TABLE 5-10 Summary of Developmental Neurotoxicity Studies in Humans

Study Site

Size of Cohort Identified and Enrolled

Exposure Biomarker

MeHg or Total Hg Concentration

Age at Assessment

Number of Children Assessed

End Points

Reference

Amazon

351

Child hair

Mean, 11.0 ppm; 80% > 10 ppm

7-12 years

354 (Table 1)

Fingertapping, WISC-III: digit span forward, Santa Ana dexterity test, Stanford-inet: copying, bead memory

Grandjean et al.1999

Ecuador

75 (36 children, 39 adults)

Blood

Mean, 17.5 mg/L (3.0 in 34 controls)

Children: 3-15 years

Adults: 16-57 years

19-40

Pure tone conduction threshold BAEP

Counter et al. 1998

Faroe Islands

182

Maternal hair

Geometric mean, 4.1 ppm; range, 2.5-7.4 ppm

2 wk, adjusted for gestational age

182

Neurological exam

Steuerwald et al. 2000

   

Umbilical cord blood

Geometric mean, 20.4 µg/L; range, 11.8-40.0 µg/L

       
   

Umbilical cord serum

Geometric mean, 2.5 µg/L; range, 1.7-3.7 µg/L

       
 

1,023

Maternal hair

Geometric mean, 4.3 ppm; interquartile range, 2.6-7.7 ppm

Maternal interview “during the first year”

583

Developmental milestones

Grandjean et al. 1995



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