Points of time, investigated mediums, methods of analysis, and reporting of results of metal ion measurement in included epidemiological studies.

Studies were summarized due to multiple reporting of identical patient population.
2: Incl. all kinds of metal ion measurement in urin, e.g. 12- or 24 h urine.
3: AAS  =  All procedures of atomic absorption spectrometry.
4: ICP-MS  =  all procedures of inductively coupled plasma mass spectrometry.
n. r.  =  Not reported.
SD: Standard deviation; SEM: Standard error of the mean; IQR: Interquartile range.