The First Symposium on Nutrition, Environment and Cancer, Ankara, Turkey

Cancer has been known for millennia, but the understanding we have of its origins and causes are comparatively recent. Ancient Egyptians first recorded cancer as a disease some 4500 years ago. However, it wasn’t until the 18th century that observations on environmental cancers were made, as people started to look for a connection between certain environments, including working practices and human cancer incidence patterns. The idea emerged that the causes of cancer may be divided roughly into two broad categories: exogenous (environmental and occupational) and endogenous (something inherent in the person). While this has been a useful distinction, advances in genetics now seem to be blurring the boundary. The result is that cancer research has concentrated on the identification of environmental and occupational causes of human cancer. By the late 19th century the study of cancer tissues had revealed that cancer cells were markedly different in biology and cell structures when compared with the normal cells in the surrounding tissue. During the 20th century, the research in cancer increased in an almost exponential fashion. Advances in genetics, biochemistry and molecular biology has begun to allow some insight into what was happening when a normal cell was changed into a cancerous one and often why it happened (oncogenesis). Cancer can take many forms and is usually named after the cell type fromwhich it is transformed. Once a cancer cell has arisen, clonal expansion without regard for the surrounding tissue, accounts for the clinical symptoms of the disease. As the tumour grows, continuous de-differentiation occurs and cells break away (metastases) to form new cancers at other sites in the body. It is this metastatic growth that accounts for the most of mortality from this disease. A few tumour types are so aggressive in their development that they kill the host before metastases even begins. One such cancer is mesothelioma, which is a cancer of the lining of the body cavity and named for its development from the mesothelium. Although these cancers had been known for a long time, only in the last 40–50 years have they been accepted as real mesothelial neoplasms, and not secondary tumours. In 1960, Wagner, Sleggs and Marchand described 33 cases of malignant pleural mesothelioma that they believed had developed through environmental exposure to crocidolite, or blue asbestos. Up to this time, human tumours, for which an external cause had been suggested, were believed to arise through heavy occupational exposure. That tumours could arise through specific environmental exposure meant that a very much larger population could be at risk.