Feces silver

Silver concentrations in muscle of Antarctic birds were low (0.01 mg/kg DW) when compared to livers (0.02 to 0.46 mg/kg DW) or feces (0.18 mg/kg DW Szefer et al. 1993). Silver concentrations in avian tissues, especially in livers, were elevated in the vicinity of metals-contaminated areas and in diving ducks from the San Francisco Bay (Table 7.5). Birds with elevated concentrations of silver in tissues — as much as 44 mg/kg DW in liver in the common eider (Somateria mollissima) — seemed outwardly unaffected (Bryan and Langston 1992). 

Because many silver compounds dissolve in water and do not evaporate, the most common way that silver may enter the body of a person near a hazardous waste site is by drinking water that contains silver or eating food grown near the site in soil that contains silver. Silver can also enter the body when soil that has silver in it is eaten. Most of the silver that is eaten or breathed in leaves the body in the feces within about a week. Very little passes through the urine. It is not known how much of the silver that enters the body through the skin leaves the body. Some of the silver that is eaten, inhaled, or passes through the skin may build up in many places in the body. More information on how silver enters and leaves the body can be found in Chapter 2. 

There are reliable and accurate ways of measuring silver in the body. Silver can be measured in the blood, urine, feces, and body tissues of exposed individuals. Because urine and blood samples are easy to get, these fluids are most often used to find out if a person has been exposed to silver in the last week or so. Silver builds up in the body, and the best way to learn if past exposure has occurred is to look for silver in samples of skin. Tests for silver are not commonly done at a doctor s office because they require special equipment. Although doctors can find out if a person has been exposed to silver by having blood or skin samples examined, they can not tell whether any health effects will occur. Information about tests for measuring silver in the body is in Chapters 2 and 6. 

The clearance of radioactive silver metal dust in a man who was accidentally exposed illustrated the rapid removal of silver from the lungs primarily by ciliary action, with subsequent ingestion and ultimate elimination in the feces (Newton and Holmes 1966). Lung clearance fit a biexponential profile, with biological half-lives of 1 and 52 days. Radioactive silver was detected in the feces up to 300 days after exposure, but was not detected in urine samples (collected up to 54 days after exposure). 

No studies were located concerning the excretion of silver by humans or animals following dermal exposure to elemental silver or silver compounds. Once absorption through the skin and distribution to bodily tissues occurs, it can be expected that elimination would be similar to that of silver absorbed via oral or inhalation exposure, that is, primarily via the feces, with minimal amounts excreted in the urine. 

Silver removal from the liver by biliary excretion was demonstrated by Scott and Flamilton (1950). Control rats and rats with ligated bile ducts were administered radioactive metallic silver by intramuscular injection. In rats with ligated bile ducts, excretion of silver in the feces was 19%, compared to 97% in controls. Deposition in the liver of rats with ligated bile ducts was 48% and 2.5% in the gastrointestinal tract compared to 0.36% and 1.12%, respectively in the controls (Scott and Flamilton 1950). Klaassen (1979b) determined that biliary excretion accounted for between 24% and 45% of the silver administered to rats. The concentration of silver in the bile was estimated to be... 

Because silver is eliminated primarily through the feces, recent exposure is most easily monitored through fecal analysis. Measurements of silver in the blood are also significant and indicate exposure to the metal. However, silver is not always detected in the urine samples of workers with known exposure to the chemical, and is not as reliable a biomarker as feces and blood. DiVincenzo et al. (1985), for example, detected silver in 100% of feces samples and only 6% of urine samples from workers chronically exposed to silver compounds in air. Increased blood silver levels, above the detection limit for silver (0.6 pig/100 mL blood), have been associated with inhalation exposure to the metal in a study by Rosenman et al. (1979). 

Biomarkers of Exposure and Effect. Silver can be detected in blood, urine, feces, hair, and skin biopsy specimens. The best indictor of recent exposure to silver or silver compounds is detection of silver levels in feces and blood. Intermediate as well as long-term exposures are best monitored by measuring silver in blood or skin biopsy specimens. Argyria, the change in skin color associated with silver exposure, is also an indicator of chronic exposure. No other biomarkers for silver have been developed. Development of alternative biomarkers capable of detecting early exposure to low levels of silver would be useful in determining the possible toxic effects of this metal. 

Exposure Levels in Humans. Silver has been detected in the blood, tissues, urine, and feces of humans. The only biological monitoring studies located consisted of small numbers of worker populations in chemical manufacturing industries. Studies that better characterize important sources of general population exposure and define populations with potentially high exposure, such as those located near hazardous waste sites, would be helpful. More specific information concerning the chemical from of silver present at hazardous waste sites would also be useful. These data would assist in developing a more accurate estimate of the potential for silver exposure from hazardous waste sites contaminated with the metal. 

DiVincenzo et al. (1985) employed the GFAAS technique to evaluate human samples for biological monitoring of silver exposure levels in the workplace. The authors determined the total silver concentration in urine, blood, feces, and hair with detection limits of 0.005 pig/L, 0.5 pg/100 ml, 0.2 p gig, and 0.02 pg/g, respectively. 

Methods for Determining Biomarkers of Exposure and Effect. Existing methods of measuring levels of silver in blood, urine, feces, hair, and tissues are extremely sensitive and can measure levels in the low ppm to ppt. These methods are accurate and reliable and can be used to measure both background levels of exposure and levels at which biological effects occur. No additional analytical methods for determining trace levels of silver in biological materials are needed. 

Because chlorine is inactivated by blood, serum, feces, and protein-containing materials, surfaces should be cleaned before chlorine disinfectant is applied. Undissociated hypochlorous acid (HOC1) is the active biocidal agent. When pH is increased, the less active hypochlorite ion, OC1 , is formed. When hypochlorite solutions contact formaldehyde, the carcinogen /v.v-chloromethyl is formed. Rapid evolution of irritating chlorine gas occurs when hypochlorite solutions are mixed with acid and urine. Solutions are corrosive to aluminum, silver, and stainless steel. 

Gregus and Klaassen carried out a comparative study of fecal and urinary excretion and tissue distribution of eighteen metals in rats after intravenous injection. Total (fecal + urinary) excretion was relatively rapid (over 50% of the dose in 4 days) for cobalt, silver and manganese between 50 and 20% for copper, thallium, bismuth, lead, cesium, gold, zinc, mercury, selenium and chromium and below 20% for arsenic, cadmium, iron, methylmercury and tin. Feces was the predominant route of excretion for silver, manganese, copper, thallium, lead, zinc, cadmium, iron and methylmercury whereas urine was the predominant route of excretion of cobalt, cesium, gold, selenium, arsenic and tin. Most of the metals reached the highest concentration in liver and kidney. However, there was no... 

In practice, only a small proportion of the silver presented to a wound site in a dressing is involved in antimicrobial action. Most remains within the dressing or binds to proteins in the wound or wound debris. Very little is systanically absorbed. Even if absorbed sys-temically, silver is exaeted out of the body, mainly via the biliary route in feces. Some is also excreted in urine. Silver is not absorbed into the central or peripheral nervous systems. 

Figure 4.2. Data for the stationary rate of 2D nucleation of silver on the cubic fece of a single silver crystal obtained at f = 318K [4.16] and plotted according to the classical nucleation theory (equation (4.8)).

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