Tungsten is a transition metal found, along with chromium, molybdenum and seaborgium, in Group VI of the Periodic Table of elements. Since its discovery in the last quarter of 18th century, tungsten-based products have been in use in a wide range of applications stretching from daily household necessities to highly specialized components of modern science and technology. As new applications and uses are discovered continuously, interest on and demand for tungsten, already an essential commodity, are projected to increase steadily in the years to come. Unavoidably, as is the case with other natural materials and/or non-renewable resources, increased demand and use of tungsten will spawn (a) increased interactions with other materials and/or non-sustainable practices, (b) a greater number of possible entry points into the natural and human environment and (c) a higher probability of deliberate or accidental releases. Currently, the existing knowledge base does not provide clear information about the behavior of tungsten-based products in the environment. The toxicological profile of tungsten, including possible effects on living organisms and exposure pathways, remains rather sketchy, narrow and fragmentary. Regulation of tungsten, both in terms of environmental and occupational safety and health, is at present limited in comparison with other metals. This pattern of environmental obscurity has been unequivocally disrupted by the events of Fallon, Nevada and the possible implication of tungsten to an acute lymphocytic leukemia (ALL) cluster. Tungsten is now the focus of scrutiny as it currently occupies the top of 'to do' lists of various regulatory, health and environmental agencies. The occurrence of a childhood leukemia cluster in Fallon, Nevada prompted a wide investigation that involved several local, state and federal agencies led by the Centers of Disease Control (CDC). In essence, the objective of this investigation was to assess whether environmental causes were responsible for the cluster. The 16 reported leukemia cases within the time frame of 1997-2001, were well above the average for Nevada (3.0 cases/100,000 children/5 years). Several possible causes were proposed, such as jet fuel (JP-8) from a nearby military base or from a JP-8 pipeline running through the city, high levels of arsenic and other metals in the drinking water supplies, industrial pollution from a local tungsten smelting facility, and agrochemical contamination resulting from agricultural pesticide/fungicide use. Although the exact causes of leukemia are not well known, genetic and/or environmental factors may trigger the disease including ionizing and electromagnetic radiation, infectious and chemical agents. Physiologically, it exists as an ion in the body. (A3184).