What is chromium?
Chromium is a transition metal that occurs naturally, mainly bound to minerals. It is mainly chromite (chrome ironstone) with a chromium content of 46%. A total of about 100 chromium-bearing minerals are known. It is mined at shallow depths in opencast mines. Ferchromide and grimaldiite are rarer.
The metal is very wear-resistant and hard. Industry uses this property in electroplating, among other things, in which metallic materials are given long-lasting, corrosion-protecting hard and bright chrome plating.
The various colour pigments of the chromium compounds are not only used in the paint industry. Dyeing, pickling, bleaching and impregnating are possible applications in leather, textile and carpet manufacturing, glass and ceramic production and in producing fireworks and matches. The most beautiful use of chrome yellow was in Vincent van Gogh’s sunflower paintings. Chrome oxide green is used to colour bottle glass.
Especially the stable hexavalent compounds, chromium(VI), are particularly fascinating from a technical point of view – besides chromium(III). Hexavalent chromium has significant harmfulness – it is highly toxic.
How does chromium get into drinking water?
Many chromium compounds are difficult or impossible to dissolve in water. Chromite can be washed out of rock strata and enter groundwater. The content in surface waters is about 0,002 milligrams per litre, in drinking water on average 0,05 milligrams – so it is naturally shallow.
Trivalent chromium enters the environment from industrial wastewater from metal processing. However, the pollution is much more problematic from hexavalent chromium from leather processing, which is used for tanning and dyeing. Another source of contamination is illegally disposed of household waste. The toxic substance can also enter the water cycle from inadequately secured landfills and via emissions from waste incineration plants.
How does chromium affect the human body?
Due to the low drinking water concentration, health damage via food intake is not to be expected. The estimated daily requirement of chromium for adults is about 40-70 micrograms (µg) per day, according to the European Food Safety Authority (EFSA) recommendations. Expert opinions vary widely; others prefer up to 300µg. Foods rich in chromium are Whole grain products, cheese, meat, liver, nuts, prunes, sugar beet syrup and the yeast in beer! There is currently no definitive and uniform opinion on the effect of organic chromium as a vital trace element for, for example, carbohydrate and fat metabolism. In 2014, the element was removed from the list of essential minerals by the European Food Safety Authority because a beneficial effect could not be proven, and deficiency symptoms could not be detected.
The hexavalent is mutagenic and carcinogenic, unlike the harmless trivalent chromium(III). Numerous studies on employees of chromium-processing industrial plants have confirmed the risk of lung cancer from chromate-containing specks of dust. It is mainly absorbed through the respiratory tract, skin, or orally. The damage to health is manifold. They range from respiratory irritation, contact eczema, diarrhoea, bronchitis, and gastritis to chromate lung cancer and chromate ulcers. Ingestion of 1-2g is considered a lethal dose.
The occupational air limit value for chromium VI (Hexavalent chromium) in the UK is currently 0.05 mg/m3 (as an 8-hour time-weighted average). No specific AGW has been set for chromium III (trivalent chromium). Still, a general AGW of 0.1 mg/m3 applies to “other insoluble inorganic substances”.
At the beginning of 2015, the EU decided that the chromium (VI) content in leather products that come into contact with the skin must not exceed 3mg/kg.
Drinking water contaminated by chromium: What to do?
The limit value of the UK Drinking Water Ordinance and the WHO (World Health Organisation) 2006 for the parameter chromium is uniformly 50µg/L total chromium, i.e. for chromium(III) and (VI).
The toxic hexavalent chromium compounds are classified in water hazard class 3 and are thus considered highly hazardous to water. Drinking water suppliers successfully treat contaminated wastewater with ion exchange, oxidation, precipitation and aeration chemical processes.
Have chromium levels of your tap water tested
Presumably, according to the Drinking Water Ordinance, none of the drinking water that regional waterworks treat is contaminated with chromium. However, the question of possible pollutant contamination of the well water arises for operators of private well systems, primarily if they are located near industrial plants. Here, in particular, it is recommended that chromium levels be checked regularly.
A water test of IVARIO can show exactly which substances (e.g. lead, nitrate, nitrite, iron, arsenic, phosphate, germs) are present in tap water and in what concentrations. The analysis results are easy to understand and are clearly presented.