This guideline summarizes pertinent information about yttrium and yttrium compounds (measured as yttrium) for workers and employers as well as for physicians, industrial hygienists, and other occupational safety and health professionals who may need such information to conduct effective occupational safety and health programs. Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine periodically whether new information is available.

This guideline applies to elemental yttrium and to all of the compounds of yttrium. Examples of yttrium compounds are yttrium oxide, yttrium acetate, yttrium bromide, yttrium chloride, yttrium phosphide, yttrium sulfate, yttrium vanadate, and yttrium nitrate hexahydrate. For illustrative purposes, the chemical and physical properties of several of these compounds are presented below.

Yttrium

SUBSTANCE IDENTIFICATION

* Formula

Y

* Structure

(For Structure, see paper copy)

* Synonyms

Yttrium-89

* Identifiers

1. CAS 7440-65-5

2. RTECS ZG2980000

3. Specific DOT number: None

4. Specific DOT label: None

* Appearance and odor

Yttrium is an odorless, lustrous, dark gray metal. It is an element that belongs to the rare earth group of metals.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Atomic number: 39

2. Atomic weight: 88.9

3. Boiling point (760 torr): 3338 degrees C (6040.4 degrees F)

4. Specific gravity (water = 1): 4.47 at 25 degrees C (77 degrees F)

5. Vapor density: Not applicable

6. Melting point: 1522 degrees C (2771.6 degrees F)

7. Vapor pressure at 20 degrees C (68 degrees F): Negligible

8. Solubility: Insoluble in water; soluble in dilute acids and alkalies

9. Evaporation rate: Not applicable

Yttrium nitrate hexahydrate

SUBSTANCE IDENTIFICATION

* Formula

Y(NO(3))(3)*6H(2)O

* Structure

(For Structure, see paper copy)

* Synonyms

Nitric acid, yttrium(3(+))salt, hexahydrate; yttrium (III) nitrate hexahydrate

* Identifiers

1. CAS 13494-98-9

2. RTECS ZG3750000

3. Specific DOT number: None

4. Specific DOT label: None

* Appearance and odor

Yttrium nitrate hexahydrate is an odorless, colorless to pink crystalline solid.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 383

2. Boiling point (760 torr): Decomposes

3. Specific gravity (water = 1): 2.68 at 20 degrees C (68 degrees F)

4. Vapor density: Not applicable

5. Melting point: 100 degrees C (212 degrees F) (loses water)

6. Vapor pressure at 20 degrees C (68 degrees F): Negligible

7. Solubility: Soluble in water, alcohol, ether, and nitric acid

8. Evaporation rate: Not applicable

Yttrium chloride

SUBSTANCE IDENTIFICATION

* Formula

YCl(3)

* Structure

(For Structure, see paper copy)

* Synonyms

Yttrium trichloride

* Identifiers

1. CAS 10361-92-9

2. RTECS ZG3150000

3. Specific DOT number: None

4. Specific DOT label: None

* Appearance and odor

Yttrium chloride is a shiny, white, odorless solid.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 195.3

2. Boiling point (760 torr): 1507 degrees C (2744.6 degrees F)

3. Specific gravity (water = 1): 2.67 at 20 degrees C (68 degrees F)

4. Vapor density: Not applicable

5. Melting point: 721 degrees C (1328 degrees F)

6. Vapor pressure at 20 degrees C (68 degrees F): Negligible

7. Solubility: Soluble in water and alcohol

8. Evaporation rate: Not applicable

Yttrium oxide

SUBSTANCE IDENTIFICATION

* Formula

Y(2)O(3)

* Structure

(For Structure, see paper copy)

* Synonyms

Yttria

* Identifiers

1. CAS 1314-36-9

2. RTECS ZG385000

3. Specific DOT number: None

4. Specific DOT label: None

* Appearance and odor

Yttrium oxide is a noncombustible, colorless to yellow, odorless solid.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 225.8

2. Boiling point (760 torr): 4300 degrees C (7772 degrees F)

3. Specific gravity (water = 1): 5.01 at 20 degrees C (68 degrees F)

4. Vapor density: Not applicable

5. Melting point: 2410 degrees C (4370 degrees F)

6. Vapor pressure at 20 degrees C (68 degrees F): Negligible

7. Solubility: Insoluble in water; soluble in alcohol and acids; insoluble in alkalies

8. Evaporation rate: Not applicable.

* Reactivity

1. Conditions contributing to instability: Heat.

2. Incompatibilities: Yttrium dust is flammable when it reacts with air, and it burns vigorously in halogen vapors at temperatures above 200 degrees C (392 degrees F). Contact of yttrium nitrate with combustible materials may cause fires and explosions.

3. Hazardous decomposition products: Toxic gases (such as oxides of nitrogen, chlorine, and carbon monoxide) may be released in a fire involving yttrium or an yttrium compound.

4. Special precautions: None.

* Flammability

There are no National Fire Protection Association fire hazard ratings for yttrium or the yttrium compounds.

1. Flash point: Not applicable.

2. Autoignition temperature: Not applicable.

3. Flammable limits in air: Not applicable.

4. Extinguishant: Use an extinguishant that is suitable for the materials involved in the surrounding fire.

Fires involving yttrium or an yttrium compound should be fought upwind and from the maximum distance possible. Keep unnecessary people away; isolate hazard area and deny entry. Emergency personnel should stay out of low areas and ventilate closed spaces before entering. Firefighters should wear a full set of protective clothing, including a self-contained breathing apparatus, when fighting fires involving yttrium or an yttrium compound.

* Warning properties

Yttrium and its compounds are odorless. These substances are therefore considered to have inadequate odor warning properties.

* Eye irritation properties

No quantitative data are available on the eye irritation threshold for yttrium and yttrium compounds. These substances are not known to be eye irritants.

EXPOSURE LIMITS

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for yttrium and the compounds of yttrium (measured as yttrium) is 1 milligram per cubic meter (mg/m(3)) of air as an 8-hour time-weighted average (TWA) concentration [29 CFR 1910.1000, Table Z-1-A]. The National Institute for Occupational Safety and Health (NIOSH) has not issued a recommended exposure limit (REL) for yttrium and yttrium compounds. The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned yttrium and its compounds a threshold limit value (TLV) of 1 mg/m(3) (measured as yttrium) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1988, p. 38]. The OSHA and ACGIH limits are based on the risk of pulmonary effects associated with exposure to yttrium or its compounds.

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to yttrium and yttrium compounds can occur via inhalation, ingestion, and eye or skin contact.

* Summary of toxicology

1. Effects on Animals: In experimental animals, exposure to yttrium or a compound of yttrium causes damage to the lungs and liver. The toxicity of yttrium is low orally and high parenterally; toxicity also varies greatly with different yttrium compounds [Clayton and Clayton 1981, p. 1678]. The intraperitoneal LD(50)s in rats is 45 mg/kg for yttrium chloride [RTECS 1989c], 362 mg/kg for yttrium nitrate [Sax and Lewis 1989, p. 3508], and 230 mg/kg for yttrium oxide [RTECS 1989d]. The lowest lethal subcutaneous dose of yttrium nitrate hexahydrate in mice is 16.6 g/kg [RTECS 1989b]. Rats injected intra-peritoneally with 60 mg/kg yttrium every other day for 5 months survived and showed no accumulation of yttrium in their bones [ACGIH 1986, p. 641(86)]. A single intra-tracheal dose of 50 mg yttrium oxide produced diffuse granulomatous nodules and emphysema in rats within 8 months of exposure [Clayton and Clayton 1981, p. 1682]. Inhalation of yttrium citrate (at an unspecified concen-tration) caused dyspnea and pulmonary edema in rats [Proctor and Hughes 1978, p. 511]. Rats exposed to yttrium chloride by inhalation (at an unspecified concen-tration) developed liver edema (with portal congestion), pleural effusions, and pulmonary hyperemia [Proctor and Hughes 1978, p. 511]. Application of a 0.1 M solution of yttrium chloride to the intact eye of a rabbit caused no detectable damage; the same application to eyes from which the corneal epithelium had been removed produced corneal opacification [Grant 1986, p. 986].

2. Effects on Humans: Based on effects seen in animals, exposure to yttrium or to a compound of yttrium would be expected to cause lung disease in humans. Workers exposed to an average airborne concentration of yttrium europium vanadate dust experienced mild eye, skin, and upper respiratory tract irritation; however, the authors of this study attributed these effects to the vanadium component of the dust [ACGIH 1986, p. 641(86)].

* Signs and symptoms of exposure

1. Acute exposure: Based on effects seen in animals, the signs and symptoms of acute exposure to yttrium or a compound of yttrium would be expected to include those associated with fibrotic lung disease, such as shortness of breath, cough, chest pain, and cyanosis.

2. Chronic exposure: No signs or symptoms of chronic exposure to yttrium or to a compound of yttrium have been reported.

* Emergency procedures:

In the event of an emergency, remove the victim from further exposure, send for medical assistance, and initiate the following emergency procedures:

1. Eye exposure: If yttrium or an yttrium compound gets into the eyes, immediately flush the eyes with large amounts of water for a minimum of 15 minutes, lifting the lower and upper lids occasionally. If irritation persists, get medical attention as soon as possible.

2. Skin exposure: If yttrium or an yttrium compound contacts the skin, the contaminated skin should be washed with soap and water. If irritation persists, get medical attention.

3. Inhalation: If yttrium dust is inhaled, move the victim at once to fresh air and get medical care as soon as possible. If the victim is not breathing, perform cardiopulmonary resuscitation; if breathing is difficult, give oxygen. Keep the victim warm and quiet until medical help arrives.

4. Ingestion: If yttrium or an yttrium compound is ingested, give the victim several glasses of water to drink and then induce vomiting by having the victim touch the back of the throat with the finger or by giving syrup of ipecac as directed on the package. Do not force an unconscious or convulsing person to drink liquids or to vomit. Get medical help immediately. Keep the victim warm and quiet until medical help arrives.

5. Rescue: Remove an incapacitated worker from further exposure and implement appropriate emergency procedures (e.g., those listed on the Material Safety Data Sheet required by OSHA's Hazard Communication Standard, 29 CFR 1910.1200). All workers should be familiar with emergency procedures and the location and proper use of emergency equipment.

EXPOSURE SOURCES AND CONTROL METHODS

The following operations may involve yttrium and yttrium compounds and lead to worker exposures to this substance:

Yttrium:

• Purification and manufacture of yttrium-containing alloys
• Use in iron and other alloys for electronic devices
• Use as a deoxidizer for vanadium and other nonferrous metals and in coatings of high-temperature alloys and special semiconductors
• Manufacture of lasers and in nuclear technology

Yttrium oxide:

• Manufacture of yttrium-iron-garnet (YIG) and yttrium-aluminum-garnet (YAG) for use as electronic components in telephones, radar, and space communications networks, and as simulated diamonds
• Manufacture of ceramics for use in high-temperature furnaces and high-intensity incandescent lamps
• Manufacture of lasers and in nuclear technology
• Use in phosphors for color TV tubes and as a stabilizer for high-temperature service materials (zirconia and silicon nitride refractories)
• Use in mantles for gas and acetylene lights

Yttrium acetate:

• Use in analytical chemistry

Yttrium chloride:

• Use in analytical chemistry and in the preparation of the pure metal

Yttrium sulfate:

• Use as a chemical reagent

Methods that are effective in controlling worker exposures to yttrium and yttrium compounds, depending on the feasibility of implementation, are

• Process enclosure,
• Local exhaust ventilation,
• General dilution ventilation, and
• Personal protective equipment.

The following publications are good sources of information on control methods:

1. ACGIH [1986]. Industrial ventilation--a manual of recommended practice. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

2. Burton DJ [1986]. Industrial ventilation--a self study companion. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

3. Alden JL, Kane JM [1982]. Design of industrial ventilation systems. New York, NY: Industrial Press, Inc.

4. Wadden RA, Scheff PA [1987]. Engineering design for control of workplace hazards. New York, NY: McGraw-Hill.

5. Plog BA [1988]. Fundamentals of industrial hygiene. Chicago, IL: National Safety Council.

MEDICAL MONITORING

Workers who may be exposed to chemical hazards should be monitored in a systematic program of medical surveillance that is intended to prevent occupational injury and disease. The program should include education of employers and workers about work-related hazards, placement of workers in jobs that do not jeopardize their safety or health, early detection of adverse health effects, and referral of workers for diagnosis and treatment. The occurrence of disease or other work-related adverse health effects should prompt immediate evaluation of primary preventive measures (e.g., industrial hygiene monitoring, engineering controls, and personal protective equipment). A medical monitoring program is intended to supplement, not replace, such measures. To place workers effectively and to detect and control work-related health effects, medical evaluations should be performed (1) before job placement, (2) periodi-cally during the period of employment, and (3) at the time of job transfer or termination.

* Preplacement medical evaluation

Before a worker is placed in a job with a potential for exposure to yttrium or an yttrium compound, the examining physician should evaluate and document the worker's baseline health status with thorough medical, environmental, and occupational histories, a physical examination, and physiologic and laboratory tests appropriate for the anticipated occupational risks. These should concentrate on the function and integrity of the respiratory system. Medical monitoring for respiratory disease should be conducted using the principles and methods recommended by NIOSH and the American Thoracic Society.

A preplacement medical evaluation is recommended to assess an individual's suitability for employment at a specific job and to detect and assess medical conditions that may be aggravated or may result in increased risk when a worker is exposed to yttrium or an yttrium compound at or below the prescribed exposure limit. The examining physician should consider the probable frequency, intensity, and duration of exposure as well as the nature and degree of any applicable medical condition. Such conditions (which should not be regarded as absolute contraindications to job placement) include a history and other findings consistent with diseases of the respiratory system.

* Periodic medical examinations and biological monitoring

Occupational health interviews and physical examinations should be performed at regular intervals during the employment period, as mandated by any applicable Federal, State, or local standard. Where no standard exists and the hazard is minimal, evaluations should be conducted every 3 to 5 years or as frequently as recommended by an experienced occupational health physician. Additional examinations may be necessary if a worker develops symptoms attributable to exposure to yttrium or an yttrium compound. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of yttrium or its compounds on the respiratory system. Current health status should be compared with the baseline health status of the individual worker or with expected values for a suitable reference population.

Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. No biological monitoring test acceptable for routine use has yet been developed for yttrium or its compounds.

* Medical examinations recommended at the time of job transfer or termination

The medical, environmental, and occupational history interviews, the physical examination, and selected physiologic or laboratory tests that were conducted at the time of placement should be repeated at the time of job transfer or termination to determine the worker's medical status at the end of his or her employment. Any changes in the worker's health status should be compared with those expected for a suitable reference population.

WORKPLACE MONITORING AND MEASUREMENT PROCEDURES

Determination of a worker's exposure to airborne yttrium or an yttrium compound (measured as yttrium) is made using a mixed cellulose ester filter (0.8 micron). Samples are collected at a maximum flow rate of 2 liters per minute until a maximum air volume of 960 liters is collected. Analysis is conducted by atomic absorption spectroscopy. This method is included in the OSHA In-House Methods File.

PERSONAL HYGIENE PROCEDURES

If yttrium or an yttrium compound contacts the skin, workers should wash the affected areas with soap and water.

Clothing contaminated with yttrium or its compounds should be removed immediately, and provisions should be made for the safe removal of the chemical from the clothing. Persons laundering the clothes should be informed of the hazardous properties of yttrium and its compounds.

A worker who handles yttrium or a compound of yttrium should thoroughly wash hands, forearms, and face with soap and water before eating, using tobacco products, or using toilet facilities.

Workers should not eat, drink, or use tobacco products in areas where yttrium or its compounds are handled, processed, or stored.

STORAGE

Yttrium and any of its compounds should be stored in a cool, dry, well-ventilated area in tightly sealed containers that are labeled in accordance with OSHA's Hazard Communication Standard [29 CFR 1910.1200]. Containers of yttrium or a compound of yttrium should be protected from physical damage and should be stored separately from combustible materials, halogens, heat, sparks, and open flame. Because empty containers that formerly contained yttrium or its compounds may still hold product residues, they should be handled appropriately.

SPILLS AND LEAKS

In the event of a spill or leak involving yttrium or an yttrium compound, persons not wearing protective equipment and clothing should be restricted from contaminated areas until cleanup has been completed. The following steps should be undertaken following a spill or leak:

1. Do not touch the spilled material.

2. Notify safety personnel.

3. Remove all sources of heat and ignition.

4. Ventilate the area of the spill or leak.

5. Collect spilled material in the most convenient and safe manner for reclamation or for disposal in a secured landfill.

EMERGENCY PLANNING, COMMUNITY RIGHT-TO-KNOW, AND HAZARDOUS WASTE MANAGEMENT REQUIREMENTS

The Environmental Protection Agency's (EPA's) regulatory requirements for emergency planning, community right-to-know, and hazardous waste management may vary over time. Users are therefore advised to determine periodically whether new information is available.

* Emergency planning requirements

Yttrium and its compounds are not subject to EPA emergency planning requirements under the Superfund Amendments and Reauthorization Act (Title III).

* Reportable quantity requirements (releases of hazardous substances)

Employers are not required by the emergency release notification provisions of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) [40 CFR Part 355.40] to notify the National Response Center of an accidental release of yttrium or an yttrium compound; there is no reportable quantity for this substance.

* Community right-to-know requirements

Employers are not required by Section 313 of the Superfund Amendments and Reauthorization Act (SARA) to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of yttrium emitted or released from their facility annually.

* Hazardous waste management requirements

EPA considers a waste to be hazardous if it exhibits any of the following characteristics: ignitability, corro-sivity, reactivity, or toxicity, as defined in 40 CFR 261.21-261.24. Under the Resource Conservation and Recovery Act (RCRA), EPA has specifically listed many chemical wastes as hazardous. Although yttrium and its compounds are not specifically listed as hazardous wastes under RCRA, EPA requires employers to treat any waste as hazardous if it exhibits any of the characteristics discussed above.

Providing more information about the removal and disposal of specific chemicals is beyond the scope of this guideline. EPA, U.S. Department of Transportation, and State and local regulations should be followed to ensure that removal, transport, and disposal of this substance are conducted in accordance with existing regulations. To be certain that chemical waste disposal meets EPA regulatory requirements, employers should address any questions to the RCRA hotline at (202) 382-3000 (in Washington, D.C.) or toll-free at (800) 424-9346 (outside Washington, D.C.). In addition, relevant State and local authorities should be contacted for information on any requirements they may have for the waste removal and disposal of this substance.

RESPIRATORY PROTECTION

* Conditions for respirator use

Good industrial hygiene practice requires that engineering controls be used where feasible to reduce workplace concentrations of hazardous materials to the prescribed exposure limit. However, some situations may require the use of respirators to control exposure. Respirators must be worn if the ambient concentration of yttrium or one of its compounds exceeds prescribed exposure limits. Respirators may be used (1) before engineering controls have been installed, (2) during work operations such as maintenance or repair activities that involve unknown exposures, (3) during operations that require entry into tanks or closed vessels, and (4) during emergency situations. If the use of respirators is necessary, the only respirators permitted are those that have been approved by NIOSH and the Mine Safety and Health Administration (MSHA).

* Respiratory protection program

Employers should institute a complete respiratory protection program that, at a minimum, complies with the requirements of OSHA's Respiratory Protection Standard [29 CFR 1910.134]. Such a program must include respirator selection (see Table 1), an evaluation of the worker's ability to perform the work while wearing a respirator, the regular training of personnel, fit testing, periodic workplace monitoring, and regular respirator maintenance, inspection, and cleaning. The implementation of an adequate respiratory protection program (including selection of the correct respirator) requires that a knowledgeable person be in charge of the program and that the program be evaluated regularly. For additional information on the selection and use of respirators and on the medical screening of respirator users, consult the NIOSH Respirator Decision Logic [NIOSH 1987b] and the NIOSH Guide to Industrial Respiratory Protection [NIOSH 1987a].

Table 1 lists the respiratory protection that NIOSH recommends for workers exposed to yttrium or to a compound of yttrium. The recommended protection may vary over time because of changes in the exposure limit for yttrium or its compounds or in respirator certification requirements. Users are therefore advised to determine periodically whether new information is available.

PERSONAL PROTECTIVE EQUIPMENT

Protective clothing should be worn to prevent skin contact with yttrium or an yttrium compound. Chemical protective clothing should be selected on the basis of available performance data, manufacturers' recommendations, and evaluation of the clothing under actual conditions of use. No reports have been published on the resistance of various protective clothing materials to permeation by yttrium or an yttrium compound. If permeability data are not readily available, protective clothing manufacturers should be requested to provide information on the best chemical protective clothing for workers to wear when they are exposed to yttrium or one of its compounds.

If yttrium or a compound of yttrium is dissolved in water or an organic solvent, the permeation properties of both the solvent and the mixture must be considered when selecting personal protective equipment and clothing.

Safety glasses, goggles, or faceshields should be worn during operations in which yttrium or one of its compounds might contact the eyes (e.g., through dust particles). Eyewash fountains and emergency showers should be available within the immediate work area whenever the potential exists for eye or skin contact with any of these substances. Contact lenses should not be worn if the potential for such exposure exists.

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