Mercury is a naturally occurring metal that has several forms. The metallic mercury is a shiny, silver-white, odorless liquid. If heated, it is a colorless, odorless gas. Mercury combines with other elements to form inorganic mercury compounds. Mercury also combines with carbon to make organic mercury compounds. The most common form of organic mercury, methyl mercury, is produced mainly by microscopic organisms in the water and soil. Organic mercury can accumulate in microorganisms, water plants, and eventually sport fish tissue. It is a cause of consumption warnings for sport fish from some inland lakes and rivers, especially in the northern United States.

Lead has a tendency to be complexed and precipitated by a large number of substances. When released to land, lead binds to soils and does not migrate to ground water. In water, it binds to sediments, and it does not accumulate in fish. This is why it is seldom found in ground waters or natural waters in more than trace quantities, under 10 g/L. However, source waters that contain lead are an indication that intrusions from industrial, mine, or smelter wastes may have occurred. Typically, the source water contains less lead than the water at the “point-of-use”. Studies indicate that nearly all the lead in users’ tap water does not come from the primary water source or from the municipal treatment plant, but is a result of corrosion of lead containing materials that contact water after leaving the treatment plant. Lead can enter the home drinking water by leaching from lead service connections, from lead solder used in copper piping, and from brass fixtures.

The presence of arsenic (As) in nature is due mainly to natural deposits of metalloids in the earth’s crust and usually in ancient rock formations. Arsenic enters ground water through erosion or from manmade sources such as wood preservative, petroleum production, semi-conductor manufacture or due to misuse of animal feed additives and arsenic-containing pesticides (e.g. Paris green). Since soluble arsenic is tasteless and colorless, a chemical water analysis is necessary to detect its presence. Higher levels of arsenic tend to be found more in ground water sources than in surface water sources (lakes and rivers) of drinking water. Compared to the rest of the United States, the western states have more water systems with arsenic levels greater than 10 micrograms per liter (µg/L, ppb).

Copper is a metallic element that is essential to human health. Too little is unhealthy and too much can lead to copper poisoning. The body cannot synthesize copper so the human diet must supply regular amounts for absorption. The daily requirement is about 2 mg of copper intake per day to maintain a balance of 75-100mg in the adult body2. In the UK, it is now recommended that the daily intake should range from 0.4 mg/day for 1-3 year old children to 1.2 mg/day for adults4. Maximum intake of copper should not exceed 12 mg/day for adult males and 10 mg/day for adult females4. Recent surveys show only 25% of the US population consume the amount of copper per day estimated to be adequate by the US Food and Nutritional Board of the National Academy of Sciences. Ironically, the US Centers for Disease Control (CDC) has reported cases of copper poisoning.

Siltation is water pollution caused by particulate material, with a particle size dominated by silt or clay. It refers both to the increased concentration of suspended sediments and to the increased accumulation (temporary or permanent) of fine sediments on bottoms where they are undesirable. While the sediment in transport is in suspension, it acts as a pollutant for those who require clean water, such as for cooling or in industrial processes, and it includes aquatic life that are sensitive to suspended material in the water.