Effects and blood concentrations of cobalt after ingestion of 1 mg/d by human volunteers for 90 d.
BACKGROUND
Over-the-counter cobalt supplements are available for sale in the United States, but little is known regarding their clinical effects and biokinetic distribution with long-term use.


OBJECTIVE
We assessed blood kinetics, biochemical responses, and clinical effects in 5 adult men and 5 adult women who voluntarily ingested ∼ 1.0 mg Co/d (0.080-0.19 mg Co · kg⁻¹ · d⁻¹) of a commercially available cobalt supplement over a 3-mo period.


METHODS
Volunteers were instructed to take the cobalt dietary supplement in the morning according to the manufacturer's label. Blood samples were collected and analyzed for a number of biochemical variables before, during, and after dosing. Hearing, vision, cardiac, and neurologic functions were also assessed in volunteers before, during, and after dosing.


RESULTS
After ∼ 90 d of dosing, mean cobalt blood concentrations were lower in men than in women. Mean cobalt whole blood and serum concentrations in men were 20 μg/L (range: 12-33 μg/L) and 25 μg/L (range: 15-46 μg/L), respectively. In women, mean cobalt whole blood and serum concentrations were 53 μg/L (range: 6-117 μg/L) and 71 μg/L (range: 9-149 μg/L), respectively. Estimated red blood cell (RBC) cobalt concentrations suggested that cobalt was sequestered in RBCs during their 120-d life span, which resulted in a slower whole blood clearance compared with serum. The renal clearance of cobalt increased with the serum concentration and was, on average, lower in women (3.5 ± 1.3 mL/min) than in men (5.5 ± 1.9 mL/min). Sex-specific differences were observed in cobalt absorption and excretion. There were no clinically significant changes in biochemical, hematologic, and clinical variables assessed in this study.


CONCLUSIONS
Peak cobalt whole blood concentrations ranging between 9.4 and 117 μg/L were not associated with clinically significant changes in basic hematologic and clinical variables.
From Cardno ChemRisk LLC, San Francisco, CA (DJP, JMO, DAG, and BLF); Cardno ChemRisk LLC, Boulder, CO (BET); and Cardno ChemRisk LLC, Pittsburgh, PA (KMU).
Brooke E
BE
Tvermoes
Kenneth M
KM
Unice
Dennis J
DJ
Paustenbach
Brent L
BL
Finley
Joanne M
JM
Otani
David A
DA
Galbraith
D000328:Adult; D003035:Cobalt / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood / Q000652:urine; D019587:Dietary Supplements / Q000009:adverse effects*; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D006207:Half-Life; D006801:Humans; D007408:Intestinal Absorption; D007700:Kinetics; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D010352:Patient Dropouts; D015203:Reproducibility of Results; D012727:Sex Characteristics; D036401:Toxicity Tests, Chronic; D014481:United States; D055815:Young Adult
D003035:Cobalt