Chromium-6 in Indiana and Michigan Drinking Water 2026: What EPA's Proposed Rule and Public Data Show

In March 2023, EPA proposed a maximum contaminant level of 0.02 mg/L specifically for chromium-6, five times stricter than the existing total-chromium limit of 0.1 mg/L that has been in place since 1991. The Environmental Working Group's tap-water database documents hexavalent chromium detections in Indiana and Michigan public water systems, often far above EWG's health-protective threshold of 0.02 parts per billion even when utilities are in full compliance with federal law. A reverse osmosis system certified to NSF/ANSI 58 for chromium reduction is the most reliable point-of-use option available to homeowners before the federal rule is finalized. (Source: EPA proposed NPDWR for Chromium-6, March 27, 2023, epa.gov/sdwa/chromium-drinking-water.)

What chromium-6 is and why it is regulated separately from total chromium

Chromium exists in several oxidation states, but two matter most for drinking water: chromium-3 (trivalent) and chromium-6 (hexavalent). Chromium-3 is considered an essential trace nutrient and is found in many foods. Chromium-6 is the oxidized form associated with carcinogenicity, specifically in occupational inhalation studies and in animal ingestion studies reviewed by the National Toxicology Program (NTP). The NTP concluded in its 2008 technical report that chromium-6 is reasonably anticipated to be a human carcinogen based on sufficient evidence in laboratory animals (NTP Technical Report 546, 2008).

The current federal MCL of 0.1 mg/L for total chromium was set by EPA in 1991 and covers both chromium-3 and chromium-6 combined. Because utilities report total chromium, a system could theoretically have measurable hexavalent chromium while remaining in full compliance. EPA recognized this gap and, citing the NTP findings and subsequent epidemiological work, proposed a dedicated chromium-6 MCL in its 2023 rulemaking. California, which has its own robust drinking water program, finalized a chromium-6 MCL of 0.010 mg/L effective January 2024, the lowest enforceable limit in the country (California State Water Resources Control Board).

How chromium-6 enters Indiana and Michigan water systems

Chromium enters drinking water through two pathways: natural geological weathering and industrial discharge. In the Midwest, naturally occurring chromium is associated with ultramafic and mafic bedrock formations and with glacial till deposits that contain chromite minerals. USGS groundwater studies have documented naturally occurring chromium in aquifers across the Great Lakes region, particularly in areas where glacial deposits overlie chromium-bearing bedrock (USGS Upper Midwest Water Science Center).

Industrial chromium discharges are the second pathway. Historical and current discharges from metal finishing operations, electroplating facilities, leather tanning operations, and chrome-bearing coal ash have introduced chromium-6 into surface water and groundwater in both Indiana and Michigan. Many of these discharges date to manufacturing expanses from 1940 through the 1980s and the contamination can persist for decades in sediment and aquifer systems. Utilities drawing from surface water sources, such as the White River for Indianapolis or the Great Lakes for western Michigan cities, must account for variable upstream chromium inputs that are harder to eliminate at the source than groundwater contamination.

The data: what EWG's tap-water database shows and how to read it

The Environmental Working Group compiles state-reported monitoring data from utilities across the country and makes it searchable at the utility level (ewg.org/tapwater). EWG applies its own health-protective guideline for chromium-6 of 0.02 parts per billion, derived from a California Office of Environmental Health Hazard Assessment analysis. This is 5,000 times stricter than the existing federal MCL of 100 parts per billion for total chromium, and 1,000 times stricter than EPA's 2023 proposed MCL of 20 parts per billion specifically for chromium-6.

The gap matters because it explains how a utility can publish a CCR showing full compliance while EWG flags the same utility for chromium-6 detections above its health-protective threshold. Both statements can be true simultaneously: the utility meets every current legal requirement, and independent health analysis suggests the current limits may not fully protect long-term health. This is precisely the data gap that EPA's 2023 proposed rulemaking is designed to close.

Regulatory timeline: where the federal chromium-6 rule stands in 2026

Sources: EPA Safe Drinking Water Information System, Federal Register, NTP, California State Water Resources Control Board. Verify current rule status at epa.gov/sdwa/chromium-drinking-water.

What Indiana and Michigan homeowners should check right now

Every public utility serving more than 25 people is required by the Safe Drinking Water Act to publish an annual Consumer Confidence Report (CCR). Indiana utilities must file with IDEM (Indiana Department of Environmental Management), and Michigan utilities with EGLE (Department of Environment, Great Lakes, and Energy). Both states make CCR data searchable online. When you pull your utility's most recent CCR, look for these items specifically:

• Total chromium: the number reported and the federal MCL of 0.1 mg/L. Full compliance means the reported level is below 0.1 mg/L, but that does not tell you the chromium-6 fraction specifically.
• Detection vs. non-detect: utilities must note whether a contaminant was detected at all, even below the MCL. Non-detect for total chromium is the strongest result; any detection warrants the follow-up question of what fraction is hexavalent.
• UCMR4 results (2018-2020): EPA's fourth Unregulated Contaminant Monitoring Rule required a sample of large utilities to test specifically for hexavalent chromium. Check whether your utility participated and what it reported. This data is searchable at EPA's UCMR data portal (epa.gov/dwucmr).

Treatment: what actually removes chromium-6 at the residential level

Not all residential water treatment removes hexavalent chromium. Chromium-6 is a soluble anion in most drinking water and passes through many standard filter media without meaningful reduction. The two technologies with strong documented performance are reverse osmosis and strong-base anion exchange resin, with RO being the practical choice for residential applications.

Reverse osmosis certified to NSF/ANSI 58 for chromium reduction achieves greater than 95 percent removal in certified testing. The certification requires the manufacturer to demonstrate performance at defined influent concentrations and flow rates, which means the marketing claim is backed by third-party verification. When choosing an RO system, confirm that the NSF/ANSI 58 certificate specifically lists hexavalent chromium (Cr-6), not just total chromium, in its performance data table. Some older certifications tested only trivalent chromium.

Granular activated carbon (GAC), the technology in most pitcher filters and refrigerator filters, has limited effectiveness against dissolved chromium-6. GAC removes organic compounds primarily through adsorption, but hexavalent chromium is an inorganic anion and does not adsorb well onto standard carbon surfaces. Some catalytic carbon and iron-modified media show improved chromium-6 reduction in laboratory settings, but residential GAC filters are not generally certified for this purpose and should not be relied on as the primary chromium-6 control. Our reverse osmosis systems page covers the certified options we install across the service area.

How to compile this data yourself

Every number in this article comes from public databases. Here is the lookup workflow we used, so you can verify results for your specific utility or check for updates after EPA finalizes the rule:

1. CCR for your utility: Search your utility name at Indiana's IDEM CCR portal (in.gov/idem) or Michigan's EGLE portal (michigan.gov/egle).
2. UCMR4 hexavalent chromium data: EPA's UCMR data tool at epa.gov/dwucmr lets you filter by state and contaminant to find hexavalent chromium results for systems that participated in UCMR4.
3. EWG tap-water database: Enter your ZIP code at ewg.org/tapwater to see utility-level chromium-6 data compared against EWG's health guideline of 0.02 ppb.
4. EPA proposed rule status: The EPA chromium-6 rulemaking page at epa.gov/sdwa/chromium-drinking-water is updated when the final rule publishes or the timeline changes.

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