Metals
What does the evidence say about cobalt in people?
ATSDR's October 2024 profile sets an acute oral minimal risk level of 0.03 mg cobalt/kg/day and an intermediate oral level of 0.02 mg/kg/day. For metal-on-metal hips, SCENIHR said a whole-blood cobalt level for clinical concern was expected inside 2 to 7 µg/L and that the exact level was not determined. Critical values for systemic effects after those implants were not established.
Reference values
The saved ATSDR profile is dated October 2024. The acute oral minimal risk level of 0.03 mg Co/kg/day and the intermediate oral minimal risk level of 0.02 mg Co/kg/day were read from that file. The corpus also records inhalation minimal risk levels from the same profile: acute 0.0003 mg/m3, intermediate 0.00008 mg/m3, and chronic 0.0001 mg/m3. It records that WHO has no drinking-water guideline value for cobalt. ATSDR cobalt profile.
IARC 2023 groupings recorded in the corpus as checked against volume 131: cobalt metal without tungsten carbide, and soluble cobalt(II) salts, Group 2A; cobalt(II) oxide Group 2B; cobalt(II,III) oxide, cobalt(II) sulfide, and other cobalt(II) compounds Group 3. IARC volume 131. The corpus notes that cobalt is essential only as part of vitamin B12. Absorption wording beyond that was not re-extracted.
Metal-on-metal hips
SCENIHR in 2014 said screening should use whole blood, with cobalt as the reference substance. It said the threshold for clinical concern was expected within 2 to 7 µg/L cobalt in whole blood and that the exact level still had to be determined. Recommendations were based on local effects. Critical values for systemic effects had not been established. SCENIHR 2014.
The MHRA medical device alert MDA/2017/018, retrieved for this site, says there is no agreed whole-blood metal threshold that predicts outcome or mandates revision. It says rising blood metal levels may indicate potential for soft-tissue reaction, and that imaging should carry more weight than an isolated blood metal level. A figure of 7 ppb appears in the draft corpus but was not in the alert page retrieved here, so it is not stated as fact. MHRA MDA/2017/018.
NHANES 2017 to 2018
| Analyte | Geometric mean (95% CI) | 50th | 95th (95% CI) | n |
|---|---|---|---|---|
| Blood cobalt | 0.173 (0.167 to 0.180) | 0.160 (0.150 to 0.160) | 0.430 (0.380 to 0.480) | 3520 |
| Urine cobalt | 0.424 (0.398 to 0.451) | 0.437 (0.412 to 0.451) | 1.61 (1.37 to 1.83) | 2808 |
Related pages
Sources
Heavy Metal Index
Heavy Metal Index: Cobalt. This Heavy Metal Index URL returned HTTP 200 on 15 October 2026. Figures on this page are not copied from that index. They come from the sources named above.
What's safe to buy
The Heavy Metal Tested and Certified public register listed no licensees on 15 October 2026. That page reported 0 certified brands and 0 certified products, and it stated that no brand has completed the three-lot baseline. A specimen layout on the register is an illustration, not a licensee. This page does not name or rank any brand.
The program states that certification is a measurement of a product against a published limit, not a statement that the product is safe. If a licensee is later listed for this category, it will be on the register.
This page summarizes cited documents. It does not diagnose or prescribe. Reviewed 15 October 2026.