The present study had a few limitations. We did not examine all
renal effect markers but selected to examine urinary excretion of
β2-microglobulin (one of the most validated markers for screening
of early cadmium nephrotoxicity), calcium, and total protein (late
renal effect). Given the cross-sectional nature of the survey, we
could not indicate a temporal sequence of the study variables and
renal effects might precede cadmium exposure in the children. We
did not include all possible factors affecting renal functions in the
analysis. This study using spot morning urine samples might have
a problem of more variability of renal marker values compared to
use of 24-h or first morning urine samples.