According to medical records, the incidence of cancer in the second half of the 20th century is nearly 10 times higher than that in the first half of the 20th century, becoming the first killer threatening human life
The average life expectancy of human beings is about 30 years at the beginning of the 20th century, 40 years in the middle of the 20th century, and about 65 years at present. The average life expectancy in developed countries with high incidence of cancer is generally more than 70 years.
 This shows that the global ecological imbalance caused by the rapid economic development marked by high technology in the second half of the 20th century is an important cause of cancer