Arsenic

3. What are the levels of exposure to arsenic?

• 3.1 How much arsenic is there in the environment?
• 3.2 What levels of arsenic are found in living organisms?
• 3.3 What levels of arsenic are humans exposed to?

3.1 How much arsenic is there in the environment?

Arsenic concentrations in air range from very low (0.02 to 4 ng/m³) in remote and rural areas, to low (3 to about 200 ng/m³) in urban areas. Much higher concentrations (more than 1000 ng/m³) can be found near some industrial sources such as smelters, although in some countries, very high levels are no longer found because of measures taken to reduce pollution.

Concentrations of arsenic in open ocean seawater are typically low (1–2 µg/litre). In rivers and lakes, concentrations are somewhat higher but generally below 10 µg/litre. Exceptions are near man-made sources such as pesticide manufacturing or mining, where individual samples in surface waters may be 1000 times higher (up to 5000 µg/litre). Arsenic levels in groundwater are typically as low as in open ocean water (about 1–2 µg/litre), except in areas with volcanic rock and sulphide mineral deposits where arsenic levels can range up to 3000 µg/litre.

In sediment, arsenic concentrations range from 5 to 3000 mg/kg. The higher levels are found in areas contaminated by mining and smelting. In soil, concentrations range from 1 to 40 mg/kg, usually averaging around 5 mg/kg. Naturally elevated levels of arsenic in soils may be associated with the presence of sulphide ores in the rock layers below the soil. Soils heavily contaminated by activities such as mining of gold and arsenic, metal smelting and agricultural chemical application can have concentrations of arsenic up to several thousand milligrams per kg (mg/kg) or more. More...

3.2 What levels of arsenic are found in living organisms?

Sea-living plants and animals normally contain organic arsenic residues. These are generated from inorganic forms of arsenic, either by microbes or by the plants and animals themselves. Amounts range from less than 1 to more than 100 mg/kg. Arsenic can build up (bioaccumulate) in the bodies of aquatic organisms, particularly those living in the sea. Arsenic concentrations in freshwater and land-living animals and plants are usually less than 1 mg/kg. Land-living plants may accumulate arsenic via uptake through the roots from the soil or by deposition of airborne arsenic on the leaves. Arsenic levels are higher in living organisms collected near man-made sources of arsenic or in areas with volcanic activity. Up to 3000 mg/kg has been found in some species at arsenical mine sites. More...

3.3 What levels of arsenic are humans exposed to?

Exposure of the general population to arsenic occurs mainly through food and water and in most areas, food is the main source. The daily intake of arsenic from food and beverages is generally between 20 and 300 µg/day. Arsenic in food is mainly in the form of organic arsenic, which is generally thought to pose less health problems than inorganic arsenic (see questions 5 to 8). About one-quarter of the arsenic present in the diet is inorganic arsenic, mainly from foods such as meat, poultry, dairy products and cereals. Fish and shellfish contain the highest concentrations of arsenic, but the proportion of inorganic arsenic in fish is very low, below 1%. In some areas, where levels of arsenic in groundwater are high, drinking water may be the main source of intake. In drinking water, arsenic is present in the more toxic, inorganic form.

Arsenic which is breathed in contributes around 1 µg/day in a non-smoker, 10 times as much in a smoker, and more in polluted areas. Contaminated soils such as mine tailings are also a potential source of arsenic exposure

The amount of arsenic absorbed into the body from all sources can be assessed on an individual basis by measuring the concentration of inorganic arsenic and its metabolites in urine. Generally, it ranges from 5 to 20 µg arsenic per litre of urine (µg/litre), but may even exceed 1000 µg/litre. (see 4.2)

In workplaces with up-to-date occupational hygiene practices, exposure concentrations generally do not exceed 10 micrograms per cubic meter of air (µg/m³). However, in some workplaces arsenic concentrations several hundred times higher have been reported. More...