Background: We assessed the association of groundwater chemicals with systolic blood
pressure (SBP) and diastolic blood pressure (DBP). Methods: Blood pressure data for ≥35-year-olds
were from the Bangladesh Demographic and Health Survey in 2011. Groundwater chemicals in
3534 well water samples from Bangladesh were measured by the British Geological Survey (BGS)
in 1998–1999. Participants who reported groundwater as their primary source of drinking water
were assigned chemical measures from the nearest BGS well. Survey-adjusted linear regression
methods were used to assess the association of each groundwater chemical with the log-transformed
blood pressure of the participants. Models were adjusted for age, sex, body mass index, smoking
status, geographical region, household wealth, rural or urban residence, and educational attainment,
and further adjusted for all other groundwater chemicals. Results: One standard deviation (SD)
increase in groundwater magnesium was associated with a 0.992 (95% confidence interval (CI): 0.986,
0.998) geometric mean ratio (GMR) of SBP and a 0.991 (95% CI: 0.985, 0.996) GMR of DBP when
adjusted for covariates except groundwater chemicals. When additionally adjusted for groundwater
chemicals, one SD increase in groundwater magnesium was associated with a 0.984 (95% CI: 0.972,
0.997) GMR of SBP and a 0.990 (95% CI: 0.979, 1.000) GMR of DBP. However, associations were
attenuated following Bonferroni-correction for multiple chemical comparisons in the full-adjusted
model. Groundwater concentrations of calcium, potassium, silicon, sulfate, barium, zinc, manganese,
and iron were not associated with SBP or DBP in the full-adjusted models. Conclusions: Groundwater
magnesium had a weak association with lower SBP and DBP of the participants