# CRITERIA DOCUMENT: RECOMMENDATIONS FOR AN OCCUPATIONAL EXPOSURE STANDARD FOR ORGANOTIN COMPOUNDS
recommends that employee exposure to organotin compounds in the workplace be controlled by adherence to the following sections. The standard is designed to protect the health and provide for the safety of employees for up to a 10-hour work shift in a 40-hour workweek over a normal working life. Compliance with all sections of the standard should prevent adverse effects of organotin compounds on the health of employees and provide for their safety. Although NIOSH considers the workplace environmental limit to be a safe level based on current information, the employer should regard it as the upper boundary of exposure and make every effort to maintain the exposure as low as is technically feasible. The criteria and standard will be subject to review and revision as necessary.
Organotin is the common name assigned to the group of compounds having at least one covalent bond between carbon and tin. The term "organotin" will be used throughout the document to refer to such compounds. Major subgroups will be referred to as mono-, di-, tri-, and tetraorganotins.
The "action level" is set at half the recommended timeweighted average (TWA) workplace concentration limit. An employee is exposed or potentially exposed to organotins if that employee is involved in the occupational handling of the compounds or works in a plant containing organotins. "Occupational exposure" occurs when exposure exceeds the action level or if skin or eye contact with organotins occurs.
"Overexposure" to organotins occurs if an employee is known to be exposed to the organotins at a concentration in excess of the TWA concentration limit, or is exposed at any concentration sufficient to produce irritation of eyes, skin, or upper or lower respiratory tract. If exposure to other chemicals occurs, the employer shall comply also with the provisions of applicable standards for these other chemicals. "Emergency" is defined as any disruption in work process or practice, such as, but not limited to, equipment failure, rupture of containers, or failure of control equipment, which is likely to result in unexpected exposure to organotin compounds in quantities which may cause physical harm.
Section 1 -Environmental (Workplace Air)

# (a) Concentration
The employer shall control exposure to organotin compounds so that no employee is exposed at a concentration greater than 0.1 milligram, measured as tin, per cubic meter (mg/cu m) of air, determined as a TWA concentration for up to a 10-hour work shift in a 40-hour workweek.

# (b) Sampling and Analysis
Environmental samples shall be collected and analyzed as described in Appendices I and II, or by any methods shown to be at least equivalent in accuracy, precision, and sensitivity to the methods specified.

# Section 2-Medical
Medical surveillance shall be provided to employees or prospective employees who may be occupationally exposed to organotin compounds.
(a)
Preplacement examinations shall include at least:
(1) Comprehensive medical and work histories. (E) Neurologic examination to detect any prior history or evidence of increased intracranial pressure.
If spinal fluid pressure is measured, the Queckenstedt maneuver should be performed.
(F) Urinalysis.
(3) An evaluation of the employee's ability to use positive or negative pressure respirators.
(4) Prospective employees or employees with evidence of a medical condition which could be directly or indirectly aggravated by exposure to organotin compounds should be counseled concerning the advisability of their working with or continuing to work with these compounds.
(b) Periodic examination shall be made available on at least an annual basis or at some other interval determined by the responsible physician. These examinations shall include at least:
(1) Interim medical and work histories.
(2) Physical examination as outlined in paragraph (a)(2) of this section, except that the neurologic examination may be omitted at the discretion of the responsible physician.
(c) Initial medical examinations shall be made available to all employees within 6 months of the promulgation of a standard based on these recommendations. These examinations shall follow the requirements of the preplacement examination. The employer shall provide appropriate medical services to any employee with adverse health effects reasonably assumed or shown to be due to exposure to organotin compounds in the workplace.
(f) The employer or successor thereto shall ensure that pertinent medical records are kept for all employees exposed to organotin compounds in the workplace for at least 5 years after termination of employment. (e) All warning signs and labels shall be printed in English and in the predominant language of non-English-reading employees, unless the employer uses equally effective means to ensure that non-English-reading employees know the hazards associated with organotin compounds and the areas in which there may be occupational exposure to organotins. Employers shall ensure that employees unable to understand these signs and labels also know these hazards and the locations of these areas.

# Section 4 -Personal Protective Equipment and Clothing
The employer shall use engineering controls and safe work practices to keep the concentration of airborne organotins at or below the limit specified in Section 1(a) and shall provide protective clothing impervious to organotins to prevent skin and eye contact. Emergency equipment shall be located at clearly identified stations within the work area and shall be adequate to permit all employees to escape safely from the area.
Protective equipment suitable for emergency use shall be located at clearly identified stations outside the work area.
(a) Protective Clothing
The employer shall provide chemical safety goggles or face shields and goggles and shall ensure that employees wear the protective equipment during any operation in which organotins may enter the eyes.
The employer shall provide appropriate impervious clothing, including gloves, aprons, suits, boots, or face shields (8-inch minimum) and goggles and shall ensure that employees wear protective clothing where needed to prevent skin contact.

# (b) Respiratory Protection
(1) Engineering controls shall be used whenever feasible to maintain organotin concentrations at or below the TWA concentration limit.
Respiratory protective equipment shall be used in the following circumstances :
(A) During the time necessary to install or test the required engineering controls.
(B) For operations such as maintenance and repair activities causing brief exposure at concentrations in excess of the TWA concentration limit.
(C) During emergencies when concentrations of airborne organotins might exceed the TWA concentration limit.
(D) When engineering controls are not feasible to maintain atmospheric concentrations below the TWA concentration limit.
(2) When a respirator is permitted by paragraph (b)(1) of this section, it shall be selected and used in accordance with the following requirements:
(A)
The employer shall establish and enforce a respiratory protective program meeting the requirements of 29 CFR 1910.134.

# (B)
The employer shall provide respirators in accordance with Table 1-1 and shall ensure that employees use the respirators provided. The respiratory protective devices provided in conformance with Table 1-1 shall comply with the standards jointly approved by NIOSH and the Mining Enforcement and Safety Administration (formerly Bureau of Mines) as specified under the provisions of 30 CFR 11. Respirator Type
Less than or equal to 2.5
(1) Full facepiece respirator with combination high efficiency filter and organic vapor canis ter (pesticide respirator) (2) Supplied-alr respirator with full facepiece operated in demand (negative pressure) mode (3) Self-contained breathing apparatus with full facepiece operated in demand mode
Less than or equal to 50.0
(1) Supplied-air respirator with full facepiece operated in continuous-flow (positive pressure) mode, worn with impervious clothing (2) Supplied-air respirator with full facepiece operated in pressure-demand (positive pressure) mode, worn with impervious clothing (3) Powered air-purifying respirator with hood, helmet, or full facepiece and with combination high efficiency filter and organic vapor canister Greater than 50.0
(1) Self-contained breathing apparatus with full facepiece operated in pressure-demand mode (2) Combination supplied-air respirator with full facepiece and auxiliary self-contained air supply operated in the pressure-demand mode Emergency (entry into area of unknown concentration for emergency purposes, such as firefighting)
(1) Self-contained breathing apparatus with full facepiece operated in pressure-demand mode, worn with impervious clothing (2) Combination supplied-air respirator with full facepiece and an auxiliary self-contained air supply operated in the pressure-demand mode, worn with impervious clothing Escape (from area of unknown con centration)
(1) Self-contained breathing apparatus with full facepiece operated in pressure-demand mode (2) Gas mask with full facepiece and with combination high efficiency filter and either front-or back-mounted organic vapor canister (C) Respirators specified for use in higher concentrations of organotins may be used in atmospheres of lower concentrations.
(D) When a self-contained breathing apparatus is permitted in accordance with Table 1-1, it shall be used pursuant to the following requirements:
(i) The employer shall provide initial training and refresher courses on the use, maintenance, and function of self-contained breathing apparatus.
(ii) If the self-contained breathing apparatus is operated in the negative-demand mode, a supervisor shall check employees and ensure that the respirators have been properly adjusted prior to use.
(iii) Whenever a self-contained breathing apparatus is supplied for escape purposes, the respirator shall be operated in the pressure-demand mode.
Section 5 -Informing Employees of Hazards from Organotins Employers shall take all necessary steps to ensure that employees are instructed in and follow the procedures specified below and any others appropriate for the specific operation or process for all work areas where there is a potential for emergencies involving organotins.
(1) Instructions shall include prearranged plans for obtaining emergency medical care and for transportation of injured employees.
(2) Approved eye, skin, and respiratory protection as specified in Section 4 shall be used by personnel essential to emergency operations.
Employees not essential to emergency operations shall be evacuated from hazardous areas where inhalation, ingestion, or direct skin or eye contact may occur. The perimeter of these areas shall be delineated, posted, and secured.
(3) Only personnel properly trained in the procedures and adequately protected against the attendant hazards shall shut off sources of organotins, clean up spills, and repair leaks. Spills and leaks shall be attended to immediately to minimize the possibility of exposure.
(4) Any spills of organotins shall be cleaned up immediately.
(5) Eyewash fountains and emergency showers shall be provided in accordance with 29 CFR 1910.151.

# (b) Control of Airborne Organotins
Engineering controls, such as process enclosure or local exhaust ventilation, shall be used whenever feasible, to keep organotin concentrations within the recommended environmental limit. Ventilation systems shall be designed to prevent the accumulation or recirculation of organotins in the workplace environment and to effectively remove organotins from the breathing zones of employees. Exhaust ventilation systems discharging to outside air must conform to applicable local, state, and federal air pollution regulations and must not constitute a hazard to employees. Ventilation systems shall be subject to regular preventive maintenance and cleaning to ensure effectiveness, which shall be verified by airflow measurements taken at least every 3 months.

# (c) Storage
Containers of organotins shall be kept tightly closed at all times when not in use. Containers shall be stored in a safe manner to minimize accidental breakage or spillage and to prevent contact with strong oxidizers.
(d)

# Handling and General Work Practices
(1) Before maintenance work is undertaken, sources of organotins shall be shut off.
If concentrations at or below the TWA environmental concentration limit cannot be assured, respiratory protective equipment, as described in Section 4 of this chapter, shall be used during such maintenance work.
(2) Employees who have skin contact with organotins shall immediately wash and shower, if necessary, for at least 15 minutes to remove all traces of organotins from the skin. Contaminated clothing shall be removed immediately and disposed of or cleaned before reuse. If contaminated clothing is to be reused, it shall be stored in a container, such as a plastic bag, which is impervious to the compound, prior to cleaning.
Personnel involved in cleaning contaminated clothing shall be informed of the hazards involved and be provided with safety guidelines on the handling of these compounds. (1) A program of personal monitoring shall be instituted to identify and measure, or permit calculation of, the exposure of each employee occupationally exposed to organotins. Source and area monitoring may be used to supplement personal monitoring.
(2) Samples representative of the exposure in the breathing zone of the employee shall be collected in all personal monitoring.
Procedures for the calibration of equipment, sampling, and analysis of organotin samples shall be as provided in Section 1(b).
(3) For each TWA concentration determination, a sufficient number of samples shall be taken to characterize the employee's exposure.
Variations in the employee's work schedule, location, and duties and changes in production schedules shall be considered when samples are collected.
(4) If an employee is found to be exposed above the action level, the exposure of that employee shall be monitored at least once every 3 months. If an employee is found to be overexposed, the exposure of that employee shall be measured at least once every week, control measures shall be initiated, and the employee shall be notified of the exposure and of the control measures being implemented. Such monitoring shall continue until two consecutive determinations, at least 1 week apart, indicate that the employee's exposure no longer exceeds the recommended environmental concentration limit; quarterly monitoring may then be resumed.

# (b) Recordkeeping
Employers or their successors shall keep records of environmental monitoring for each employee for at least 5 years after the individual's employment has ended. These records shall include the name and social security number of the employee being monitored, duties and job locations within the work site, dates of measurements, sampling and analytical methods used and evidence for their accuracy, duration of sampling, number of samples taken, results of analyses, TWA concentrations based on these samples, and any personal protective equipment in use by the employee.
Records for each employee, indicating date of employment with the company and changes in job assignment, shall be kept for the same 5-year duration.  NIOSH estimates that 30,000 employees in the United States may be exposed to organotin compounds.

# Historical Reports
The earliest known report of an organotin compound was made in 1849 by Frankland  describing the preparation of various ethylmetal compounds, including an unidentified ethyltin derivative. Frankland  was later able to characterize this compound as diethyltin diiodide, and he prepared, in addition, diethyltin oxide and dichloride and a compound he believed to be tetraethyltin.
The first reference to biologic effects of organotin compounds was made in 1858 by Buckton , who noted that the chloride form of a class of compounds he called stannic bis-ethyls had a "powerfully pungent odour" and, when heated, produced a vapor that "painfully attacks the skin of the face" and caused fits of sneezing. Eleven years later, Jolyet and Cahours  experienced similar effects while conducting a comparative study of the toxic effects of diethyltin dichloride, trialkyltin chloride, and tetraethyltin on dogs. In the dogs, the diethyltin derivative had a strong purgative effect when administered by ingestion or by intravenous or subcutaneous injection. The latter two compounds were more noxious than was the diethyltin derivative. However, the diethyltin chloride, iodide, and sulfate were particularly distinguished, showing more powerful purgatory properties either by ingestion or injection (iv or subcutaneous).
White , in 1881, noted that the vapor of triethyltin acetate produced headache, general weakness, nausea, diarrhea, and albuminuria, and that tetraethyltin caused severe headaches in the investigator. Chronic exposure studies on rabbits and dogs showed the presence of central nervous system (CNS) effects, motor disturbance, spasm of the gastrointestinal tract and, at high doses, death.
During the early 1940's, the sternutatory, irritative, and lachrimatory properties in humans and animals of triethyltin iodide were studied for possible war-related applications . None of these effects were considered potent enough to warrant using the organotins as a war-related material.   and by exploratory surgery in others , appeared to have been an acute cerebral, medullary, and meningeal edema , However, despite the extensive listing of observed signs and symptoms, abnormal physical findings were not apparent in many victims , Of the 98 patients who died, 51 had shown no prior clinical signs.
Of the 103 patients who eventually recovered, 46 showed no neurologic signs or symptoms during the course of their illness, even when convalescence lasted several months .
Gruner  found that the lesions produced in the nervous system of humans by Stalinon intoxication were almost identical with those seen in the brains of monkeys and mice killed after the experimental administration of Stalinon (see Animal Toxicity for details). Macroscopically, the brain was swollen and heavy, but the meninges were dry and the ventricular system was collapsed. Microscopically, only minor lesions were detected in the cerebra.
Myelin displacement and degeneration with degeneration of the supporting and glial tissues were also observed. The axons of the central regions were irregular, but fragmentation was a rarity. The macroglia were swollen and filled with granules, with a very pale cytoplasm. The cortex was not so severely affected, but had swollen myelin sheaths, tumefaction of the oligoglia, and vasodilatation of the deep layer.

# No abnormalities
were observed in the neurons. Peripheral nerves were not discussed.
Studies of the effects of pure DEDI in experimental animals have shown that this compound does not reproduce all the effects reported from the use of Stalinon. This preparation may, therefore, have been contaminated with triethyltin iodide , monoethyltin triiodide , tetraethyltin , diethyltin dibromide, or ethyltin tribromide .
DEDI may have reacted with the isolinoleic acid esters in the medication to form tetraethyltin , a reaction demonstrated to exist by Clinical signs at 4, 12, and 24 hours for the dioctyltins were similar to those observed with the monoalkyltins but were more severe .
Macroscopic and microscopic examinations for all compounds showed that damage to the liver, kidneys, and spleen produced by a single dose of 4,000 mg/kg was of the same nature as that from the monoalkyltins  . However, similar effects were obtained with doses of 500 mg/kg of the tributyltins
, indicating that these compounds are more toxic than their monoalkyltin and dialkyltin counterparts.
Results from these studies  indicate that monoalkyltins are the least toxic and trialkyltins the most toxic of the compounds studied.
The compounds are nonspecific in their toxic actions, but the liver, kidney, and spleen are the organs most susceptible to damage.
Calley et al  used albino mice to compare the toxic effects on the liver of some butyltin derivatives. To select the proper dosage for these experiments, the single-dose oral LD50 values for white mice of a uniform weight and age were determined for tetrabutyltin (TeBT), tributyltin acetate (TBTA), dibutyltin diacetate (DBDA), and dibutyltin di(2-ethylhexoate) (DBDE), with observation for 1 week after the dose was administered.
The compounds were administered to mice in groups of 10 by intubation in doses increasing in a geometric progression by a factor of 2.
The LD50 values obtained were 6,000.0, 99.1, 109.7, and 199.9 mg/kg for TeBT, TBTA, DBDA, and DBDE, respectively.
Torack et al  induced cerebral edema and swelling in mice by administering in the diet 12-32 ppm triethyltin sulfate or triethyltin hydroxide for an unspecified period. The authors examined brain tissues microscopically to study the changes in fine structure associated with accumulation of cerebral fluid. Initially, the mice were irritable and showed prominent muscular weakness, especially of the hindlimbs. This was followed by increasing generalized rigidity of the body, with shallow respiration. Brain tissues from 25 mice were taken at varying stages of intoxication and clinical manifestations. Examination by light microscopy revealed evidences of edema in the myelinated areas of the brain, dilatation of the perivascular clear spaces, and swelling of the glial cell bodies. Electron microscope examination of brain tissues of 18 mice in the early stages of intoxication showed an enlargement of the glial cell processes, but, in the less severe lesions, the mitochondria, endoplasmic reticulum, and cell membranes appeared to be relatively normal. In the advanced stages, endothelial cells were swollen, mitochondria enlarged, and the number of microglia increased in the edematous areas. The clear glial cell membranes were ruptured, but there was no accumulation of fluid in the intracellular spaces.
Gruner  reported that mice and monkeys killed after the experimental administration of Stalinon had lesions of the CNS which were almost identical with those in humans suffering from Stalinon intoxication.
Few procedural details were provided except that the Stalinon dose in monkeys was in the same range as that administered therapeutically to humans. Macroscopically, the brain was swollen and heavy, but the meninges were dry and the ventricular system was collapsed. Microscopically, only minor lesions were detected in the cerebra. Myelin displacement and degeneration, with degeneration of the supporting and glial tissues, were also observed. The axons of the central regions were irregular, but fragmentation was rare.
The macroglia were swollen and filled with granules, with a very pale cytoplasm. The cortex was not so severely affected but had swollen myelin sheaths, tumefaction of the oligoglia, and vasodilatation of the deep layer. No abnormalities were observed in the neurons. Peripheral nerves were not discussed. Examination of the organs of both species of experimental animals showed gross vasodilation, severe edema, small hemorrhages, and proliferation of the Kupffer cells in the liver. The study indicated that the organotins produced similar CNS changes in mice, monkeys, and humans.
The influence of aliphatic chain branching on the toxicity of tetrabutyltin and tetraamyltin was examined by Caujolle et al , using the normal and iso isomers of these compounds. Groups of 10-20 male and female mice weighing 18-20 g were observed for 30 days after the oral administration of the test compound at doses of 2-40 mM/kg for tetrabutyltin, 0.5-25 mM/kg for tetraisobutyltin, 1-40 mM/kg for tetraamyltin, and 0.25-20 mM/kg for tetraisoamyltin. The animals at all dose levels displayed a loss of muscle tone; those given the higher doses had paralysis of the hindquarters and superficial respiration. Mortality rates (Table XII-4 a-d) indicated that the iso derivatives were more toxic than the normal derivatives. The butyl derivatives were found to be more toxic than their amyl counterparts. Similar findings were reported by the authors with im, iv, and ip administration of these compounds at similar doses to mice .
The toxicities of dibutyltin dichloride (DBDC), tributyltin chloride (TBTC), and tetrabutyltin (TeBT) were compared by Yoshikawa and Ishii .
Single ip injections of 1-3.7 mg/kg were administered to groups of 10 male mice. After 8 days, the surviving mice were killed and the weights of their organs, as fractions of the body weights, were compared with those of 20 untreated male mice. Mice given DBDC or TeBT had enlarged livers, but those given TBTC did not. All three compounds caused an increase in the weight of the spleen in the treated animals. Brain weight in animals treated with TBTC or TeBT was greater than that of the control mice, but this effect was not observed in DBDC-treated mice. All compounds produced increases in kidney weight.
The results indicate that TeBT had some effects similar to those of both DBDC and TBTC, but DEDC and TBTC differed in their toxic actions.
(3) Intraperitoneal Kolia and Zalesov  administered organotins by ip injection to study the influence of chemical structure on the toxicities of the compounds.
Eight hundred white mice weighing 16-17 g were used for a series of experiments in which different groups were given one of 11 triaryl-or tetraryltin derivatives in progressive doses until 100% fatality was achieved. Animals were observed over a 10-day period or until 100% fatality, and LD50's were calculated using the Litchfield and Wilcoxon method. The LD50's obtained are listed in Table XII-5, along with results of a statistical analysis comparing the toxicities of these compounds. The results indicated that the toxicity of an organotin compound was dependent upon both the type of anion and the organic side group. The halide salts appeared to be more toxic than the corresponding alkylated compounds; the bromides were more toxic than the iodides. No chlorides were used.
Toxicity decreased with an increase in methylation of the aromatic radical.
The tetraaryl derivatives were less toxic than their triaryl counterparts.
Branching of the carbon chain in the alkyl group appeared to increase the toxicity of the compound.

# (b) Rats
(1) Inhalation
Inhalation studies have been performed on rats under acute and chronic test conditions to evaluate the toxic properties of some triorganotins.
Acute dust inhalation studies  were conducted for tri-n-butyltin fluoride (TnBTF) and triphenyltin fluoride (TPTF). For
TnBTF studies, young adult albino rats with an average weight of 165 g were divided into five groups of five males and five females  . No control group was described in the studies. Animals were exposed to TnBTF in a test chamber for 4 hours, and mortality and behavioral reactions were noted. At the end of exposure, the animals were observed for an additional observed in some of these animals at autopsy were mild to severe focal discoloration of the lungs and enlarged lungs.
The acute inhalation toxicity of dimethyltin dichloride (DMDC) vapor was evaluated in the presence of varying amounts of trimethyltin chloride (TMTC) contaminant, using young adult Charles River albino rats in groups of five males and five females . Animals were exposed to DMDC for 1 hour, and mortality and behavioral reactions were observed for 21 days.
Nominal vapor concentrations were based on weight loss of the test material and total volume of air used. At the end of the 21-day period, animals were killed, and gross pathologic examination was conducted.
At DMDC concentrations of 1,910 mg/cu m (1,031 mg/cu m, as tin),
1,610 mg/cu m with 0.19% TMTC (870 mg/cu m, as tin), and 2,640 mg/cu m with 0.87% TMTC (1,428 mg/cu m, as tin), no deaths occurred . Body weight gains were normal, and autopsy revealed no gross pathologic alterations.
Hypoactivity and roughed fur were observed at these three concentrations; ptosis, enophthalmos, and salivation were present also at 2,640 mg/cu m with 0.87% TMTC. At a concentration of 2,110 mg/cu m with 2.09% TMTC
(1,142 mg/cu m, as tin), all animals died within 11 days and hypoactivity, roughed fur, ptosis, enophthalmos, anesthesia, and tremors were observed in all animals. However, autopsy revealed no abnormalities attributable to DMDC toxicity. With DMDC at a concentration of 4,080 mg/cu m with 3.59% TMTC (2,205 mg/cu m, as tin), results were similar except that all animals died within 4 days.
Similar test procedures were used to study the effects of short-term inhalation of DBDC and TMTC vapors . Rats exposed to DBDC for 1 hour at a concentration of 1,470 mg/cu m (575.0 mg/cu m, as tin) showed roughed fur, hypoactivity, ptosis, and salivation within the 14-day observation period . There were no deaths. Body weight gains were normal and autopsy revealed no gross pathologic alterations. All rats exposed to TMTC at a concentration of 8,890 mg/cu m (5,334 mg/cu m, as tin) died on the 1st day; signs included hypoactivity, roughed fur, enophthalmos, ptosis, anesthesia, and dyspnea . Autopsy revealed no abnormalities attributable to TMTC.
Two vapor inhalation studies were conducted to determine the toxic effects of tributyltin chloride (TBTC) and tributyltin bromide (TBTB) on rats . Gohlke et al   Microscopic examinations were performed on the brain, lungs, liver, and kidneys. The only significant difference from controls observed in these organs was in liver weight, which was higher than the control value after 2 months of exposure and lower 1 month after the end of exposure. Microscopically, the liver showed phagocytizing Kupffer cells, which were swollen, and proliferating, small areas of necrosis, middle-grade fibrotic expansion of the periportal areas, and fine to medium droplets of fatty degeneration. Liver damage increased in severity with length of exposure and was not reversed after exposure ceased. Four months after exposure, the kidneys showed interstitial proliferation of inflammatory cells and an accumulation of cell detritus and eosinophils in the tubules.
The brain contained massive arterial hyperemia, pronounced cerebral edema, and cellular necrosis. Brains of animals examined 1 month after the end of exposure showed signs of returning to normal. These results indicated that severe brain damage by TBTC may be asymptomatic.
Iwamoto  performed a series of inhalation experiments to study the effects of TBTB on the reproductive functions of rats. The material used was a mixture of 81.2% TBTB with small amounts of dibutyltin dibromide and hydrocarbons. Mature male and female rats weighing 200-320 and 150-180 g, respectively, were exposed to TBTB in a test chamber maintained at about 20 C at a concentration of 2 mg/cu m, measured as tin with a quartz spectrophotometer. The concentration of TBTB in the chamber was maintained by aeration of a TBTB mixture kept in the chamber. Five females exposed 5 hours/day for 38 days and mated to unexposed males during the hours of nonexposure in the last 28 days had a pregnancy rate of 60%, compared to 100% pregnancy in the controls.
Ten females exposed 5 hours/day for 6 weeks, with mating occurring during hours of nonexposure for the last 4 weeks, had a pregnancy rate of 10%. A partial recovery of reproductive capabilities in the exposed rats occurred within 16 days after exposure ended.
Three groups of five females exposed 2 hours/day for 2, 3, or 4 months, with mating occurring for the last 4 weeks, had pregnancy rates of 60%, 20%, and 0%.
A partial recovery of reproductive capabilities was observed 1 week after the exposure ended in all females exposed for 3 months and 10 days after exposure ended in all females exposed for 4 months. Two groups of five males exposed 5 hours/day for 2 or 7 weeks, followed by a 5-hour/day exposure during a 4-week mating period, impregnated all unexposed females. When five males and five females were exposed 5 hours/day for 6 weeks, with mating during the last 4 weeks, no pregnancies occurred.
The sex organs of 3 males exposed 5 hours/day for 79-80 days, 3 females exposed for 42 days, 4 females exposed for 42 days and allowed to recover for 7-28 days, 5 females exposed for 7-14 days, and 10 females exposed for 14 days with a 7-to 28-day recovery period were examined microscopically . No effects were observed in the male sex organs.
However, a slight atrophy of the glandular tissues of the uterus could be seen after 14 days of exposure.
After 42 days of exposure, a marked atrophic destruction of the glandular epithelium and a marked increase in interstitial connective tissues were seen in the uterus. No changes were observed in the ovaries.
The livers, kidneys, lungs, spleens, hearts, and adrenals of these animals also were examined microscopically . All rats developed bronchitis, with one-half showing bronchogenic pneumonitis after 14 days of exposure. After 42 days, bronchitis was milder and pneumonitis was not observed. Mild atrophy was first observed in the liver 14 days after exposure, and was more severe after 42 days. After 14 days, the lymph nodes of the spleen were slightly atrophic and an increase in splenic cells was seen. After 42 days, thickening of the medullary sheaths was noted in the spleen, with no changes in the condition of the lymph nodes. All effects were reversible, with time of recovery directly related to length of exposure. No effects were noted in the other organs examined.

# 2) Oral
Stoner et al , Barnes and Stoner , and Barnes and
Magee  used albino rats in a series of studies to compare the toxic effects of dialkyltin and trialkyltin salts administered orally in the animals' diet or by intubation. Groups of four male and four female rats were administered single doses of dibutyltin dichloride (DBDC) by intubation at concentrations of 10, 20, 50, 100, 200, and 400 mg/kg and observed for 10 days  . All rats survived except one female and one male at 200 mg/kg and two females and all males at 400 mg/kg. Rats receiving the 50-mg/kg dose were "ill" for 24-48 hours but recovered rapidly thereafter. At the end of the observation period, the survivors were killed and examined microscopically. The only tissue damage reported was an inflammatory bile-duct lesion at 20 mg/kg and at 50 mg/kg.
Three successive daily doses of DBDC at 50 mg/kg by intubation produced bile-duct damage in all rats; 9 of 18 males and 4 of 18 females died .
In a few of these cases, death was attributed to bile peritonitis or to severe liver damage produced by a rupture of the bile duct.
All survivors 15 months after treatment showed a thickened and shortened, but functional, bile duct, indicating that the impairment of function was reversible. Four successive oral doses of 50 mg/kg of the dilaurate and diisooctylthioglycolate salts of dibutyltin given daily to groups of four rats produced no toxic effects significantly different from those due to DBDC. Mice given three consecutive daily doses of 50 mg/kg DBDC sustained liver damage similar to that in rats, but effects were more severe. Guinea pigs were less susceptible, withstanding repeated daily doses of 50-100 mg/kg with no evidence of biliary tract damage.
Barnes and Magee   Barnes and Magee  showed that bile-duct lesions did not develop in rats receiving 50 mg/kg DBDC orally if the flow of bile in the duct was stopped.
The effects of pancreatic secretions on the development of bileduct lesions were examined by iv administration of either a stimulant or an inhibitor of pancreatic secretions to rats after the administration of 50 mg/kg DBDC. No differences were found in the severity of lesions in the two groups.
The distribution of tin in the tissues of bile-cannulated rats was determined using a polarographic method  . Animals were administered DBDC at 50 mg/kg by intubation, and bile and pancreatic secretions were collected for a 24-hour period. The tin concentrations in the bile and the pancreatic juice were 1.8 Mg/tnl and 0.8 jug/ml, respectively, at 12 hours, when bile-duct lesions were first observed. After 16-24 hours, the concentration of tin increased to 9.8 Mg/ml in the bile and 3.6 jug/ml in the pancreatic juice. During this period, the average concentration of tin was 5.0 Mg/ml in the blood, 61.0 Mg in the liver, and 19.0 jug in the kidneys. No tin was found in the pancreatic tissue. The authors concluded that the concentration of tin in the bile and the pancreatic juice was not \ high enough to be responsible for the observed bile-duct damage.
In another study, Barnes and Stoner  administered eight dialkyltin dichloride compounds by intubation at doses of 40, 80, and 160 mg/kg to pairs of female rats on the 1st and 4th days of the experiment.
However, six of the compounds at 160 mg/kg and dihexyltin at 80 mg/kg were administered only on the 1st day. Some of these compounds produced bileduct lesions similar to those induced by DBDC and of varying intensity ( were fed to groups of five rats for a 60-day period  . All rats had extensive CNS damage, including cerebral edema. Symptoms of intoxication appeared after 7 days of feeding and included slow breathing and hindleg paralysis. Muscular tremors were also observed at 40 ppm. These findings suggest that TETH at concentrations as low as 20 ppm is toxic when administered in the diet for 2 months.
Barnes and Stoner  reported that oral doses of triethyltin acetate at 8 mg/kg given to five female rats at 2-day intervals significantly increased the water content of the brain and of the spinal cord. Similar effects were obtained when oral doses of 200 mg/kg tri-npropyltin were administered to four female rats at 3-day intervals, when doses of 100 mg/kg tri-isopropyltin acetate were administered to five rats at 2-day intervals, or when doses of 300 mg/kg tri-n-butyltin acetate were given to four rats. No other procedures were given.

# Gaunt et al 
investigated the toxic effects of di-n-butyltin dichloride (DBDC) which was reported to contain 0.25% tri-n-butyltin chloride.
Single doses of 50 mg/kg in arachis oil given by intubation to five male and five female rats produced edema in the pancreas around the lower bile duct, with varying degrees of hyperemia of the duct occurring after 24 hours. The fragmentation of the wall of the bile duct, reported by Barnes and Magee   The granular endoplasmic reticulum showed progressive swelling but with no loss of ribosomes. The complexity of the agranular endoplasmic reticulum increased greatly after the first three doses. The bile canaliculi were completely closed by the third dose by swelling of the parenchyma cells and microvilli. Thickening of the Kupffer and endothelial lining cells was also observed. Rats recovered more rapidly from these effects after 7 days of exposure than did the mice. The authors  have suggested that early mitochondrial injury in the parenchyma cells of the liver may be a result of an interference with ATP production by dithiol inhibition, and that inhibition of other cellular functions involving active transport would lead to the observed ultrastructural damage. Albino mice, also used in this study, were found to be more sensitive than rats to the toxic effects of DBDA. after conception. There were significant differences from the controls in the number of dead fetuses, the number of fetal resorptions, and fetal and placental weights. These differences were reported by the authors to be dose dependent.
The results seem to indicate that reproduction and fetal development of rats were affected by the organotins only when exposure to these compounds occurred during gestation.
The effect of trialkyltins on the CNS has been investigated by Magee et al  using triethyltin hydroxide (TETH) in Porton-strain albino rats.
TETH dissolved in arachis oil was added daily to the powdered diet of 18 rats at a concentration of 20 ppm for 2 weeks, followed by 10 ppm for 6 weeks.
The animals were killed at the end of 8 weeks, and the brains and spinal cords were removed. Tissue samples were taken from the liver, kidneys, spleen, testes and adnexa, adrenals, pancreas, and heart of an unstated number of rats. The water content, total lipid, total phospholipid, total cholesterol, and total nucleic acids were determined for these tissues. These results were compared with those from the pairfed controls.
The first neurologic symptoms appeared 7-9 days after ingestion of the TETH diet started and included difficulty in the manipulation of the hind limbs . At this stage, an amount of food equivalent to 10 mg/kg body weight of TETH had been consumed. By 14 days, when the animals had consumed 12 mg/kg body weight, hindleg paralysis was apparent. During the 3rd week, 12 rats died. The general state of the surviving animals began to improve when TETH in the diet was reduced to 10 ppm. No further clinical improvements occurred if the rats were restored to a normal diet at the end of 8 weeks. If the 10-ppm diet was continued, tremors of the skeletal muscles appeared after a few more weeks.
An examination of tissues showed damage to the CNS only .
Microscopic examination revealed small interstitial spaces only in the white matter of the brain after 3 days. Interstitial spacing increased by the end of 9 days and by the 14th day, when severe paralyses were observed, there were marked changes in the white matter. With a reduction in the dietary concentration of TETH to 10 ppm, no further deterioration occurred.
At the end of 8 weeks, the white matter of the spinal cord and brain had a reticulated appearance. This was not found in the gray matter of the brain and cord or in the peripheral nerves but was well developed in the optic nerve. Lesions were reversed after 4 months on a normal diet. No abnormalities were found in the other organs examined.
Chemical investigations showed a significant increase in the water concentration in the brain and spinal cord of animals receiving 10 ppm TETH in the diet as compared to those of the pair-fed controls . If animals were allowed a normal diet for 130 days after consuming a diet containing 20 ppm of TETH for 14 days and 10 ppm for a further 45 days, the water concentration of the CNS returned to normal. Rats fed a diet of 20 ppm TETH for 10 or 14 days had a significant increase in the sodium concentration of the brain and cord, but no changes were detected in potassium concentrations. The concentration of sodium and potassium in the plasma were not altered in rats killed after 11-16 days on a 20-ppm diet.
Total nucleic acid, total lipid, total phospholipid, and total cholesterol in the brains and spinal cords of these animals did not differ significantly from the control values.
The effect of TETH on the permeability of the blood-brain barrier was tested using dye-injection techniques . Rats were fed a diet of 20 ppm TETH for 14 days followed by 10 ppm for either 2 or 42 days prior to injection of the dye. No abnormal staining of the CNS was observed, indicating that permeability of the barrier was not affected.
Findings by Magee et al  indicate that TETH produced a lesion of the white matter of the CNS, which was described as interstitial edema.
There were no indications that the neurons of the CNS were affected. Magee et al  also reported that a single 10 mg/kg dose of triethyltin sulfate (TETS) injected intraperitoneally- (ip) into rats significantly increased the water content of the brain and spinal cord. By contrast, even repeated oral or ip administration of diethyltin diiodide did not produce any of the neurologic effects which were observed after administration of triethyltin compounds.
Triethyltin-induced interstitial edema of the white matter of the CNS in rats has also been reported by a number of other investigators .
In addition to edema, splitting of the myelin sheath in the white matter Graham and Gonatas  reported myelin splitting of the peripheral nerves (posterior lumbosacral nerves and sciatic nerves) in rats given TETS in drinking water at a concentration of 20 mg/liter during a 22-day period.
Suzuki  gave eight newborn rats drinking water containing 5 mg TETS for 4 months and found that triethyltin-induced brain alterations were not accompanied by physical signs.
Investigations on rabbits , dogs , and mice  have
shown that triethyltin-induced CNS damage was similar to that found in rats. Aleu et al  induced cerebral edema within 5-7 days in male albino rabbits given daily ip injections of TETS at 1 mg/kg. The authors  showed that there were no changes in the extracellular spacing of the white matter of the CNS, indicating that the edema fluid may be within the myelin.
Cerebral edema was induced in 2 dogs, one receiving 2 iv injections of 1 mg/kg within 25 days, and the other 10 iv injections of 1 mg/kg within 30 days .
These studies  with triethyltin compounds described toxic effects which were similar in various animal species, but no indication of differences in severity among the animal species was provided. were more susceptible to TETH than guinea pigs, but less so to TPTA and TPTH. Both species were more susceptible to TPTA than to TPTH.
In their investigation of TPTH, Gaines and Kimbrough  found no evidence of CNS damage in male rats after 99 days on diets containing 100, 200, and 400 ppm, with 10 rats on each concentration. A significantly lower leukocyte count occurred after 99 days at 200 ppm. All animals exposed to 400 ppm died in 7-34 days from extensive intraalveolar hemorrhage of the lungs or from loss of weight. No effect was detected at 100 ppm.
In his study of the fungicide, triphenyltin acetate (TPTA), Klimmer
 administered single doses of 80-250 mg/kg of TPTA by intubation to groups of 10 rats.
Survivors had signs of general weakness and lack of mobility. From the mortality data, an oral LD50 of 136 mg/kg was obtained for a 2-to 3-week observation period. All animals had a decreased ventilatory rate, hypothermia, and coma prior to death. A macroscopic examination revealed stasis of the lung and liver and a slightly increased amount of water in the brain. A microscopic examination showed a focal liver cell necrosis with massive stasis of blood and a cloudy swelling of the tubular epithelia of the kidneys. Rabbits and guinea pigs underwent effects similar to those observed in the rats, but with no apparent increase in the proportion of water in the nerve tissues. These species were more susceptible to TPTA than rats. The LD50's were 21 mg/kg for the guinea pig and 30-50 mg/kg for the rabbit, for a 3-week observation period.
Similar, but more severe, effects and peritonitis were reported when TPTA was administered by ip injection to rats, rabbits, and guinea pigs. Urine and feces were collected daily and their mean radioactivities determined. Five males and five females were killed 7 days after exposure, and the organs were analyzed for radioactive tin. Within 7 days, 88% of the radioactive tin was excreted in the feces and 3% in the urine. Only a total of 0.5% was detected in all the organs combined at the end of 7 days.
There was no significant difference between the rates of excretion of tin by males and females. The concentration of triphenyltin in the urine and feces decreased while those of diphenyltin, monophenyltin, and inorganic tin increased during the 7-day period.
The ; no other details of the study were provided. Blood and the liver, kidneys, heart, lean muscle, and abdominal fat were taken from the controls and from the treated animals at the end of 2 years and analyzed for total tin. Dialkyltin levels were determined in individual liver samples of male dogs from several treatment groups and in female rats from the highest treatment group. In addition, brain samples from male dogs were analyzed for tin. For rats, paired composites were obtained from other tissues, including the testes. For the dogs, composite samples were taken only of the muscle and fat; pooled urine samples for the control and treatment groups were used.
The dithiol method was used in analysis for total tin and was reported to be reliable at tin concentrations as low as 5 /ig.
The dithizone method was used to determine the dialkyltins, but the sensitivity of the method was not given.
In male rats, the level of inorganic tin was highest in the liver and kidneys (Table XII -9) .
Female rats had similar levels in the liver and kidneys, the only tissues examined in these animals. For dogs, the highest levels were found in the liver, followed by the brain and kidneys (Table XII -10). Female dogs had comparable results.
Analyses of the liver of one dog from each of the six treatment groups showed that 10-13% of the total tin present in the liver was in the form of dialkyltin . Approximately 50% was in the inorganic state, which the authors believed to be a stannous compound, and the remainder was present as tin oxide.
In the rats, at least 50% of the total tin was present as a dialkyltin. The authors suggested that this figure may be lower than the actual dialkyltin concentration in the liver of the rats because of interference from the arsenic normally present in the rats' diet.
Cremer The authors administered monoethyltin trichloride (METC) orally at a dose of 25 mg/kg or ip at a dose of 12.7 mg/kg to groups of three rats. Animals were observed for a 3-day period. Feces and urine from all animals were analyzed colorimetrically for total tin using the dithiol method, which has a limit of sensitivity of 5 /ig/ml of sample.
Monoethyltin in the urine and bile was determined fluorometrically with a 98  2% recovery rate. The monoethyltin content of fecal matter was determined using a radiochemical technique with an 89-95% recovery rate.
When METC was administered orally at a dose of 25 mg/kg, 92% was excreted in the feces in 2 days, with 1-2% in the urine. By ip injection, 73% of the 12.7-mg/kg dose was excreted in the urine of uncannulated rats in 3 days. In rats whose bile ducts had been cannulated, 82% of an ip injection of 12.7 mg/kg was excreted in the urine, with less than 4% found in the bile.
Dithiol tests for inorganic tin in the urines of normal and cannulated rats which had received doses of 12.7 mg/kg were negative.
Diethyltin dichloride (DEDC) was administered by ip injection to three normal rats and three with cannulae in their bile ducts, at doses of 10 mg/kg . Urine and feces, as well as bile from the cannulated rats, were examined for tin by the dithiol method. Diethyltin in the bile was measured colorimetrically with a method having a recovery rate of 96  5%.
The diethyltin content of urine and fecal matter was analyzed using a radiochemical technique with a recovery rate of 89-95%. Following an ip injection of 10 mg/kg, 38% was excreted in the feces and 22% was excreted in the urine, while 5% was found in the carcass 6 days after exposure.
Animals receiving 10 mg/kg ip of 14C-labeled DEDC had excreted an average of 79% of the dose (36% in urine and 43% in feces), calculated as tin, after 3 days. When measured as 14C, only 46% of the dose was accounted for. This discrepancy between the recoveries of tin and 14C suggested to the authors that diethyltin was being dealkylated. An examination of the urine and feces for monoethyltin and diethyltin in rats receiving 10 mg/kg of DEDC showed that, in the urine, 31% of the 14C occurred as monoethyltin and 5% as diethyltin, while in the feces, 32% occurred as monoethyltin and 10% as diethyltin.
An examination of the bile from cannulated rats receiving DEDC at 10 mg/kg showed that only diethyltin was present.
Bridges et al  concluded that diethyltin was slowly dealkylated to monoethyltin. However, monoethyltin was not metabolized to inorganic tin. Upon ip injection of monoethyltin, monoethyltin did not enter the gut via the bile or gut wall but was primarily excreted in the urine.
Because diethyltin entered the bile after ip injections, the authors  suggested that dealkylation occurred in the gut and in the tissues.
Technical grade tricyclohexyltin hydroxide (TCHH), 95% pure, either labeled with 119Sn or unlabeled, was administered orally to rats and dogs to study its metabolism in animal tissues  . In the analysis of tissue and excreta for 119Sn-labeled TCHH, samples were combusted and the ash was analyzed for total radioactivity with a scintillation spectrometer. To identify TCHH and its possible metabolites, dicyclohexyltin oxide (DCHO) cyclohexylstannoic acid, and inorganic tin, the samples were homogenized and separated by extraction with solvents prior to ashing. Confirmation of separation and identification of the metabolites were by thin-layer chromatography. For samples containing unlabeled TCHH, the dithiol method was used to analyze for total tin, and a method developed by Getzendaner and Corbin  was used for total organotin. Inorganic tin was calculated as the difference between total tin and total organotin. Analyses of tissue samples 2, 10, and 40 days after the withdrawal of TCHH from the diet showed a decrease in total tin with time  . A detailed analysis of the muscle tissue for TCHH and its metabolites on the 2nd day showed that TCHH accounted for 61% of the total radioactivity, DCHO 18%, inorganic tin 16%, and cyclohexylstannoic acid 4.8%. These percentages decreased with time, except for that of DCHO, which increased with time.
In a 2-year feeding study, Long-Evans rats of both sexes, on daily diets containing 0, 0.73, 3, 6, and 12 mg TCHH/kg bod'y weight, showed patterns of tin distribution in their tissues similar to those observed in the 90-day feeding study  . The organs and tissues of the rats in which tin was measured in order of decreasing concentration were kidneys, liver, brain, muscle, and fat. For beagle dogs on similar diets, the distribution of tin was the same except for the kidneys and liver, where the order was reversed. The concentration of tin in the tissues of dogs and rats was proportional to the amount of TCHH ingested and increased with time during the study period. As in the 90-day study with rats, tin in the tissues was reduced when TCHH was removed from the diets of dogs and rats in the 2-year study.
Analysis of the kidney, liver, muscle, and brain from dogs and rats showed that 60-95% of the tin in these tissues was in the organotin form . Analysis of liver samples from rats on a diet of 3 mg TCHH/kg for 90 days showed that TCHH accounted for 45% of the total tin, DCHO 40%, and inorganic tin 15%. Dogs on the 3-mg TCHH/kg diet for 180 days had 3.4 ppm of tin in the liver, of which 40% was inorganic tin, 45% DCHO, and 15%
TCHH. In the kidneys, 1.3 ppm of tin was found, of which 50% was inorganic tin, 20% DCHO, and 30% TCHH. Brain tissues had 1.1 ppm tin, of which 30% was inorganic tin, 20% DCHO, and 50% TCHH.
Two dairy cows were given a ration containing 10 ppm TCHH for 2 weeks, followed by 100 ppm TCHH for 2 more weeks  . Samples of milk were collected morning and evening and combined to obtain a daily sample.
Analyses showed only trace amounts (0.01 ppm or less) of TCHH in the milk.

# 3) Dermal
The dermal effects of organotins in rats have been assessed by a number of investigators [60,83, Microscopic examination confirmed these gross findings. With Lastanox P, the findings were very similar but less severe, with skin effects disappearing by the 12th-14th day at 0.25% and by the 15th-16th day at 0.5%.
Dermal exposure at concentrations of 1, 10, 33, and 100% of Lastanox T or P produced similar effects which differed only in severity .
Erythema and edema appeared on the 1st and 2nd days, followed by granulation tissue on the 9th-12th days. All signs disappeared in 35-38 days in the 1 and 10% groups and in 45-50 days in the 33 and 100% groups.
A second group of rats received single dermal applications of From single applications of TBTB at 0.5-1.0 cc/kg and TBTC at 0.5-1.0 cc/kg using groups of 2-3 rabbits, a percutaneous minimum lethal dose of 0.7 cc/kg with a 14-day observation period was obtained for both compounds. Results of blood and urine analyses for TBTB and TBTC were reported by the author to be similar to TBTI. The cobalt test (turbidity test) results for liver function were abnormal for all animals after 4 weeks of exposure.
Pelikan  reported the effects produced by the application of bis(tributyltin) oxide (TBTO) to the eyes of rabbits. Lastanox T (20% TBTO with nonionic surface-active substances) and Lastanox P (15% TBTO with nonionic surface-active substances) served as the source of TBTO. These commercial preparations were used in concentrations of 1 and 10% and a dose of 0.03 ml was introduced into the conjunctival sacs of the left eyes of rabbits (in groups of six). This was equivalent to doses of 0.46, 0.61, showed that the skin of the eyelids and surrounding area was necrotic.
With the exception of one rabbit, total opacity of the cornea developed together with pronounced symblepharon (adherence of eyelids to eyeball) in most cases. An examination of the two rabbits that died showed that the brain, the medulla, and the abdominal organs were hyperemic.
Microscopically, the corneas were necrotic and the scleras edematous.
The irises were congested, and the lenses dislocated. Retinas were unaffected.
The spleen showed hyperplasia of the reticuloendothelial cells. Other organs were unaffected. vitro experiments to show that respiration was inhibited to a greater degree in the brain than in the liver or kidneys. Tissues from these three organs also concentrated triethyltin in vitro, so that concentrations were higher in the tissues than in the medium.
( Fifteen milligrams of a 10 or 30% solution of TBTF in propylene glycol was applied to the shaved back of each mouse in the two test groups three times weekly for 6 months. The positive control received a known carcinogen identified as R-911-10 in the same manner. The control animals were treated with 15 mg of propylene glycol. Animals were observed daily for 6 months for behavioral and skin changes. When any skin lesion reached 1 mm in diameter, it was measured and its size recorded weekly. At the end of 6 months, animals were killed, and all skin lesions were examined microscopically.
None of these animals showed signs of abnormal behavior or systemic intoxication . There were no visible skin lesions in control animals, while 56% of the positive controls had such lesions. At 10% TBTF, no lesions were observed. However, at 30% TBTF, skin irritation occurred after 3 weeks, so the concentration was reduced to 5% TBTF for the remainder of the study. Under these circumstances, 10% of the mice developed skin lesions. The author attributed these lesions to irritation from the initial application of 30% TBTF. A microscopic examination of the positive controls showed a significant incidence of cancerous lesions while the lesions at 5% TBTF were described as hypertrophic changes and inflammation of the epithelium and were not neoplastic. A postmortem examination of all animals revealed no gross pathologic changes, other than skin lesions, which could be related to TBTF or the test procedures.
Mortality was 24% in the controls, 26% in the positive controls, 22% at 10% TBTF, and 28% at 5% TBTF. These results indicate that TBTF as a 10% dermal application was not carcinogenic. The reduction in the concentration of TBTF from 30 to 5% after 3 weeks of testing makes it difficult to assess the observed effects. Organotin compounds differ in the severity of their toxic effects as well as in the organs they affect. The trialkyltins are apparently the most toxic group, followed by the dialkyltins and monoalkyltins. The tetraalkyltins are metabolized to their trialkyltin homologs , so that their effects are those of the trialkyltins, with severity dependent upon the rate of metabolic conversion. Animal species differ in their response to the dialkyltins, with mice affected most severely, followed by rats, guinea pigs, and rabbits . However, no species differences were reported for CNS damage by the trialkyltins .
Barnes and Stoner  and Caujolle et al  showed that, for each major organotin group, the ethyltin derivative was the most toxic, and the methyltins were somewhat less toxic. The homologs above ethyltin tended to show decreasing toxicity with an increase in the number of carbon atoms in the organic group bonded through a C-Sn bond. These authors  also showed that the iso-isomers were more toxic than the normal isomers. The type of anionic group influences the severity of the toxic action ; however, no general pattern of effect could be discerned from the available data. trialkyltin vapor at 900-3,200 mg/cu m, measured as tin, produced fatty changes in the liver of mice . Tributyltin chloride at a concentration of 4-6 mg/cu m, measured as tin, for 6 hours/day, 5 days/week, for 4 months produced severe liver damage in mice . Pelikan and Cerny  reported liver damage in mice 24 hours after single oral doses of 4,000 mg/kg of monoalkyltins and dialkyltins and 500 mg/kg of trialkyltins.
Barnes and Stoner  reported that dibutyltin dichloride administered by intubation in three successive daily doses of 50 mg/kg produced severe liver damage in rats. Acute inflammation of the portal tracts of the liver occurred 48 hours after a single 50-mg/kg dose of dibutyltin dichloride but was reversible  .
Inhalation studies using rats  showed that 4 hours of exposure to Ingestion studies  using D0T0 showed that the organs with the highest level of tin were the liver and kidneys of the rat and the liver of the dog. Results were similar for both males and females. In the rat, at least 50% of the total tin was present as dialkyltin, while in the dog only 10-13% was found as a dialkyltin.
Cremer  found that metabolic conversion of tetraethyltin to triethyltin occurred in the liver. A steady-state concentration was achieved in 1-2 hours after exposure, with about 25% conversion of tetraethyltin to triethyltin.
A single dose of 25 mg/cu m of TCHH labeled with 119Sn was excreted in the feces (98%) and urine (2%) by rats and guinea pigs within 9 days .
A 90-day study with Wistar rats of both sexes, using 119Sn-labeled TCHH in laboratory chow at a concentration of 100 ppm, showed that a maximum concentration of tin was obtained after 15 days.
The tin concentration was greatest in the kidneys, followed in order by the heart, liver, muscle, spleen, brain and fatty tissues, and blood. Analyses of tissues showed that 60-75% of the tin was in the organic form. Analysis of liver samples from rats on a diet of 3 mg TCHH/kg for 90 days showed 45% as TCHH, 40% as DCHO, and 15% as inorganic tin. Liver samples from dogs on a similar diet showed 15% as TCHH, 45% as TCHO, and 40% as inorganic tin.
After withdrawal of TCHH from the diet, there was a decrease in total tin content of the organs with time.
Although not reported in human exposure incidents, effects on the kidneys have been observed in animal studies .
Pelikan and Cerny  and Pelikan et al  showed that fatty degeneration and hyperemia of the kidneys occurred within 24 hours after administration of oral doses of 4,000 mg/kg for the monoalkyltins and dialkyltins and of 500 Therefore, the possibility of carcinogenic or mutagenic effects in other animal species cannot be ignored. Studies on these and other compounds in different animal species are needed to assess more fully the carcinogenic, mutagenic, and teratogenic potentials of these compounds. *"Dose" means mg/kg for oral administration, ppm in the diet, mg/cu m for inhalation, mg/kg for all routes of injection. Doses are stated in terms of the entire molecule except in inhalation studies where concentration is in terms of tin in the molecule. When repeated doses were given, the sym bol "(x)" follows the numerical dose.

# IV. ENVIRONMENTAL DATA AND BIOLOGIC EVALUATION Engineering Controls
Engineering controls must be instituted in areas where the airborne concentration of organotin dusts and vapors exceeds the TWA concentration limit, to decrease the concentration of organotins to or below the prescribed limit. Industrial experience indicates that closed-system operations are commonly used in manufacturing processes. Such systems must be used whenever feasible to control dust and vapor wherever organotin compounds are manufactured or used. Closed systems should operate under negative pressure whenever possible so that, if leaks develop, the flow will be inward.
Closed-system operations are effective only when the integrity of the system is maintained. This requires frequent inspection for, and prompt repair of, any leaks.
A ventilation system may be required if a closed system proves to be impractical and is desirable as a standby if the closed system should fail.   Chromatographic techniques used for separation of organotins have generally been followed by an appropriate sensitive colorimetric method such as pyrocatechol violet or phenylfluorone for quantitative determination of tin in the organotins identified. techniques.

# The principles set forth in Industrial Ventilation
Generally, such techniques have not been applied to analysis of organotins in air; some have been applied predominantly to analysis of inorganic tin.
Vernon  presented a method for the determination of residues of triphenyltin compounds resulting from the treatment of potatoes with triphenyltin fungicides. The analytical method used the fluorimetric measurement of the triphenyltin moiety resulting from complex-formation with 3-hydroxyflavone.
Recoveries averaging about 90% were obtained from potato samples to which 1 /g of tin as triphenyltin had been added. The limit of detection of this fluorimetric method was given as 0.16 pg of tin, with a standard deviation of  5.7%.
Atomic absorption spectrophotometric methods have been applied to the determination of tin in several types of samples. However, no study was found in which air samples obtained by personal monitoring were analyzed by atomic absorption. Jeltes  reported the determination of bis(tributyltin) oxide in high-volume air samples collected on glass-fiber filters. Following extraction of the filters with methylisobutyl ketone, the samples were analyzed by atomic absorption. To obtain a measure of filter efficiency for the collection of bis(tributyltin) oxide, sampling was done through two glass-fiber filters in series. More than 99% of the bis(tributyltin) oxide collected was obtained on the first filter. The analytical sensitivity was not stated, but the determination of milligram quantities of bis(tributyltin) oxide was reported.
An atomic absorption analytical method for the determination of tin was applied to the analysis of several metallurgical samples by Capacho-Delgado and Manning . The sensitivity for tin was about 1 ppm for 1% absorption, and the detection limit was about 0.1 ppm in a water solution.
Atomic absorption was found to be satisfactory for the determination of dibutyltin dilaurate in poultry feed formulations . Essentially, theoretical recovery was obtained in formulations with dibutyltin dilaurate concentrations from 0.02 to 0.0375%. The authors stated that the method applies to feeds with dibutyltin dilaurate concentrations from 0.02 to 0.14%.
Engberg  reported that atomic absorption was satisfactory for the determination of tin in canned food, but the colorimetric method using quercetin (3,5,7,3',4'-pentahydroxyflavone) was preferred for very low tin concentrations, such as residues of organotin compounds. Amounts of tin as low as about 40 /g were quantitatively determined by atomic absorption.
In NIOSH Analytical Methods No. P & CAM 173 , a sensitivity of 5 /ig/ml is given for the determination of tin. While this may be sufficient for some general workplace air samples, a more sensitive method is needed for personal monitoring. The pyrocatechol violet method is generally available to industry, requires no highly specialized laboratory equipment, and has been shown to provide sufficient accuracy, sensitivity, and precision within the range required to determine compliance with this standard for all organotins.
For analysis of specific organotins, any method shown to be equivalent or superior in accuracy, sensitivity, and precision may be used.
Because of its high sensitivity and the general availability of the required analytical reagents and equipment, the pyrocatechol violet method described in Appendix II is the recommended analytical technique for determination of organotins, measured as tin. If the determination of a specific organotin compound is required, it will be necessary to separate that compound from other components prior to analysis. NIOSH has not evaluated this method for the analysis of samples of organotins collected from air but believes that it should be satisfactory on the basis of published reports of its use in the analysis of solutions. If research now underway by NIOSH determines that a better method can be devised, the improved methodology will be provided.

# Biologic Evaluation
Experimental techniques for analysis of animal urine and feces have been developed  and may have potential use in monitoring employee exposure to organotin compounds.
Bridges et al  described a spectrophotometric method for the determination of organotins as tin in biologic samples. Total tin was determined by treating urine or homogenized feces with concentrated sulfuric acid followed by an excess of nitric acid.
The solution was heated until sulfur trioxide fumes appeared, then it was cooled and reheated. Dithiol was then added, and the resulting red color was measured at 530 nm with a spectrophotometer. The limit of sensitivity of the test was reported to be 5 x% of tin/ml of sample.
A colorimetric method has been described by Aldridge and Cremer  for the separation and determination of diethyltin and triethyltin compounds.
The test involved the formation of a dithizone complex with diethyltin or triethyltin. The dithizone-diethyltin complex had an absorption maximum at 510 nm in the presence of borate buffer. With triethyltin, maximum absorption was at 440 nm in the presence of borate buffer at pH 8.4, whereas maximum absorption occurred at the same wavelength (510 nm) for both the triethyltin-dithizone complex and dithizone alone in the presence of trichloroacetic acid. This method has been used successfully in the analysis of bile samples from rats for diethyltin by Bridges et al , who reported recovery of 96  5%.
However, the method was found to be unreliable with urine samples. The amount of dioctyltin dichloride (if used in the synthesis of the mercaptoacetate derivative) was specified to be not less than 95% dichloride, not more than 5% trichloride derivative, not more than 0.2% isomers of dioctyltin, and not more than 0.1% for the higher and lower Most of the animal data available was based on oral administration, and such studies are useful only in determining the type of effects that may occur from organotin exposure. Of the inhalation studies found, only one dealt with organotin air concentrations near the current TWA concentration limit of 0.1 mg/cu m, as tin; the only effect reported at this concentration was a "less than normal" weight gain in rats after a 4hour exposure .
Other inhalation studies were performed at air concentrations well above the current standard and therefore do not provide information for assessing organotin toxicity at the current standard.
Human and animal toxicity data neither support nor negate the current federal standard, which was set by analogy with mercury, selenium, and thallium.
NIOSH therefore recommends that the current standard of 0.1 mg/cu m, as tin, as a TWA concentration limit be retained for all organotin compounds until more definitive information has been obtained. NIOSH recognizes that the organotins are of varied toxicity and hazard and that a single standard, as recommended, may be unnecessarily restrictive for many of the organotins. However, because of the lack of adequate data to evaluate the health hazard of the individual compounds to which employees may be exposed, and because of the absence of a sampling and analytical method which can quantitatively separate and identify the individual components of an organotin mixture in the working environments, there is no practical alternative. Where triorganotins and tetraorganotins are present, a closed system of control must be used whenever feasible and should be used with diorganotins and monoorganotins to control airborne concentrations of organotins within the TWA concentration limit. If a closed system is not feasible, other forms of engineering controls, such as local exhaust ventilation, must be used whenever feasible.
Where engineering controls are not feasible, respirators and protective clothing must be used to prevent overexposure to organotins. During the time required to install adequate controls and equipment, to make process changes, to perform routine maintenance operations, or to make repairs, overexposure to organotins must be prevented by the use of respirators and protective clothing. Work practices must be designed to prevent skin and eye contact.
Emergency showers and eyewash fountains must be available in case of accidental contact.
Because organotins are potent systemic poisons, it is recommended that medical records be maintained for the duration of employment plus a minimum of 5 years. Personnel records, which are of vital importance in assessing a worker's exposure, should be maintained for the same period.
Many employees handle only small amounts of the organotin compounds or work in situations where, regardless of the amount used, there is only negligible contact with these compounds. Under these conditions, it should not be necessary to conduct extensive monitoring and surveillance.
However, because many of the organotins have proved to be highly irritating to the skin and eyes at low concentrations, care must be exercised to ensure adequate protection against these effects where the potential for exposure to organotin compounds exists. Concern for employee health requires that protective measures be instituted at concentrations at or below the workplace environmental limit to ensure that exposures stay below that limit. For this reason, occupational environments with concentrations at or below the action level require environmental monitoring once every year. When concentrations are above the action level, more frequent environmental monitoring is required. Therefore, when employees are working with organotin compounds that are hazardous to the skin or eyes, they must use protective clothing and equipment to prevent skin contact and appropriate eye protective devices (goggles or face shields) to reduce the possibility of eye irritation or injury.

# VI. WORK PRACTICES
Good industrial hygiene practice requires that all reasonable efforts be used to limit the possibility of any organotin contacting the skin or eyes. Whenever skin contact with an organotin occurs, prompt washing of the affected area with soap and water is necessary. When an organotin compound contacts the eyes, immediate flushing with copious amounts of water is required and should be continued for at least 15 minutes, followed by prompt attention by a physician to determine the need for further treatment. Whenever there is a possibility for contamination of the clothing by an organotin compound, extra clothing must be available for the employee's use.
Certain organotin dusts, such as triphenyltin hydroxide, which is sold commercially as the miticide Du-Ter, have been found from industrial experience  to present special problems in formulation and application. These compounds are skin irritants, and contact should be avoided and prevented by full-body protective clothing, consisting of protection for head, neck, and face, coveralls or the equivalent, and impervious gloves with gauntlets. An alternative method of preventing employee exposure to irritating organotin dusts that has been found practical in the user industries  is to purchase the dust premeasured and packaged in soluble plastic bags, and to adjust batch sizes so that the soluble plastic bag and its contents can be added to the chosen liquid vehicle without exposing employees to the hazardous dust.
In the manufacture of various organotin stabilizers, catalysts, fungicides, miticides, molluscicides, and other products, the appropriate aryltin and alkyltin halides are used as intermediates . These compounds are, in general, quite irritating to the skin.
In emergency operations or in operations in which the concentration of organotin compounds cannot easily be reduced below the TWA concentration limit, respiratory protection based upon the expected or estimated airborne concentration must be provided for use by employees. Respiratory protective devices must be maintained in good working condition and must be cleaned and routinely inspected after each use.
Gloves, aprons, goggles, face shields, and other personal protective devices must be clean and maintained in good condition. All personal protective equipment should be cleaned frequently, with inspection and replacement as necessary on a regular schedule. Employers are responsible for assuring that such equipment is stored in suitable, designated containers or locations when the equipment is not in use. The proper use of protective clothing requires that all openings be closed and that garments fit snugly about the neck, wrists, and ankles whenever the wearer is in an exposure area. Clean work clothing should be put on before each work shift. At the end of the work shift, the employee should remove the soiled clothing and shower before putting on street clothing. Soiled clothing should be deposited in a designated container and appropriately laundered before reuse.
A supply of potable water must be available near all places where there is potential contact with organotins. A water supply may be provided by a free-running hose at low pressure, or by emergency showers. Soap should be available at emergency showers. Where contact with the eyes is likely, eyewash fountains or bottles should be provided.
In all industries which must handle organotins or organotincontaining substances, written instructions informing employees of the particular hazards of the organotins, the method of handling, procedures for cleaning up spilled material, personal protective equipment to be worn, and procedures for emergencies must be on file and available to employees.
The employer must establish a program of instruction which will ensure that all potentially exposed employees are familiar with the procedures. The

# Derobert L:
Poisoning by an organic tin compound (di-iodoethyl tin or Stalinon). J Forensic Med 7:192, 1961 31. Barnes   A method for the quantitative analysis of tin in organic compounds.
J Am Chem  All pumps and flowmeters must be calibrated using a calibrated test meter or other reference, as described in the Section on Calibration of Equipment.

# Calibration of Equipment
Since the accuracy of an analysis can be no greater than the accuracy with which the volume of air is measured, the accurate calibration of a sampling pump is essential. The frequency of calibration required depends upon the use, care, and handling to which the pump is subjected. Pumps should be recalibrated if they have been abused or if they have just been repaired or received from the manufacturer. Maintenance and calibration should be performed on a routine schedule, and records of these should be maintained.
Ordinarily, pumps should be calibrated in the laboratory both before they are used in the field and after they have been used to collect a large number of field samples. The accuracy of calibration depends on the type of instrument used as a reference. The choice of calibration instrument will depend largely upon where the calibration is to be performed. For laboratory testing, a spirometer or soapbubble meter is recommended, although other calibration instruments, such as a wet test meter or dry gas meter, can be used. The actual setups will be similar for all instruments.
The calibration setup for a personal sampling pump with a membrane filter followed by a charcoal tube is shown in (1) 500 Mg/ml: Dissolve 0.2500 g of pure tin in 150 ml of concentrated hydrochloric acid. Dilute to 500 ml with water.
(2) 10 Mg/ml in 20% w/v sulfuric acid and 10% citric acid:
Place exactly 10 ml of standard tin solution, 500 figlrnl, in a flask or beaker of resistant glass, and add 50 ml of concentrated sulfuric acid and 5 ml of concentrated nitric acid. Heat to evolution of strong fumes of sulfuric acid and cool. Add concentrated sulfuric acid to bring to a total of 100 g. Place in a cooling bath and cautiously dilute with 150-200 ml of water.
Cool to room temperature and add a water solution of 50 g of citric acid. Transfer to a 500-ml volumetric flask, dilute to volume, and mix well.
(3) 0.5 Mg/ml: Prepare fresh in 5% w/v sulfuric acid and 2.5% w/v citric acid.
(4) 0.025 Mg/ml: Prepare fresh in 5% w/v sulfuric acid and 2.5% w/v citric acid.
(b) Sulfuric-citric acid solution: 5 g of sulfuric acid and 2.5 g of citric acid/100 ml in water. This mixed solution is used in preparing the calibration curve.
(c) CTAB solution: 5.5 mg/ml CTAB in water. (1) Dilute the known volume of sulfuric acid digest (one volume) with two volumes of water, mix, and cool to room temperature.
(2) Add one volume of potassium iodide solution, 20% w/v, and mix.   (1) Add 2 ml of a 5% w/v ascorbic acid solution to each aqueous extract to be read. Prepare a mixed reagent as follows: For each 100 ml (sufficient for 20 readings), place 12 mg of pyrocatechol violet in a container and dissolve in water. Add 2 ml of CTAB solution (0.55% w/v), swirl gently, and dilute to 100 ml. Mix well.
(2) Add exactly 5 ml of the mixed reagent to the sample flask, dilute to volume, and mix.
(3) Do the same to each of the other samples at about 4minute intervals.
(4) Measure each solution after 30 minutes by filling a 5cm or 10-cm cell and reading the absorbance at 660 nm.
(5) Deduct the absorbance of the blank from that of the samples. Chemical substances should be listed according to their complete name derived from a recognized system of nomenclature.
Where possible, avoid using common names and general class names such as "aromatic amine,"
"safety solvent," or "aliphatic hydrocarbon" when the specific name is known.
The "%" may be the approximate percentage by weight or volume (indicate basis) which each hazardous ingredient of the mixture bears to the whole mixture. This may be indicated as a range or maximum amount, ie, "10-40% vol" or "10% max wt" to avoid disclosure of trade secrets.
Toxic hazard data shall be stated in terms of concentration, mode of exposure or test, and animal used, eg, "100 ppm LC50-rat," "25 mg/kg LD50- Respirators shall be specified as to type and NIOSH or US Bureau of Mines approval class, ie, "Supplied air," "Organic vapor canister," etc.
Protective equipment must be specified as to type and materials of construction.

# Personal Sampling Pump D E P A R T M E N T O F H E A L T H , E D U C A T IO N , A N D W E L F A R E P U B L I C H E A L T H S E R V I C E C E N T E R FO R D IS E A S E C O N T R O L N A T I O N A L IN S T IT U T E FO R O C C U P A T I O N A L S A F E T Y A N O H E A L T H R O B E R T A. T A F T L A B O R
123. Akagi H, Takeshita R, Sakagami Y: The determination of metals in organic compounds by oxygen-flask combustion or wet combustion. Microchem J 14:199-206, 1969 132. Metallic Impurities in Organic Matter Sub-Committee:
The use of 50 per cent hydrogen peroxide for the destruction of organic matter.  *The tin salts, 80 mg/kg, were dissolved in 0.1 ml dimethylphthalate and applied on 5 successive days to the clipped skin of groups of three rats. Rats were observed for 12 days, and at necropsy the skin lesions and con dition of the bile duct were examined.
From Barnes and Stoner