Selenide ions are being increasingly being used in photoelectrochemical cell applications (Lewis, 1995). Selenium compounds are also found in internal combustion exhaust, and have been positively associated with increased mortality rates in five of six American cities surveyed by (Topeka, Kansas was the exception; the other cities surveyed were Boston, St. Louis, Knoxville, Madison, and Steubenville) (Dockery, Laden and Schwartz, 2000). The combustion of coal combustion is responsible for between 62% (Medical and Biological Effects of Environmental Pollutants- Selenium, 1976) and 85% (Eimutis, Quill & Rinaldi, 1978) of harmful selenium emissions in the United States. Furthermore, in combination with oxygen, selenium forms selenium dioxide, SeO2; the reaction of this oxide with water results in selenious acid, H2SeO3. Selenium also forms a variety of compounds in which the selenium atom bonds to both an oxygen and a halogen atom resulting in compounds such as selenium (VI) oxychloride, SeO2Cl2, which is an exceedingly potent solvent. Finally, the most important commercial compound formed from selenium is selenic acid, H2SeO4; this acid is as strong as sulfuric acid and more easily reduced (Selenium, 2004).

c. Summary of Industrial Hygiene Concerns. Selenium is a human health problem rather than a wildlife problem (Dunning, 1993). To date, though, researchers are uncertain about how selenium works in humans (Harvitz, 1997). One theory that has been advanced maintains that selenium in someway modifies the metabolism of carcinogens by detoxifying them so they have no opportunity to harm DNA; another theory suggests that selenium may help damaged cells "commit suicide," a process termed apoptosis. "This process might have the effect of reducing genetic mutations and ridding the body of precancerous cells" (Harvitz, 1997, p. 45). Still another theory maintains that selenium somehow control cancer incidence by increasing the body's own immune defenses. Critics, though, have argued that cancers caused the low levels of selenium found in the blood of patients, not the other way around. Furthermore, scientists have not eliminated the possibility that there might be some unknown factor that prevents cancer and promotes higher blood-selenium levels. "Unfortunately," as one researcher put it, epidemiological studies so far conducted have only been able to establish correlations, not causations" (Harvitz, 1997, p. 45).

d. Recommendations to Management to Reduce the Risk to Workers. Based on the foregoing,...

(2003) recommend the use of microalgae for remediation purposes.