Association of dietary intake and urinary excretion of inorganic arsenic in the Japanese subjects

Quantitative relationship between intake of inorganic arsenic (iAs) and urinary excretion of iAs and its metabolite, methylarsonic acid (MMA), was investigated for 150 adult Japanese subjects. Duplicate diet was used for the determination of intake and first void of urine on the next day of duplicate diet sampling was used for urinary iAs + MMA determination. Speciation analysis of arsenic in diet and urine was carried out with liquid chromatography-inductively coupled plasma mass spectrometry. Geometric mean iAs intake of the subjects was 0.349 μg/kg/day and that of urinary iAs + MMA concentration was 5.20 ng As/mL (specific gravity (SG) corrected) or 4.05 ng As/mg creatinine (Cre). There was a significant positive correlation between iAs intake and urinary iAs + MMA concentration: the correlation coefficient between intake and Cre-corrected urinary concentration (r = 0.544) was greater than that between intake and SG-corrected concentration (r = 0.458). The regression equation of intake-excretion was: log₁₀[dailyintake]=0.451×log₁₀[creatininecorrectedurinaryiAs+MMA]+0.814. This equation has a practical value for converting urinary As levels, measured as a biomarker of exposure in epidemiologic study, to dietary intake levels in the future risk assessment.