tailieunhanh - Environmental Life Cycle Costing - Chapter 15 (end)

Ung thư là một nhóm các bệnh đặc trưng bởi sự tăng trưởng không kiểm soát được và lây lan của các tế bào bất thường. Thuật ngữ "khối u ác tính (ung thư) thường được sử dụng ở vị trí của ung thư trong cộng đồng khoa học y tế. Thông thường nhất, các khối u ác tính phát triển trong các cơ quan lớn, chẳng hạn như phổi, gan, dạ dày, ruột, da, ngực, hoặc tuyến tụy, nhưng họ cũng có thể phát triển ở môi, lưỡi, hoặc tinh hoàn hoặc buồng trứng. Ung thư cũng có thể. | CHAPTER 15 Environmental Cancer INTRODUCTION Cancer is any of a group of diseases characterized by uncontrolled growth and spread of abnormal cells. The term malignant neoplasm tumor is often used in place of cancer in the scientific or medical community. Most commonly malignant tumors develop in major organs such as the lungs liver stomach intestines skin breasts or pancreas but they may also develop in lips tongue or the testes or ovaries. Cancer may also develop in the blood cell-forming tissues of the bone marrow the leukemias and in the lymphatic system or bones. As noted earlier cancer incidence and mortality have increased dramatically over the last century. Researchers consider that there are two main reasons for this increase the aging of the population and an increase in pollution from carcinogens present in and released into the environment through human activities. Indeed nearly 30 of the total mortality in many industrialized countries is attributed to cancer. In the . cancer remains the number-two killer accounting for nearly one fourth of all deaths. Despite the recent decline in the mortality rate the total number of cancer deaths continues to rise as the elderly population increases. For example in the . the toll in 1980 was 416 509 in 1995 it was 538 455 1 and in 1999 it was estimated to be 564 One of the most common characteristics of the development of a neoplasm in an organism is the long period of time between the initial application of a carcinogenic cancer-causing agent or carcinogen and the appearance of a neoplasm. The latency period varies with the type of carcinogen its dosage and certain characteristics of the target cells within the host. In humans cancer may not be manifested until 10 or more years after an initial exposure to a particular carcinogen. 219 2001 by CRC Press LLC 220 ENVIRONMENTAL TOXICOLOGY Table Speculative Proportion of Cancer Deaths Attributed to Various Factors Factor or Class of Factors .