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The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

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E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Tributyltin (TBT)

Trade and Other Names: Trade names include Alumacoat, Bioclean, FloTin, Fungitrol, TinSan, Ultrafresh and Vikol.

Regulatory Status: Some applications are Restricted Use, primarily those involving potential exposures to non-target aquatic organisms, such as may occur with use of TBT-containing marine paints [1]. Tributyltin is in EPA toxicity class II - moderately toxic. Depending on the product, labels will be required to display the Signal Words DANGER or WARNING.

These paint uses are now regulated under the Organotin Antifouling Paint Control Act of 1988. This Act sets guidelines on the amount and rate of TBT compounds leaching from marine paints into the aquatic environment.

Chemical Class: trialkyl organotin compound

Introduction: The tributyltin compounds are a subgroup of the trialkyl organotin family of compounds. They are the main active ingredients in biocides used to control a broad spectrum of organisms. Uses include wood treatment and preservation, antifouling of boats (in marine paints), antifungal action in textiles and industrial water systems, such as cooling tower and refrigeration water systems, wood pulp and paper mill systems, and breweries. It is also used for control of shistosomiasis in various parts of the world [188].

Tributyltin compounds are present in varying proportions in commercial products; ready-to-use wood preservatives typically contain as little as 0.3% TBT, but some products used only in manufacturing may contain as much as 48% [160].

Unless otherwise specified, all toxicity and environmental chemistry data presented are for tributyltin oxide, a representative compound.

Formulation: Tributyltin compounds are present in varying proportions in commercial products; ready-to-use wood preservatives typically contain as little as 0.3% TBT, but some products used only in manufacturing may contain as much as 48% [160].

Toxicological Effects:

• Acute toxicity: Acute toxicity of organotin compounds is strongly influenced by the length of the alkyl chains attached to the tin [160,191]. Tributyltin (TBT) is generally less toxic than trimethyl- and triethyltins [160]. Generally, the toxicity of organotin compounds is influenced more by the alkyl substituents than the ionic substituent, which may form the rest of the molecule (for example, salicylate, acrylate, etc.) [191]. Tributyltin compounds are moderately toxic via both ingestion and dermal absorption. Reported oral LD50 values for tributyltin oxide (TBTO) range from 55 to 87 mg/kg in mice and rats [191,192]. Dermal LD50 values are 200 mg/kg in rats and mice, [191,192] and 900 mg/kg in rabbits [31,192]. The tributyltin compounds may be strongly irritating to the skin in humans, especially the hair follicles, and skin exposure may result in chemical burns in only a few minutes if the concentration of tributyltin is high enough [191]. Shipyard workers exposed to TBT (occupationally exposed to dusts and vapors) developed irritated skin, dizziness, difficulty breathing, and flu-like symptoms [8]. Other mucous membranes such as the eyes and nasal passages may also become irritated upon exposure.
• Chronic toxicity: Although the effects of tributyltin on humans are uncertain, there have been cases of human exposure reported. Underwear treated with TBT caused severe skin irritation in wearers, and shipyard workers occupationally exposed reported reduced sense of smell, chronic headaches, and feelings of musculoskeletal stiffness [191]. Prolonged exposure to organotin compounds has produced bile duct damage in several mammalian species [191] and TBT may be a potent immunotoxic agent [192]. One study of male rats fed TBTO daily for 6 weeks resulted in decreased resistance to infection [193,194].
• Reproductive effects: Data regarding reproductive effects are limited. In one study, increased fetal mortality was observed in rats at doses of 16 mg/kg/day [195].
• Teratogenic effects: In a teratology study of tributyltin acetate on pregnant Wistar rats, a dose of 16 mg/kg/day administered on days 7 to 17 of pregnancy resulted in increased fetal mortality, incidence of cleft palate, irregularities in rib cage, and decreased fetal birth weights [195]. Tributyltin was associated with offspring behavior abnormalities in another study of rats at doses up to 5 mg/kg/day [196]. These effects are unlikely in humans at expected exposure levels.
• Mutagenic effects: Tributyltin did not appear to be mutagenic in a large battery of mutagenicity assays, but produced DNA nucleotide base pair substitutions (point mutations) in one bacterial strain tested [192]. It produced mutations in Chinese hamster ovary cells as well [192]. The evidence for mutagenicity is inconclusive.
• Carcinogenic effects: While one study indicates that rats have developed pituitary gland tumors after exposure to high doses of TBT, the evidence is not conclusive [8] and the carcinogenic status of TBT is still uncertain [191].
• Organ toxicity: In mammals, high levels of TBTO can affect the endocrine glands, upsetting the hormone levels in the pituitary, gonad, and thyroid glands. Large doses of TBT have been shown to damage the reproductive and central nervous systems, bone structure, and the liver bile duct of mammals. TBT compounds can also damage the immune system.

• Fate in humans and animals: In mice, TBTO is excreted mainly unchanged via the feces, indicating low absorption by the body. In mammalian species, tributyl compounds may be metabolized to dibutyltin derivatives and related metabolites [192]. An undetermined amount of this compound is known to remain in fat, liver, kidney, and lung tissues.

Ecological Effects:

• Effects on birds: No treatment-related mortality was observed in a 13-week study of toxic effects of TBTO in Japanese quail at dietary levels of 150 ppm; at 375 ppm, egg production, eggshell thickness, fertility, and hatchability were reduced [197]. Thus, tributyltin can be considered moderately toxic to birds.
• Effects on aquatic organisms: Tributyltin compounds are highly to very highly toxic to many species of aquatic organisms. TBT exposure to non-target aquatic organisms such as mussels, clams, and oysters, at low levels, may cause structural changes, growth retardation, and death [198,199]. TBT is very highly toxic to crustaceans. Lobster larvae show a nearly complete cessation of growth at just 1.0 ug/L TBT [200]. Molluscs, used as indicators of TBT pollution because of their high sensitivity to these chemicals, react adversely to very low levels of TBT (0.06-2.3 ug/L). They release TBT very slowly from their bodies after it has been absorbed. Imposex, the development of male characteristics in females, has been initiated by TBT exposure in several snail species. In laboratory tests, reproduction was inhibited when female snails exposed to 0.05 ug/L of TBT developed male characteristics [200]. Imposex was also noted in the mud snail, or dogwhelk, at less than 3 ppt TBT [200]. Oysters in France and England's marine waters are adversely affected by TBT exposure. TBT-exposed oysters have abnormal shell development, poor weight gain, brittle shells, and imposex. TBT toxicity in the field may be substantially underestimated in laboratory studies [200]. TBT binds to the sides of containers and plankton which contributes to this underestimation of its potential toxicity. Generally, the larvae of any tested species are more sensitive to tributyltin exposure than are the adults. TBTO has been shown to inhibit cell survival of marine unicellular algae at very low concentrations; the 72-hour EC50 ranges from 0.33 ug/L to 1.03 ug/L [200]. TBT is lipophilic and tends to accumulate in oysters, mussels, crustaceans, molluscs, fish, and algae. Freshwater species will bioaccumulate more TBT than will marine organisms. Oysters bioaccummulate TBT compounds readily, reach an equilibrium uptake soon after exposure, and are slow to release this chemical. Oysters exposed to very low TBTO concentrations bioaccumulated TBT 1000 to 6000 fold. Juvenile chinook salmon accumulate TBT immediately upon exposure to low TBT concentrations. TBT and its metabolite, DBT, were found in the salmon's muscle tissue [201].
• Effects on other organisms: No data are currently available.

Environmental Fate:

• Breakdown in soil and groundwater: Under aerobic conditions, tributyltin takes 1 to 3 months to degrade [201]. But in anaerobic (airless) soils, this compound will persist for more than 2 years. Tributyltin compounds may be moderately to highly persistent. Degradation depends on temperature and the presence of microorganisms. The breakdown of TBT leads eventually to the tin ion [201]. All of the breakdown products are less toxic than TBT itself. It has not been found in groundwater.
• Breakdown in water: Because of the low water solubility of TBT and other properties, it will bind strongly to suspended material such as organic material or inorganic sediments [160] and precipitate to the bottom sediment [201]. Rates of sedimentation vary with location, organic content, particle size, and type of material. Reported half-lives of the compound in freshwater are 6 to 25 days; in seawater and estuarine locations, it is 1 to 34 weeks, depending on the initial concentration [202]. Because of the low levels of UV light beyond the topmost few centimeters, it is unlikely photolysis plays a major role in degradation of tributyltin compounds [202]. Levels up to 0.800 ug/L have been found along the East Coast of the United States. In the Great Lakes, concentrations from 0.020 to 0.840 ug/L have been recorded. In San Diego Bay a concentration of 1.0 ug/L TBT has been found [198].
• Breakdown in vegetation: No data are currently available.

Physical Properties:

• Appearance: The physical property data presented are for tributyltin oxide, which is a slightly yellow, combustible liquid [8].
• Chemical Name: Bis(tributyltin)oxide [8]
• CAS Number: 56573-85-4
• Molecular Weight: 595.62
• Water Solubility: ca. 4 mg/L @ 20 C and pH 7.0 [8]
• Solubility in Other Solvents: Not Available
• Melting Point: 53 C [8]
• Vapor Pressure: 0.1 mPa @ 20 C [8]
• Partition Coefficient: 5500 in 32% seawater [203]
• Adsorption Coefficient: Not Available

Exposure Guidelines:

• ADI: Not Available
• MCL: Not Available
• RfD: 0.00003 mg/kg/day [13]
• PEL: 0.1 mg/m3 (as Sn) (8-hour) [14]
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

Agtrol Chemical Products
7322 Southwest Freeway
Suite 1400
Houston, TX 77074

• Phone: Not Available
• Emergency: Not Available
  

References:

References for the information in this PIP can be found in Reference List Number 10

DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide product labeling or other regulatory requirements. Please refer to the pesticide product labeling.