At a glance
| Chemical family | Transition metal (Cr, atomic number 24); multiple oxidation states with substantially different toxicity profiles — hexavalent Cr-VI (carcinogenic), trivalent Cr-III (trace nutrient), metallic Cr-0 (low residential risk in stainless steel) |
| CAS number | 7440-47-3 (elemental); 18540-29-9 (Cr-VI chromate); 16065-83-1 (Cr-III); various CAS for specific chromium compounds |
| Classification | IARC Group 1 (Chromium(VI) compounds, carcinogenic to humans, Monograph Vol 100C, 2012); IARC Group 3 (metallic chromium and trivalent chromium compounds, not classifiable); EPA total chromium drinking water MCL 100 ppb (no separate federal Cr-VI MCL); California Cr-VI drinking water MCL 10 ppb; California Public Health Goal 0.02 ppb Cr-VI |
| Where you encounter it | Cr-III (the nutrient form): stainless steel cookware (low release with normal use); meat and some vegetables (dietary); chromium picolinate supplements (Cr-III, weight-loss/blood-sugar claims contested). Cr-VI (the toxic form): drinking water from specific contaminated areas (Hinkley CA, North Carolina coal ash regions, some industrial sites); cement and concrete (causes chromate dermatitis in construction workers — EU restricted Cr-VI in cement 2005); leather tanning (banned in EU consumer leather 2014); electroplating shops (occupational); welding fumes; CCA pressure-treated wood combines chromium with arsenic |
| Sleep micro environment relevance | Low for general population — bedrooms are not a primary Cr-VI exposure pathway. Relevant in households where a member works in chromate trades (electroplating, welding, leather tanning, cement) and brings take-home dust home on clothing |
| Activated carbon capture | Not applicable for VOC capture. For drinking water with elevated Cr-VI, NSF/ANSI 58 (reverse osmosis) and specifically-certified NSF/ANSI 53 hexavalent chromium reduction filters are the validated technologies. Inferred from established residential Cr-VI water remediation engineering; generic activated carbon for VOC capture is not the relevant technology |
What it is
Chromium — chemical symbol Cr, CAS 7440-47-3, atomic number 24 — is a hard, lustrous transition metal that exists in nature primarily in chromite ore (FeCr₂O₄). The biological behavior depends almost entirely on oxidation state. Hexavalent chromium (Cr-VI) is a strong oxidizer that crosses cell membranes via sulfate and phosphate transporters; once inside cells, it reduces to Cr-III through enzymatic and non-enzymatic pathways, producing reactive intermediates (Cr-V, Cr-IV, free radicals) that damage DNA. This is the chemistry behind the Cr-VI carcinogenicity classification. Trivalent chromium (Cr-III) is poorly absorbed across cell membranes and does not produce the reactive intermediates that drive Cr-VI cytotoxicity; it is considered a trace nutrient at low doses, though the essentiality status has been questioned in recent reviews. Metallic chromium (Cr-0) is the form in stainless steel and chrome plating, generally inert under normal residential use conditions.
The Cr-VI vs Cr-III distinction is critical because "chromium" on a water quality report or food label refers to different things depending on the analytical method. Total chromium lumps both forms together; speciation analysis is required to assess Cr-VI specifically. Cr-VI converts to Cr-III at low pH and in the presence of organic matter, but persists in some groundwater geochemical conditions — which is what made the Hinkley contamination so consequential. Historical industrial Cr-VI uses included leather tanning, chrome-yellow and chrome-green pigments, CCA wood preservation, cooling-tower corrosion inhibition, and electroplating; many have been restricted or phased out. Current US chromate-trade occupational exposures are primarily welding (stainless steel fume contains Cr-VI), electroplating, cement/concrete work, and some specialty pigment manufacture.
Where you encounter it
Cr-III: stainless steel cookware
Stainless steel cookware releases primarily Cr-III at low rates during normal cooking with intact cookware. The release rate is higher with heavily scratched or damaged pans, very acidic foods cooked for extended periods, and the first few uses of brand-new stainless cookware. The released chromium is overwhelmingly Cr-III rather than the toxic Cr-VI — the chemistry of cooking does not oxidize stainless steel-derived Cr-III to Cr-VI under any normal conditions. Replace heavily damaged pans; avoid extended cooking of highly acidic foods (tomato-heavy dishes, vinegar-based reductions) in old or scratched stainless cookware as a general practice.
Cr-III: dietary and supplemental
Meat (especially organ meats), whole grains, broccoli, and brewer's yeast are common dietary Cr-III sources. The adult adequate intake estimate is 25-35 µg/day (Cr-III). Chromium picolinate supplements market Cr-III for weight loss and blood sugar control; the evidence base for clinically meaningful effects at typical supplement doses is weak. Vincent 2017 in Journal of Trace Elements in Medicine and Biology reviewed the evolving status of chromium as an essential nutrient, noting that the essentiality classification has been questioned in recent decades. Peer-reviewed
Cr-VI: drinking water in specific contaminated areas
The Hinkley, California case is the textbook contamination scenario: Pacific Gas and Electric used hexavalent chromium as a cooling-tower corrosion inhibitor at the Hinkley natural-gas compressor station from 1952 to 1966, with discharge to unlined ponds that contaminated underlying groundwater used for residential wells. The 1993 PG&E settlement raised public awareness of Cr-VI as a drinking-water contaminant and contributed to California setting the most stringent residential Cr-VI standards in the US. Other documented Cr-VI groundwater contamination includes North Carolina coal-ash impoundment areas and various industrial-legacy regions nationally. EPA total chromium drinking-water surveillance data shows detectable chromium in many US public water systems; speciation (Cr-VI specifically) is less commonly reported.
Cr-VI: occupational and industrial
Chromate-trade occupational exposures produce the cancer epidemiology evidence underlying the IARC Group 1 classification. Stainless steel welding fume contains Cr-VI; cement and concrete contain Cr-VI as a contaminant that causes chromate dermatitis in construction workers (the EU restricted Cr-VI in cement to <2 ppm in 2005 to address this); electroplating shops produce Cr-VI aerosols; leather tanning historically used Cr-VI (banned in EU consumer leather since 2014 for skin-contact products). For households with members in these trades, take-home contamination via clothing and footwear is a documented pathway.
Cr-VI: legacy CCA pressure-treated wood
Chromated copper arsenate (CCA) pressure-treated wood combines hexavalent chromium with arsenic in the wood preservation chemistry. Pre-2004 CCA-era decks, play structures, and raised garden beds release both compounds at slowly-decaying rates. The arsenic concern (see the arsenic page) typically dominates the bedroom-relevant exposure framing, but the chromium contribution is real and the dermatitis risk from CCA wood splinters has been documented in case reports.
What the research says
Cr-VI carcinogenicity — IARC Group 1
The IARC Monograph Volume 100C (2012) classified chromium(VI) compounds as Group 1 carcinogenic to humans based on sufficient evidence for lung cancer in inhalation-exposed occupational populations (chromate production workers, chromate pigment workers, chromium platers, stainless steel welders), with growing evidence for sinonasal cancer. Regulatory Metallic chromium and trivalent chromium compounds were classified as Group 3 (not classifiable). The form-specific classification is the central regulatory and risk-assessment point.
Chromate worker mortality studies
The chromate-worker cohort literature — chromium-pigment workers in West Germany, chromate production workers in Maryland (Baltimore plant), stainless steel welders in multiple countries — established the dose-response between chronic Cr-VI inhalation and lung cancer mortality. The Baltimore cohort followed by Gibb and colleagues documented elevated lung cancer SMRs across multiple decades. The dose-response in occupational settings is well-characterized; the extrapolation to environmental low-dose ingestion exposure is the contested area driving EPA's prolonged IRIS reassessment for Cr-VI.
Cr-VI ingestion and the NTP TR-546 bioassay
The 2008 NTP Technical Report 546 on sodium dichromate dihydrate (Cr-VI) in drinking water reported significant tumor incidence in rats and mice at exposures relevant to environmental contamination scenarios — small intestine adenomas and carcinomas in mice, oral cavity tumors in rats. Regulatory The NTP findings substantially strengthened the case for treating ingested Cr-VI as a carcinogenicity concern, not just the inhalation route that had anchored the historical occupational epidemiology. The bioassay results underpinned California's 2011 Public Health Goal of 0.02 ppb Cr-VI in drinking water — a level approximately 5,000 times lower than the federal total chromium MCL of 100 ppb.
Regulatory landscape — federal vs California gap
The US EPA federal drinking-water MCL for total chromium is 100 ppb, set in 1991 and unchanged. Regulatory There is no separate federal MCL for Cr-VI specifically. The EPA has had a draft Cr-VI IRIS toxicity assessment in development since the late 2000s; the eventual finalization may inform a federal Cr-VI-specific MCL but has not done so as of 2026. California has set state-level standards substantially stricter than the federal total chromium MCL: California's Office of Environmental Health Hazard Assessment Public Health Goal for Cr-VI is 0.02 ppb; the California Cr-VI MCL is 10 ppb. Regulatory The gap between federal and California standards reflects ongoing scientific and regulatory disagreement about the appropriate uncertainty factors for extrapolating from occupational inhalation epidemiology and rodent ingestion bioassays to chronic low-dose human ingestion risk.
Cr-III essentiality status — under reconsideration
Trivalent chromium was historically classified as an essential trace nutrient based on glucose-tolerance factor research from the 1950s-1970s. More recent biochemical work has questioned the essentiality status: the molecular glucose-tolerance factor concept did not survive subsequent purification efforts, and no specific biological function for Cr-III at trace dietary intake has been definitively established. Peer-reviewed — Vincent 2017 reviewed the evolving status The practical implication for residential exposure framing is that Cr-III dietary supplementation for general-population health benefit is less well-supported than the historical literature suggested; the EFSA, IOM, and other agencies have moved toward more cautious essentiality framings in recent reviews.
What helps reduce exposure
For private well households in known Cr-VI contamination regions: test for hexavalent chromium specifically. Total chromium testing alone is not adequate — speciation analysis is required. State health departments in California, North Carolina, and other regions with documented Cr-VI contamination can provide guidance on certified testing laboratories.
For municipal water customers: review the annual Consumer Confidence Report (CCR). EPA-regulated public water systems report annual water quality data including chromium results. If chromium is detected near the federal MCL of 100 ppb, contact the water utility for more detailed information about Cr-VI versus Cr-III speciation.
For elevated Cr-VI: install certified reverse osmosis or NSF/ANSI 53 hexavalent-chromium-specific filtration. NSF/ANSI 58 (reverse osmosis) is the most thoroughly validated for Cr-VI. NSF/ANSI 53 filters specifically certified for hexavalent chromium reduction are also effective (verify the specific Cr-VI claim).
For stainless steel cookware: replace heavily scratched or damaged pans. Avoid cooking highly acidic foods for prolonged periods in old or damaged stainless cookware. The released chromium is overwhelmingly Cr-III, but minimizing leaching is reasonable practice.
For chromate-trade occupational households: enforce work-clothing separation. Workers in electroplating, welding, cement, and similar Cr-VI-exposed trades should change out of work clothing at the workplace or immediately on returning home, and wash work clothing separately from household laundry. The take-home pathway is documented across multiple occupational exposures.
For pre-2004 CCA-treated wood: handle as both arsenic and chromium source. The same mitigations applied for arsenic (sealing, replacement, avoidance of food contact and play surfaces) reduce chromium exposure simultaneously since both compounds are co-released from the wood matrix.
What does NOT help
- Avoiding all chromium. Cr-III is considered a trace nutrient (though the essentiality status has been questioned). Cr-III in food and water at typical exposures is not the concern; the concern is Cr-VI specifically.
- Generic "water filtration" claims without Cr-VI specificity. Total chromium reduction is not the same as Cr-VI reduction. Verify the specific NSF/ANSI 53 certification language for hexavalent chromium.
- Activated-carbon-only pitcher filters. Standard activated carbon is not validated for Cr-VI removal. NSF/ANSI 53 specifically certified for hexavalent chromium or NSF/ANSI 58 reverse osmosis is required.
- Chromium picolinate supplements for weight loss or blood sugar. The evidence is weak at typical supplement doses; high-dose chronic chromium picolinate use has raised safety concerns in some case reports. The American Diabetes Association does not recommend chromium supplementation for diabetes management.
- Discarding stainless steel cookware. Cr-III release from intact stainless steel under normal cooking conditions is low and is not the toxic Cr-VI form. Replacement is appropriate for heavily damaged pans rather than as a general recommendation.
Open research questions
- Cr-VI ingestion carcinogenicity at environmentally relevant doses — the contested area driving EPA's prolonged IRIS reassessment for Cr-VI. The occupational inhalation dose-response is established; the chronic low-dose ingestion extrapolation is the regulatory uncertainty. Speculation re: low-dose extrapolation; established at higher chronic occupational exposures
- Cr-III essentiality status reassessment — the historical "essential trace nutrient" classification has been questioned. The implications for dietary recommendations and supplementation are an active area. Speculation re: definitive essentiality conclusion; recent evidence suggests cautious framing
- Cr-VI vs Cr-III in residential dust — settled dust speciation data is sparse; the household dust contribution to total daily Cr-VI exposure relative to drinking water is not well characterized. Speculation
- Take-home contamination from Cr-VI-exposed occupations — the chromate-trade occupational literature has not produced parallel residential dust burden studies analogous to the lead, mercury, and PFAS take-home literature. Inferred from parallel heavy-metal take-home contamination literature
Citations
- International Agency for Research on Cancer (2012). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 100C: Arsenic, Metals, Fibres and Dusts — Chromium(VI) compounds Group 1; metallic chromium and Cr-III Group 3. Lyon: IARC. iarc.who.int — Monograph 100C PDF Regulatory
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Chromium. atsdr.cdc.gov/ToxProfiles/tp7.pdf Regulatory
- US Environmental Protection Agency. Chromium in Drinking Water — total chromium MCL 100 ppb (1991). epa.gov/dwreginfo/chromium-drinking-water Regulatory
- US Environmental Protection Agency. Chromium (VI) — IRIS assessment status. iris.epa.gov Regulatory — draft IRIS reassessment in development
- US Environmental Protection Agency. Chromium III — IRIS assessment. iris.epa.gov Regulatory
- California Office of Environmental Health Hazard Assessment (2011). Public Health Goal for Hexavalent Chromium in Drinking Water — 0.02 µg/L (ppb). oehha.ca.gov Regulatory
- National Toxicology Program (2008). Toxicology and Carcinogenesis Studies of Sodium Dichromate Dihydrate (CAS No. 7789-12-0) in F344/N Rats and B6C3F1 Mice (Drinking Water Studies). NTP Technical Report Series No. 546. ntp.niehs.nih.gov/tr546 Regulatory — significant tumor incidence at environmentally relevant ingestion exposures
- Vincent JB (2017). New evidence against chromium as an essential trace element. Journal of Trace Elements in Medicine and Biology, 43:18-30. DOI 10.1016/j.jtemb.2017.07.014 Peer-reviewed
- Costa M, Klein CB (2006). Toxicity and carcinogenicity of chromium compounds in humans. Critical Reviews in Toxicology, 36(2):155-163. DOI 10.1080/10408440500534032 Peer-reviewed
- Sedman RM, Beaumont J, McDonald TA, Reynolds S, Krowech G, Howd R (2006). Review of the evidence regarding the carcinogenicity of hexavalent chromium in drinking water. Journal of Environmental Science and Health, Part C, 24(1):155-182. DOI 10.1080/10590500600614337 Peer-reviewed
Frequently asked questions
What's the difference between Cr-VI and Cr-III?
Hexavalent chromium (Cr-VI) and trivalent chromium (Cr-III) are the same element in different oxidation states with substantially different toxicology. Cr-VI is a strong oxidizer that crosses cell membranes via sulfate and phosphate transporters; once inside cells, it reduces to Cr-III and produces reactive intermediates that damage DNA. Cr-VI is IARC Group 1 (carcinogenic to humans, lung cancer in inhalation-exposed workers, with growing evidence for ingestion). Cr-III does not readily cross cell membranes, is considered a trace nutrient at low doses (RDA-equivalent 25-35 µg/day, though essentiality is now contested), and is IARC Group 3 (not classifiable). The difference matters: "chromium" on a water quality report or a food label refers to different things depending on context.
Is chromium in stainless steel cookware dangerous?
No, for normal use with intact cookware. Stainless steel releases primarily Cr-III (the nutrient form), and the release rate from intact stainless steel during cooking is low. Heavily scratched or damaged pans, very acidic foods cooked for extended periods, and the first few uses of brand-new stainless cookware can release somewhat higher amounts. Replace heavily damaged pans; avoid extended cooking of highly acidic foods (tomato-heavy dishes, vinegar-based reductions) in old or scratched stainless; the released chromium is overwhelmingly Cr-III rather than the toxic Cr-VI.
Was the Erin Brockovich case about chromium?
Yes — specifically hexavalent chromium (Cr-VI). The 1993 settlement between Pacific Gas and Electric and residents of Hinkley, California addressed Cr-VI contamination of groundwater from PG&E's natural-gas compressor station, where Cr-VI was used as a cooling-tower corrosion inhibitor from 1952 to 1966. The case raised public awareness of Cr-VI as a drinking-water contaminant and contributed to California setting a Public Health Goal for Cr-VI in drinking water at 0.02 ppb in 2011 — substantially stricter than the federal EPA Maximum Contaminant Level of 100 ppb for total chromium (which does not separately address Cr-VI specifically).
Do chromium supplements work for weight loss?
The evidence is weak. Chromium picolinate supplements (a Cr-III form) have been marketed for weight loss and blood sugar control since the 1990s, but systematic reviews and meta-analyses have generally not supported clinically meaningful effects at typical supplement doses. Some studies suggest modest effects on glucose metabolism in specific populations (insulin-resistant adults); the weight-loss claims are less well-supported. High-dose chronic chromium picolinate supplementation has raised safety concerns in some case reports. The American Diabetes Association does not recommend chromium supplementation for diabetes management.
Is chromium in drinking water regulated?
The EPA Maximum Contaminant Level for total chromium in drinking water is 100 ppb, set in 1991 and unchanged. There is no separate federal MCL for Cr-VI specifically. California has set a state MCL for Cr-VI of 10 ppb and a Public Health Goal of 0.02 ppb (substantially stricter than the federal total chromium MCL). The EPA has been developing an updated IRIS toxicity assessment for Cr-VI for many years; the eventual finalization may inform a federal Cr-VI-specific MCL but has not done so as of 2026.
Can you remove hexavalent chromium from water?
Yes, with appropriate certified filtration. NSF/ANSI 58 (reverse osmosis) reliably removes Cr-VI from drinking water. NSF/ANSI 53 filters specifically certified for hexavalent chromium reduction are also effective (verify the specific Cr-VI claim — not all NSF 53 filters cover it). Some ion-exchange systems with anion-exchange resin are effective. Standard activated-carbon-only pitcher filters without specific Cr-VI certification do not reliably remove Cr-VI. For households in known Cr-VI contamination areas, point-of-use reverse osmosis at the kitchen sink is typically the cost-effective intervention.
Does chromium cause cancer?
Form-specific answer. Hexavalent chromium (Cr-VI) compounds are IARC Group 1 — carcinogenic to humans — based on lung cancer in occupationally exposed chromate workers (electroplating, chromate production, stainless steel welding). Trivalent chromium (Cr-III) compounds and metallic chromium are IARC Group 3 — not classifiable as to carcinogenicity. The cancer concern centers entirely on Cr-VI. The "chromium causes cancer" framing without specifying valence state is misleading because the same word "chromium" refers to chemicals with substantially different cancer risk profiles.
Related compounds
Embr Sleep is a sleep environment company researching the chemistry of the bedroom. See the methodology page for how this Atlas tags claims by evidence strength. For broader context on cookware and household chemistry choices, see non-toxic bedroom.
Last reviewed 2026-05-25. If you find a factual error, contact us.