**1.1 Colorectal cancer is an ancient disease**

*Homo sapiens* and other species have suffered from cancer since ancient times. However, while cancer incidences in other animals are very low, human's internal organs tend to be exposed to a lot of risk factors which can develop into cancer [1, 2]. Therefore, the management of risk factors, at community and household levels, becomes the focus in environmental health and oncology.

Both the incidence and mortality rate of all types of cancer in humans have been increasing over time. Determining etiology and causality is difficult and research findings are inconsistent among populations, which lead us to the question of whether scientists' observation was incorrect or risk factors of cancer are different in different populations. Although an estimated 80% of cancer cases, in general, and 98% of colorectal cancer cases, in particular, were associated with environmental factors [3], it is uncertain to determine what the situation will be in a defined population.
