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Volatile Organic Chemicals
Volatile Organic Chemicals (VOCs) are synthetic organic compounds that vaporize at relatively low temperatures (normal room temperature, for example). They are used in many solvents including benzene, produced by petroleum refining; dichlorobenzene, used in the production of pesticides and as a solvent; and methylene chloride, used in manufacturing cleaners. VOCs pose a possible health risk because a number of them are known carcinogens or probable carcinogens (cancer causing).

Radioactivity
Radioactivity is given off by radiological contaminants like radium, plutonium, uranium and radon. It occurs in water due to natural radioactive mineral deposits, as well as, fall-out from nuclear detonations, and from various medical/scientific research and industrial processes. It is important to monitor for radioactivity in drinking water because excessive levels may increase the risk of cancer.

Synthetic Organic Chemicals
Synthetic Organic Chemicals (SOCs) are man-made organic chemicals and have no natural source in the environment. Testing for SOCs in our potable water system is a prudent way to analyze for any industrial sources of contamination. The SOCs of interest include several herbicides, insecticides and pesticides. Two examples are: glyphosate, used in broad-spectrum herbicides and alachlor, an herbicide used primarily on corn and soybeans. The Agency tested for 32 regulated and 10 unregulated SOCs in 102 groundwater sources plus 4 surface water sources. The results showed that the contaminant levels were well-below the USEPA-established standards for drinking water, with the exception of one well (F-8). In this instance, the annual running average for Ethylene Dibromide (EDB) exceeded the USEPA Maximum Contaminant Level (MCL) by a factor of 1.6. EDB is a health concern at certain levels of exposure. This organic chemical has several commercial uses and was once commonly used as a pesticide. When soil and climactic conditions are favorable, EDB may get into drinking water by runoff into surface water or by leaching into groundwater. This chemical has been shown to cause cancer in laboratory animals when the animals are exposed at high levels over their lifetimes. Chemicals that cause cancer in laboratory animals also may increase the risk of cancer in humans who are exposed over long periods of time. USEPA has set the drinking water standard for EDB at 0.00005 mg/l to reduce the risk of cancer or other health effects which have been observed in laboratory animals. To eliminate any possible health concerns , the Agency shut down well F-8, as of October 17, 1996, to protect the integrity of our public drinking water supply. Additional monitoring for EDB at well F-8 and nine other wells in the vicinity of F-8 is ongoing to ascertain that the water is consistently within Guam Primary Safe Drinking Water Regulations and USEPA standards. The Agency is in the process of obtaining the best available technology to remove this contaminant from our groundwater source and hopes to have this on line by the end of spring, 1997 or in early summer, 1997.

Inorganic Chemicals
Inorganic chemicals (IOCs) include such things as metals and salts (lead, iron, nitrate and sulfate, for example). IOCs in water are derived from natural geologic formations of the area, as well as, from numerous human activities. At low levels, many of these chemicals are essential for life and optimum health, but elevated concentrations may cause a variety of adverse health effects.