Monitoring of cadmium toxicity in a Thai population with high-level environmental exposure

This study evaluated the utility of single and combined measurements of cadmium toxicity markers for surveillance purposes, using a sample of 224 individuals, 30–87 years of age, who were residents of cadmium polluted area in Mae Sot District, Tak Province, Thailand. Urinary cadmium levels excreted by them ranged between 1 and 58 μg/g creatinine with geometric mean of 8.2 μg/g creatinine which was 16-fold greater than the average for the general Thai population of 0.5 μg/g creatinine. The urinary markers evaluated were total protein, albumin, N-acetyl-β-d-glucosaminidase (NAG), lysozyme, β2-microglobulin (β2-MG) and α1-microblobulin (α1-MG). Among these markers, only NAG showed a positive correlation with urinary cadmium in both male and female subjects with and without disease (r = 0.43–0.71). Further, the prevalence rates for urinary NAG above 8 units/g creatinine (NAG-uria) increased with exposure levels in a dose dependent manner (p = 0.05) among subjects with disease. In contrast, however, increased prevalence of β2-MG above 0.4 mg/g creatinine (β2-MG-uria) was associated with cadmium above 5 μg/g creatinine only in those without disease (POR = 10.6 and 7.8 for 6–10 and >10 μg/g creatinine). Prevalence rates for abnormal excretion of all other markers, except albumin, were markedly increased among those having β2-MG-uria with and without disease (χ2-test, p ≤ 0.001–0.02). Thus, urinary β2-MG and NAG should be used together with urinary cadmium in the monitoring of renal toxicity in a population exposed to high-level cadmium coupled with high prevalence of chronic diseases.