CITY OF FAIRFIELD - PUBLIC WATER SYSTEM 4810003
REPORT ON SYSTEM’S WATER QUALITY RELATIVE TO PUBLIC HEALTH GOALS
Background:
Provisions of the California Health and Safety Code § 11670(b) (Reference No. 1) specify that public water systems serving more than 10,000 service connections prepare a special report initially by July 1, 1998, and subsequently every three years if their water quality measurements have exceeded any Public Health Goals (PHGs). PHGs are non-enforceable goals established by the Cal-EPA’s Office of Environmental Health Hazard Assessment (OEHHA). The law also requires that where OEHHA has not adopted a PHG for a constituent, the water suppliers are to use the Maximum Contaminant Level Goals (MCLGs) adopted by USEPA. Only constituents which have a California primary drinking water standard and for which either a PHG or MCLG has been set are to be addressed. (Reference No. 2 is a list of all regulated constituents with MCLs and PHGs or MCLGs.)
This report provides the information required by the law (Reference No. 1). If a constituent was detected in the System’s water supply from 2022 through 2024 at a level exceeding the applicable PHG or MCLG, the following information is incorporated: the numerical risk associated with the Maximum Contaminant Level (MCL), PHG or MCLG, and the category or type of risk to health that could be associated with each constituent. Also explained are the best treatment technologies available that could reduce the constituent level, and an estimate of the cost to install that treatment if it is appropriate and feasible.
What is an MCL?
The highest level of a contaminant allowed in drinking water set by the State Water Resources Control Board (SWRCB) and the USEPA . Primary MCLs are set as close to the corresponding PHG (or MCLG ) as is economically and technologically feasible. In some cases, it may not be feasible for the SWRCB to set the drinking water standard for a contaminant at the same level as the PHG. The technology to treat the chemicals may be unavailable, or the treatment may be very costly. The SWRCB must consider these factors when developing a drinking water standard.
What is a Primary Drinking Water Standard?
The National Primary Drinking Water Regulations are legally enforceable primary standards.
Primary drinking water standards are
set to limit levels of contaminants that may pose a health risk.
Contaminants monitored are categorized as inorganic and organic chemicals, microorganisms, disinfection byproducts, disinfectants and radionuclides. Primary drinking water standards establish an MCL by considering contaminant impact on human health, and the technological and economic feasibility for removal by a treatment facility. The State Water Resources Control Board reviews each primary drinking water standard once every five years. Any revision must maintain or strengthen public health protection.
What Are PHGs?
PHGs are set by the California Office of Environmental Health Hazard Assessment (OEHHA), which is part of Cal-EPA, and are based solely on public health risk considerations. A PHG is the level of a chemical contaminant in drinking water that does not pose a significant risk to health. None of the practical risk-management factors that are considered by the USEPA or the SWRCB in setting drinking water standards are considered in developing PHGs. These factors include analytical detection capability, treatment technology availability, benefits and costs.
PHGs are non-enforceable and are not required to be met by any public water system. MCLGs are the federal equivalent to PHGs.
Water Quality Data Considered:
All water quality data collected by our water system from 2022 through 2024 for purposes of determining compliance with drinking water standards was considered. This data was summarized in our 2022, 2023, and 2024 Annual Consumer Confidence Reports, which were made available to customers before July 1 of each year following the monitoring year. Our water system is in full compliance with the Federal and State regulations. If you require further information concerning contaminants and their potential health effects, please contact Jenell Pratt at (707) 437-5386.
Guidelines Followed:
There is no regulatory guidance explaining requirements for the preparation of Public Health Goal reports. However, The Association of California Water Agencies (ACWA) formed a workgroup, which prepared guidelines for water utilities to use in preparing these required reports. These guidelines were used in the preparation of this report.
Best Available Treatment Technology and Cost Estimates:
The USEPA and the SWRCB adopt Best Available Technologies (BATs), which are the best- known methods of reducing contaminant levels to the MCL. Costs can be estimated for such technologies. However, since many PHGs and all MCLGs are set much lower than the MCL, it is neither always possible nor feasible to determine what treatment is needed to further reduce a constituent to the PHG or MCLG. Many MCLGs are zero and estimating the costs to reduce a constituent to zero is difficult. It is not possible to verify by analytical means that the level was lowered to zero. In some cases, installing treatment to further reduce already very low levels of one constituent may have adverse effects on other aspects of water quality.
§ 116470(b)(5) of the Health and Safety Code requires an estimate of the aggregate costs and the cost per customer of utilizing a best available technology. A cost estimate should only be calculated when the PHG/MCLG level is clearly exceeded - not momentarily, or only on one sample.
Constituents Detected That Exceed a PHG or an MCLG:
The following is a discussion of contaminant results that were detected above the PHG or MCLG. In general, compliance of these contaminants, apart from total coliforms, is based on yearly averages. Yearly average results for these contaminants were below the PHG, but it is important to highlight in seldom instances, the exceedance of the PHG.
Arsenic
Health Risk
Category
California PHG
(mg/L)
Cancer Risk at
the PHG
California
MCL (mg/L)
Cancer Risk at
the California
MCL
Carcinogenicity
(causing cancer)
4x10-6
1x10-6
0.01 2.5x10-3
(2.5 per
thousand)
Arsenic is a naturally occurring contaminant from the erosion of natural deposits, runoff from orchards and a waste product of glass and electronics production. The MCL for arsenic is 10 µg/L. Based on compliance testing of our drinking waters from 2022 through 2024, results ranged from non-detect to 2 µg/L. Of twenty-four samples collected, one exceeded the PHG of 4x10
-6 mg/L. MCL compliance of arsenic is based on the average of four consecutive quarterly results. Yearly averages of arsenic results are below the PHG.
The category of health risk for arsenic is carcinogenicity (causes cancer). The numerical cancer risk at the PHG is one excess cancer case per million people exposed during a lifetime (1x10 -6).
The numerical cancer risk at the California MCL is (2.5x10-3) 2.5 excess cancer cases per thousand people exposed. Some people who drink water containing arsenic in excess of the MCL over many years may experience skin damage or circulatory system problems, and may have an increased risk of getting cancer.
Bromate
Health Risk
Category
California PHG
(mg/L)
Cancer Risk at
the PHG
California
MCL (mg/L)
Cancer Risk at
the California
MCL
Carcinogenicity
(causing cancer)
1x10-4
1x10-6
0.01 1x10-4
(one per ten
thousand)
Bromate is a byproduct of drinking water disinfection. The MCL for bromate is 10 µg/L. Based on compliance testing of our drinking waters from 2022 through 2024, results ranged from non- detect to 2.0 µg/L. Of thirty-six samples collected, three exceeded the PHG of 0.10 µg/L. MCL compliance of bromate is based on a yearly running average. The yearly running average for bromate is below the PHG.
The category of health risk for bromate is carcinogenicity (causes cancer). The numerical cancer risk at the PHG is one excess cancer case per million people exposed during a lifetime (1x10 -6).
The numerical cancer risk at the California MCL is one excess cancer case per ten thousand people exposed (1x10
-4). Some people who drink water containing bromate in excess of the MCL over many years man have an increased risk of getting cancer.
Strontium-90
Health Risk
Category
California PHG
(pCi/L)
Cancer Risk at
the PHG
California
MCL (pCi/L)
Cancer Risk at
the California
MCL
Carcinogenicity
(causing cancer)
0.35 1x10-6
8 2 x10-5
(two per hundred
thousand)
Strontium-90 is a radioactive contaminate that may enter the water supply from the decay of natural and man-made deposits. The MCL for strontium-90 is 8 pCi/L. Based on compliance sampling of our source waters from 2022 through 2024, results varied from non-detect to
0.545 pCi/L. Of the twelve samples collected, three samples exceeded the PHG of 0.35 pCi/L.
Compliance of strontium-90 is based on result averages of four consecutive quarters. Average yearly results were below the PHG.
The category of health risk for Strontium-90 is carcinogenicity (causes cancer). The numerical cancer risk at the PHG is one excess cancer case per million people exposed during a lifetime (1x10
-6). The numerical cancer risk at the California MCL is two excess cancer cases per hundred thousand people exposed. Some people who drink water containing strontium-90 in excess of the MCL over many years may have an increased risk of getting cancer.
Tritium
Health Risk
Category
California PHG
(pCi/L)
Cancer Risk at
the PHG
California
MCL (pCi/L)
Cancer Risk at
the California
MCL
Carcinogenicity
(causing cancer)
400
1x10-6
20,000
5x10-5
(5 per hundred
thousand)
Tritium is a radioactive contaminate that may enter the water supply from the decay of natural and man-made deposits. The MCL for tritium is 20,000 pCi/L. Based on compliance sampling of our source waters from 2022 through 2024, results varied from non-detect to 988 pCi/L. Of twelve samples collected, one sample exceeded the PHG of 400 pCi/L. Compliance of tritium is
based on result averages of four consecutive quarters. Average yearly results were below the PHG.
The category of health risk for tritium is carcinogenicity (causes cancer). The numerical cancer risk at the PHG is one excess cancer case per million people exposed during a lifetime (1x10 -6).
The numerical cancer risk at the California MCL is five excess cancer cases per hundred thousand people exposed. Some people who drink water containing tritium in excess of the MCL over many years may have an increased risk of getting cancer.
Uranium
Health Risk
Category
California PHG
(pCi/L)
Cancer Risk at
the PHG
California
MCL (pCi/L)
Cancer Risk at
the California
MCL
Carcinogenicity
(causing cancer)
0.43 1x10-6
20 5x10-5
(5 per hundred
thousand)
Uranium is a radioactive contaminate that may enter the water supply from the erosion of natural deposits. The MCL for uranium is 20 pCi/L. Based on compliance sampling of our source waters from 2022 through 2024, results varied from non-detect to 0.72 pCi/L. Of twelve samples collected, one sample exceeded the PHG of 0.43 pCi/L. Compliance of uranium is based on result averages of four consecutive quarters. Average yearly results were below the PHG.
The category of health risk for uranium is carcinogenicity (causes cancer). The numerical cancer risk at the PHG is one excess cancer case per million people exposed during a lifetime (1x10 -6).
The numerical cancer risk at the California MCL is five excess cancer cases per hundred thousand people exposed. Some people who drink water containing uranium in excess of the MCL over many years may develop kidney problems and or an increased risk of getting cancer.
Radium - 226
Health Risk
Category
California PHG
(pCi/L)
Cancer Risk at
the PHG
California
MCL (pCi/L)
Cancer Risk at
the California
MCL
Carcinogenicity
(causing cancer)
0.05 1x10-6
5 (combined
Ra226+228)
1x10-4
(one per ten
thousand)
Radium-226 is a radioactive contaminate that may enter the water supply from the erosion of natural deposits. The MCL is based on the sum of both radium-226 and radium-228 and is 5 pCi/L. Based on compliance sampling of our source waters from 2022 through 2024, results varied from non-detect to 0.105 pCi/L. Of twelve samples collected, two samples exceeded the
PHG of 0.05 pCi/L. Compliance of radium-226 is based on the addition of radium 226 and radium 228 results and averaged over four consecutive quarters. Average yearly results were below the PHG.
The category of health risk for radium-226, is carcinogenicity (causes cancer). The numerical cancer risk at the PHG is one excess cancer case per million people exposed during a lifetime (1x10
-6). The numerical cancer risk at the California MCL is one excess cancer case per ten thousand people exposed. Some people who drink water containing radium-226 in excess of the MCL over many years may have an increased risk of getting cancer.
Radium – 228
Health Risk
Category
California PHG
(pCi/L)
Cancer Risk at
the PHG
California
MCL (pCi/L)
Cancer Risk at
the California
MCL
Carcinogenicity
(causing cancer)
0.019
1x10-6
5 (combined
Ra226+228)
3x10-4
(three per ten
thousand)
Radium-228 is a radioactive contaminate that may enter the water supply from the erosion of natural deposits. The MCL for combined radium (radium-226 + radium-228) is 5 pCi/L. Based on compliance sampling of our source waters from 2022 through 2024, results varied from non- detect to 1.17 pCi/L. Of twelve samples collected, nine samples exceeded the PHG of
0.019 pCi/L. Compliance of radium-228 is based on the addition of radium 226 and radium 228 results and averaged over four consecutive quarters. Average yearly results were below the PHG.
The category of health risk for radium-228, is carcinogenicity (causes cancer). The numerical cancer risk at the PHG is one excess cancer case per million people exposed during a lifetime (1x10
-6). The numerical cancer risk at the California MCL is three excess cancer cases per ten thousand people exposed. Some people who drink water containing radium-228 in excess of the MCL over many years may have an increased risk of getting cancer.
Coliform Bacteria:
During 2022, 2023 and 2024, approximately 140 to 175 samples were collected each month for coliform analysis. Occasionally, sample results were positive for coliform bacteria, but repeat samples were negative and required follow-up actions were taken. During two of these thirty-six months, coliform levels were found positive in 1.4% of the samples.
The MCL for coliform is 5% positive samples of all samples collected per month. The MCLG is zero. The coliform drinking water standard minimizes the possibility of water containing pathogens, which are organisms that can cause waterborne disease. Because coliform is only a surrogate indicator of the potential presence of pathogens, it is not possible to state a specific
numerical health risk. While USEPA normally sets MCLGs “at a level where no known or anticipated adverse effects on persons would occur,” it is indicated that it is infeasible with the analysis of coliforms.
Coliform bacteria are indicator organisms that are ubiquitous in nature and are not generally considered harmful. They are used because of the ease in monitoring and analysis. If a positive sample is found, it indicates a potential problem that needs to be investigated, and subsequent sampling/testing is performed. It is not unusual for a system to occasionally have a positive sample. It is difficult, if not impossible, to ensure that a system will never get a positive sample.
Chlorine is added to the drinking water to ensure that the water served is microbiologically safe.
Chlorine residual levels are carefully controlled to provide the best health protection without causing the water to have undesirable taste and odor or increasing the disinfection byproduct level. This careful balance of treatment process is essential to consistently supplying our customers with safe drinking water.
Other equally important measures that we have implemented include an effective cross- connection control program, maintenance of a disinfectant residual throughout our system, and an effective monitoring and surveillance program. We also maintain positive pressures in our distribution system. Our system has already taken all of the steps described as “best available technology” for coliform bacteria in Section 64447, Title 22, CCR.
Recommendations for Further Action:
The drinking water quality of the City of Fairfield Public Water Utility System meets all State Water Resources Control Board and USEPA drinking water standards set to protect public health. The PHG and MCLG detections mentioned above represent a momentary exceedance, rather than a clear exceedance (constant levels above the PHG and MCLG). Therefore, a specific cost estimate is not required, and no action is proposed.
REFERENCE:
No.1 Excerpt from California Health & Safety Code: § 116470(b) No.2 Table of Regulated Constituents with MCLs, PHGs, MCLGs
State of California
HEALTH AND SAFETY CODE
Section 116470
116470. (a) As a condition of its operating permit, every public water system shall annually prepare a consumer confidence report and mail or deli ver a cop y of that report to each customer, other than an occupant, as defined in Section 799.28 of the Civil Code, of a recreational v ehicle park. A public w ater system in a recreational vehicle park with occupants as defined in Section 799.28 of the Ci vil Code shall prominently display on a bulletin board at the entrance to or in the office of the park, and make available upon request, a copy of the report. The report shall include all of the following information:
(1) The source of the water purveyed by the public water system. (2) A brief and plainly w orded definition of the terms “maximum contaminant level,” “primary drinking water standard,” and “public health goal.” (3) If any regulated contaminant is detected in public drinking water supplied by the system during the past year , the report shall include all of the follo wing information:
(A) The level of the contaminant found in the drinking water, and the corresponding public health goal and primary drinking water standard for that contaminant. (B) Any violations of the primary drinking water standard that have occurred as a result of the presence of the contaminant in the drinking water and a brief and plainly worded statement of health concerns that resulted in the regulation of that contaminant. (C) The public water system’s address and phone number to enable customers to obtain further information concerning contaminants and potential health effects. (4) Information on the le vels of unre gulated contaminants, if an y, for which monitoring is required pursuant to state or federal law or regulation. (5) Disclosure of an y v ariances or e xemptions from primary drinking w ater standards granted to the system and the basis therefor. (b) On or before July 1, 1998, and e very three years thereafter , public w ater systems serving more than 10,000 service connections that detect one or more contaminants in drinking w ater that exceed the applicable public health goal, shall prepare a brief written report in plain language that does all of the following:
(1) Identifies each contaminant detected in drinking w ater that e xceeds the applicable public health goal.
(2) Discloses the numerical public health risk, determined by the office, associated with the maximum contaminant le vel for each contaminant identified in paragraph (1) and the numerical public health risk determined by the office associated with the public health goal for that contaminant.
(3) Identifies the category of risk to public health, including, b ut not limited to, carcinogenic, mutagenic, teratogenic, and acute toxicity, associated with exposure to the contaminant in drinking water, and includes a brief plainly worded description of these terms.
(4) Describes the best available technology, if any is then available on a commercial basis, to remove the contaminant or reduce the concentration of the contaminant. The public water system may, solely at its o wn discretion, briefly describe actions that have been tak en on its o wn, or by other entities, to pre vent the introduction of the contaminant into drinking water supplies.
(5) Estimates the aggre gate cost and the cost per customer of utilizing the technology described in paragraph (4), if an y, to reduce the concentration of that contaminant in drinking water to a level at or below the public health goal. (6) Briefly describes what action, if any, the local water purveyor intends to take to reduce the concentration of the contaminant in public drinking water supplies and the basis for that decision.
(c) Public water systems required to prepare a report pursuant to subdivision (b) shall hold a public hearing for the purpose of accepting and responding to public comment on the report. Public water systems may hold the public hearing as part of any regularly scheduled meeting.
(d) The department shall not require a public w ater system to take any action to reduce or eliminate any exceedance of a public health goal. (e) Enforcement of this section does not require the department to amend a public water system’s operating permit.
(f) Pending adoption of a public health goal by the Office of Environmental Health Hazard Assessment pursuant to subdivision (c) of Section 116365, and in lieu thereof, public water systems shall use the national maximum contaminant level goal adopted by the United States En vironmental Protection Agency for the corresponding contaminant for purposes of complying with the notice and hearing requirements of this section.
(g) This section is intended to provide an alternative form for the federally required consumer confidence report as authorized by 42 U.S.C. Section 300g-3(c). (Repealed and added by Stats. 1996, Ch. 755, Sec. 12. Effective January 1, 1997.) DRAFT – FOR REVIEW ONLY
OFFICE OF ENVIRONMENTAL HEALTH HAZARD ASSESSMENT
Public Health Goals
Health Risk Information
for Public Health Goal
Exceedance Reports
February 2025
Pesticide and Environmental Toxicology Branch
Office of Environmental Health Hazard Assessment
California Environmental Protection Agency
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 1
Health Risk Information for
Public Health Goal Exceedance Reports
Prepared by
Office of Environmental Health Hazard Assessment
California Environmental Protection Agency
February 2025
NEW for the 2025 Report: New in this document are newly established Public Health Goals (PHGs) for perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and five haloacetic acids: monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid.
Background: Under the Calderon-Sher Safe Drinking Water Act of 1996 (the Act), public water systems with more than 10,000 service connections are required to prepare a report every three years for contaminants that exceed their respective PHGs.1 This document contains health risk information on drinking water contaminants to assist public water systems in preparing these reports. A PHG is the concentration of a contaminant in drinking water that poses no significant health risk if consumed for a lifetime. PHGs are developed and published by the Office of Environmental Health Hazard Assessment (OEHHA) using current risk assessment principles, practices and methods.2
The water system’s report is required to identify the health risk category (e.g., carcinogenicity or neurotoxicity) associated with exposure to each contaminant in drinking water that has a PHG and to include a brief, plainly worded description of these risks. The report is also required to disclose the numerical public health risk, if available, associated with the California Maximum Contaminant Level (MCL) and with the PHG for each contaminant. This health risk information document is prepared by OEHHA every three years to assist the water systems in providing the required information in their reports.
1 Health and Safety Code Section 116470(b)
2 Health and Safety Code Section 116365
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 2
Numerical health risks: Table 1 presents health risk categories and cancer risk values for chemical contaminants in drinking water that have PHGs.
The Act requires that OEHHA publish PHGs based on health risk assessments using the most current scientific methods. As defined in statute, PHGs for non-carcinogenic chemicals in drinking water are set at a concentration “at which no known or anticipated adverse health effects will occur, with an adequate margin of safety.” For carcinogens, PHGs are set at a concentration that “does not pose any significant risk to health.” PHGs provide one basis for revising MCLs, along with cost and technological feasibility.
OEHHA has been publishing PHGs since 1997 and the entire list published to date is shown in Table 1.
Table 2 presents health risk information for contaminants that do not have PHGs but have state or federal regulatory standards. The Act requires that, for chemical contaminants with California MCLs that do not yet have PHGs, water utilities use the federal Maximum Contaminant Level Goal (MCLG) for the purpose of complying with the requirement of public notification. MCLGs, like PHGs, are strictly health based and include a margin of safety. One difference, however, is that the MCLGs for carcinogens are set at zero because the US Environmental Protection Agency (US EPA) assumes there is no absolutely safe level of exposure to such chemicals. PHGs, on the other hand, are set at a level considered to pose no significant risk of cancer; this is usually no more than a one-in-one-million excess cancer risk (1×10 -6) level for a lifetime of
exposure. In Table 2, the cancer risks shown are based on the US EPA’s evaluations.
For more information on health risks: The adverse health effects for each chemical with a PHG are summarized in a PHG technical support document. These documents are available on the OEHHA website (https://oehha.ca.gov/water/public-health -goals- phgs).
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 3
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Alachlor carcinogenicity
(causes cancer)
0.004 NA5,6 0.002 NA
Aluminum neurotoxicity and
immunotoxicity
(harms the nervous and
immune systems)
0.6 NA 1 NA
Antimony hepatotoxicity
(harms the liver)
0.001 NA 0.006 NA
Arsenic carcinogenicity
(causes cancer)
0.000004
(4×10-6)
1×10-6
(one per
million)
0.01 2.5×10-3
(2.5 per
thousand)
Asbestos carcinogenicity
(causes cancer)
7 MFL7
(fibers >10
microns in
length)
1×10-6 7 MFL
(fibers >10
microns in
length)
1×10-6
(one per
million)
Atrazine carcinogenicity
(causes cancer)
0.00015 1×10-6 0.001 7×10-6
(seven per
million)
Barium cardiovascular toxicity
(causes high blood
pressure)
2 NA 1 NA
1 Based on the OEHHA PHG technical support document unless otherwise specified. The categories are the hazard traits defined by OEHHA for California’s Toxics Information Clearinghouse (online at:
https://oehha.ca.gov/media/downloads/risk-assessment//gcregtext011912.pdf). 2 mg/L = milligrams per liter of water, equivalent to parts per million (ppm) 3 Cancer Risk = Upper bound estimate of excess cancer risk from lifetime exposure. Actual cancer risk may be lower or zero. 1×10-6 means one excess cancer case per million people exposed. 4 MCL = maximum contaminant level.
5 NA = not applicable. Cancer risk cannot be calculated. 6 The PHG for alachlor is based on a threshold model of carcinogenesis and is set at a level that is believed to be without any significant cancer risk to individuals exposed to the chemical over a lifetime. 7 MFL = million fibers per liter of water.
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 4
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Bentazon hepatotoxicity and
digestive system toxicity
(harms the liver,
intestine, and causes
body weight effects8)
0.2 NA 0.018 NA
Benzene carcinogenicity
(causes leukemia)
0.00015 1×10-6 0.001 7×10-6
(seven per
million)
Benzo[a]pyrene carcinogenicity
(causes cancer)
0.000007
(7×10-6)
1×10-6 0.0002 3×10-5
(three per
hundred
thousand)
Beryllium digestive system toxicity
(harms the stomach or
intestine)
0.001 NA 0.004 NA
Bromate carcinogenicity
(causes cancer)
0.0001 1×10-6 0.01 1×10-4
(one per
ten
thousand)
Cadmium nephrotoxicity
(harms the kidney)
0.00004 NA 0.005 NA
Carbofuran reproductive toxicity
(harms the testis)
0.0007 NA 0.018 NA
Carbon
tetrachloride
carcinogenicity
(causes cancer)
0.0001 1×10-6 0.0005 5×10-6
(five per
million)
8 Body weight effects are an indicator of general toxicity in animal studies.
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 5
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Chlordane carcinogenicity
(causes cancer)
0.00003 1×10-6 0.0001 3×10-6
(three per
million)
Chlorite hematotoxicity
(causes anemia)
neurotoxicity
(causes neurobehavioral
effects)
0.05 NA 1 NA
Chromium,
hexavalent
carcinogenicity
(causes cancer)
0.00002 1×10-6 0.010 5×10-4 (five
per ten
thousand)
Copper digestive system toxicity
(causes nausea,
vomiting, diarrhea)
0.3 NA 1.3 (AL9) NA
Cyanide neurotoxicity
(damages nerves)
endocrine toxicity
(affects the thyroid)
0.15 NA 0.15 NA
Dalapon nephrotoxicity
(harms the kidney)
0.79 NA 0.2 NA
Di(2-ethylhexyl)
adipate (DEHA)
developmental toxicity
(disrupts development)
0.2 NA 0.4 NA
Di(2-ethylhexyl)
phthalate
(DEHP)
carcinogenicity
(causes cancer)
0.012 1×10-6 0.004 3×10-7
(three per
ten million)
9 AL = action level. The action levels for copper and lead refer to a concentration measured at the tap. Much of the copper and lead in drinking water is derived from household plumbing (The Lead and Copper Rule, Title 22, California Code of Regulations [CCR] section 64672.3).
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 6
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
1,2-Dibromo-3-
chloropropane
(DBCP)
carcinogenicity
(causes cancer)
0.000003
(3x10-6)
1×10-6 0.0002 7×10-5
(seven per
hundred
thousand)
1,2-Dichloro-
benzene
(o-DCB)
hepatotoxicity
(harms the liver)
0.6 NA 0.6 NA
1,4-Dichloro-
benzene
(p-DCB)
carcinogenicity
(causes cancer)
0.006 1×10-6 0.005 8×10-7
(eight per
ten million)
1,1-Dichloro-
ethane
(1,1-DCA)
carcinogenicity
(causes cancer)
0.003 1×10-6 0.005 2×10-6
(two per
million)
1,2-Dichloro-
ethane
(1,2-DCA)
carcinogenicity
(causes cancer)
0.0004 1×10-6 0.0005 1×10-6
(one per
million)
1,1-Dichloro-
ethylene
(1,1-DCE)
hepatotoxicity
(harms the liver)
0.01 NA 0.006 NA
1,2-Dichloro-
ethylene, cis
nephrotoxicity
(harms the kidney)
0.013 NA 0.006 NA
1,2-Dichloro-
ethylene, trans
immunotoxicity
(harms the immune
system)
0.05 NA 0.01 NA
Dichloromethane
(methylene
chloride)
carcinogenicity
(causes cancer)
0.004 1×10-6 0.005 1×10-6
(one per
million)
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 7
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
2,4-Dichloro-
phenoxyacetic
acid (2,4-D)
hepatotoxicity and
nephrotoxicity
(harms the liver and
kidney)
0.02 NA 0.07 NA
1,2-Dichloro-
propane
(propylene
dichloride)
carcinogenicity
(causes cancer)
0.0005 1×10-6 0.005 1×10-5
(one per
hundred
thousand)
1,3-Dichloro-
propene
(Telone II)
carcinogenicity
(causes cancer)
0.0002 1×10-6 0.0005 2×10-6
(two per
million)
Dinoseb reproductive toxicity
(harms the uterus and
testis)
0.014 NA 0.007 NA
Diquat ocular toxicity
(harms the eye)
developmental toxicity
(causes malformation)
0.006 NA 0.02 NA
Endothall digestive system toxicity
(harms the stomach or
intestine)
0.094 NA 0.1 NA
Endrin neurotoxicity
(causes convulsions)
hepatotoxicity
(harms the liver)
0.0003 NA 0.002 NA
Ethylbenzene
(phenylethane)
hepatotoxicity
(harms the liver)
0.3 NA 0.3 NA
Ethylene
dibromide (1,2-
Dibromoethane)
carcinogenicity
(causes cancer)
0.00001 1×10-6 0.00005 5×10-6
(five per
million)
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 8
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Fluoride musculoskeletal toxicity
(causes tooth mottling)
1 NA 2 NA
Glyphosate nephrotoxicity
(harms the kidney)
0.9 NA 0.7 NA
Haloacetic acids:
dibromoacetic
acid
carcinogenicity
(causes cancer)
0.00003 1×10-6 0.06* 2×10-3
(two per
thousand)10
Haloacetic acids:
dichloroacetic
acid
carcinogenicity
(causes cancer)
0.0002 1×10-6 0.06* 3×10-4
(three per
ten
thousand)11
Haloacetic acids:
monobromo-
acetic acid
musculoskeletal toxicity
(causes muscular
degeneration)
0.025 NA 0.06* NA
Haloacetic acids:
monochloro-
acetic acid
general toxicity
(causes body and organ
weight changes8)
0.053 NA 0.06* NA
Haloacetic acids:
trichloroacetic
acid
carcinogenicity
(causes cancer)
0.0001 1×10-6 0.06* 6×10-4
(six per ten
thousand)12
Heptachlor carcinogenicity
(causes cancer)
0.000008
(8×10-6)
1×10-6 0.00001 1×10-6
(one per
million)
* For total haloacetic acids (the sum of dibromoacetic acid, dichloroacetic acid, monobromoacetic acid, monochloroacetic acid, and trichloroacetic acid). There are no MCLs for individual haloacetic acids. 10 Based on 0.060 mg/L dibromoacetic acid; the risk will vary with different combinations and ratios of the other haloacetic acids in a particular sample.
11 Based on 0.060 mg/L dichloroacetic acid; the risk will vary with different combinations and ratios of the other haloacetic acids in a particular sample.
12 Based on 0.060 mg/L trichloroacetic acid; the risk will vary with different combinations and ratios of the other haloacetic acids in a particular sample.
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 9
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Heptachlor
epoxide
carcinogenicity
(causes cancer)
0.000006
(6×10-6)
1×10-6 0.00001 2×10-6
(two per
million)
Hexachloro-
benzene
carcinogenicity
(causes cancer)
0.00003 1×10-6 0.001 3×10-5
(three per
hundred
thousand)
Hexachloro-
cyclopentadiene
(HCCPD)
digestive system toxicity
(causes stomach
lesions)
0.002 NA 0.05 NA
Lead developmental
neurotoxicity
(causes neurobehavioral
effects in children)
cardiovascular toxicity
(causes high blood
pressure)
carcinogenicity
(causes cancer)
0.0002 <1×10-6
(PHG is
not based
on this
effect)
0.015
(AL9)
2×10-6
(two per
million)
Lindane
(γ-BHC)
carcinogenicity
(causes cancer)
0.000032 1×10-6 0.0002 6×10-6
(six per
million)
Mercury
(inorganic)
nephrotoxicity
(harms the kidney)
0.0012 NA 0.002 NA
Methoxychlor endocrine toxicity
(causes hormone
effects)
0.00009 NA 0.03 NA
Methyl tertiary-
butyl ether
(MTBE)
carcinogenicity
(causes cancer)
0.013 1×10-6 0.013 1×10-6
(one per
million)
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 10
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Molinate carcinogenicity
(causes cancer)
0.001 1×10-6 0.02 2×10-5
(two per
hundred
thousand)
Monochloro-
benzene
(chlorobenzene)
nephrotoxicity
(harms the kidney)
0.07 NA 0.07 NA
Nickel developmental toxicity
(causes increased
neonatal deaths)
0.012 NA 0.1 NA
Nitrate hematotoxicity
(causes
methemoglobinemia)
45 as
nitrate
NA 10 as
nitrogen
(=45 as
nitrate)
NA
Nitrite hematotoxicity
(causes
methemoglobinemia)
3 as
nitrite
NA 1 as
nitrogen
(=3 as
nitrite)
NA
Nitrate and
Nitrite
hematotoxicity
(causes
methemoglobinemia)
10 as
nitrogen13
NA 10 as
nitrogen
NA
N-nitroso-
dimethyl-amine
(NDMA)
carcinogenicity
(causes cancer)
0.000003
(3×10-6)
1×10-6 none NA
Oxamyl general toxicity
(causes body weight
effects)
0.026 NA 0.05 NA
13 The joint nitrate/nitrite PHG of 10 mg/L (10 ppm, expressed as nitrogen) does not replace the individual values, and the maximum contribution from nitrite should not exceed 1 mg/L nitrite-nitrogen.
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 11
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Pentachloro-
phenol (PCP)
carcinogenicity
(causes cancer)
0.0003 1×10-6 0.001 3×10-6
(three per
million)
Perchlorate endocrine toxicity
(affects the thyroid)
developmental toxicity
(causes neurodevelop-
mental deficits)
0.001 NA 0.006 NA
Perfluorooctane
sulfonic acid
(PFOS)
carcinogenicity
(causes cancer)
1×10-6 1×10-6 NA NA
Perfluoro-
octanoic acid
(PFOA)
carcinogenicity
(causes cancer)
7×10-9 1×10-6 NA NA
Picloram hepatotoxicity
(harms the liver)
0.166 NA 0.5 NA
Polychlorinated
biphenyls
(PCBs)
carcinogenicity
(causes cancer)
0.00009 1×10-6 0.0005 6×10-6
(six per
million)
Radium-226 carcinogenicity
(causes cancer)
0.05 pCi/L 1×10-6 5 pCi/L
(combined
Ra226+228)
1×10-4
(one per
ten
thousand)
Radium-228 carcinogenicity
(causes cancer)
0.019 pCi/L 1×10-6 5 pCi/L
(combined
Ra226+228)
3×10-4
(three per
ten
thousand)
Selenium integumentary toxicity
(causes hair loss and
nail damage)
0.03 NA 0.05 NA
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 12
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Silvex (2,4,5-TP) hepatotoxicity
(harms the liver)
0.003 NA 0.05 NA
Simazine general toxicity
(causes body weight
effects)
0.004 NA 0.004 NA
Strontium-90 carcinogenicity
(causes cancer)
0.35 pCi/L 1×10-6 8 pCi/L 2×10-5
(two per
hundred
thousand)
Styrene
(vinylbenzene)
carcinogenicity
(causes cancer)
0.0005 1×10-6 0.1 2×10-4
(two per
ten
thousand)
1,1,2,2-
Tetrachloro-
ethane
carcinogenicity
(causes cancer)
0.0001 1×10-6 0.001 1×10-5
(one per
hundred
thousand)
2,3,7,8-Tetra-
chlorodibenzo-p-
dioxin (TCDD, or
dioxin)
carcinogenicity
(causes cancer)
5×10-11 1×10-6 3×10-8 6×10-4
(six per ten
thousand)
Tetrachloro-
ethylene
(perchloro-
ethylene, or
PCE)
carcinogenicity
(causes cancer)
0.00006 1×10-6 0.005 8×10-5
(eight per
hundred
thousand)
Thallium integumentary toxicity
(causes hair loss)
0.0001 NA 0.002 NA
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 13
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Thiobencarb general toxicity
(causes body weight
effects)
hematotoxicity
(affects red blood cells)
0.042 NA 0.07 NA
Toluene
(methylbenzene)
hepatotoxicity
(harms the liver)
endocrine toxicity
(harms the thymus)
0.15 NA 0.15 NA
Toxaphene carcinogenicity
(causes cancer)
0.00003 1×10-6 0.003 1×10-4
(one per
ten
thousand)
1,2,4-Trichloro-
benzene
endocrine toxicity
(harms adrenal glands)
0.005 NA 0.005 NA
1,1,1-Trichloro-
ethane
neurotoxicity
(harms the nervous
system),
reproductive toxicity
(causes fewer offspring)
hepatotoxicity
(harms the liver)
hematotoxicity
(causes blood effects)
1 NA 0.2 NA
1,1,2-Trichloro-
ethane
carcinogenicity
(causes cancer)
0.0003 1x10-6 0.005 2×10-5
(two per
hundred
thousand)
Trichloro-
ethylene (TCE)
carcinogenicity
(causes cancer)
0.0017 1×10-6 0.005 3×10-6
(three per
million)
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 14
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Trichlorofluoro-
methane
(Freon 11)
accelerated mortality
(increase in early death)
1.3 NA 0.15 NA
1,2,3-Trichloro-
propane
(1,2,3-TCP)
carcinogenicity
(causes cancer)
0.0000007
(7×10-7)
1x10-6 0.000005
(5×10-6)
7×10-6
(seven per
million)
1,1,2-Trichloro-
1,2,2-trifluoro-
ethane
(Freon 113)
hepatotoxicity
(harms the liver)
4 NA 1.2 NA
Trihalomethanes:
Bromodichloro-
methane
carcinogenicity
(causes cancer)
0.00006 1x10-6 0.080# 1.3×10-3
(1.3 per
thousand)14
Trihalomethanes:
Bromoform
carcinogenicity
(causes cancer)
0.0005 1x10-6 0.080# 2×10-4
(two per ten
thousand)15
Trihalomethanes:
Chloroform
carcinogenicity
(causes cancer)
0.0004 1x10-6 0.080# 2×10-4
(two per ten
thousand)16
# For total trihalomethanes (the sum of bromodichloromethane, bromoform, chloroform, and dibromochloromethane). There are no MCLs for individual trihalomethanes. 14 Based on 0.080 mg/L bromodichloromethane; the risk will vary with different combinations and ratios of the other trihalomethanes in a particular sample.
15 Based on 0.080 mg/L bromoform; the risk will vary with different combinations and ratios of the other trihalomethanes in a particular sample.
16 Based on 0.080 mg/L chloroform; the risk will vary with different combinations and ratios of the other trihalomethanes in a particular sample.
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 15
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Trihalomethanes:
Dibromochloro-
methane
carcinogenicity
(causes cancer)
0.0001 1x10-6 0.080# 8×10-4
(eight
per ten
thousand)17
Tritium carcinogenicity
(causes cancer)
400 pCi/L 1x10-6 20,000
pCi/L
5×10-5
(five per
hundred
thousand)
Uranium carcinogenicity
(causes cancer)
0.43 pCi/L 1×10-6 20 pCi/L 5×10-5
(five per
hundred
thousand)
Vinyl chloride carcinogenicity
(causes cancer)
0.00005 1×10-6 0.0005 1×10-5
(one per
hundred
thousand)
Xylene neurotoxicity
(affects the senses,
mood, and motor
control)
1.8 (single
isomer or
sum of
isomers)
NA 1.75 (single
isomer or
sum of
isomers)
NA
# For total trihalomethanes (the sum of bromodichloromethane, bromoform, chloroform, and dibromochloromethane). There are no MCLs for individual trihalomethanes. 17 Based on 0.080 mg/L dibromochloromethane; the risk will vary with different combinations and ratios of the other trihalomethanes in a particular sample.
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 16
Table 2: Health Risk Categories and Cancer Risk Values for Chemicals without California Public Health Goals
Chemical Health Risk Category1
US EPA
MCLG2
(mg/L)
Cancer
Risk3
at the
MCLG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Disinfection byproducts (DBPs)
Chloramines acute toxicity
(causes irritation)
digestive system toxicity
(harms the stomach)
hematotoxicity
(causes anemia)
45,6 NA7 none NA
Chlorine acute toxicity
(causes irritation)
digestive system toxicity
(harms the stomach)
45,6 NA none NA
Chlorine dioxide hematotoxicity
(causes anemia)
neurotoxicity
(harms the nervous
system)
0.85,6 NA none NA
Radionuclides
1 Health risk category based on the US EPA MCLG document or California MCL document unless otherwise specified.
2 MCLG = maximum contaminant level goal established by US EPA. 3 Cancer Risk = Upper estimate of excess cancer risk from lifetime exposure. Actual cancer risk may be lower or zero. 1×10-6 means one excess cancer case per million people exposed. 4 California MCL = maximum contaminant level established by California. 5 Maximum Residual Disinfectant Level Goal, or MRDLG.
6 The federal Maximum Residual Disinfectant Level (MRDL), or highest level of disinfectant allowed in drinking water, is the same value for this chemical. 7 NA = not available.
Office of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 17
Table 2: Health Risk Categories and Cancer Risk Values for Chemicals without California Public Health Goals
Chemical Health Risk Category1
US EPA
MCLG2
(mg/L)
Cancer
Risk3
at the
MCLG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Gross alpha
particles8
carcinogenicity
(causes cancer)
0 (210Po
included)
0 15 pCi/L9
(includes
radium but
not radon
and
uranium)
up to 1x10-3
(for 210Po,
the most
potent alpha
emitter)
Beta particles
and photon
emitters8
carcinogenicity
(causes cancer)
0 (210Pb
included)
0 50 pCi/L
(judged
equiv. to 4
mrem/yr)
up to 2x10-3
(for 210Pb,
the most
potent beta-
emitter)
8 MCLs for gross alpha and beta particles are screening standards for a group of radionuclides.
Corresponding PHGs were not developed for gross alpha and beta particles. See the OEHHA memoranda discussing the cancer risks at these MCLs at
http://www.oehha.ca.gov/water/reports/grossab.html.
9 pCi/L = picocuries per liter of water.