Beryllium in Drinking-Water: Background Document for Development of WHO Guidelines for Drinking-water Quality
Major Uses and Sources in Drinking-Water
The primary source of beryllium compounds in water is most likely from coal burning and other industries using beryllium in natural forms. Other sources of beryllium in surface water include deposition of atmospheric beryllium and weathering of rocks and soils containing beryllium.
In most natural waters, the majority of beryllium will be adsorbed to suspended matter or in sediment, rather than dissolved. For example, in the Great Lakes in the United States of America (USA), beryllium is present in sediment at concentrations several orders of magnitude higher than its concentration in water. Beryllium in sediment is primarily adsorbed to clay, but some beryllium may be in sediment as a result of the formation and precipitation of insoluble complexes. At neutral pH, most soluble beryllium salts dissolved in water will be hydrolysed to insoluble beryllium hydroxide, and only trace quantities of dissolved beryllium will remain. However, at high pH, water-soluble complexes with hydroxide ions may form, increasing the solubility and mobility of beryllium. Solubility may also increase at low pH; detectable concentrations of dissolved beryllium have been found in acidified waters.
Environmental Levels and Human Exposure
Atmospheric beryllium concentrations at rural sites in the USA ranged from 0.03 to 0.06 ng/m3. Lower levels may be found in less industrialized countries. Also in the USA, concentrations of 0.04–0.07 ng/m3 have been reported at suburban sites and 0.1–0.2 ng/m3 at urban industrial sites. A survey of beryllium concentrations in Japanese cities reported an average concentration of 0.042 ng/m3 and a maximum concentration of 0.222 ng/m3. Urban areas in Germany had beryllium concentrations in air ranging from 0.06 to 0.33 ng/m3.
Beryllium is not likely to be found in natural water above trace levels as a result of the insolubility of oxides and hydroxides at the normal pH range. There are only limited data on beryllium concentrations in water except from the USA, where a specific survey was carried out to support possible regulation (Table 1).
Surface waters have been reported to contain beryllium at concentrations up to 1000ng/l. Beryllium concentrations ranged from
Estimated Total Exposure and Relative Contribution of Drinking-Water
The general population may be exposed to trace amounts of beryllium by inhalation of air, consumption of drinking-water and food, and inadvertent ingestion of dust. The estimated total daily beryllium intake in the USA was 423 ng, with the largest contributions from food (120 ng/day, based on daily consumption of 1200 g of food containing a beryllium concentration of 0.1 ng/g fresh weight) and drinking-water (300 ng/day, based on daily intake of 1500 g of water containing beryllium at 0.2 ng/g), with smaller contributions from air (1.6 ng/day, based on daily inhalation of 20 m3 of air containing a beryllium concentration of 0.08 ng/m3) and dust (1.2 ng/day, based on daily intake of 0.02 g/day of dust containing beryllium at 60 ng/g). The concentration used for beryllium in food was the midpoint of a range of values reported for a variety of foods in an Australian survey. The concentration used for beryllium in drinking-water was based on a survey of 1577 drinking-water samples throughout the USA, where beryllium was detected in 5.4% of samples with mean and maximum concentrations of 190 and 1220 ng/l, respectively. The concentration used for beryllium in air was taken as a likely average concentration in a residential area based on air sampling results reported above. The concentration used for beryllium in household dust was estimated by assuming an indoor air concentration of 0.1 ng/m3 and an air to dust ratio of 600. Although intakes from air and dust are minor under background conditions, these can be important pathways of exposure in the vicinity of a point source. Beryllium intake through air and dust can be increased 2–3 orders of magnitude in the vicinity of a point source, such as a coal-fired power plant. Tobacco smoke is another potential source of exposure to beryllium in the general population. Beryllium levels of 0.47, 0.68 and 0.74 μg/cigarette were found in threebrands of cigarettes. Between 1.6% and 10% of the beryllium content, or 0.008–0.074 μg/cigarette, was reported to pass into the smoke during smoking. Assuming the smoke is entirely inhaled, an average smoker (20 cigarettes per day) might take in approximately 1.5 μg of beryllium per day (3 times the combined total of the other routes). Other potential exposures to beryllium in the general population from consumer products are limited but may include leaching of beryllium from beryllium–nickel dental alloys and emission of beryllium from the mantle of gas lanterns.
Treatment and Control Methods and Technical Achievability
Jar tests followed by centrifugation were used to evaluate beryllium removal by coagulation and lime softening. With an initial beryllium concentration of 18 μg/l in river water, removals of 85% and 80% were achieved using aluminium sulfate (2.5 mg/l as aluminium) and iron(III) chloride (10 mg/l as iron), respectively, at a final pH of 6.5. Using the same procedure but without coagulant, 28% removal was obtained. Removal increased with increasing raw water pH in the range pH 6–9, but the percentage removal was unaffected by the initial beryllium concentration in the range 5–50 μg/l. Removal of beryllium at 20 μg/l spiked into groundwater increased with lime dose in the range 75–450 mg/l; at the maximum dose, 99% removal occurred (Lytle, Summers & Sorg, 1992). Physicochemical treatment of domestic wastewater containing trace metals showed that clarification and filtration using lime (415 mg/l; pH 11.5) as a coagulant removed 99.4% beryllium from an initial concentration of 100 μg/l. When aluminium sulfate (18 mg/l as aluminium; pH 6.4) was used, the removal was 98.1%; with iron(III) chloride (40 mg/l as iron; pH 6.2), the removal was 94%. Activated carbon only slightly increased removals with the lime and aluminium sulfate systems, but increased cumulative removal to 98.7% with the iron(III) chloride system (Hannah, Jelus & Cohen, 1977).
Beryllium can be found in trace levels in many different areas of the United States. As an element, beryllium is naturally occurring, however, anthropogenic processes i.e., the combustion of fossil fuels, have caused an increase to these levels at the earth’s surface. Beryllium levels in soil range from 0.5 ppb to 1,312 ppm, with an estimated average of 1.780 ppm. These statistics are based on the results of more than 488,000 soil and sediment samples, analyzed and recorded in the National Geochemical Database. This database, a government sponsored program, conducted by the Department of Energy, was begun in 1974, as the National Uranium Resource Evaluation (NURE) / Hydrochemical and Stream Study Reconnaissance (HSSR). The program sampled 320 quadrangles in 33 states and was completed in 1980.
The distribution or relative abundance of elements in soils and other surficial materials is determined not only by the elemental content of the bedrock or other deposits from which the materials originated, but also by effects of climate and biological factors as well as influences of agricultural and industrial operations that have acted on the materials for various periods of time.
Beryllium, atomic number 4, is among the lightest of elements with an atomic weight of 9.012 . A fairly rare element, it ranks 44th in abundance. Beryllium (Be) is a hard grayish-white metal of the alkaline earth family. It occurs in nature as a mineral component.
There are some forty-odd recognized mineral forms of beryllium. These beryllium-containing minerals usually occur in pegmatites, in granites, in syentites, and occasionally in gneisses and mica sheets. At present, only beryl and bertrandite ores are mined commercially.
The ideal beryl formula – Be3 Al2 Si6 O18
The standard beryl formula – Be3 R3+ · Si6 O18
The standard bertrandite formula – Be4 Si2 O7 (OH)2
The standard phenakite formula – BeSiO4
(Geological Survey Paper – 818A – 1973) ( Sinkankas 1981)
Erosion of Beryllium Bearing Minerals
The sedimentary cycle begins when the parent rock is broken down by weathering (physical, chemical, or biological). Weathering is the first phase of the sedimentary cycle and is responsible for eroding and fracturing rocks, for liberating rock particles and for removing soluble chemicals from the surface of rocks. Once liberated, small rock particles left by weathering are available for movement within the environment. (Mason & Dragun 1996)
Weathering effects cause erosion or disintegration of beryllium ore bearing minerals by mechanisms similar to other types of rocks. In the case of known beryllium-bearing minerals, beryllium is typically locked within a silicate matrix. Degradation of the ore body by weathering exposes the individual beryllium minerals but does not liberate beryllium as a soluble species because the beryllium silicate structure remains intact. The hydrothermic geological processes which generated the present day beryllium mineralization are no longer sufficiently active to re-mobilize beryllium.
Transport of Beryllium within the Environment
When ore bearing material has been sufficiently weathered–to a point that individual mineral particles are liberated–natural transport forces such as wind, rain, and snow can mobilize the freed particles.
Particle Movement by Wind
Mineral or soil particles that are sufficiently small, may be picked up and carried aloft by surface and prevailing winds. While prevailing winds may carry extremely light particles high into the atmosphere, most particles are too large and too heavy to be carried into the upper atmosphere. A more common fate for these particles is deposition by surface winds onto adjacent land or water surfaces. Beryllium silicate particles from ores are typically far too large and heavy to be taken into the upper atmosphere. Thus, airborne beryllium silicate particles will most likely settle onto adjacent land and water surfaces. (Mason & Dragun 1996)
Two extremely rare, unstable isotopes of beryllium, 7Be and 10Be, are formed in the upper stratosphere by cosmic ray interactions. The lifetime of 7Be is too short for significant deposition from the stratosphere. The lifetime of 10Be is much longer, but the relative amount of deposition of 10Be from the stratosphere onto terrestrial surfaces is minuscule. Beryllium-containing ore bodies, and consequently products manufactured from these ore-bodies, contain only the stable isotope, 9Be.
Particles produced from anthropogenic processes, i.e., the burning of coal, or the manufacture of products, are generally much too large and too heavy to move into the upper atmosphere. Beryllium particles produced from anthropogenic processes, almost always enter the atmosphere as BeO. Generally, deposition of the beryllium particles occurs near the emission source. Once deposition takes place, these BeO particles either remain inert or, if exposed to water, may begin a slow hydrolysis to Be(OH)2. (Toxicological Profile for Beryllium – 1991)
Beryllium is naturally emitted to the atmosphere by windblown dusts and volcanic particles. However, the major source of beryllium emissions to the environment is the combustion of coal and fuel oil. (Cleverly 1989, EPA 1987, Fishbein 1981).
Combustion of a beryllium-containing material such as coal or fuel oil releases the beryllium as BeO.
Average Beryllium Content in Coal 1.90 ppm
Average Beryllium Content of Coal Ash 28.35 ppm
Average Ash Content of Coal 11.00%
(Refer to the Beryllium Content of American Coals – 1084 K – 1961)
Average Beryllium Content of Fuel Oil 0.1 – 0.2 ppm
(Toxicological Profile for Beryllium – 1991)
It is estimated that approximately 67.4 million tons of coal ash is produced annually, with 59.7 million tons being land disposed. (Handbook on Fossil Fuel Scrubber Sludges – 1988)
The U.S. Department of Health and Human Services estimates that approximately 790,000 tons of fuel oil ash is land disposed annually. (Handbook on Fossil Fuel Scrubber Sludges – 1988)
In 1987, the EPA estimated that approximately 200 metric tons of beryllium are released into the atmosphere above the United States each year from the combustion of coal” (U.S. EPA 1987).
Particle Movement by Water
Beryllium enters water as a result of the natural degradation process.
Additionally, Beryllium enters water as a result of anthropogenic processes, i.e., the burning of coal, or the smelting of metals, generally as BeO.
Beryllium Oxide in Water: Once in water, beryllium oxides will begin a slow hydrolysis to beryllium hydorxide (Be(OH)2 ). Beryllium hydroxide is not soluble in water.
Particle movement in water is a function of water turbulence and velocity. Particles that contain chemical compounds which are water soluble, are easily carried as dissolved species, even at low seasonal velocity. Particles, such as beryllium, that contain chemical compounds that are largely water insoluble, have a low aqueous solubility, and must be carried in suspension. Particles carried in suspension are much more influenced by turbulence and velocity effects. These particles will be carried in suspension as long as the water velocity remains constant. In deeper areas, where the water pools, or areas along the outer edge where the water slows down, particle sedimentation or drop out usually begins. (Mason & Dragun – 1996)
In the case of beryllium, like most metals, once these particles drop out of suspension, they tend to be captured by clay minerals (sorbed), by the surfaces of mineral grains. These sorbed constituents, would require a significant increase in water velocity for them to be returned to the water column. Beryllium has a very low aqueous solubility in water, and is probably precipitated, or adsorbed into solids, soon after introduction to the aqueous environment. The estimated average concentration of beryllium in any fresh surface water system is 1mg/L. (Toxicological Profile for Beryllium – 1991)
Particles that drop out, through this process, are Be(OH)2 , and will remain Be(OH)2 , unless they reach a fluoride source, or extremely strong acids (pH <0), or strong bases (pH >14). BeO and Be(OH)2 are almost impervious to dilute acid and alkaline attack.
Beryllium is not a bioaccumulative chemical of concern . (40 CFR Part 132 Table 6 B). Beryllium in soil does not dissolve in water but remains bound to the soil. Once in the soil the beryllium is not very likely to move deeper into the ground and enter groundwater.
Beryllium Released by Degrading Plants
Beryllium has been detected in U.S. orchard leaves and various trees and shrubs at concentrations of 26 ppb to 1.0 ppm. Beryllium can also be found in many plants, especially large leaf varieties, where beryllium is concentrated in the stalks, with lower quantities in the flowers and leaves. (Toxicological Profile for Beryllium – 1991)
It is believed that beryllium is most likely taken into the plant as an oxy-organic compound similar to commercially produced oxy-organic compounds such as beryllium oxalate trihydrate (BeC2O4 · 3H2O), or beryllium basic acetate Be4O(C2H3O2)6. When plant degradation takes place, the oxy-organic compound of beryllium will also decay. Since organic matter consists of amino compounds, carbohydrates, lipids, phenols, and humic compounds, it is possible that some of these compounds produced by the degradation process may retain the beryllium. However, as degradation becomes more complete, beryllium would likely convert to beryllium hydroxide Be(OH)2.
Conclusions by WHO
Beryllium is rarely, if ever, found in drinking-water at concentrations of concern. Therefore, it is not considered necessary to set a formal guideline value.
A health-based value for beryllium in drinking-water would be 12 μg/l based on an allocation of 20% of the tolerable daily intake (TDI) of 2 μg/kg body weight, derived from the dog study by Morgareidge, Cox & Gallo (1976) (see section 3.2.2), to drinking-water and assuming a 60 kg adult drinking 2 litres of water per day. This allocation is probably conservative, as the limited data on food indicate that exposure from this source is likely to be well below the TDI.
Although beryllium appears to be found in drinking-water sources and drinking-water at low concentrations, the database on occurrence is limited, and there may be specific circumstances in which concentrations can be elevated due to natural sources where the pH is either below 5 or above 8 or there is high turbidity.
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