5.1.3. Thai Population

Even though the environmental exposure of the general population in Thailand to Cd and Pb is low [293], a Bangkok study has shown that even a urinary Cd excretion rate (ECd) as low as 0.38 μg/<sup>L</sup> (0.44 μg/g creatinine) was associated with a decrease in eGFR [12]. The risk of a decrease in eGFR was 2.9-fold higher in those who had ECd in the highest quartile. Likewise, in those with [Pb]u in the highest quartile, the risk of eGFR decrease was 2.3-fold higher than those in the lowest quartile of [Pb]u [12]. Of note, a positive association between eGFR levels and serum ferritin in men suggested a protective e ffect of adequate body iron status. Women may be more predisposed to absorption of ingested Cd and Pb because of their lower levels of body iron stores [12].

In a Cd-polluted region of Thailand, more than half (66%) of the residents had elevated Cd body burdens, reflected by ECd ≥ 2 μg/g creatinine, and the prevalence of CKD was 16.1% [294]. In a 5-year follow up study, a further decrease in eGFR was observed in residents who had high Cd exposure (ECd ≥ 5 μg/g creatinine) [229]. These findings sugges<sup>t</sup> that nephron loss associated with high Cd exposure and increasing kidney dysfunction continues even when the consumption of Cd-contaminated rice is reduced [229]. Other studies have reported an even greater e ffect of Cd on eGFR in women who had hypertension [51,52], as has been noted in the U.S. population study [46].
