Exposure to toxic chemical elements (Pb, Cd, and Hg) and its association with sustained high blood pressure among secondary school attending adolescents in Northwestern Tanzania

Lead (Pb), cadmium (Cd), and mercury (Hg) are common pollutants in low- and middle-income countries and are among the WHO's 10 toxic chemical elements of major public health concern. Adolescents may be at higher risk of exposure to toxic elements due to patterns of their behavior. We conducted a cross-sectional study to assess the burden and risk factors for exposure to Pb, Cd, and Hg, and their association with high BP among school-attending adolescents in Mwanza City, Tanzania. A WHO STEPs instrument was used to collect data on socio-demographic and behaviors risks for high BP. Standard procedures were followed to collect anthropometric, BP measurements, and dried blood spot (DBS) samples. We assessed total composition of Pb, Cd, and Hg of the DBS samples using inductively coupled plasma mass spectrometry. We used linear and logistic regressions to assess risks for exposure and association with sustained high BP respectively. We enrolled 500 adolescents with a median age of 14 years from 3 randomly selected public schools. We found high prevalence of exposure to high blood levels of; Pb (47.7 %), Cd (17.8 %), and Hg (9.8 %). The median, interquartile range (IQR) blood levels for Pb, Cd and Hg were 4.74 (2.16-8.36) μg/dL, 0.03 (0.00-0.32) μg/dL, and 0.31 (0.10-0.74) μg/dL respectively. Exposure was associated with being younger, and male (for Pb); having stunted growth (for Cd); and being older, female, and having ever drank alcohol (for Hg). Higher blood levels of Pb were associated with sustained high BP.