Excretion of selenium

No studies were located regarding the excretion of selenium by humans or other animals after dermal exposure to elemental selenium or selenium compounds. 

Excretion of selenium by humans occurs in the urine, feces, expired air, and sweat, but urine and feces are the major routes of elimination. Some of the selenium in feces may be due to bilary excretion (Levander and Baumann 1966a, 1966b). Elimination is reduced in selenium-deficient individuals and may represent a mechanism by which selenium levels are regulated (Martin et al. 1989a Swanson et al. 1991). Methylation is an important mechanism of detoxification for selenium dimethyl selenide is exhaled, and the trimethylselenonium ion is the major urinary metabolite of selenium. Experiments in mice suggest that the hepatic toxicity of selenium may be at least partly due to depression of selenium methylation in the liver, resulting in the accumulation of excess selenides (Nakamuro et al. 2000). 

A susceptible population will exhibit a different or enhanced response to selenium than will most persons exposed to the same level of selenium in the environment. Reasons may include genetic makeup, age, health and nutritional status, and exposure to other toxic substances (e.g., cigarette smoke). These parameters result in reduced detoxification or excretion of selenium, or compromised function of organs affected by selenium. Populations who are at greater risk due to their unusually high exposure to selenium are discussed in Section 6.7, Populations With Potentially High Exposures. 

In humans and animals, intravenous and oral administration data indicate that the major route of selenium excretion is in the urine (Byard and Baumann 1967 Davidson-York et al. 1999 Finley 1998 Griffiths et al. 1976 Palmer et al. 1970 Patterson et al. 1989 Shiobara et al. 1998 Swanson et al. 1991). Excretion of selenium in feces constitutes a minor pathway immediately following exposure but the amount excreted can be equal to that excreted in urine depending on the chemical form of selenium administered, the size of the dose, and the length of time since dosing. Both human and animal studies indicate that the... 

Gortner RA, Lewis HB. 1939. The retention and excretion of selenium after the administration of sodium selenite to white rats. J Pharmacol Exp Ther 67 358-364. 

Komsta-Szumska E, Reuhl KR, Miller DR. 1983. The effect of methylmercury on the distribution and excretion of selenium by the guinea pig. Arch Toxicol 54 303-310. 

Levander OA, Baumann CA. 1966b. Selenium metabolism. VI. Effect of arsenic on the excretion of selenium. Toxicol Appl Pharmacol 9 106-115. 

Lisk DJ, Bache CA, Essick LA, et al. 1988. Absorption and excretion of selenium and barium in humans from consumption of brazil nuts. Nutrition Reports International 38(1) 183-192. 

McConnell KP, Roth DM. 1966. Respiratory excretion of selenium. Proc Soc Exp Biol Med 123 919-921. 

Oster O, Prellwitz W. 1990. The renal excretion of selenium. Biol Trace Elem Res 24(2) 119-146. 

Lung excretion of selenium 75 and liver function. Int J Appl Radiat Isot 19 669-684. 

Paul and coworkers (1989) have investigated the antidotal actions of several compounds on the acute toxicity of selenium in rats. Male Wistar rats were injected sodium [ Sejselenite subcutaneously in this study. Intraperitoneal administration of diethyldithiocarbamate or treatment with citrate salt of bismuth, antimony, or germanium, administered subcutaneously, reduced selenium-induced loss of body weight in the animals. Germanium citrate and bis(carboxyethyl)germanium sesquiox-ide promoted increases in the 24-hour urinary excretion of selenium when administered 15 minutes after sodium selenite. 

Hawkes, W.C., Alkan, F.Z., and Oehler, L. (2003) Absorption, distribution and excretion of selenium from beef and rice in healthy North American men. J. Nutr., 133, 3434-3442. 

Ingested selenium is absorbed in the intestine, mainly in the duodenum. Thence, it is bound to a protein and transported in the blood to the tissues, where it is incorporated into tissue protein as selenocysteine and selenomethionine in the latter process, selenium replaces the sulfur in the amino acids cysteine and methionine. Excretion of selenium is largely by way of the kidneys, although small amounts are excreted in the feces and in sweat. 

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