When you think of uranium, you probably think about nuclear power-plants and radioactivity; you probably don’t want to go anywhere near it. And you’re right, because uranium can weaken the immune system. In this article, we’ll explore how uranium (and its by-product radon) get into the drinking water system, their impact on health, and how you can remove them from your tap water.
Uranium is a weakly radioactive, silvery metal found in the earth’s crust. It is naturally present, in small quantities (a few parts per million), in soil, rock and water. Because of its radioactivity, uranium can be enriched and used in nuclear power plants and nuclear weapons. It is mined from uranium-containing minerals such as uraninite.
Although it is a natural component of rock and soil, we’re exposed to higher levels of uranium because of human activity. The main reasons uranium ends up in the environment are mining, coal-combustion, and phosphate fertilizers.
Because it is ubiquitous to our environment, most people are exposed to a certain amount of uranium. While the amount of uranium in the air is very small, it can contaminate water and food.
Your level of exposure also depends on where you live and work. People who work in phosphate fertilizer factories, live near nuclear testing facilities (present or past), live or work near coal-fired power plants, are at high risk of being exposed to higher levels of uranium.
Another source of uranium exposure is drinking water.
Groundwater sources are in constant contact with rocks. The natural weathering of these rocks dissolves the uranium present there, and this ends up in the water. If water is stored in rock or soil aquifers, some of the uranium present in the soil and rock ends up leaching into the water, and flowing through the tap. [ref]
Water sources that are close to nuclear plants and military facilities are likely to be contaminated with radioactive chemicals, including uranium.
Water sources that are close to intensive agriculture are likely to be contaminated with agricultural runoff, such as phosphate fertilizers which contain uranium. [ref: https://en.wikipedia.org/wiki/Fertilizer]
Even though uranium is best known for its radioactivity, its use in the nuclear industry contributes very little to the presence of uranium in the environment. According to the RIVM, uranium’s chemical toxicity is more harmful than its potential environmental impact through radioactivity.
Ingested uranium is eliminated during digestion. Only between 0.5-5% of it is absorbed. However, these small amounts can bioaccumulate in the body, staying in bone tissue and causing potential health problems.
Uranium is not only weakly radioactive, it is a toxic metal. That means that it can affect the normal functioning of the kidneys, brain, nervous system, liver and heart. In animal tests, it causes birth defects and damages the immune system.
Uranium is mentioned in the latest European Drinking Water Directive, but the Directive does not provide any limits at present. Article 25 states that:
This means that currently, most European governments adhere to the guideline limits set out by the World Health Organization: 30 micrograms (μg) per litre. [ref]
In the 1998 edition of its Guidelines for Drinking-water Quality, the World Health Organization (WHO) recommended that uranium in drinking water should not exceed 2 μg/l. This recommendation was based on a tolerable daily intake (TDI) of 0.6 micrograms per kilogram per day (μg/kg/day). [ref] For an average adult weighing 70kg, this equates to a TDI of 42 μg of uranium per day.
In 2011, the WHO drastically increased the limit value of uranium in drinking water to 30 μg/l, stating that there was “no evidence of renal damage [in humans]”. However, this decision has come under fire from some scientists who state that the new limit may fail to protect people with hypertension or osteoporosis, pre-existing kidney disease, or anyone who has been exposed to uranium long-term [ref]
In 2014 the Dutch National Institute for Public Health and the Environment (RIVM) proposed two limit values for uranium in water:
Uranium is listed as a specific pollutant in the Dutch decree on the Water Framework Directive, because it is regularly detected in surface waters in the Netherlands, at concentrations above the current AA-EQS standard .
The WHO’s new guide value for uranium in water has not been taken up at the national level. The French Agency for Food, Environmental and Occupational Health Safety (ANSES) has kept the value of 15 micrograms per litre.
In France, two studies have been carried out to assess the radiological quality of tap water, the most recent in 2011. The analysis, carried out and published by the French Nuclear Safety Authority (ASN), the General Health Administration (DGS) and the Institute for Radiological Protection and Reactor Safety (IRSN), concluded that “the radiological quality of the water is overall satisfactory.”
The radiological quality of the water has been evaluated for around 97% of the population. Of the samples tested:
Given that the latest analysis was carried out over ten years ago, it is hard to know the current state of radioactivity of tap water in France.
It is not known precisely how much uranium is present in the water, because Italy’s public water network is managed on a regional level. The most recent report by the Italian Institute for Environmental Protection and Research (ISPRA), entitled “Guidelines for the planification of campaigns to measure radioactivity in drinking waters” states:
“Precise information gathering regarding which radionuclides are most present in Italian drinking water has been carried out in very few regions; in particular, there is insufficient information on the concentrations of radium 226 and uranium. What’s more, the analytical sensitivity of the measurements, both of uranium and of radium 226, is not always adequate to the requirements of the European Directive 51/2013.”
For the moment, there are no planned monitoring programs that would cover 100% of the population, throughout all regions.
It is therefore difficult to know how much uranium (and radon) is present in tap water in Italy.
The uranium concentration in groundwater in Germany varies depending on the geologic composition of the rocks that are in contact with the water. Leaks from the use of phosphate fertilizers on agricultural land may also affect uranium levels. Occasionally, very high uranium concentrations can occur in groundwater within a single federal state, however the uranium concentration in the majority of samples treated by water companies is below 1 μg/l.
Uranium levels in German groundwater fluctuate between < 0.001 μg/l and approx. 10 μg/l. Higher uranium concentrations are found in surface water (0.04 μg/l in river water and 3.3 μg/l in seawater). Soils and sediments close to former uranium mining regions also contain more uranium.
In Germany, a maximum value of 10 μg/l uranium in drinking water has been in force since 1st November 2011. According to the Drinking Water Commission of the Federal Ministry of Health at the Federal Environment Agency, if this guide value is observed, the water is safe to drink for all age groups, including infants.
Where there’s uranium, there’s radon. As uranium decays, it turns into radon – a radioactive, colorless, odorless and tasteless gas. This gas dissolves in water, which is why it ends up in drinking water. According to the WHO, standard water treatment, storage and distribution usually reduce radon concentration. That’s because when water is in contact with the atmosphere, the radon it contains evaporates into the air (for example when it flows from the tap, when it is stored in water towers, or when it is in water treatment facilities). Levels of radon in surface water are typically lower than in ground water because the gas is released into the atmosphere.
Because of its gaseous form, it enters the body through the respiratory system rather than the digestive system. For that reason, it is considered more appropriate to measure radon in indoor air than in drinking water. It is understood that the radon from drinking water contributes very little to the quantity of radon in indoor air – most of it comes from the rocks and soil underneath the building. Furthermore, it is challenging to measure active radon concentrations in water because of how easily it is released from water.
Radon in water is measured by becquerels (Bq), which indicates an element’s radioactive quality. Radioactivity refers to the amount of ionizing radiation released when an element (such as uranium or radon) spontaneously emits energy as a result of radioactive decay (or disintegration) of an unstable atom. Radioactivity is also the term used to describe the rate at which radioactive material emits radiation, or how many atoms in the material disintegrate in a given time period. The unit used to measure radioactivity is Becquerel (Bq). 1Bq represents a rate of radioactive decay equal to 1 disintegration per second.
Even though uranium is radioactive, its chemical toxicity is what the WHO takes into consideration. As such, it is measured in micrograms per litre, rather than Bq per litre. Radon is considered toxic because of its radioactive properties, and as such is measured in Bq.
The WHO’s guidance limit for radon in drinking water is 100 Bq per litre.
In Europe, the level of radon is regulated by the Council Directive on the protection of the health of the general public with regard to radioactive substances in water intended for human consumption, and is also set at 100 Bq per litre.
The legislation states that “The level set by a Member State may be higher than 100 Bq/l but lower than 1 000 Bq/l. In order to simplify national legislation Member States may choose to adjust the parametric value to this level.”
Some European countries have chosen to do so. In Ireland, Portugal and Spain, the level is 500 Bq per litre. In Finland, it is 1 000 Bq per litre.
When inhaled, radon damages the lungs and has been linked with lung cancer . The WHO estimates that between 3-14% of lung cancers are caused by radon .
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