A refractometer determined specific gravity of each sample (PAL-10S, Atago Inc.). UCd was measured at the Michigan Department of Community Health as part of the U.S. Centers for Disease Control (CDC) Laboratory Response Network Program. Briefly, urine samples were diluted 1:10 with a diluent composed of 2.0% nitric acid, internal standards and 0.05% Triton X; and Cd concentrations were determined using ICP-MS (DRCII, PerkinElmer, USA). The analytical accuracy using QMEQAS08U urinary standard reference material (Institut national de santé publique du Québec, INSPQ) was 101.1% (n = 8). All samples were above the analytical detection limit of 0.15 μg/L.