4.7.1 drinking water
The USEPA suggested a level of silver in drinking water of not more than 50 µg/L to protect people from possible long-term health effects due to long exposure. In May 1989, a short-term exposure limit (from 1 to 10 days) of 1.142 mg/L was proposed. For occupational exposures OSHA set a legal limit of 10 µg/m3 of silver in the workplace air (Anon. 1990). Health and Welfare Canada and the US Public Health Service recommended a maximum acceptable concentration of 50 µg/L of silver in drinking water (HWC 1978). At this concentration it would take 27 years to ingest the human toxic dose of 1 gram of silver, assuming no elimination and a 2 litre per day intake. This recommedation has since been dropped. In practice, elimination is over 90% of the ingested dose so it would take several life-times.
The Australian criteria for raw domestic water supplies are 50 µg/L (Hart 1974; Anon., Aust., 1992) and in 1980 the IWD, Water Quality Branch, also recommended this level of silver for water supplies which are used without treatment or with only simple filtration. When water received chemical treatment, the recommended silver concentrationwas 200 µg/L (Taylor et al. 1980). The latest guidelines, (CCME 1987; Anon., H. & W. Can., 1993), make no recommendation for silver in drinking water.
literature criteria for the protection of
drinking water.
criteria* |
jurisdiction |
references |
50 (MCL) |
EPA-regulation |
USEPA 1987 |
90 (SMCL) |
EPA-proposed regulation |
USEPA 1989 |
50 |
FDA-permissible bottled water regulation |
USFDA 1988 |
50 |
EPA-recommended limit guideline |
USEPA 1985 |
50 |
EPA-ambient water criteria guideline |
USEPA 1980b |
50 (maximum) |
USA individual states-regulations |
CELDS 1989 |
50 |
Australia |
ANON 1992 |
* in µg/L, mcl is maximum contaminant level and smcl is secondary maximum contaminant level.
4.7.2 recreation and aesthetics
The recommended level was 50 µg/L of total silver (Taylor et al. 1980). The aquatic life level is much lower so there is adequate protection for recreation and sport fishing in areas where aquatic life is being protected. The latest guidelines, (Anon., H. & W. Can., 1992), make no recommendation for silver in recreational water.
4.7.3 wildlife and livestock
There are no data to set a criterion for livestock or wildlife. Toxicity to animals is low and elimination is rapid. Surface waters have low silver levels and should not be a problem (Taylor et al. 1980). The aquatic life level is much lower than any wildlife or livestock criterion would need to be so there is adequate protection in areas where aquatic life is being protected. For confined livestock or laboratory animals, the human drinking water criterion is proposed.