| Number | Metals | Country of study subjects | References |
| 1 | Mercury | Canada | Genuis et al., 2011 [20] | 2 | USA | Robinson and Skelly, 1983 [21] | 3 | USA | Sunderman 1978 [22] | 4 | USA | Lovejoy et al., 1973 [23] |
| 5 | Cadmium | Australia | Stauber and Florence, 1988 [24] | 6 | Australia | Stauber and Florence, 1987 [25] | 7 | USA | Robinson and Weiss, 1980 [26] | 8 | USA | Cohn and Emmett, 1978 [27] | 9 | Canada | Genuis et al., 2011 [20] | 10 | UK | Omokhodion and Howard, 1994 [28] |
| 11 | Arsenic | Canada | Genuis et al., 2011 [20] | 12 | Bangladesh | Yousuf et al., 2011 [29] |
| 13 | Lead | Australia | Lilley et al., 1988 [30] | 14 | Australia | Stauber and Florence, 1988 [24] | 15 | Australia | Stauber and Florence, 1987 [25] | 16 | Canada | Genuis et al., 2011 [20] | 17 | UK | Omokhodion and Crockford, 1991 [31] | 18 | UK | Omokhodion and Crockford, 1991 [32] | 19 | USA | Cohn and Emmett, 1978 [27] | 20 | USA |
Hohnadel et al., 1973 [33] | 21 | Tropics | Omokhodion and Howard, 1991 [34] | 22 | Russia |
Parpaleĭ et al., 1991 [35] | 23 | Germany | Haber et al., 1985 [36] |
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