The current aquatic-life standard for iron is less than 1.0 mg/L based on toxic effects. (It is one of the few iron standards for which the standard is not calculated based on hardness.)
Learn more by visiting the Iron page in our Indoor Drinking Water Section.
Aluminum is one of the most abundant elements in the earth's crust and occurs in many rocks and ores, but never as a pure metal. The presence of aluminum ions in streams may result from industrial wastes but is more likely to come from the wash water of drinking water treatment plants. Many aluminum salts are readily soluble, however, there are some that are very insoluble. Those that are insoluble will not exist long in surface water, but will precipitate and settle. Waters containing high concentrations of dissolved aluminum can become toxic to aquatic life if the pH is lowered (as in acid rain). For water wells, we have seen elevated levels of aluminum in the well water in the following cases: movement of grout materials for geothermal or ground source heating and cooling systems, turbid waters (the aluminum is leached from sediment particles when the sample is preserved by adding acid), leaching from cooking materials (pots, pans, and some cups), leaching from piping caused by corrosion or microbiologically-induced corrosion, corrosion of a water heater, and very low pH waters. The highest level we have ever detected was 80 mg/L in a leachate from a coal spoil pile and in well water it was 8 mg/L, associated with corrosion and nuisance bacteria; the water was gray.
Surface water - 0.75 mg/L . The secondary drinking water standard set for aesthetic issues is 0.2 mg/L.
Learn more by visiting the Aluminum page in our Indoor Drinking Water Section.
Cadmium is a non-essential element which diminishes plant growth. It is considered to be a potential carcinogen. It also has been shown to have toxic effects on the kidneys and reproductive organs and to cause bone defects and high blood pressure.Cadmium is widely distributed in the environment at low concentrations. It can be found in fairly high concentrations in sewage sludge. Primary industrial uses for cadmium are plating, battery manufacture, pigments, and plastics.
The standard for domestic water supply is <0.01 mg/L. The allowable level for aquatic life is derived using a formula involving hardness. At a hardness of 100, a cadmium limit of 0.001 mg/L is considered protective.
Learn more by visiting the Cadmium page in our Indoor Drinking Water Section.
The primary natural source of lead is the mineral galena (lead sulfide, PbS). It also occurs as a carbonate, a sulfate, and in several other compounds. The solubility of these minerals and also of lead oxides and other inorganic salts is low. Major modern day uses of lead are for batteries, pigments, and other metal products. In the past, lead was used as an additive in gasoline and became dispersed throughout the environment in the air, soils, and waters as a result of automobile exhaust emissions. For years this was the primary source of lead in the environment. However, since the replacement of leaded gasoline with unleaded gasoline in the mid-1980's, lead from that source has virtually disappeared. Mining, smelting, and other industrial emissions and combustion sources and solid waste incinerators are now the primary sources of lead. Another source of lead is paint chips and dust from buildings built before 1978 and from bridges and other metal structures.
Lead is not an essential element. In humans it can affect the kidneys, the blood, and, most importantly, the nervous system and brain. Even low levels in the blood have been associated with high blood pressure and reproductive effects. It is stored in the bones.
Lead reaches water bodies either through urban runoff or from discharges such as those from sewage treatment plants and industrial plants. It may also be transferred from the air to surface water through precipitation (rain or snow). Toxic to both plant and animal life, lead's toxicity depends on its solubility and this, in turn, depends on the pH and hardness.
Learn more by visiting the Lead page in our Indoor Drinking Water Section.
Zinc is found naturally in many rock-forming minerals. Because of its use in the vulcanization of rubber, it is generally found at higher levels near highways. It also may be present in industrial discharges and sewage sludge. It is used to galvanize steel, and is found in batteries, plastics, wood preservatives, antiseptics, and in rat and mouse poison.
Zinc is an essential element in the diet. It is not considered very toxic to humans or other organisms.
The standard for aquatic life has been set at less than 0.106 mg/L, based on a hardness of 100 mg/L.
Learn more by visiting the Zinc page in our Indoor Drinking Water Section
Learn more by visiting these additional Metals pages in our Drinking Water Section.