| European Union’s Assessment | World Health Organization (WHO) and the European Union’s Assessment of Human Consumption of Silver in Drinking Water Guidelines
Who’s Guidelines for Drinking-water Quality, set up in Geneva, 1993, and are the international reference point for standard setting and drinking-water safety.
Element/
substance | Symbol/
formula | Normally found in fresh water/surface water/ground water | Health based guideline by the WHO | | Aluminum | Al | | 0,2 mg/l | | Ammonia | NH4 | < 0,2 mg/l (up to 0,3 mg/l in anaerobic waters) | No guideline | | Antimony | Sb | < 4 μg/l | 0.005 mg/l | | Arsenic | As | | 0,01 mg/l | | Asbestos | | | No guideline | | Barium | Ba | | 0,3 mg/l | | Berillium | Be | < 1 μg/l | No guideline | | Boron | B | < 1 mg/l | 0,3 mg/l | | Cadmium | Cd | < 1 μg/l | 0,003 mg/l | | Chloride | Cl | | 250 mg/l | | Chromium | Cr+3, Cr+6 | < 2 μg/l | 0,05 mg/l | | Colour | | | Not mentioned | | Copper | Cu | | 2 mg/l | | Cyanide | CN- | | 0,07 mg/l | | Dissolved oxygen | O2 | | No guideline | | Fluoride | F | < 1,5 mg/l (up to 10) | 1,5 mg/l | | Hardness | mg/l CaCO3 | | No guideline | | Hydrogen sulfide | H2S | | No guideline | | Iron | Fe | 0,5 - 50 mg/l | No guideline | | Lead | Pb | | 0,01 mg/l | | Manganese | Mn | | 0,5 mg/l | | Mercury | Hg | < 0,5 μg/l | 0,001 mg/l | | Molybdenum | Mb | < 0,01 mg/l | 0,07 mg/l | | Nickel | Ni | < 0,02 mg/l | 0,02 mg/l | | Nitrate and nitrite | NO3, NO2 | | 50 mg/l total nitrogen | | Turbidity | | | Not mentioned | | pH | | | No guideline | | Selenium | Se | < < 0,01 mg/l | 0,01 mg/l | | Silver | Ag | 5 – 50 μg/l | No guideline | | Sodium | Na | < 20 mg/l | 200 mg/l | | Sulfate | SO4 | | 500 mg/l | | Inorganic tin | Sn | | No guideline | | TDS | | | No guideline | | Uranium | U | | 1,4 mg/l | | Zinc | Zn | | 3 mg/l | | The EU standards are more recent (1998), complete and strict than the WHO standards (1993). Here is a comparative table of both WHO and EU standards: | | | WHO standards | EU standards | | | 1993 | 1998 | | Suspended solids | No guideline | Not mentioned | | COD | No guideline | Not mentioned | | BOD | No guideline | Not mentioned | | Oxidisability | | 5.0 mg/l O2 | | Grease/oil | No guideline | Not mentioned | | Turbidity | No guideline(1) | Not mentioned | | pH | No guideline(2) | Not mentioned | | Conductivity | 250 micros/cm | 250 micros/cm | | Color | No guideline(3) | Not mentioned | | Dissolved oxygen | No guideline(4) | Not mentioned | | Hardness | No guideline(5) | Not mentioned | | TDS | No guideline | Not mentioned | | | | | | cations | | | | (positive ions) | | | | Aluminum (Al) | 0.2 mg/l | 0.2 mg/l | | Ammonia (NH4) | No guideline | 0.50 mg/l | | Antimony (Sb) | 0.005 mg/l | 0.005 mg/l | | Arsenic (As) | 0.01 mg/l | 0.01 mg/l | | Barium (Ba) | 0.3 mg/l | Not mentioned | | Berillium (Be) | No guideline | Not mentioned | | Boron (B) | 0.3 mg/l | 1.00 mg/l | | Bromate (Br) | Not mentioned | 0.01 mg/l | | Cadmium (Cd) | 0.003 mg/l | 0.005 mg/l | | Chromium (Cr) | 0.05 mg/l | 0.05 mg/l | | Copper (Cu) | 2 mg/l | 2.0 mg/l | | Iron (Fe) | No guideline(6) | 0.2 | | Lead (Pb) | 0.01 mg/l | 0.01 mg/l | | Manganese (Mn) | 0.5 mg/l | 0.05 mg/l | | Mercury (Hg) | 0.001 mg/l | 0.001 mg/l | | Molibdenum (Mo) | 0.07 mg/l | Not mentioned | | Nickel (Ni) | 0.02 mg/l | 0.02 mg/l | | Nitrogen (total N) | 50 mg/l | Not mentioned | | Selenium (Se) | 0.01 mg/l | 0.01 mg/l | | Silver (Ag) | No guideline | Not mentioned | | Sodium (Na) | 200 mg/l | 200 mg/l | | Tin (Sn) inorganic | No guideline | Not mentioned | | Uranium (U) | 1.4 mg/l | Not mentioned | | Zinc (Zn) | 3 mg/l | Not mentioned | | | | | | anions | | | | (negative ions) | | | | Chloride (Cl) | 250 mg/l | 250 mg/l | | Cyanide (CN) | 0.07 mg/l | 0.05 mg/l | | Fluoride (F) | 1.5 mg/l | 1.5 mg/l | | Sulfate (SO4) | 500 mg/l | 250 mg/l | | Nitrate (NO3) | (See Nitrogen) | 50 mg/l | | Nitrite (NO2) | (See Nitrogen) | 0.50 mg/l | | | | | | microbiological | | | | parameters | | | | Escherichia coli | Not mentioned | 0 in 250 ml | | Enterococci | Not mentioned | 0 in 250 ml | | Pseudomonas | | | | aeruginosa | Not mentioned | 0 in 250 ml | | Clostridium | | | | perfringens | Not mentioned | 0 in 100 ml | | Coliform bacteria | Not mentioned | 0 in 100 ml | | Colony count 22oC | Not mentioned | 100/ml | | Colony count 37oC | Not mentioned | 20/ml | | | | | | other parameters | | | | Acrylamide | Not mentioned | 0.0001 mg/l | | Benzene (C6H6) | Not mentioned | 0.001 mg/l | | Benzo(a)pyrene | Not mentioned | 0.00001 mg/l | | Chlorine dioxide (ClO2) | 0.4 mg/l | | | 1,2-dichloroethane | Not mentioned | 0.003 mg/l | | Epichlorohydrin | Not mentioned | 0.0001 mg/l | | Pesticides | Not mentioned | 0.0001 mg/l | | Pesticides - Total | Not mentioned | 0.0005 mg/l | | PAHs | Not mentioned | 0.0001 mg/l | | Tetrachloroethene | Not mentioned | 0.01 mg/l | | Trichloroethene | Not mentioned | 0.01 mg/l | | Trihalomethanes | Not mentioned | 0.1 mg/l | | Tritium (H3) | Not mentioned | 100 Bq/l | | Vinyl chloride | Not mentioned | 0.0005 mg/l | (1) Desirable: Less than 5 NTU
(2) Desirable: 6.5-8.5
(3) Desirable: 15 mg/l Pt-Co
(4) Desirable: less than 75% of the saturation concentration
(5) Desirable: 150-500 mg/l
(6) Desirable: 0.3 mg/l
Assessment dateThe risk assessment was originally conducted in 1993. The Final Task Force Meetingin 2003 agreed that this risk assessment be brought forward to this edition of the Guidelines for Drinking-water Quality.
Principal reference
WHO (2003) Selenium in drinking-water. Background document for preparation of WHO Guidelines for drinking-water quality. Geneva, World Health Organization (WHO/SDE/WSH/03.04/13).
12.106 Silver
Silver occurs naturally mainly in the form of its very insoluble and immobile oxides, sulfides and some salts. It has occasionally been found in groundwater, surface waterand drinking-water at concentrations above 5mg/litre. Levels in drinking-water treated with silver for disinfection may be above 50mg/litre. Recent estimates of daily intake is about 7mg per person.Only a small percentage of silver is absorbed. Retention rates in humans and laboratoryanimals range between 0 and 10%.The only obvious sign of silver overload is argyria, a condition in which skin and hair is heavily discolored by silver in the tissues. An oral NOAEL for argyria inhumans for a total lifetime intake of 10 g of silver was estimated on the basis of humancase reports and long-term animal experiments.The low levels of silver in drinking-water, generally below 5mg/litre, are not relevant to human health with respect to argyria. On the other hand, special situations exist where silver salts may be used to maintain the bacteriological quality of drinking-water. Higher levels of silver, up to 0.1 mg/liter (this concentration gives a total dose over 70 years of half the human NOAEL of 10 g), could be tolerated in such cases without risk to health.There are no adequate data with which to derive a health-based guideline value for silver in drinking-water.
History of guideline development
The 1958, 1963 and 1971 WHO International Standards for Drinking-water did not refer to silver. In the first edition of the Guidelines for Drinking-water Quality, published in 1984, it was not considered necessary to establish a guideline value for silver in drinking-water. No health-based guideline value for silver was proposed in the 1993 Guidelines. Where silver salts are used to maintain the bacteriological quality of 12. CHEMICAL FACT SHEETS 435 drinking-water, levels of silver up to 0.1 mg/liter can be tolerated without risk to health.
Assessment date
The risk assessment was originally conducted in 1993. The Final Task Force Meeting in 2003 agreed that this risk assessment be brought forward to this edition of the Guidelines for Drinking-water Quality.
Principal reference
WHO (2003) Silver in drinking-water. Background document for preparation of WHO Guidelines for drinking-water quality. Geneva, World Health Organization (WHO/SDE/WSH/03.04/14). |
|
