Health Risk in a Geographic Area of Thailand with Endemic Cadmium Contamination: Focus on Albuminuria

An increased level of cadmium (Cd) in food crops, especially rice is concerning because rice is a staple food for over half of the world’s population. In some regions, rice contributes to more than 50% of the total Cd intake. Low environmental exposure to Cd has been linked to an increase in albumin excretion to 30 mg/g creatinine, termed albuminuria, and a progressive reduction in the estimated glomerular filtration rate (eGFR) to below 60 mL/min/1.73 m(2), termed reduced eGFR. However, research into albuminuria in high exposure conditions is limited. Here, we applied benchmark dose (BMD) analysis to the relevant data recorded for the residents of a Cd contamination area and a low-exposure control area. We normalized the excretion rates of Cd (E(Cd)) and albumin (E(alb)) to creatinine clearance (C(cr)) as E(Cd)/C(cr) and E(alb)/C(cr) to correct for differences among subjects in the number of surviving nephrons. For the first time, we defined the excretion levels of Cd associated with clinically relevant adverse kidney health outcomes. E(alb)/C(cr) varied directly with E(Cd)/C(cr) (β = 0.239, p < 0.001), and age (β = 0.203, p < 0.001), while normotension was associated with lower E(alb)/C(cr) (β = −0.106, p = 0.009). E(Cd)/C(cr) values between 16.5 and 35.5 ng/L of the filtrate were associated with a 10% prevalence of albuminuria, while the E(Cd)/C(cr) value of 59 ng/L of the filtrate was associated with a 10% prevalence of reduced eGFR. Thus, increased albumin excretion and eGFR reduction appeared to occur at low body burdens, and they should form toxicity endpoints suitable for the calculation of health risk due to the Cd contamination of food chains.