The pathways of impact of the environment on the human body evidently are the systems that are exposed to hazardous materials, covering the external skin, and the internal respiratory and alimentary systems, each with an array of organs and functions, and with an ultimate bearing on the structures and organs of the body as a whole. While many ailments like asthma and allergies are known to be environment linked, cancer is the most significant in the environmental health profile. Tobacco is a known cause of cancer of the lungs, bladder, mouth, pharynx, pancreas, stomach, larynx, esophagus and possibly colon. In addition to tobacco use, certain chemicals can also cause cancer such as asbestos, benzene, vinyl chloride, arsenic, aflatoxin, DDT, formaldehyde and ionizing radiation (IR) such as x-rays, and radon have also been proven to cause cancer in humans. While tobacco and other environmental toxins are the causes of cancer, all smokers or those exposed to environmental hazards do not get cancer, indicating the importance of genetic alterations that occur in the DNA. Alterations in the sequences of certain genes, which are inherited, are equally responsible for carcinogenesis. A combination of tobacco exposure and genetic alterations will increase the risk for malignant transformation of normal cells. Our studies also revealed an increased correlation between tobacco use and cancer incidence. The fishermen in the coastal area of the Thiruvananthapuram city are regularly using tobacco (mostly chewing) when they are occupied with fishing and an increased incidence of oral cancer is also observed in this area. Another important observation is that in some families blood relations in two or more generations are affected by this deadly disease indicating the gene environment interaction. Environmental Cancer – An assay The environment provides humans with essential life support systems, which is comprised of, air, water and land, but it also subjects man to a variety of hazards, which may jeapordize his health. If health is ‘a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity’ (WHO) it represents a balanced relationship of the body and mind and complete adjustment to the total environment. Disease, on the other hand, is maladjustment or maladaptation in an environment, a reaction for the worse between man and hazards or adverse influences in his external environment. The response of the individual to these influences is conditioned by his genetic make-up or internal environment. Environmental pollution may be described as the unfavorable alteration of our surroundings and occurs mainly from the action of man. Environmental pollution takes place through changes in energy patterns, radiation levels, chemical and physical constitutions and abundances of organisms. Pollution includes the release of materials into the atmosphere which make the air unsuitable for breathing, harm the quality of water or soil, and release substances which damage the health of human beings, plants and animals. Though the other environmental pollutants, odour and noise only initiate or disturb, they can also sometimes be a danger to health. The effects of pollution to our biosphere are numerous and are increasing alarmingly. The pathways of impact of the environment in the human body evidently are the systems that are exposed to hazardous materials, covering the external skin, and the internal respiratory and alimentary systems, each with an array of organs and functions, and with an ultimate bearing on the structures and organs of the body as a whole. Biological Aspects of Chemical Carcinogenesis Carcinogenesis is a multiple step process. One of the characteristics of chemical or physical carcinogenesis is the usually extended period of time (latent period) between contact with the carcinogen and the appearance of a tumor. The latent periods of occupational cancers may extend from one to several years and commonly to several decades. Initiation and promotion are two stages in the development of tumors. Initiation is caused by chemical, physical, or biological agents, which irreversibly and heritably alter the cell genome. The mechanism of promotion is not well understood. There are many kinds of promoting agents with diverse molecular structures: phorbol esters, estrogen, prolactin, other endogenous hormones, drugs, and others. These changes trigger cell proliferation, an apparently necessary process in the "fixation" or expression of tumor initiation. Tumor promotion as studied in the animal model of skin carcinogenesis results mainly in the formation of papillomas and occasionally in the progression of papillomas to carcinomas. Progression, the third definable stage of neoplastic development, is separable from promotional stage. Furthermore, following the initiation-promotion stages of induction of skin carcinogenesis, a high incidence of carcinomas can be produced by subsequent applications of a different initiating agent, suggesting a second event ("second hit") in the induction of carcinomas. Molecular genetic mechanisms are implicated in tumor progression, leading to chromosomal rearrangements or mutations that activate proto-oncogenes. Thus, it appears that of the three stages of carcinogenesis initiation, promotion, and progression initiation, most certainly, and progression, most likely, involve molecular genetic changes. The Effects of the Environment on Carcinogenesis The environment in which we live can be considered as having three fundamental sets of components: Physical (energy of one form or another), Chemical (matter i.e. substances whether natural or man-made), Biological (living things). Hazards can present themselves to us in various media e.g. air, water and soil. The influence they can exert on human health is very complex and may be modulated by our genetic make up, psychological factors and by the perceptions of the risks that they present. The cause and development of nearly every human disease is in some way related to environmental factors. Diet and nutrition, infectious agents, toxic chemicals, physical factors and physiological stress all play a role in the onset or progress of human diseases.