Environmental agent

A. de Bmin, Biochemical Toxicology of Environmental Agents, Elsevier Publishing Co., Amsterdam, 1976, p. 185. 

Total frequencies of environmental illness are difficult to measure. When causes can be identified, however, scientists observe that frequencies of occurrence of a particular illness vary directly with the severity and extent of exposure. Particularly frequent in the workplace are skin lesions from many different causes and pulmonary diseases related to the inhalation of various dusts, such as coal dust (black lung), cotton dust (brown lung), asbestos fibers (asbestosis), and silica dust (silicosis). Environmental agents can also cause biological effects without overt clinical illness (for example, chromosome damage from irradiation). 

The National Institute of Environmental Health Sciences (NIEHS) is the principal federal agency for biomedical research on the effects of chemical, physical, and biologic environmental agents on human health and well-being. ContactNAEiTS, PO Box 12233, 104 T.W. Alexander Drive, Research Triangle Park, NC 27709 Phone 919-541-3212. 

Immunologic Toxicity—The occurrence of adverse effects on the immune system that may result from exposure to environmental agents such as chemicals. 

Carcinogenicity of NDELA. Our special interest in NDELA as a constituent of tobacco products and as an environmental agent relates to the observation that this nitrosamine induces carcinoma of the liver as well as of the kidney in rats (21,22) and carcinoma of the nasal cavity and papillomas of the trachea in hamsters (23). Recently, Lijinsky reported that NDELA admini-... 

The process for assessing environmental health risks Is complex Information regarding 1) the environmental agent, 2) the pathways by which exposure occurs, and 3) the biologic effects observed after exposure must be assembled and simultaneously evaluated Incomplete knowledge or Inadequate methodology In any of these three areas can severely Inhibit accurate or useful estimates of health risk ... 

Even though exposure to environmental agents such as agricultural chemicals, pesticides, and radiation has been associated with leukemia, none of these agents is linked conclusively with the development of leukemia. An increased frequency of ALL is associated with higher socioeconomic status. It is postulated that less social contact in early infancy and thus a late exposure to some common infectious agents may have some impact.7 In most individual instances, there is no reasonable or obvious explanation for the development of leukemia. 

Synthetic polymers are best known for their insulating dielectric properties which have been exploited for numerous applications in both the electrical and electronic industries. It was found recently that some polymers can also be rendered conductive by an appropriate treatment, thus opening the way to a new field of applications of these materials (2, 3). Usually, electrical conductivity is obtained by doping a neutral polymer, rich in unsaturation, with donor or acceptor molecules. These polymers are rather difficult to synthesize, which makes them very expensive besides they are often sensitive to environmental agents, like oxygen or humidity, thus restricting their practical use to oxygen-free systems. 

Aluminum is the metal that forms a resilient, transparent surface layer of its oxide, A1203. This layer protects the metal from most corrosive environmental agents. 

Omenn, G.S. and A.G. Motulsky, "Eco-genetics genetic variation in susceptibility to environmental agents," In Cohen B.H., Lilienfeld A.M., and Huang P.C. (eds), Genetic Issues in Public Health and Medicine. Springfield, IL CC Thomas, pp. 83-111 (1978). 

This chapter reviewed current research pertaining to selected environmental agents and autoimmune diseases (Table 25.3). Other infectious agents (e.g., parvovirus, varicella), occupational exposures (e.g., mercury), dietary factors (dietary supplements, nutrients such as antioxidants, and specific proteins in wheat and other grains implicated in celiac disease), and stress have been the focus of additional research that was not included in this review. 

Environmental agents that influence microsomal reactions will influence hexachloroethane toxicity. The production of tetrachloroethene as a metabolite is increased by agents like phenobarbital that induce certain cytochrome P-450 isozymes (Nastainczyk et al. 1982a Thompson et al. 1984). Exposure to food material or other xenobiotics that influence the availability of mixed function oxidase enzymes and/or cofactors will change the reaction rate and end products of hexachloroethane metabolism and thus influence its toxicity. 

Indoor and outdoor exposure to many chemical substances (formaldehyde, asbestos, PVC, many metals, like Cr, As, Be, Ti, V, pesticides and nitrosoamines) can also spur the development of cancer. Here we can only state that the International Agency for Research of cancer has identified 60 environmental agents that can aggravate cancer for humans during exposure to polluted urban air (Misch, 1994). 

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