Table 1.
Overview of examples of epidemiological studies investigating the association of toxic metals with ASD. The toxic metals discussed in this review are highlighted. Systematic reviews and meta-analyses are highlighted.
| Sample | Participants | Finding in ASD Participants | Reference |
|---|---|---|---|
| Hair | 32 autistic children and 32 controls (4.1 ± 0.8 years) | Pb↑, Cu↑, Hg↓, Zn↓ | [15] |
| Mercury intoxication-associated urinary porphyrins | 28 individuals with ASD | Hg ↑ | [17] |
| Hair | 18 children with ASD (3.5 ± 1.1 years) | Hg↑ levels significantly correlate with CARS1 scores | [19] |
| Urine | 129 individuals with ASD (14.1 ± 1.4 years) and 86 controls (14.7 ± 1.2 years) | Cd↑, Mn↑ significantly correlate with CARS 1 scores | [20] |
| Blood | 48 children with ASD (5.5 ± 2.1 years) | 19% had a Pb level of concern (greater than 0.1 μmol/L) | [21] |
| Hair | 40 ASD boys and 40 controls (4.2 ± 2.2 years) | Sb↔, U↑, As↔, Be↔, Hg↑, Cd↔, Pb↑, Al↔ | [22] |
| Hair | 1967 children with ASD | Zn↓, Mg↓, Al↑, Cd↑, Pb↑, Hg↑, As↑ | [23,24] |
| Blood, urine, hair | 17 ASD children (11.5 ± 3.2 years) and 20 controls (10.4 ± 3.2 years) | Hg↔, Pb↔, Al↔, Cd↔ | [25] |
| Teeth | 15 ASD children (6.1 ± 2.2 years) and 11 controls (7 ± 1.7 years) | Hg↑, Pb↔, Zn↔ | [26] |
| Hair, urine | 25 ASD children (5.3 ± 1.9 years) and 25 controls (6.3 ± 2.3 years) | Hair: of 39 elements: As↑, Cd↑, Ba↑, Ce↓, Hg↑, Pb↑, Zn↓, Mg↓ Urine: of 39 elements: Cd↓, Al↑, Ba↑, Ce↓, Hg↑, Pb↑, Cu↑ |
[27] |
| Blood erythrocytes | 83 ASD children (7.3 ± 3.7 years) and 89 controls (11.4 ± 2.2 years) | Hg ↑ | [28] |
| Mercury intoxication-associated urinary porphyrins | 106 ASD children (mean 6.4 years) and 12 controls (mean 7.4 years) | Hg ↑ | [29] |
| Hair | 65 ASD children (8.8 ± 0.5 years) and 80 controls (7.2 ± 0.7 years) | of 20 metals: Hg↑, Pb↑, As↑, Sb↑, Cd↑, Ca↓, Cu↓, Cr↓, Mn↓, Mg↓, Fe↓, Co↓, Se↑ | [30] |
| Hair | 27 ASD children (5.3 ± 1.5 years) and 27 controls (5.5 ± 1.4 years) | Pb↑, Al↑, Si↑, Mo↑, V↑, Cr↑, Cd↑, Co↑, Ni↑, B↑, Ba↑, Mg↑, Ca↓, Zn↓, Fe↑, Cu↓ | [31] |
| Hair | 30 ASD children (5.3 ± 1.6 years) and 30 controls (5.1 ± 1.5 years) | Ca↓, Pb↑, As↑ | [32] |
| 7 | 478 mother-child pairs | Gestational As↔, Cd↑, Pb↑, Mn↔, Hg↔ | [33] |
| Teeth | 80 ASD children and 113 controls (including twins) | Altered Zn-Cu cycles | [34] |
| Teeth | 20 ASD discordant twin pairs, 12 ASD concordant twin pairs, 44 Non-ASD twin pairs | Pb↑, Mn↓, Zn↓, Mn and Pb significantly correlate with ADOS-2 and SRS-2 scores 2 | [35] |
| Blood | 2473 children | Pb↑, at 7–8 years significantly correlate with ASSQ and SRS 3 | [36] |
| Hair | 175 ASD children and 211 controls (including twins) | Zn, Li, Cu dysregulation | [37] |
| Hair, blood, urine, teeth | Meta-analysis of 48 studies with (ASD/control) samples: Sb (181/185) As (561/583) Cd (628/645) Pb (1508/1424) Mn (598/656) Hg (2246/2120) Ni (271/305) |
As↔, Cd↔, Ni↔, Pb↑ (hair, blood, erythrocyte), Hg↑ (erythrocyte), Mn↔, Sb↑ (hair) | [38] |
| Hair, blood, urine | Meta-analysis of 18 studies for Al, 18 for Cd, and 23 for Hg with (ASD/control) samples: Al (1246/1199) Cd (1029/1030) Hg (1347/1348) |
Hg↑ (hair, blood, urine), Al↑ (hair, urine), Cd↓ (hair, urine) | [39] |
1 CARS: Childhood Autism Rating Scale. 2 ADOS-2: Autism Diagnostic Observation Schedule Second Edition, SRS-2: Social Responsiveness Scale Second Edition. 3 ASSQ: Autism Spectrum Screening Questionnaire, SRS: Social Responsiveness Scale.