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City of Redwood City 2016 Public Health(9.A. - Page 13 <br /> Health Risks <br /> The OEHHA characterizes Cr6 as carcinogenic. However, most studies of chromium toxicity <br /> relate to inhaling airborne Cr6 in the workplace rather than ingesting it in drinking water. <br /> The OEHHA calculated the PHG based on the carcinogenic risk. Non-carcinogenic risks have <br /> also been associated with inhalation and/or oral ingestion of Cr6, including reproductive <br /> toxicity (developmental, male reproductive, and female reproductive toxicity), liver toxicity <br /> (mild chronic inflammation, fatty changes), and toxicity of blood-forming tissues. <br /> The OEHHA calculated health-protective levels based on carcinogenic and non-carcinogenic <br /> effects. The health-protective level for carcinogenic effects is one-hundredth of the level <br /> based on non-carcinogenic effects; thus, the carcinogenic risk was used to calculate the <br /> PHG. The cancer risk associated with lifetime consumption of water at the PHG is one in one <br /> million excess cancer cases. Cancer risk at the MCL is five per ten thousand excess cancer <br /> cases. <br /> BATs and Treatment Cost <br /> Although Title 22, CCR lists three treatment processes as BATs for Cr6 MCL compliance, <br /> there is little information available about their treatment performance and costs pertaining <br /> to large drinking water systems comparable to the WS. However, ACWA guidelines provide <br /> the unit costs of leading technologies for treating Cr6. Anion exchange is potentially capable <br /> of reducing Cr6 to the PHG. <br /> Because SFPUC supplies treated drinking water to Redwood City it is likely that treatment <br /> would need to be performed at their facilities. SFPUC developed a cost assessment for <br /> anion exchanges with an accuracy range of -50 to +30 percent, the 20-year annualized <br /> capital and O&M cost of anion exchange treatment is estimated at $835 million for the <br /> entire regional water system. The share of that cost for Redwood City based on it portion of <br /> SFPUC water supply would be $37.2 million. This amount equates to an annual water bill <br /> increase of 285 percent for Redwood City water customers. <br /> III. SUMMARY AND CONCLUSION <br /> The drinking water in the City of Redwood City meets all standards established by California <br /> State Water Resources Control Board, Division of Drinking Water and USEPA to protect <br /> public health. Currently the best available technology is in use to control lead levels in <br /> drinking water, and no additional treatment is recommended at this time that could lower <br /> the levels of lead in a cost effective manner. However, homeowners may reduce their risk <br /> of lead exposure by following some measures to that effect. <br /> IV. ATTACHMENTS: <br /> A. Excerpt from California Health & Safety Code: Section 116470 (b), (c), (d), (e), and (f) <br /> B. Table of Regulated Constituent with MCL and PHG <br /> C. OEHHA Fact Sheet for Hexavalent Chromium <br /> 7 <br />