Arsenic in drinking water – a danger?

What is arsenic?

Arsenic is a semi-metal that usually occurs bound as a sulphide. It is generally known for its high toxicity. The element was already described in antiquity. The name arsenic has only been in use since the 19th century. Depending on the modification, the element has metallic or non-metallic properties. Arsenic is used in many different ways. As an alloying component of other metals (copper and lead), it increases their hardness.

Arsenic compounds play an important role in the production of microchips, as insecticides and fungicides for pest control, as wood preservatives and in the glass industry. Its use in medicine has a long history. Arsenic-containing minerals were used against fever, malaria, rheumatism, diabetes and syphilis. Fowler’s solution (potassium arsenite) gained fame as a remedy and aphrodisiac. Arsenic-containing medicines are used today in cancer therapy. Arsenic sulphides are part of traditional Chinese medicine. In painting, arsenic was valued for its yellow colour pigments.

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How does arsenic get into drinking water?

Arsenic compounds are highly soluble in water. They enter groundwater through the leaching of weathering, arsenic-containing rock and release from sedimentary layers. In areas with volcanic activity, vast quantities of arsenic are released; these re-enter the water cycle through the atmosphere. The arsenic input in seawater is about 2-4 parts per billion and in rivers only 0.5-2 ppb. Mining and industry are major contributors to the spread of arsenic. Fossil fuel combustion (coal), exhaust fumes from copper smelting, unsecured landfills and use in agriculture promote pollution on a large scale. Arsenic particles leach into the soil and end up in surface waters. Soil contamination in the vicinity of disused, old mines is still possible in some cases at levels of 30 grams per kilogram of soil.

Examples of contamination can be found in the areas of South West London and Devon. In the 1960s, waste from an arsenic processing plant was dumped in some areas of South West London, particularly in the Mitcham area, resulting in high levels of arsenic in the soil. A copper mine in Devon, which was in operation in the 19th century, produced large quantities of arsenic as a by-product which leached into the soil in the surrounding area.

How does arsenic affect the human body?

The deadly effect of arsenic poisoning is well known in literature and film. The chance of being misinterpreted as a cholera disease made arsenic popular as a murdering poison because of its symptoms. In fact, the harmful substance is mostly ingested via contaminated drinking water. Normally, the assumed necessary amount is supplied through food. A size derived from animal experiments is 15-25 micrograms daily for humans. The total amount of arsenic in the body is between 0.5-15 mg.

Ingested arsenic from cereals, fish, seafood and dairy products is excreted or stored in the skin, hair, bones, nails and teeth. Long-term effects cause serious organ damage. Pigmentation disorders and hair loss are clearly visible. The toxicity of inorganic arsenic compounds is higher than that of organic ones. Acute poisoning is characterised by vomiting, diarrhoea, cardiac arrhythmia and hallucinations. Chronic courses of disease over several years are less pronounced and unspecific (headaches, depression, sleep disorders). As the arsenic concentration in water fluctuates, tap water is not recommended for preparing baby food.

Drinking water contaminated by arsenic: What to do?

The Drinking Water Ordinance provides for a limit value of 10 µgAs/l, which is also fixed by the World Health Organisation (WHO) and the European Drinking Water Ordinance. In many countries outside Europe – especially in parts of Asia – these guideline values are not nearly reached. Mass poisoning manifests itself in increased incidences of skin cancer and tumours. In January 2020, the Food Standards Agency (FSA) published a report stating that rice cakes, rice cereals and baby rice products sold in the UK may contain high levels of arsenic. The FSA recommended that parents should limit the number of rice products they give their babies and also increase the variety of foods to reduce the risk of excessive arsenic exposure.

Inorganic arsenic can be reliably removed from raw water using ion exchange, membrane filtration (reverse osmosis) or coagulation (flocculation). Strong bio accumulators (ferns) are successfully planted for ecological soil treatment. When digging new good installations, the necessary lowering of the water table can have undesirable side effects: Arsenic previously bound in sedimentary rock and therefore harmless reacts with atmospheric oxygen and possibly enters the groundwater.

Have arsenic levels tested

The Drinking Water Ordinance guarantees that drinking water must be ‘wholesome’ and this is defined in law mainly by setting standards for a wide range of substances, organisms and properties of water in regulations. It is also obligatory for well operators to constantly check their well water in the interest of their own health. A water test can tell you whether your drinking water contains problematic levels of arsenic. The sample is analysed in an accredited laboratory and presented to you clearly. At the same time, you can find out other classic parameter values (e.g. lead, nitrate, nitrite, iron, ammonium, phosphate, boron, selenium and legionella) for your own drinking water.

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