Table 3:
The mean (95% CI) of the concentration of heavy metals mg/kg in classroom dust samples in various countries
| Heavy metal (mg/kg) | Hong Kong | Malaysia | China | Iran | South Africa | Nigeria | Mexico | Ghana |
|---|---|---|---|---|---|---|---|---|
| Arsenic | NR | NR | 13.7 (12.4–14.9) | 2.8 (2.2–3.4) | 1.6 (1.4–1.4) | 2.0 (1.6–2.2) | NR | NR |
| Barium | NR | 30.9 (20.8–40.9) | 979.8 (962.6–997.0) | NR | NR | 59.9 (57.8–61.9) | 56.6 (52.2–61.0) | NR |
| Cadmium | 8.5 (7.7–9.2) | 2.7 (1.8–7.2) | 0.2 (0.2–0.2) | 1.0 (0.9–1.2) | 0.7 (0.5–0.9) | 4.31 (3.9–12.6) | 4.2 (4.0–4.4) | NR |
| Cobalt | NR | NR | 43.4 (40.9–45.8) | 6.4 (6.2–6.5) | 5.9 (5.8–6.1) | 21.9 (19.2–24.6) | 2.2 (2.1–2.4) | 0.576 (1.1–2.2) |
| Chromium | NR | 14.4 (9.5–19.3) | 123.2 (52.4–194.1) | NR | 49.6 (32.4–6.8) | 26.2 (4.5–56.8) | 11.2 (10.9–11.5) | 381.3 (258.3–504.3) |
| Copper | 247.4 (239.5–255.2) | 77.4 (46.1–200.9) | 57.6 (22.9–92.2) | 40.0 (32.2–47.8) | NR | 40.9 (24.4–57.3) | 26.3 (22.6–30.0) | NR |
| Iron | NR | 4027.8 (3213.4–4842.1) | NR | 16945.5 (-) | NR | 13.7 (11.3–16.1) | NR | NR |
| Lead | 99.1 (194.6–205.3) | 162.4 (28.2–353.0) | 135.2 (34.4–236.1) | 258.8 (242.4–275.2) | 50.9 (49.8–52.0) | 25.7 (22.1–29.4) | 36.2 (35.2–37.1) | 4.8 (3.9–5.7) |
| Manganese | 224.3 (219.4–229.2) | 121.0 (112.3–129.7) | 561.6 (554.7–568.5) | 288.9 (279.3–298.4) | NR | 254.0 (248.5–259.5) | NR | NR |
| Nickel | NR | 28.5 (9.7–66.6) | 31.8 (23.7–39.8) | 50.1 (42.3–57.8) | 21.2 (20.4–21.9) | 12.7 (9.2–16.2) | 4.7 (4.0–5.4) | NR |
| Zinc | 2293.5 (2004.0–2582.9) | 261.2 (192.3–714.7) | 342.2 (59.5–624.9) | 258.8 (185.8–331.8) | 186.1 171.5–200.7) | 121.0 (87.5–154.4) | 387.9 (325.1450.9) | NR |
NR=no reported