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Yohimbe, ext.(CAS No. 85117-22-2)

Identification and Related Records

Yohimbe, ext.
【CAS Registry number】
Yohimbe, ext.
Einecs 285-574-2
【Molecular Formula】
C8H10 (Products with the same molecular formula)
【Molecular Weight】
【Canonical SMILES】

Chemical and Physical Properties

【Melting Point】
-47.4 deg C
【Boiling Point】
139.07 deg C
Miscible in acetone, alcohol, ether, benzene; soluble in chloroform
In water, 1.61X10+2 mg/L at 25 deg C.
Clear, colorless liquid
Color: Saybolt units +30 (research, pure & technical grades)
【Spectral properties】
Index of refraction: 1.4973 at 20 deg C/D
Negligible absorption above 290 nm
IR: 3578 (Coblentz Society Spectral Collection)
UV: 317 (Sadtler Research Laboratories Spectral Collection)
1H NMR: 202 (Varian Associates NMR Spectra Catalogue)
C13 NMR: 297 (Johnson and Jankowski, Carbon-13 NMR Spectra, John Wiley and Sons, New York)
Raman 81 (Dollish et al., characteristic Raman Frequencies of organic compounds, John Wiley and Sons, New York)
MASS: 1349 (NIST/EPA/MSDC Mass Spectral Database, 1990 version); 326 (Atlas of Mass Spectral Data, John Wiley & Sons, New York)
【Computed Properties】
Molecular Weight:106.165 [g/mol]
Molecular Formula:C8H10
H-Bond Donor:0
H-Bond Acceptor:0
Rotatable Bond Count:0
Exact Mass:106.07825
MonoIsotopic Mass:106.07825
Topological Polar Surface Area:0
Heavy Atom Count:8
Formal Charge:0
Isotope Atom Count:0
Defined Atom Stereocenter Count:0
Undefined Atom Stereocenter Count:0
Defined Bond Stereocenter Count:0
Undefined Bond Stereocenter Count:0
Covalently-Bonded Unit Count:1
Feature 3D Ring Count:1
Effective Rotor Count:0
Conformer Sampling RMSD:0.4
CID Conformer Count:1

Safety and Handling

【Skin, Eye, and Respiratory Irritations】
Xylene vapor may cause irritation of the eyes, nose, and throat. At high concentrations, xylene vapor may cause severe breathing difficulties which may be delayed in onset. Repeated or prolonged exposure ... may cause a skin rash. /Xylenes/
Vapor irritates eyes and mucous membranes ... Liquid irritates eyes and mucous membranes. /Xylenes/
【Cleanup Methods】
Stop discharge if possible. Keep people away. Call fire department. Avoid contact with liquid and vapor. Isolate and remove discharged material. Notify local health and pollution control agencies.
For spills on land, absorb remaining xylene with sand or vermiculite and put in metal containers for disposal. Activated carbon may be used on undissolved portion. /Xylenes/
For spills on water, contain and apply a universal gelling agent to solidify trapped mass then remove it. /Xylenes/
Soil: construct barriers to contain spill or divert to impermeable holding area. Remove material with pumps or vacuum equipment. Absorb residual liquid with natural or synthetic sorbents, shovel into containers with covers. /Xylenes/
Water: contain with booms, weirs, or natural barriers. Use (oil) skimming equipment or suction hoses to remove slick, followed by application of sorbents. /Xylenes/
Air: use water spray to control flammable vapor. Control runoff for later treatment and/or disposal. /Xylenes/
Spillage disposal: Shut off all possible sources of ignition. Wear face shield, goggles, laboratory coat, and nitrile rubber gloves. Cover spill with a 1:1:1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite) and sand, then shovel into bucket and transport to fume hood for atmospheric evaporation. Ventilate site of spillage well to evaporate remaining liquid and dispel vapor. /Xylenes/
Environmental considerations - air spill: Apply water spray or mist to knock down vapors. Vapor knockdown water is corrosive or toxic and should be diked for containment. /Xylenes/
Environmental considerations - water spill: Use natural barriers or oil spill control booms to limit spill travel. Use surface active agent (e.g., detergent, soaps, alcohols), if approved by EPA. Inject "universal" gelling agent to solidify encircled spill and increase effectiveness of booms. If dissolved, in region of 10 ppm or greater concentration, apply activated carbon at ten times the spilled amount. /Xylenes/
Environmental considerations - land spill: Dig a pit, pond, lagoon, holding area to contain liquid or solid material. /SRP: If time permits, pits, ponds, lagoons, soak holes, or holding areas should be sealed with an impermeable flexible membrane liner./ Dike surface flow using soil, sand bags, foamed polyurethane, or foamed concrete. Absorb bulk liquid with fly ash, cement powder, or commercial sorbents. Apply "universal" gelling agent to immobilize spill. Apply appropriate foam to diminish vapor and fire hazard. /Xylenes/
【Fire Fighting Procedures】
Foam, dry chemical or carbon dioxide. Water may be ineffective. Cool exposed containers with water.
If material on fire or involved in fire: Do not extinguish fire unless flow can be stopped or safely confined. Use water in flooding quantities as fog. Solid streams of water may spread fire. Cool all affected containers with flooding quantities of water. Apply water from as far a distance as possible. Use foam, dry chemical, or carbon dioxide. /Xylenes/
【Fire Potential】
Dangerous, when exposed to heat or flame
Grade: 95% (technical); 99%, 99.9% (research)
Present in high octane gasoline at 12.03 wt%
【DOT Emergency Guidelines】
/GUIDE 130: FLAMMABLE LIQUIDS (NON-POLAR/WATER-IMMISCIBLE/NOXIOUS)/ Fire or Explosion: HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. Vapors may form explosive mixtures with air. Vapors may travel to source of ignition and flash back. Most vapors are heavier than air. They will spread along ground and collect in low or confined areas (sewers, basements, tanks). Vapor explosion hazard indoors, outdoors or in sewers. Runoff to sewer may create fire or explosion hazard. Containers may explode when heated. Many liquids are lighter than water. /Xylenes/
/GUIDE 130: FLAMMABLE LIQUIDS (NON-POLAR/WATER-IMMISCIBLE/NOXIOUS)/ Health: May cause toxic effects if inhaled or absorbed through skin. Inhalation or contact with material may irritate or burn skin and eyes. Fire will produce irritating, corrosive and/or toxic gases. Vapors may cause dizziness or suffocation. Runoff from fire control or dilution water may cause pollution. /Xylenes/
/GUIDE 130: FLAMMABLE LIQUIDS (NON-POLAR/WATER-IMMISCIBLE/NOXIOUS)/ Public Safety: CALL Emergency Response Telephone Number ... . As an immediate precautionary measure, isolate spill or leak area for at least 50 meters (150 feet) in all directions. Keep unauthorized personnel away. Stay upwind. Keep out of low areas. Ventilate closed spaces before entering. /Xylenes/
/GUIDE 130: FLAMMABLE LIQUIDS (NON-POLAR/WATER-IMMISCIBLE/NOXIOUS)/ Protective Clothing: Wear positive pressure self-contained breathing apparatus (SCBA). Structural firefighters' protective clothing will only provide limited protection. /Xylenes/
/GUIDE 130: FLAMMABLE LIQUIDS (NON-POLAR/WATER-IMMISCIBLE/NOXIOUS)/ Evacuation: Large spill: Consider initial downwind evacuation for at least 300 meters (1000 feet). Fire: If tank, rail car or tank truck is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. /Xylenes/
/GUIDE 130: FLAMMABLE LIQUIDS (NON-POLAR/WATER-IMMISCIBLE/NOXIOUS)/ Fire: CAUTION: All these products have a very low flash point: Use of water spray when fighting fire may be inefficient. Small fires: Dry chemical, CO2, water spray or regular foam. Large fires: Water spray, fog or regular foam. Do not use straight streams. Move containers from fire area if you can do it without risk. Fire involving tanks or car/trailer loads: Fight fire from maximum distance or use unmanned hose holders or monitor nozzles. Cool containers with flooding quantities of water until well after fire is out. Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank. ALWAYS stay away from tanks engulfed in fire. For massive fire, use unmanned hose holders or monitor nozzles; if this is impossible, withdraw from area and let fire burn. /Xylenes/
/GUIDE 130: FLAMMABLE LIQUIDS (NON-POLAR/WATER-IMMISCIBLE/NOXIOUS)/ Spill or Leak: ELIMINATE all ignition sources (no smoking, flares, sparks or flames in immediate area). All equipment used when handling the product must be grounded. Do not touch or walk through spilled material. Stop leak if you can do it without risk. Prevent entry into waterways, sewers, basements or confined areas. A vapor suppressing foam may be used to reduce vapors. Absorb or cover with dry earth, sand or other non-combustible material and transfer to containers. Use clean non-sparking tools to collect absorbed material. Large spills: Dike far ahead of liquid spill for later disposal. Water spray may reduce vapor; but may not prevent ignition in closed spaces. /Xylenes/
/GUIDE 130: FLAMMABLE LIQUIDS (NON-POLAR/WATER-IMMISCIBLE/NOXIOUS)/ First Aid: Move victim to fresh air. Call 911 or emergency medical service. Give artificial respiration if victim is not breathing. Administer oxygen if breathing is difficult. Remove and isolate contaminated clothing and shoes. In case of contact with substance, immediately flush skin or eyes with running water for at least 20 minutes. Wash skin with soap and water. Keep victim warm and quiet. In case of burns, immediately cool affected skin for as long as possible with cold water. Do not remove clothing if adhering to skin. Effects of exposure (inhalation, ingestion or skin contact) to substance may be delayed. Ensure that medical personnel are aware of the material(s) involved and take precautions to protect themselves. /Xylenes/
【Reactivities and Incompatibilities】
An attempt to chlorinate xylene with 1,3-dichloro-5,5-dimethyl-2,4-imidazolidindione (dichlorohydrantoin) caused a violent explosion. The haloimide undergoes immediate self accelerating decomp in the presence of solvents. /Xylenes/
Can react with oxidizing materials.
Strong oxidizers, strong acids.
【Other Preventative Measures】
SRP: The scientific literature for the use of contact lenses in industry is conflicting. The benefit or detrimental effects of wearing contact lenses depend not only upon the substance, but also on factors including the form of the substance, characteristics and duration of the exposure, the uses of other eye protection equipment, and the hygiene of the lenses. However, there may be individual substances whose irritating or corrosive properties are such that the wearing of contact lenses would be harmful to the eye. In those specific cases, contact lenses should not be worn. In any event, the usual eye protection equipment should be worn even when contact lenses are in place.
SRP: Contaminated protective clothing should be segregated in such a manner so that there is no direct personal contact by personnel who handle, dispose, or clean the clothing. Quality assurance to ascertain the completeness of the cleaning procedures should be implemented before the decontaminated protective clothing is returned for reuse by the workers. All contaminated clothing should not be taken home at end of shift, but should remain at employee's place of work for cleaning.
SRP: Local exhaust ventilation should be applied wherever there is an incidence of point source emissions or dispersion of regulated contaminants in the work area. Ventilation control of the contaminant as close to its point of generation is both the most economical and safest method to minimize personnel exposure to airborne contaminants.
Skin that becomes contaminated with xylene should be promptly washed with soap or mild detergent and water to remove any xylene. Employees who handle liquid or solid xylene should wash their hands thoroughly with soap or mild detergent and water before eating, smoking, or using toilet facilities. /Xylenes/
A major concern in the painting studio is solvents, /including xylene/. ... Precautions include ... use of dilution and local exhaust ventilation, control of storage areas, disposal of solvent soaked rags in covered containers, minimizing skin exposure and the use of respirators and other personal protective equipment. The control of fire hazards is also important, since many of the solvents are highly flammable. /Xylenes/
The worker should immediately wash the skin when it becomes contaminated.
Work clothing that becomes wet should be immediately removed due to its flammability hazard (i.e., for liquids with a flash point
Personnel protection: Avoid breathing vapors. Keep upwind. ... Do not handle broken packages unless wearing appropriate personal protective equipment. ... /Xylenes/
If material not on fire and not involved in fire: Keep sparks, flames, and other sources of ignition away. Keep material out of water sources and sewers. Build dikes to contain flow as necessary. Attempt to stop leak if without undue personnel hazard. Use water spray to knock-down vapors. /Xylenes/
【Protective Equipment and Clothing】
Employees should be provided with and required to use impervious clothing, gloves, face shields (eight-inch minimum) ... to prevent repeated or prolonged skin contact with liquid or solid xylene. Clothing contaminated with xylene should be placed in closed containers for storage until it can be discarded or until provision is made for the removal of xylene from the clothing. If the clothing is to be laundered ... the person performing the operation should be informed of xylene's hazardous properties. /Xylenes/
Breakthrough times /for natural rubber, neoprene, and polyvinyl chloride/ less (usually significantly less) than one hr reported by (normally) two or more testers. /Xylenes/
Breakthrough times /for polyvinyl alcohol/ greater than one hr reported by (normally) two or more testers. Some data suggesting breakthrough times /for nitrile rubber/ of approx an hour or more. /Xylenes/
Wear appropriate personal protective clothing to prevent skin contact.
Wear appropriate eye protection to prevent eye contact.
Respirator Recommendations: Up to 900 ppm Assigned Protection Factor (APF) Respirator Recommendation APF = 10 Any chemical cartridge respirator with organic vapor cartridge(s). Substance reported to cause eye irritation or damage; may require eye protection. APF = 25 Any powered, air-purifying respirator with organic vapor cartridge(s). Substance reported to cause eye irritation or damage; may require eye protection. APF = 10 Any supplied-air respirator. Substance reported to cause eye irritation or damage; may require eye protection. APF = 50 Any self-contained breathing apparatus with a full facepiece.
Respirator Recommendations: Emergency or planned entry into unknown concentrations or IDLH conditions: Assigned Protection Factor (APF) Respirator Recommendation APF = 10,000 Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode. APF = 10,000 Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained positive-pressure breathing apparatus.
Respirator Recommendations: Escape conditions: Assigned Protection Factor (APF) Respirator Recommendation APF = 50 Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted organic vapor canister/Any appropriate escape-type, self-contained breathing apparatus.
Personnel protection: ... Wear appropriate chemical protective clothing. Wear positive pressure self-contained breathing apparatus.
【Octanol/Water Partition Coefficient】
log Kow = 3.20
【Disposal Methods】
Generators of waste (equal to or greater than 100 kg/mo) containing this contaminant, EPA hazardous waste number U239 and F003, must conform with USEPA regulations in storage, transportation, treatment and disposal of waste. /Xylenes/
Xylene is a waste chemical stream constituent which may be subjected to ultimate disposal by controlled incineration. /Xylenes/
A good candidate for fluidized bed incineration at a temperature range of 450 to 980 deg C and residence times of seconds for liquids and gases, and longer for solids. A good candidate for rotary kiln incineration at a temperature range of 820 to 1,600 deg C and residence times of seconds for liquids and gases, and hours for solids. A good candidate for liquid injection incineration at a temperature range of 650 to 1,600 deg C and a residence time of 0.1 to 2 seconds. /Xylenes/
Recommendable methods: Incineration, use as a boiler fuel, & evaporation.
Xylene is a waste chemical stream constituent which may be subjected to ultimate disposal by controlled incineration.

Use and Manufacturing

【Use and Manufacturing】
Methods of Manufacturing

The Mitsubishi Gas Chemical Company process is another commercial method for separating the meta isomer from mixed xylenes using a hydrofluoric acid-borofluoride separation technique.
Xylene is produced primarily by the catalytic reforming of naphtha streams, which are rich in alicyclic hydrocarbons. The aromatic reformate fractions consist mainly of benzene, toluene and mixed xylenes, xylenes representing the largest fraction. The xylene isomers are separated from the reformate by extraction and distillation on the basis of differences in boiling point... 4-xylene is separated by continuous crystallization or adsorption from the mixed xylenes or isomerized from the 3-xylene/4-xylene distillate; 3-xylene is obtained by selective crystallization or solvent extraction of meta-para mixtures.
U.S. Exports

(1980) 6.80X10+9-1.10X10+10 G (EST)
U.S. Imports

(1978) 1.26X10+10 G
(1982) 1.02X10+9 G
(1986) 7.62X10+5 gal
U.S. Production

(1979) 4.13X10+10 G (EST)
(1980) 4.59X10+10 G (EST)
1,3-Dimethylbenzene is listed as a High Production Volume (HPV) chemical (65FR81686). Chemicals listed as HPV were produced in or imported into the U.S. in >1 million pounds in 1990 and/or 1994. The HPV list is based on the 1990 Inventory Update Rule. (IUR) (40 CFR part 710 subpart B; 51FR21438).
Production volumes for non-confidential chemicals reported under the Inventory Update Rule. Year Production Range (pounds) 1986 >100 million - 500 million 1990 >100 million - 500 million 1994 >100 million - 500 million 1998 >100 million - 500 million 2002 >100 million - 500 million
Consumption Patterns

In 1976, 32 thousand metric tons of m-xylene were used in the manufacturing of isophthalic acid in the USA.
【Sampling Procedures】

Biomedical Effects and Toxicity

【Biomedical Effects and Toxicity】
Xylenes are rapidly absorbed by the respiratory tract with uptake increased by physical exercise. Absorption is also positively correlated with the amount of body fat. Liquid m-xylene is well absorbed through the skin, but dermal absorption of m-xylene vapor (up to 600 ppm) does not appear to be appreciably absorbed. Xylenes are highly soluble in blood and fat, and are distributed widely in the body. Xylenes undergo extensive metabolism and are primarily excreted as metabolites in the urine with small amounts released unchanged in expired air. About 90% of the absorbed dose is excreted in the urine as methylhippuric acid, the glycine conjugate of methylbenzoic acid, following inhalation or dermal (liquid) exposure.
Whole body exposure of mice to 14C-m-xylene vapor for 10 minutes showed that absorption was mainly via respiration. ... Almost complete absorption of 1.8 g m-xylene ...was observed in orally dosed rodents. Absorption after oral administration was rapid and peak levels of m-xylene were seen 20 minutes after a dose of 0.27 mg/kg. After oral administration, absorption rate was faster in females.
Dermal absorption has been studied by in vivo exposure of rat skin to liquid or vapor. Permeability constants were determined and were higher than those for humans. In excised rat skin preparations, duration of exposure correlated with level of skin penetration; rate was 0.967 nmole/sq cm/min. Skin:air partition coefficient for m-xylene was 50.4+/-1.7 and this correlated with the permeability constant.
In rats and mice, m- and p-xylene are distributed primarily to lipid-rich tissues, such as fat, blood, and brain and also in organs highly perfused with blood such as kidney and liver. Small amounts of p-xylene and o-xylene cross the placenta and distribute to amnionic fluid and fetal tissue. Oral administration of m-xylene to rats led to distribution of 14C-m-xylene in adipose tissue, approximately 0.3% of dose in female and 0.1% in males.
... Percutaneous absorption rate of m-xylene in humans was approx 2 ug/square cm/min through the skin of the hands. Percutaneously absorbed m-xylene was primarily excreted into urine as methylhippuric acid. A small amt of xylene was also detected in expired air.
Excretion of m-xylene from most tissues takes place rapidly (elim half-time about 0.5-1.0 hr within 1st hours). Therefore acute effects on CNS are probably short lived. Elimination from adipose tissue is slow. [RIIHIMAKI V, SAVOLAINEN K; ANN OCCUP HYG 23: 411-22 (1980)] PubMed Abstract
After an oral dose of radiolabeled m-xylene, rats excreted most of the radioactivity [50- 59%] in urine within 12 hours of dosing, with expired air secondary [8-22%]. m-Methylhippuric acid conjugates were 67-75% of the label with xylenol , 2-18%, and unchanged m-xylene approx. 1%. Excretion in expired air was less in males (8%) than in females (22%), suggesting a higher metabolic capacity in males. After dermal administration, the primary route of excretion of m-xylene was in expired air (62% of dose) with 43% in urine. Most of the air excretion was in the first 24 hours. Less than 0.5% was excreted in feces. The urinary metabolites of xylenes are similar when dosing is by different routes but the quantities of the different metabolites vary more with degree of absorption than with dose or duration of exposure.
Mated CD mice admin by gavage unlabeled m-xylene (9 am, noon, 3 pm) on days 6-15 or 12-15 of gestation @ 1 ml/kg. Once only, on days 12 or 15 of gestation @ 9 am in both exposure periods dams received labeled m-xylene. Max concn of (14)C in maternal liver was 2 hr after exposure on either days 12 or 15 of gestation. Amt of (14)C @ 2 hr after exposure & rate of elim from maternal liver during 24 hr after exposure was greater for dams exposed on days 6-15 than those exposed on days 12-15. In fetal tissue highest amt of (14)C was 2 hr after exposure, but @ 24 hr after exposure very little could be found. Principal routes of (14)C elimination were by kidneys & expired air.
... Inhalation experiments showed that 72% of absorbed m-xylene was excreted in the urine of male volunteers as m-methylhippuric acid during and within 18 hr after the end of exposure.
Six human male volunteers at rest in a treatment chamber were exposed to 95 ppm of laboratory grade m-xylene for 6 hr/day for five consecutive days. The final 3 hr of exposure on the fifth day was at a level of 200 ppm. The absorption rate of xylene, including both pulmonary and percutaneous routes of exposure, was about 60% (54-58%) and did not vary during the exposure period.
Humans exposed to 46 or 92 ppm of o-, m-, p-xylene or a mixture (1:1:1) of the three for 8 hr absorbed approx 64% of the inhaled xylene. No difference in the absorption rate was reported due to level of exposure, length of exposure, or the type and/or mixture of the xylene isomers. The absorption of xylene appeared to vary among individuals due to differences in ventilation rate. ... Individuals with an increased ventilation rate retained less xylene.
Groups of five male Wister rats were exposed to 300 ppm of technical grade xylene (85% m-xylene, 15% other isomers) for 6 hr/day, 5 days a week for 5, 9, 14, or 18 weeks. Analysis of the perirenal fat by gas chromatography indicated that 67.6, 57.4, 40.7, and 36.6 mg/g of tissue was present after 5, 9, 14, or 18 weeks of exposure, respectively. The gradual decrease in the xylene content of perirenal fat as the length of exposure was increased may have been the result of an incr metabolic rate.
Male Wister rats exposed to xylene in air (80% m-xylene, 12% p-xylene) for 6 hr/day, 5 days/week for 2 weeks accumulated 64.8 mg xylene/g of perirenal fat after five exposures and 127.0 mg xylene/g of perirenal fat after 10 exposures to xylene.
In ... studies with volunteers, lung retention of meta-xylene was about 60% to 75%. When volunteers immersed their hands in liquid meta-xylene, it was absorbed at 2 ug/sq cm per min. A nine-fold interindividual variation in skin absorption rate was observed among volunteers. The amount of meta-xylene absorbed after whole-body exposure of volunteers to 600 ppm (2600 mg/cu m) vapor, excluding inhalation, for 3.5 hours was equivalent to the amount absorbed after inhalation exposure to 20 ppm (87 mg/cu m) for the same duration.
In male rats exposed to meta-xylene vapor at concentrations of 200, 1700 or 3200 mg/cu m for 6 hours on five days per week for two weeks, xylene concentrations in brain and perirenal fat were increased during the second week of exposure.
Most of the xylene that is absorbed is excreted rapidly into the urine as metabolites. When rabbits were given oral doses of up to 1.8 g each of the three isomers, separately, well over 50% of the radioactivity was recovered in urine within 24 hours.
When 3 mmol/kg ortho-, meta-, or para-xylene were given intraperitoneally to rats, urinary excretion of thiocompounds was highest with ortho-xylene and much lower with meta-xylene and para-xylene.
Two adult male and two adult female white volunteers were exposed by inhalation, in a dynamic, controlled-environment exposure chamber, to various concn of toluene (21-66 ppm) or m-xylene (25-50 ppm) in order to establish the influence of exposure concn, duration of exposure, variation of concn within day, and work load on respective biological exposure indices. The concn of unchanged solvents in end-exhaled air and in blood as well as the urinary excretion of hippuric acid and m-methyl-hippuric acid were determined. The results show that doubling the exposure concn for both solvents led to a proportional incr in the concn of unchanged solvents in alveolar air and blood at the end of a 7-hr exposure period. Cumulative urinary excretion of the respective metabolites exhibited a nearly proportional incr. Adjustment of exposure concn to account for a prolongation of the duration of exposure resulted in essentially identical cumulative urinary excretion of the metabolites. Induced within-day variations in the exposure concn led to corresponding but not proportional changes in alveolar concn for both solvents, depending on whether or not sampling preceded or followed peak exposure to solvent. At the end of repeated 10-min periods of physical exercise at 50 W, alveolar air concn of both solvents were incr by 40%. Experimental data collected during the present study were adequately simulated by physiologically based toxicokinetic modeling. These results suggest that alveolar air solvent concn is a reliable index of exposure to both toluene and m-xylene under various experimental exposure scenarios. [Lapar'e S et al; Int Arch Occup Environ Health 64 (8): 569-80 (1993)] PubMed Abstract
Studies in mice ... and rats ... indicate that the distribution of m-xylene ... and /its/ metabolites is characterized by high uptake in lipid-rich tissues, such as brain and fat. High uptake also occurs in well-perfused organs, such as the liver and kidney. Using low-temperature (cryogenic) whole-body autoradiography of male mice exposed by inhalation to (14-C)-m-xylene for 10 minutes, ... /identified/ a high level of unmetabolized m-xylene (volatile radioactivity) in body fat, bone marrow, white matter of the brain, spinal cord, spinal nerves, liver, and kidney immediately after exposure. High levels of metabolites (nonvolatile radioactivity) were present in the blood, liver, lung, kidney, and adrenal medulla. Unmetabolized m-xylene persisted in the central nervous system and spinal nerves for up to 1 hour postexposure, whereas a considerable amount persisted in body fat at 4 to 8 hours after exposure. Metabolites were detectable post-exposure in the adrenal medulla for 0.5 hours, in the liver for 2 hours, in the kidney for up to 8 hours, in bile for 2 to 8 hours, in the intestinal lumen for up to 24 hours, and in the nasal mucosa and bronchi for 2 to 24 hours. No radioactivity was detectable by 48 hours. In male Sprague-Dawley rats exposed to 2,000 ppm m-xylene vapor 4 hours/day for 5 consecutive days, m-xylene concentrations were measured in tissues by gas chromatography (Ito et al. 2002). The highest concentrations of m-xylene were observed in peri-intestinal fat and subcutaneous fat, whereas concentrations more than 40 times lower were detected in lung, spleen, testis, heart, kidney, liver, and psoas muscle. In the brain subdivided into four parts, the concentration of m-xylene was 3 to 6 times lower than in subcutaneous fat...
In humans, /following inhalation/ about 95% of absorbed xylene is biotransformed and excreted as urinary metabolites, almost exclusively as methylhippuric acids; the remaining 5% is eliminated unchanged in the exhaled breath ... . Less than 0.005% of the absorbed dose of xylene isomers is eliminated unchanged in the urine, and
A relatively constant retention, average 59%, was reported in ... exposed to varying m-xylene concentrations in the range of 304-957 mg/cu m (70-220 ppm), both at rest and while undergoing intermittent physical exercise ... A slight reduction in retention was noted when resting individuals subsequently underwent moderately heavy physical exercise. Increased pulmonary ventilation during exercise was found to be associated with a corresponding increase in total uptake of xylenes ...
During inhalation exposure in resting subjects, a levelling of the blood xylene concentration began after about 15 min of exposure to 435-870 mg/cum (100-200 ppm) xylene. Light exercise increased the blood level of xylene and indications of plateauing were noted after about 2 hr ... An exposure to 435-1261 mg/cu m (100-290 ppm) m-xylene revealed a rapid rise in xylene blood levels during the first hour. Repeated exposure to 430 mg/cum for 4.5 days (6 hr/day) gave rising pre-exposure morning blood levels, indicating some accumulation of m-xylene ...
Dermal absorption has been studied following hand immersion in liquid m-xylene for 15-20 min. Absorption, estimated from the urinary level of the metabolite m-methylhippuric acid, was recorded to be about 2 ug/sq cm per min in eight volunteers ... The amount absorbed (about 35 mg) through both hands was estimated to be equal to the amount absorbed through inhalation of 435 mg/cu m (100 ppm) during the same time ...
Dermal exposure of m-xylene vapor has been investigated in volunteers exposed to 1305 mg/cu m (300 ppm) (two men) or 2610 mg/cu m (600 ppm) (three men) for 3.5 hr. Inhalation was excluded by means of a full facepiece supplied-air respirator with overpressure inside the mask. The volunteers were dressed in pyjamas and performed exercise to raise the skin temperature and perspiration ...
Dermal absorption appeared to be directly dependent on vapor concentration. At 2610 mg/cu m the absorption was calculated to be approximately 0.01 ug/sq cm per min. In a further experiment, three subjects were exposed to 87 mg/cu m (20 ppm) without respirator. In this case both pulmonary and dermal absorption could occur. The total absorption of m-xylene in this experiment was calculated to be of the same order of magnitude as after dermal-only exposure to 2610 mg/cu m.
Pulmonary retention of m-xylene /in humans/ became relatively constant at about 60% after the first 5-10 min of exposure to 430 mg/cu m (100 ppm) ... The determination was made by measurement of atmospheric and exhaled concentrations. In a previous study ... a pulmonary retention of 62-64% was reported for each xylene isomer at exposure levels of 196-391 mg/cu m (45-90 ppm) for up to 7 hr.
... Volunteers were exposed to 391-870 mg/cum (90-200 ppm) m-xylene 6 hr per day 5 days per week (plus an additional day after the weekend) ... The proportion of absorbed m-xylene distributed to subcutaneous fat was calculated to be about 4% in resting individuals and 8% in those undergoing exercise.
The concentration of m-xylene in perirenal fat and cerebrum was positively correlated to exposure levels in rats exposed to 217 to 3262 mg/cu m (50 to 750 ppm) m-xylene 6 hr/day, 5 days/week for 1-2 weeks ... Accumulation in perirenal fat has also been shown in rats exposed to 1305 mg/cu m (300 ppm) xylene (80% m-xylene, 12% p-xylene) 6 hr/day, 5 days/week for 1-2 weeks ...
Two adult male and two adult female volunteers were exposed by inhalation to
When male mice were exposed to about 1435 mg/cu m (330 ppm) m-xylene for 10 min, high levels of radioactivity was found immediately post-exposure in body fat, bone-marrow, brain (white matter), spinal cord, spinal nerves, liver and kidney. Radioactivity in the nervous system and fatty tissues was due to xylene alone and was present for 1 and 8 hr, respectively. High levels of xylene metabolites were recorded in blood, lung, liver and kidney for up to 8-hr post-exposure and in intestinal contents, bronchi and nasal mucosa up to 24 hr ...
When volunteers were exposed to a constant concentration of about 391-870 mg/cu m (90-200 ppm) m-xylene over 5 days, at least 97% was calculated to be excreted as m-methylbenzoic acid conjugates. 2,4-Dimethylphenol conjugates accounted for 1-2% of the metabolites.
The bioavailability of soil-adsorbed m-xylene was assessed in male and female rats gavaged with an aqueous suspension of (14)C-m-xylene alone or adsorbed to sandy or clay soil. Sex-related differences were observed in the rat and the amount of m-xylene-derived radioactivity absorbed and excreted in the presence of the soils. A higher peak plasma concentration of radioactivity was observed in females following treatment with sandy soil-adsorbed m-xylene. Further, sandy and clay soil-adsorbed chemicals demonstrated significantly longer absorption half-lives, while sandy soil produced a shorter elimination half-life versus m-xylene alone in female rats. Increased bioavailability of sandy soil-adsorbed m-xylene in females was evidenced by a significantly increased area under the plasma concentration time curve. Neither of the soils altered the max plasma concentration, the rate at which xylene-derived radioactivity was absorbed or eliminated, or the plasma concentration time curve in male rats. Fat contained the highest tissue concentration of xylene-derived radioactivity in all treatment groups of both sexes. Further, in all male and female treatment groups of both sexes. Further, in all male and female treatment groups m-xylene was primarily metabolized and excreted in urine with methyl hippuric acid identified as the main urinary metabolite. Sandy soil slightly delayed urinary excretion in females while both soils increased expired air excretion in males compared to m-xylene alone. Methylhippuric acid was the main urinary metabolite in all groups. [Turkall RM et al; Toxicol Lett 63 (1): 57-67 (1992)] PubMed Abstract
That vapors may ... be absorbed through the skin of male human volunteers aged 20 to 35 years wearing supplied air respirators and light pajamas and socks was demonstrated for exposures of 600 ppm of xylene ... at 25 deg C at 50% RH for 3.5 hr. The estimated dermal exposure compared with inhalation exposure over the same exposure time frame, assuming inhalation and skin to be the only two absorption routes ... /was/ 1.4% ... The dermal exposure absorption uptake for xylene was calculated to be 6 nmol/sq cm/hr even though liquid xylene can penetrate skin quickly at 1.13 umol/sq cm/hr. /Xylene/
In a ... study with 20 ppm xylene, the uptake from inhalation alone was 57.7% ... but with much interindividual variability. Dermally absorbed xylene in the form of urinary methylhippuric acid was excreted 2 to 4 hr later than absorbed xylene from inhalation. ... Delays of several minutes occurred in the percutaneous absorption of liquid ... xylene, but these delays increased to about 1 hr for xylene ... to achieve a steady state. /Xylene/
Studies in humans and animals have shown that xylenes are well absorbed by the inhalation and oral routes. Approximately 60% of inspired xylene is retained and approximately 90% of ingested xylene is absorbed. Absorption of xylene also occurs by the dermal route, but to a much lesser extent than by the inhalation and oral routes especially following exposure to xylene vapor. Following absorption, xylene is rapidly distributed throughout the body by way of the systemic circulation. In the blood, xylene is primarily bound to serum proteins. Xylene accumulates primarily in adipose tissue. ... In humans, about 95% of the absorbed xylene is excreted in the urine, with about 5% excreted unchanged in the exhaled air. Elimination from most tissue compartments is rapid, with slower elimination from muscle and adipose tissue. /Xylene/
In a study with 1305 mg/cu m m-xylene, no accumulation in perirenal fat or brain tissue was recorded after one week ... When rats were exposed to 1305 mg/cu m xylene (19.2% o-xylene, 43.0% m-xylene, 19.5% p-xylene, 18.3% ethylbenzene) during 6 hr/day, 5 days/week for 18 weeks, a progressive increase of xylene levels in perirenal fat was demonstrated over the first 2 weeks followed by a decline ... . The decline was attributed to xylene inducing its own metabolism.

Environmental Fate and Exposure Potential

【Environmental Fate/Exposure Summary】
The rate constant for the vapor-phase reaction of 3-xylene with photochemically-produced hydroxyl radicals has been measured as 2.36X10-11 cu cm/molecule-sec at 25 deg C(1). This corresponds to an atmospheric half-life of about 16.3 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(2). 3-Xylene is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(3). 3-Xylene does not contain chromophores that absorb at wavelengths >290 nm(3) and therefore is not expected to be susceptible to direct photolysis by sunlight(SRC).
3-Xylene reacts with hydroxyl radicals in the troposphere(1,2,3,4) with a half-life ranging from 1.0 in summer to 10 hr in winter(1) or a typical loss of 86%/day(4). The rate constant for the vapor-phase reaction of 3-xylene with nitrate radicals has been measured as 7.6X10-17 cu cm/molecule-sec at 25 deg C(5). Products from the gas-phase reaction of nitrate with 3-xylene were 3-methylbenzaldehyde and 3-methylbenzyl nitrate(6). This corresponds to an atmospheric half-life of about 210 days at an atmospheric concn of 5X10+8 nitrate radicals per cu cm(5). The rate constant for the vapor-phase reaction of 3-xylene with ozone has been measured as 6X10-22 cu cm/molecule-sec at 24 deg C(7). This corresponds to an atmospheric half-life of about 54 years at an atmospheric concentration of 7X10+11 ozone molecules per cu cm(7).
3-Xylene has an ozone formation potential, relative to ethene, of 27.3 during 0-2 days and 47.4 for 0-4 days; this suggests that this compound has a low to medium ability to produce ozone(1). In an ordinary Swedish environment and a high NOx environment, the ozone formation potential, relative to ethene, for 3-xylene are 47.4 and 88.4, respectively(1). 3-Xylene has a moderately high photochemical reactivity under smog conditions, higher than the other xylene isomers, with loss rates varying from 9-42% per hr(2,3,4,5). Under simulated atmospheric conditions, glyoxal, propanalone, and formaldehyde were formed as products from the degradation of 3-xylene(6). The photooxidation of 3-xylene results in the production of carbon monoxide, formaldehyde, glyoxal, methylglyoxal, 3-methylbenzyl nitrate, m-tolualdehyde, 4-nitro-3-xylene, 5-nitro-3-xylene, 2,6-dimethyl-p-benzoquinone, 2,4-dimethylphenol, 6-nitro-2,4-dimethylphenol, 2,6-dimethylphenol, 4-nitro-2,6-dimethylphenol at 6.1, 2.9, 3.1, 20.6, 1.1, 18.1, 1.5, 0.6, 13.8, 0.2, 11.7, 0.2, and 7.6 as % reacted carbon, respectively(7). Irradiation of wood smoke resulted in the degradation of 3-and 4-xylene, combined, from initial concentrations of 14, 40, and 12 ppb to 7, 19, and 3 ppb, respectively, in three experiments(8).
3-Xylene in water with added humic substances was 50% degraded following 3 hours irradiation suggesting that indirect photooxidation in the presence of humic acids may play an important role in the abiotic degradation of 3-xylene(1). The corresponding tolualdehyde and methyl benzyl alcohol were produced during this process(1). The photolysis of jet fuel JP-4 in water resulted in the degradation of 3- and 4-xylene, combined, from 1.46 to 1.38 to 1.34 to 1.20 mg/L in 0, 7, 14, and 21 days, respectively, in pond water(2).

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