SHORT RESEARCH AND DISCUSSION ARTICLE A possible role of biogenic silica in esophageal cancer in North China? Changhong Lian 1 & Xinxin Zuo 2 & Linwei Tian 3 Received: 14 November 2018 /Accepted: 22 January 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Certain areas in North China have the highest incidence of esophageal squamous cell carcinoma (ESCC) in the world, which has not seen convincing explanation by any risk factor yet. Biogenic silica in millet bran was linked to ESCC in the early 1980s but the hypothesis was largely dismissed because of the lack of geographic correlation between millet consumption and ESCC. Later epidemiological studies disclosed the linkage of wheat consumption in North China to ESCC instead. Now, we hypothesize silica phytoliths (silicified bodies that have definite shapes) from wheat chaff are a major etiologic factor of ESCC in this region. This hypothesis is supported by the potentially high abundance of silica phytoliths on the bracts of wheat (Triticum aestivum) in North China due to favorable Si-accumulation genotype, arid climate, and siallitic soil with bioavailable Si. These silica phytoliths can contaminate wheat flour and cause repeated local injuries in the esophagus and stimulate proliferation by providing anchorage. Keywords Environmental geochemistry . Esophageal squamous cell carcinoma (ESCC) . Biogenic silica . Wheat chaff . Silica phytolith . Siallitic soil . Aridity Some especially high incidence of esophageal cancer in the world are seen in the BCentral Asian Esophageal Cancer Belt^ extending from Iran and Afghanistan to China along the Silk Road, where esophageal squamous cell carcinoma (ESCC) is the predominant histological type (Craddock 1993). The most studied places on this belt are the three North China provinces of Henan, Hebei, and Shanxi, bordering on the Taihang Mountain range. Certain areas in this region have the highest age-standardized incidence rates of esophageal cancer in the world, exceeding 100 per 100,000 population (Lin et al. 2017). Despite decades of research and intervention programs, the epidemic of ESCC in this region has not seen convincing explanation by any risk factor yet (Lin et al. 2017) and the incidence has not seen a substantial decrease (He and Shao 2011). There might be some unknown risk factors not under control and the lingering high incidence of ESCC in North China calls for new etiological hypotheses. Previously explored risk factors of ESCC included alcohol and tobacco, pickled vegetables and nitrosamines, thermally hot food, vitamin and mineral deficiencies, and silica fibers from millet bran (Craddock 1993). Alcohol and tobacco were not found to be important etiologic factors according to case- control studies in North China (Li et al. 1989). The researchers failed to detect nitrosamine-DNA adducts in human esopha- gus tissues (Kamangar et al. 2009). Comparative surveys in high- and low-incidence areas and laboratory investigations did not support the linkage between thermally hot meals and ESCC (McCormack et al. 2017). The micronutrient hypothe- sis of the ESCC etiology was not supported by the two large chemoprevention trials: the Linxian Dysplasia Trial on a com- bination of 26 vitamins and minerals and the Linxian General Population Trial (Kamangar et al. 2009). Overall mortality or cancer incidence was not reduced by the nutritional interven- tion, either (Wang et al. 2013). Dr. C. H. O’Neill (Imperial Cancer Research Fund, London, UK) first reported the linkage between biogenic silica fibers in millet bran and ESCC development in North China (O’Neill et al. 1982). Sharply pointed silica fragments were detected in the esophagus of the ESCC patients. These silica fibers lodged in the esophageal tumors and throughout the depth of the mucosa. The findings of O’Neill was challenged by Rensburg (1982) for Responsible editor: Philippe Garrigues * Linwei Tian linweit@hku.hk 1 Department of Surgical Oncology, Heping Hospital, Changzhi Medical College, Changzhi, China 2 State Key Laboratory for Subtropical Mountain Ecology, College of Geogrophical Sciences, Fujian Normal University, Fuzhou, China 3 School of Public Health, The University of Hong Kong, 7 Sassoon Road, Hong Kong, SAR, China Environmental Science and Pollution Research https://doi.org/10.1007/s11356-019-04332-w