Table 1.

Biomarkers of manganese exposure

Acute Exposures			Cumulative Exposures
Blood	Urine	Saliva	Hair	Nails	Bone
Most widely used biomarker of Mn exposure38	Poor correlation between Mn exposure and Mn levels in urine39	Although levels are present at concentrations similar to blood, saliva is an alternative noninvasive biomarker for Mn exposure39	Quantifies longer-term cumulative exposures transpiring over several months40	Fingernails and toenails are noninvasive measures that represent aggregate exposures spanning from several months to approximately 1 y37	Approximately 40% of Mn is stored in bone45
Mn in blood has a short half-life of hours10	Past studies have not made significant observations using urine as a Mn biomarker38	Saliva Mn levels seem to linearly increase with exposure39	Exogenous contamination is a significant concern40	Mn concentrations quantified in nails have been associated with levels of Mn in the striatum and midbrain regions41,42 of the brain	Estimated half-life of Mn in bone is 8 y10
Optimal for acute exposures37 such as occupational settings	The future use of urine as a marker of Mn exposure is not recommended30	Use of saliva as a Mn biomarker is questionable10,38,39	Used as a noninvasive biomarker in many studies40		Bone Mn concentrations have been correlated with Mn levels in the brain, specifically the striatum, hippocampus, and choroid plexus43