Since some children′s families in the contaminated areas might
not highly be exposed to cadmium and some in the comparison
areas might have high exposure, we combined children of both
samples and used urinary cadmium levels, a good biomarker of
long-term cadmium exposure, to evaluate the cadmium effect on
renal function markers and blood pressure. Correlations of urinary
cadmium with renal function markers and blood pressure were
analyzed with Spearman′s rank correlation. To determine doseeffect
relationship, we tested the relation of renal function and
blood pressure across tertiles of urinary cadmium. For analysis, we
categorized each renal effect marker using two reference levels
(normal/average and clinically relevant levels) for healthy Thai or
general children of primary school age (ATSDR, 2012; Davis and
Avner, 2007; Vachvanichsanong et al., 2000; Vogt and Avner, 2007).
The levels in the analysis were β2-MG Z200 and Z300 μg/g
creatinine respectively, urinary calcium Z105 and Z200 mg/g
creatinine, and urinary total protein Z100 and Z200 mg/g
creatinine.