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Table 5 Characteristics of relevant biomarkers used in children

From: Biomarkers of environmental manganese exposure and associations with childhood neurodevelopment: a systematic review and meta-analysis

Biomarkers Characteristics Advantages Limitations
Hair Reflects the exposure during the 2–4 months before sampling [81] Easy to collect, store and manipulate, non-invasive, most consistent and valid biomarker in pediatric epidemiology [85] Pigmentation and potential external contamination [86]
Blood With a half-life of 4 or 39 days due to different elimination pathways [79] Obtained easily and less influence of external contamination [87] Correlated poorly with exposure [88]
Teeth Reflects the exposure from 13 to 16 weeks after gestation to approximately one year of age [83] Non-invasive, provides precise exposure information, distinguishes the prenatal and postnatal exposure [82] Caries and teeth with attrition contained less metal [89], relatively difficult to obtain and measure
Saliva and urine secretes 0.8 to 1.5 L of saliva each day, only a small fraction of Mn eliminates in urine [90] Non-invasive and easy to collect [90] Correlated poorly with exposure [88, 91, 92], fairly large variation [93]
Toe nail Reflects an exposure of 7–12 months before sampling [94, 95] Easy collection, storage and transport [96], correlated with exposure [91] Difficult to collect sufficient toenail from infants and potential external contamination [97]
Cord blood Reflects an exposure of the last trimester [97] Correlated with manganese in dentin [98] Not feasible to obtain at different stages of pregnancy [98]
Maternal blood Mn enters the fetus via an active transport mechanism [99] Readily sampled [98] Maternal Mn biomarkers may not accurately reflect Mn levels in fetal tissues [98]
  1. Mn Manganese
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