he thought of contracting a difficult-to-diagnose and potentially fatal disease by drinking a glass of water is disturbing enough. Imagine how unsettling it must be, then, to contemplate the possibility of developing symptoms (see sidebar on page 457A) of such an illness six months or more after being occupationally or recreationally exposed to contaminated surface water or sediment, or possibly by drinking water from a contaminated source. Melioidosis (Whitmore's disease) is such a soil-and waterborne illness.Isolated cases of the illness have occurred in the Western Hemisphere in Brazil, Ecuador, Guyana, Haiti, Mexico, Panama, and Peru. A clustered outbreak of the disease caused by the bacterium Burkholderia pseudomallei occurred in Western Australia in 1997. Up to five confirmed cases occur annually among travelers and immigrants in the United States.
Prospects for halting it or even slowing its rate are bleak, but perhaps not hopeless.
Their sources, fate and transport, health effects, and relative toxicity are being studied intensively, but the exact mechanisms of their formation are not yet fully understood No community enjoys having national attention focused on it because of a contamination episode. But that is what happened in January to Times Beach, Mo., situated on the Meramec River, about 30 miles southwest of St. Louis. Electronic and print media carried the news-complete with photographs of "space-suited" technicians taking soil and water samples, while unprotected citizens looked on-that the environmental contaminant commonly known as dioxin might be present in the area. Reportedly, the largest concentration was found in roadway soil; it was well in excess of the one part per billion (ppb) "hazardous dose" level set by the national Centers for Disease Control.According to EPA, soil samples taken before the area was flooded in early January "indicated the presence of dioxin in roadway soil." Whatever dioxin may have been found is believed to have been contained in herbicides mixed with waste oil sprayed on the community's unpaved roads during the early 1970s. However, after the flood, Rita Lavelle, EPA assistant administrator for Solid Waste and Emergency Response, said that samples taken "from at ieast 20 surfaces in the garbage and debris showed no detectable dioxin." It is very likely that not everyone will agree with this assessment, and the Times Beach controversy will continue for some time to come.The chemical to which the media and EPA were referring is actually 2,3,7,8 -tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). Fears about this compound are understandable when one considers that its LD50-the dosage at which 50% of test animals die-can range as low as 0.6-2.0 Mg/kg of body weight for guinea pigs.To be sure, the sensitivity of laboratory animals to 2,3,7,8-TCDD is not uniform. The LD50 is given in the literature as 22-45 Mg/kg for rats and as about 280 Mg/kg for mice. Fred Hile-man of Monsanto Research Corpora-
Aquifers are fragile water resources whose properties are markedly different from those of surface water. They supply many human needs. Their protection is vital, so tight rules about monitoring them, and keeping contaminants out, are coming. ES&T's Julian Josephson surveys this situation Groundwater-about 50% of the U.S. population, or more than 110 million people, are dependent upon it for drinking, cooking, washing, industrial, agricultural, and many other uses.
Humic substancesBecause of known and perceived threats to safe water, interest in the fate and transport of humics and their reactions with metals, anions, and organics, as well as chlorine, is increasing sharply
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