Chromium-6 in LA Tap Water: What the Data Actually Shows

Yes, chromium-6 (hexavalent chromium) is in LA tap water at typical concentrations of 0.1 to 0.3 parts per billion (ppb) in LADWP source water and finished tap water. There is currently no federal Maximum Contaminant Level (MCL) specifically for chromium-6. The federal limit covers total chromium (Cr-3 plus Cr-6) at 100 ppb. California has proposed a state level Cr-6 MCL of 10 ppb, currently under regulatory review. The Environmental Working Group's health based goal is 0.02 ppb. So LA tap water sits well below the proposed California regulatory limit but well above the EWG health guideline. Chromium-6 is classified by the EPA as "likely carcinogenic to humans" by oral exposure. Reverse osmosis removes 95 to 99 percent of chromium-6, the most reliable residential treatment. This is informational, not medical advice. If you have specific health concerns, consult a physician.

Is Chromium-6 in LA Tap Water?

Yes, chromium-6 is detected in LA tap water at low concentrations, typically 0.1 to 0.3 ppb based on LADWP source water monitoring. This is below the proposed California state MCL of 10 ppb but above the EWG health based guideline of 0.02 ppb. LADWP reports total chromium and chromium-6 in its annual Consumer Confidence Report.

Chromium-6 enters LA water from two sources. Natural geological occurrence: Colorado River water (delivered via the Metropolitan Water District) flows through chromium bearing rock formations. Industrial legacy: Cr-6 has been used in metal plating, leather tanning, paint pigments, and cooling tower corrosion control for decades; legacy contamination from manufacturing sites can reach groundwater used for drinking water.

How Much Chromium-6 Is Safe?

There is no scientifically agreed "safe" level of chromium-6 ingestion. The EPA has not set a federal Maximum Contaminant Level. California proposed a state MCL of 10 ppb, currently under regulatory review. EWG sets a health based guideline of 0.02 ppb assuming a 1 in 1 million lifetime cancer risk. Different agencies use different risk assumptions.

The relevant numbers in plain language:

• EPA federal MCL for Cr-6: None exists.
• EPA federal MCL for total chromium: 100 ppb (covers Cr-3 plus Cr-6 combined).
• California proposed Cr-6 MCL: 10 ppb (under regulatory review).
• California 2014 Cr-6 MCL: Set at 10 ppb, withdrawn in 2017 after a court ruling that the state failed to consider economic feasibility properly.
• EWG health based goal: 0.02 ppb (assumes 1 in 1 million cancer risk).
• NIH National Toxicology Program: Chromium-6 listed as "known to be a human carcinogen" by inhalation; "likely carcinogenic" by ingestion.

What Removes Chromium-6 from Water?

Reverse osmosis (RO) and strong base anion exchange are the two residential technologies that remove chromium-6 effectively. RO removes 95 to 99 percent. Anion exchange removes 90 to 95 percent. Activated carbon does not remove chromium-6 reliably. Utility scale treatment uses reduction coagulation filtration, which is not available as a residential system.

Treatment Effectiveness Comparison

Method	Cr-6 Removal	Residential?	Notes
Reverse Osmosis (RO)	95 to 99%	Yes	NSF/ANSI 58 certified. Standard recommendation.
Strong Base Anion Exchange	90 to 95%	Yes (specialty)	Requires specific resin certified for Cr-6.
Reduction Coagulation Filtration	95% plus	No	Utility scale only.
Activated Carbon	Less than 30%	Yes	Not effective. Do not rely on carbon for Cr-6.
Standard sediment filter	0%	Yes	No removal.
Boiling	0% (concentrates)	n/a	Boiling does not remove Cr-6 and concentrates it through evaporation.

For residential use, the practical recommendation is an under sink reverse osmosis system at the kitchen tap, NSF/ANSI 58 certified specifically for chromium reduction. Whole house RO is technically possible but expensive. Most LA homes pair whole house carbon (for chloramines and TTHM) with under sink RO (for Cr-6, lead, sodium, fluoride, and PFAS) at the drinking water tap.

Is Chromium-6 Cancerous?

Yes, chromium-6 is classified as a carcinogen. The National Toxicology Program lists Cr-6 as "known to be a human carcinogen" by inhalation. By oral exposure (drinking water), the EPA classifies it as "likely carcinogenic to humans" based on rodent studies showing increased intestinal tumors. The cancer risk depends on dose and duration of exposure.

The Hinkley, California case made chromium-6 widely known. Pacific Gas and Electric Company used Cr-6 as a corrosion inhibitor at its compressor station in Hinkley (about 2.5 hours from LA in San Bernardino County) from 1952 to 1966. Cr-6 leaked into local groundwater at concentrations far exceeding any drinking water standard. The community filed a class action lawsuit famously documented in the 2000 film "Erin Brockovich." PG&E settled in 1996 for $333 million, the largest direct action lawsuit settlement in US history at the time, plus subsequent settlements.

Hinkley levels were measured at hundreds of ppb in some private wells. LADWP source water is several orders of magnitude lower, in the 0.1 to 0.3 ppb range. The Hinkley case demonstrates what extreme industrial contamination looks like; routine LA tap water exposure is a different scale of concern.

Is LA Water Contaminated?

LA water is not "contaminated" in the legal sense. LADWP consistently meets all federal Safe Drinking Water Act standards and has not had a Maximum Contaminant Level violation in recent reporting years. However, the water does contain low concentrations of regulated and unregulated substances including chromium-6, TTHM, HAA5, and trace metals. "Legally compliant" and "health protective" are not the same standard.

The honest framing: LA tap water is among the cleaner large city water supplies in the United States by federal compliance metrics. It is not pure water. Routine home filtration (whole house carbon plus under sink RO) reduces multiple legally allowed but health relevant substances simultaneously, including Cr-6.

How Chromium-6 Gets Into Drinking Water

• Natural geology. Cr-6 occurs naturally in soil and rock formations, especially in the western US. Colorado River water picks up trace Cr-6 as it flows through chromium bearing geology.
• Industrial discharge (legacy). Metal plating shops, paint and pigment manufacturing, leather tanneries, and cooling tower operations have historically discharged Cr-6 into wastewater and groundwater. Some legacy sites still contribute despite cleanup efforts.
• Industrial discharge (current). Some active industrial users still discharge Cr-6 under regulated permits.
• Pipe corrosion. Cr-6 used in cooling tower corrosion inhibitors can enter potable water systems where industrial water connects to municipal supply.
• Atmospheric deposition. Cr-6 emitted from industrial processes settles onto surface water sources.

California's Chromium-6 Regulatory History

California has been the primary regulatory venue for Cr-6 in drinking water for over a decade.

1. 2014: California State Water Resources Control Board adopted the first state level Cr-6 MCL at 10 ppb, the only such standard in the United States.
2. 2017: A California court invalidated the 10 ppb MCL after the California Manufacturers and Technology Association sued, arguing the state had not adequately considered economic feasibility per Health and Safety Code Section 116365(b). The MCL was withdrawn pending re analysis.
3. 2024: California proposed a new Cr-6 MCL at 10 ppb with updated economic analysis. Currently under regulatory review.
4. Federal level: The EPA has not proposed a federal Cr-6 MCL. Total chromium remains regulated at 100 ppb (1991 standard).

If California's proposed 10 ppb MCL takes effect, LA tap water remains compliant (current levels are 0.1 to 0.3 ppb, far below 10 ppb). Federal regulation remains uncertain.

What LADWP Customers Should Do

For most LADWP customers, the recommended approach is:

1. Check your specific zone in the current LADWP CCR. Detected Cr-6 levels can vary by source blend. See our LADWP water quality report decoded guide for how to read the CCR.
2. If you want to reduce Cr-6 exposure at the kitchen tap, install an under sink RO system. NSF/ANSI 58 certified for chromium and chromium-6 reduction. Standard residential cost is $400 to $1,200 installed.
3. Pair RO with whole house carbon for general water quality. Together they handle Cr-6, chloramines, TTHM, lead from pipes, sodium, fluoride, and PFAS.
4. Test your specific tap if you have health concerns. Independent lab testing for Cr-6 costs approximately $50 to $150 and confirms what your specific tap delivers (vs. the system wide average).
5. Consult a physician for medical questions. This article is informational, not medical advice. If you have specific health concerns, professional medical guidance is appropriate.

Honest Hedging on This Topic

Chromium-6 in drinking water is a topic where honest uncertainty is appropriate:

• The EPA has not set a federal Cr-6 MCL because the science on safe oral exposure levels is contested. Different agencies have set different guidelines based on different risk assumptions.
• EWG's 0.02 ppb health goal assumes a 1 in 1 million lifetime cancer risk. Other risk assessments (1 in 100,000 or 1 in 10,000) yield higher acceptable exposure levels.
• LADWP source water Cr-6 levels are well below any proposed regulatory limit but well above the most conservative health based goals.
• Whether routine LA tap water exposure presents meaningful cancer risk over a lifetime is not definitively answered by current science. Reasonable experts disagree.
• Home RO is a low cost, low risk way to reduce exposure if you prefer to act conservatively.

What is not honest is implying LA water is uniquely contaminated or that immediate health damage is occurring at LADWP detected levels. The Hinkley case represents extreme industrial contamination at hundreds of ppb. LA tap water at 0.1 to 0.3 ppb is several orders of magnitude lower.

Authoritative References

• EPA Chromium in Drinking Water
• California State Water Resources Control Board Chromium-6 page
• EWG Tap Water Database (search by zip code for LADWP Cr-6 detections)
• NIH National Toxicology Program Report on Carcinogens (chromium-6 classification)

Free LA Water Test (Including Chromium-6 Awareness)

Water2O has been testing and treating LA tap water since 2011. Our standard free in home test covers hardness, chloramines, chlorine, TDS, pH, iron, and sodium. For Cr-6 specifically we coordinate independent lab testing if you want a number for your tap. We install NSF/ANSI 58 certified RO systems specifically rated for chromium reduction, with our 12 year warranty.

500+ systems installed. WQA certified. NSF certified. Family owned and operated since 2011, serving LA, Ventura, Orange, and Riverside Counties.

Schedule Your Free Water Test or call (410) 262-9888

Related reading: Does LA have hard water? covers hardness ranges by neighborhood. LADWP water quality report decoded walks through the full CCR. Southern California water softener guide covers whole home water treatment options.

Last updated: May 2026. This article is informational, not medical advice. For specific health concerns about chromium-6 exposure, consult a physician.