Aluminum dissolves from clay minerals in acidified soils and can thus enter well water. Another source is unsuitable sacrificial anodes in hot water tanks. The drinking water ordinance provides for a limit of 0.2 mg per liter, since aluminum is suspected of having negative effects, especially on the nerves of the human body (Alzheimer's disease).
Barium is a non-essential alkaline earth metal. It occurs in nature only in compounds, not in elemental form. Drinking water is usually low in barium and contains less than 100 micrograms of barium per liter. The average daily intake of an adult is 500 micrograms. Vegetarians consume up to 1000 micrograms, which is safe for health. The foods with the highest barium content are nuts, fish and seaweed.
Older buildings may still have sections of lead in the pipes. Depending on water conditions, lead can dissolve out of the pipe wall if the water is allowed to stand in the pipe for a long time. Lead can also be released as a by-product of zinc when galvanized steel pipes corrode. The limit value for lead is 10 micrograms/liter. This value is so low to avoid chronic exposure, which can damage the blood-forming system and the nervous system, especially in young children and pregnant women.
Cadmium can come from impurities in galvanized pipes or from cadmium-containing solder joints in containers and extraction devices. Cadmium lodges in the skeleton and stresses the kidneys.
In Germany, a limit value of 0.05 mg per liter of drinking water applies to chromium. Chromium is an essential trace element. Since the requirement is very low, the toxicity threshold is also low, especially for the hexavalent form. Chromium is used to refine fittings and can pollute the water in this way.
Iron in drinking water is not hazardous to health, but it has undesirable effects such as turbidity and discoloration of the water, bad taste, laundry stains, precipitation and sedimentation. There is also an increased risk of water contamination. In oxygen-deficient groundwater, it is present in the trivalent form. If it is pumped up the well and comes into contact with the air, it oxidizes to the water-insoluble trivalent form and forms brown-red precipitates. If iron levels are elevated in buildings connected to the public network, this may indicate corrosion in the piping system (old pipes, dead pipe sections, very rarely used taps). The limit value of 200 micrograms/liter is therefore based on the protection of pipes/electrical appliances and aesthetic sensation (color) or good taste. So, for example, you could safely drink a water with 3 mg iron/liter, only it is a brown and bad tasting broth.
Copper is a vital trace element (formation of red and white blood cells, function of the central nervous system. However, at elevated concentrations due to corrosion in the piping system, long-term intake can cause health disorders. Young children are particularly sensitive (liver load).
Manganese is essential for human life and is found in appreciable quantities only in well water. In oxygenated water it precipitates as manganese dioxide. In the pipe network, soft, black-brown greasy deposits then form, which can also render the solenoid valves in washing machines and dishwashers inoperable. The effect of chlorination can be reduced or even cancelled out by the oxidation of manganese, which can become a problem for water hygiene. Above 0.5 mg manganese/liter, the taste of water is negatively affected. Black-brown stains may appear when washing clothes. The low limit value for manganese (50 micrograms/liter) therefore has technical and hygienic reasons.
Nickel usually comes from chrome-plated fittings (faucets, etc.). Especially newly installed faucets and old damaged faucets emit more nickel. Before drawing drinking water, you should drain about 250 ml of water to flush the faucet. Nickel is an essential trace element. It is used in very small amounts, so the threshold of toxicity is very low. It causes allergies.
Zinc is one of the essential trace elements that the human body absolutely needs. In the body zinc fulfills important tasks, e.g. as a component of enzymes, insulin activation, amino acid metabolism, hormone balance. In drinking water it often occurs as a corrosion product of galvanized steel pipes. In case of increased zinc concentrations, lead and cadmium should also be kept in mind. There is a guideline value (not limit value) of 5 mg/l for drinking water. However, zinc gives the water a bitter taste already from 2 mg/l.