This study aims at evaluating the suitability of adjusting urinary concentrations
of arsenic, or any other urinary biomarker, for variations in urine dilution by creatinine
and specific gravity in a malnourished population. We measured the concentrations
of metabolites of inorganic arsenic, creatinine and specific gravity in spot urine
samples collected from 1466 individuals, 5-88 years of age, in Matlab, rural Bangladesh,
where arsenic-contaminated drinking water and malnutrition are prevalent (about 30%
of the adults had body mass index (BMI) below 18.5 kg/m(2)). The urinary concentrations
of creatinine were low; on average 0.55 g/L in the adolescents and adults and about
0.35 g/L in the 5-12 years old children. Therefore, adjustment by creatinine gave
much higher numerical values for the urinary arsenic concentrations than did the corresponding
data expressed as microg/L, adjusted by specific gravity. As evaluated by multiple
regression analyses, urinary creatinine, adjusted by specific gravity, was more affected
by body size, age, gender and season than was specific gravity. Furthermore, urinary
creatinine was found to be significantly associated with urinary arsenic, which further
disqualifies the creatinine adjustment.