Approximately 73,000,000 Bangladeshis are drinking well water with arsenic (As) concentrations greater than or equal to the 50 micrograms per liter (μg/L) national standard. Over 900,000 excess deaths are expected from lung, bladder, kidney, and skin cancers caused by chronic arsenic poisoning from drinking this well water. As sea levels continue to rise due to climate change and the annual floods and cyclones in Bangladesh increase in area and duration, reduction and the salt effect will increase the release of arsenic into Bangladesh’s drinking well water. This is a significant threat to public health. As the concentration of dissolved oxygen (DO; O2(aq)) decreases, the concentration of arsenic increases (p-value = 0.0028). Relatedly, as the oxidation-reduction potential (ORP) decreases, the concentration of arsenic increases (p-value = 1.3 × 10−5). These results suggest that arsenic is released from sediments into Bangladesh’s drinking well drinking water by reduction. As the specific conductance (SC) increases, the concentration of arsenic increases (p-value = 0.023). This result suggests that arsenic is also released from sediments into this water by the salt effect. Reduction and the salt effect will likely release arsenic and other toxic ions into coastal aquifers worldwide.