Table 2.
Studies assessing the connection between exposure to Mn and neurodevelopmental disturbances in children.
| Neurodevelopmental Disturbances |
Biomarkers | Population | Major Conclusion | Ref. |
|---|---|---|---|---|
| IQ Decrement | hair, blood | infants and toddlers | higher hair Mn concentrations are associated with lower IQ scores; blood biomarkers give inconsistent findings |
[299] |
| Cognitive Functions | blood, hair, air | perinatal and childhood exposure (38 children from USA (near the Ohio River) | Mn exposure has negative impacts on cognition and behavior | [300] |
| umbilical cord serum | 933 mother–newborn pairs in Shanghai, China | above 5 μg L−1 in three-day-olds showed cognitive deficits in NBNA test | [301] | |
| blood | 6 to 12 months, 448 children born in Mexico City |
U-shaped association between Mn level and mental development scores on the BSID | [302] | |
| cord blood | 2-year-old children in Taiwan (230 pairs) | Mn level was associated with decrements in cognitive and language subscales of CDIIT | [303] | |
| Intellectual Ability | blood and hair | children aged 7–9 years, (n = 404) from Marietta and Cambridge, Ohio |
both low and high Mn concentrations in blood and hair were negatively associated with the total IQ scores | [23] |
| blood | children 8–11 years, 1089 children living in in South Korea | high Mn is associated with lower scores in thinking, reading, calculations, and LQ in the LDES and a higher commission error in the CPT; low Mn is associated with lower color scores in the Stroop test | [304] | |
| hair | children aged 14–45 months (n = 60) from Pennsylvania, USA | no evidence of an association between Mn concentrations and BSID scores in a region of low-level Mn exposure | [305] | |
| blood, drinking water |
prenatal and early childhood (2–3 year old), 524 children from the Sirajdikhan and Pabna Districts of Bangladesh | Mn content in water was associated with fine motor scores in an inverse U-relationship, the adverse effects of Mn was observed in the case of lower Pb level | [306] | |
| umbilical cord blood samples |
in utero exposure, 2 years of age (230) from Taiwan | Mn above the 75th percentile had a significant adverse association with the overall, cognitive, and language quotients of the CDIIT | [303] | |
| blood | adolescents aged 11–14 years (n = 299) from USA | Mn was not associated with cognitive and behavioral outcomes at the low exposure levels | [307] | |
| drinking water | from fetal life to school age (5, 10 years), 1265 children in rural Bangladesh | none of the Mn exposures was associated with the children’s cognitive abilities; prenatal Mn exposure was positively associated with cognitive function in girls, boys were unaffected | [308] | |
| Executive Function | blood, hair, drinking water |
children aged 6–12 years old (n = 63) from Brasil | blood Mn was associated with visual attention, negatively associated with visual perception and phonological awareness; hair Mn was inversely associated with working memory; Mn from drinking water associated with inhibition of written language and executive functions | [309] |
| hair | 7- and 12-year-old children (n = 70) living near a ferromanganese alloy plant | airborne Mn exposure may be associated with lower IQ and neuropsychological performance in tests of executive function of inhibition responses, strategic visual formation, and verbal working memory in TAVIS-3R, WCST, WISC-III Digit Span subtest and Corsi Block | [109] | |
| Memory | hair and blood | children aged 7–11 years, 174 children living in the Molango State of Mexico | Mn levels showed a negative association with the CAVLT, WRAML scores | [108] |
| Academic Achievement | drinking water | children aged 8–11 years, 840 children living in Araihazar, Bangladesh | no significant relation was observed | [310] |
| Effects on Motor Functions | drinking water | children aged 20–40 months, 524 children, in the Sirajdikhan and Pabna Districts of Bangladesh | Mn < 400 μg/L, Mn is beneficial to fine motor development, whereas at Mn > 400 μg/L, Mn exposure is detrimental for motor function | [306] |
| blood | children ages 7–9 years, 55 children residing in Marietta, Ohio, USA | Mn exposure was significantly associated with poor postural balance | [298] | |
| hair, blood | 7 and 11 years old, 195 children (100 exposed and 95 unexposed) from Mexico | negative association of Mn exposure on motor speed and coordination was shown | [311] | |
| Behavior | blood | children/adolescent | association between early life exposure to Mn and children/adolescent behavior | [312] |
| blood | 5–15 years, 92 children from rom Al Ain Educational Zone, UAE | Mn was significantly associated with ADHD | [313] | |
| prenatal and postnatal enamel regions of deciduous teeth | 84 (aged 9–14 years) Caucasian children |
no significant differences in Mn level for children with ASDs compared with TD children, children with ASDs have slightly lower Mn levels, no significant differences between children with HDB and TD children | [314] | |
| drinking water | 8–11 years (201 children) in Bangladesh |
positive dose–response relationship between Mn level and CBCL-TRF total scores | [315] |
Abbreviations: Intelligence quotient (IQ); the Learning Disability Evaluation Scale (LDES); the Child Behavior Checklist (CBCL); continuous performance test (CPT); the learning quotient (LQ); the Bayley Scales of Infant Development III (BSID); the Comprehensive Developmental Inventory for Infants and Toddlers (CDIIT); The Wechsler Intelligence Scale for Children (WISC); the Conners–Wells’ Adolescent Self-Report Scale Long Form (CASS:L); the Strengths and Difficulties Questionnaire (SDQ); Test of Visual Attention (TAVIS-3R); cognitive flexibility (WCST); verbal and visual working memory (WISC-III Digit Span subtest and Corsi Block); the Neonatal Behavioral Neurological Assessment (NBNA); Bayley Scales of Infant Development (BSID); high levels of disruptive behavior (HDB), typically developing (TD) children; the standardized Child Behavior Checklist-Teacher’s Report Form (CBCL-TRF).