Previous studies have identified genetic factors and Epstein-Barr virus underlying nasopharyngeal carcinoma. A hypothesis postulated that the local buildup of HCl, mediated by hydrogen bond donors and acceptors and basic amino acids, causes cancer. Nasopharyngeal carcinoma incidences are high in the humid southern coastal China, Southeast Asia, and Mediterranean regions, but not in the noncoastal and nonhumid southern Yunnan Province, China, and nonhumid Central China. The nearly saturated humidity in the Huinan period in Guangdong can trigger the expression of proteins with extensive hydrogen bonding to protons, augmenting the formation of HCl that is mutagenic. Given that the Epstein-Barr virus carries high content of hydrogen bond donors and acceptors, the moist environment in the nasal cavity may enable the virus to colonize the site, compounding pertinent investigations as both virus and high humidity are likely to trigger carcinogenesis. Therefore, the phenomena of exceptionally high humidity in regions with high nasopharyngeal cancer rates warrant further investigations.

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