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Table 2 Characteristics of included studies, by researching regions

From: The trend of lead poisoning rate in Chinese population aged 0–18 years old: a meta-analysis

  Eastern zone18–50 Central zone51–56 Western zone57–68 National wide69–72
Number of studies 33 6 12 4
Published year
1990–2000 9 1 5 0
2001–2005 15 4 3 4
2006–2012 9 1 4 0
Sample size
<500 8 2 7 0
500–1499 15 3 3 0
1500–2999 8 1 1 0
≥3000 2 0 1 4