyzed publicly available data in CA state database
2,737 public water systems (i.e., “Producers”)
2011 to 2015 time period
Applied a new “cumulative risk” methodology to data

4. Local/National/International Media picked up story

5. EWG “Commentary” Findings
Up to 15,449 lifetime cancer cases could be related to drinking water
Represents 0.04% of 38.7 million CA resident population
American Cancer Society  38% lifetime cancer development risk & 20% cancer death risk in USA
Percent of estimated cancer risk due to specific contaminants
Arsenic = 47% (has enforceable MCL)
Disinfection Byproducts = 34% (has enforceable MCL)
Hexavalent chromium = 16% (MCL to be reissued)
All others (radiologicals, VOCs) = 3% (have enforceable MCLs)

6. Conclusions Highest estimate risks found in small water systems
Defined as serving <10,000 people
31% of estimated cancers found in 495 small systems serving <10% of state population
Limited water supply options, funding, trained personnel, capacity for treatment
Only 10 public small systems in OCWD service area
OCWD does sampling, testing, reporting on their behalf
OCWD + Producers demonstrate that their water supplies meet all state and federal standards