P-Xylene

log Kow = 3.15

3.15

3.42

Sweet

Aromatic odor

Characteristic odor

0.861 at 68 °F (USCG, 1999) - Less dense than water; will float

0.86104 at 20 °C/4 °C

Critical density: 2.64 mmol/cu cm; Critical volume: 379.0 cu cm/mol

Relative density (water = 1): 0.86 (20 °C)

0.86

0.603 mPa.s at 25 °C

0.65 mPa*s at 20 °C

Colorless plates or prisms at low temp

Colorless liquid [Note: A solid below 56 degrees F]

Color: Saybolt units +30 (research, pure & technical grades)

Insoluble. (NTP, 1992)

In water, 1.62X10+2 mg/L at 25 °C

In water, 165 mg/L at 25 °C (average of 15 literature values ranging from 130-215 mg/L at 25 °C)

Miscible in alcohol, ether, acetone, benzene; soluble in chloroform

Solubility in water, g/l at 25 °C: 0.2 (very slightly soluble)

0.02%

81 °F (NTP, 1992)

25.0 °C (77.0 °F) - closed cup

77 °F (25 °C) (Closed cup)

25 °C c.c.

81 °F

280.9 °F at 760 mmHg (NTP, 1992)

138.3 °C

p-Xylene and m-xylene cannot be separated by distillation because their boiling points are too close.

138 °C

281 °F

Warning

H226: Flammable liquid and vapor [Warning Flammable liquids]

P210, P233, P240, P241, P242, P243, P261, P264, P271, P280, P302+P352, P303+P361+P353, P304+P340, P317, P321, P332+P317, P362+P364, P370+P378, P403+P235, and P501 (click each P-code to see the statement)

This chemical does not meet GHS hazard criteria for 0.8% (11 of 1380) of reports.

Danger

H226 (99.2%): Flammable liquid and vapor [Warning Flammable liquids]

Chemical: Benzene, 1,4-dimethyl-

Benzene, 1,4-dimethyl- is listed on the EPA's Chemical Data Reporting (CDR) system. Manufacturers and importers of Benzene, 1,4-dimethyl- are required to report information about their production and use of this chemical to the EPA under the Toxic Substances Control Act (TSCA). (40 eCFR Part 711)

Status: Active Update: 19-01-2023 https://echa.europa.eu/registration-dossier/-/registered-dossier/15791

Benzene, 1,4-dimethyl-: HSNO Approval: HSR001048 Approved with controls

The New Jersey Worker and Community Right to Know Act requires public and private employers to provide information about hazardous substances at their workplaces. (N.J.S.A. 34:5A-1 et. seq.)

Behavior in Fire: Vapor is heavier than air and may travel considerable distance to a source of ignition and flash back. (USCG, 1999)

Flammable. Above 25 °C explosive vapour/air mixtures may be formed.

Vapors cause headache and dizziness. Liquid irritates eyes and skin. If taken into lungs, causes severe coughing, distress, and rapidly developing pulmonary edema. If ingested, causes nausea, vomiting, cramps, headache, and coma. Can be fatal. Kidney and liver damage can occur. (USCG, 1999)

A skin and eye irritant; May have CNS effects; An aspiration hazard by ingestion (may cause chemical pneumonitis); May have adverse effects on human reproduction or development, based on animal studies; [ICSC] May cause smarting and reddening of skin if spilled and allowed to remain on clothes; High vapor concentrations may cause mild smarting of eyes and respiratory system; May cause liver and kidney injury; [CHRIS] A local irritant; Inhalation of high concentrations may cause narcotic effects, severe coughing, and pulmonary edema; Ingestion may cause kidney and liver injury; [NTP] A skin irritant; Harmful by inhalation and skin absorption; May cause narcosis, lung irritation, chest pain, pulmonary edema, CNS depression, blood disorders, liver and kidney injury, and reproductive disorders; [Sigma-Aldrich MSDS] An OTO notation is recommended for p-xylene based on human and animal ototoxicity data. [2021 ACGIH] See Xylene isomers.

The major hazards encountered in the use and handling of 4-xylene stem from its toxicologic properties and flammability. Exposure to this colorless sweet-smelling liquid (solid, below 13 °C) may occur from its use as a solvent, as a component of gasoline, and as a chemical intermediate. Toxic by all routes of exposure (ie, dermal, ingestion, and inhalation), 4-xylene can cause effects including headache, dizziness, skin and eye irritation, kidney and liver damage, pulmonary edema, coma, and death. The ACGIH recommends a workplace exposure limit (TLV) of 100 ppm an 8-hr time-weighted average (TWA); however, to assure protection, wear an approved canister or air-supplied mask, face shield, plastic gloves, and boots. In emergency situations, a self-contained breathing apparatus and full protective clothing are recommended. If contact does occur, immediately flush exposed eyes with running water, wash exposed skin with soap and water, and remove contaminated clothing. Individuals with diseases of the central nervous system, liver, kidneys, and blood should be protected from exposure. 4-Xylene is easily ignitable by heat, sparks, or flame (flash point: 25 °C, closed cup), and may do so explosively in an enclosed area. Also, vapor may travel a considerable distance to a source of ignition and flash back. The heat of a fire may cause containers to explode and/or cause thermal degradation of 4-xylene, producing irritating and poisonous gases. Fires involving 4-xylene may be extinguished with dry chemical, CO2, water spray, fog, or foam. For massive fires in enclosed areas, use unmanned hose holders or monitor nozzles. If a 4-xylene tank car or truck is involved in a fire, isolate 1/2 mile in all directions. Runoff from fire control water may cause pollution and, upon entering a sewer, may create an explosion hazard. 4-Xylene should be stored in closed containers, in cool, well ventilated areas (outdoor or detached areas are preferable), away from sources of ignition, oxidizing agents, and any activity that could cause physical damage to containers. For small spills of 4-xylene, take up with sand or other non-combustible absorbent and place in containers for later disposal, or absorb on paper and evaporate in an appropriate exhaust hood. For large spills, isolate the area, dike far ahead of the spill, and collect the material for disposal. 4-Xylene is a good candidate for the Belliot process of oxidative destruction, as well as liquid injection, rotary kiln, and fluidized bed incineration. 4-Xylene may be sent to a solvent disposal company, but prior to implementing any land disposal of waste residue (including waste sludge), consult regulatory agencies for guidance.

WHO; Environmental Health Criteria 190: Xylenes (1997).[Available from, as of July 19, 2016: http://www.inchem.org/documents/ehc/ehc/ehc190.htm]

American Chemistry Council Benzene, Toluene, and Xylenes VCCEP Consortium; Xylenes Category: m-Xylene (CAS No. 108-38-3), o-Xylene (CAS No. 95-47-6), p-Xylene (CAS No. 106-42-3), Mixed Xylenes (CAS No. 1330-20-7) Voluntary Children's Chemical Evaluation Program (VCCEP) Tier 1 Pilot Submission Docket Number OPPTS - 00274D October 6, 2005. With Appendix A - Xylenes Exposure (60 pp), Appendix B -Xylenes Robust Summaries (75 pp.) and Appendix C - Xylenes PBPK Modeling (PDF) (34 pp.).[Available from, as of July 19, 2016: https://java.epa.gov/chemview]

U.S. EPA Risk Assessment Division, OPPTS; Voluntary Childrens Chemical Evaluation Program: Data Needs Assessment of Xylenes. 19 pp. (March 2007).[Available from, as of July 19, 2016: https://java.epa.gov/chemview]

National Academy of Sciences; The Alkyl Benzenes (1981)

For more Special Reports (Complete) data for 4-XYLENE (8 total), please visit the HSDB record page.

F003; When xylene is a spent solvent, it is classified as a hazardous waste from a nonspecific source (F003), as stated in 40 CFR 261.31, and must be managed according to State and/or Federal hazardous waste regulations. /Xylenes/.

U239; As stipulated in 40 CFR 261.33, when xylene, as a commercial chemical product or manufacturing chemical intermediate or an off-specification commercial chemical product or a manufacturing chemical intermediate, becomes a waste, it must be managed according to Federal and/or State hazardous waste regulations. Also defined as a hazardous waste is any residue, contaminated soil, water, or other debris resulting from the cleanup of a spill, into water or on dry land, of this waste. Generators of small quantities of this waste may qualify for partial exclusion from hazardous waste regulations (40 CFR 261.5). /Xylenes/

Pursuant to section 8(d) of TSCA, EPA promulgated a model Health and Safety Data Reporting Rule. The section 8(d) model rule requires manufacturers, importers, and processors of listed chemical substances and mixtures to submit to EPA copies and lists of unpublished health and safety studies. p-Xylene is included on this list. Effective date 10/4/82; Sunset date: 10/4/92.

Section 8(a) of TSCA requires manufacturers of this chemical substance to report preliminary assessment information concerned with production, exposure, and use to EPA as cited in the preamble in 51 FR 41329. Effective date 1/26/94; Reporting date: 3/28/94.

Fire Extinguishing Agents Not to Be Used: Water may be ineffective.

Use water spray, powder, foam, carbon dioxide. In case of fire: keep drums, etc., cool by spraying with water.

Fresh air, rest. Refer for medical attention.

First rinse with plenty of water for at least 15 minutes, then remove contaminated clothes and rinse again. Rinse and then wash skin with water and soap.

First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then refer for medical attention.

Rinse mouth. Do NOT induce vomiting. Refer for medical attention .

EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop.

(General first aid procedures)

Biological Exposure Indices (BEI) [ACGIH] - Xylenes (technical or commercial grades): 0.3 g/g creatine methylhippuric acids in urine at end of shift; [ACGIH TLVs and BEIs]

100.0 [ppm]

Suitable extinguishing media: Use water spray, alcohol-resistant foam, dry chemical, or carbon dioxide.

Advice for firefighters: Wear self-contained breathing apparatus for firefighting if necessary.

Use water spray to cool unopened containers.

Foam, dry chemical or carbon dioxide. Water may be ineffective. Cool exposed containers with water.

Keep container tightly closed in a dry and well-ventilated place. Containers which are opened must be carefully resealed and kept upright to prevent leakage.

Ambient storage temp and open (flame arrester), or pressure-vacuum.

ACCIDENTAL RELEASE MEASURES: Personal precautions, protective equipment and emergency procedures: Use personal protective equipment. Avoid breathing vapors, mist or gas. Ensure adequate ventilation. Remove all sources of ignition. Beware of vapors accumulating to form explosive concentrations. Vapors can accumulate in low areas. Environmental precautions: Prevent further leakage or spillage if safe to do so. Do not let product enter drains. Discharge into the environment must be avoided. Methods and materials for containment and cleaning up: Contain spillage, and then collect with an electrically protected vacuum cleaner or by wet-brushing and place in container for disposal according to local regulations.

SMALL SPILLS AND LEAKAGE: If you should spill this chemical, use absorbent paper to pick up all liquid spill material. Your contaminated clothing and absorbent paper should be sealed in a vapor-tight plastic bag for eventual disposal. Solvent wash all contaminated surfaces with acetone followed by washing with a strong soap and water solution. Do not reenter the contaminated area until the Safety Officer (or other responsible person) has verified that the area has been properly cleaned.

SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations. Concentrations shall be lower than applicable environmental discharge or disposal criteria. Alternatively, pretreatment and/or discharge to a permitted wastewater treatment facility is acceptable only after review by the governing authority and assurance that "pass through" violations will not occur. Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal. If it is not practicable to manage the chemical in this fashion, it must be evaluated in accordance with EPA 40 CFR Part 261, specifically Subpart B, in order to determine the appropriate local, state and federal requirements for disposal.

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.

Product: Burn in a chemical incinerator equipped with an afterburner and scrubber but exert extra care in igniting as this material is highly flammable. Offer surplus and non-recyclable solutions to a licensed disposal company. Contact a licensed professional waste disposal service to dispose of this material; Contaminated packaging: Dispose of as unused product.

p-Xylene is a waste chemical stream constituent which may be subjected to ultimate disposal by controlled incineration.

Xylene is a waste chemical stream constituent which may be subjected to ultimate disposal by controlled incineration.

Personal protection: filter respirator for organic gases and vapours adapted to the airborne concentration of the substance. Ventilation. Remove all ignition sources. Do NOT let this chemical enter the environment. Collect leaking and spilled liquid in sealable containers as far as possible. Absorb remaining liquid in sand or inert absorbent. Then store and dispose of according to local regulations.

SRP: The scientific literature for the use of contact lenses by industrial workers is inconsistent. The benefits 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 a manner such that there is no direct personal contact by personnel who handle, dispose, or clean the clothing. The completeness of the cleaning procedures should be considered before the decontaminated protective clothing is returned for reuse by the workers. Contaminated clothing should not be taken home at the end of shift, but should remain at employee's place of work for cleaning.

ACCIDENTAL RELEASE MEASURES: Personal precautions, protective equipment and emergency procedures: Use personal protective equipment. Avoid breathing vapors, mist or gas. Ensure adequate ventilation. Remove all sources of ignition. Beware of vapors accumulating to form explosive concentrations. Vapors can accumulate in low areas. Environmental precautions: Prevent further leakage or spillage if safe to do so. Do not let product enter drains. Discharge into the environment must be avoided.

Precautions for safe handling: Avoid contact with skin and eyes. Avoid inhalation of vapor or mist. Keep away from sources of ignition - No smoking. Take measures to prevent the build up of electrostatic charge.

For more Preventive Measures (Complete) data for 4-XYLENE (8 total), please visit the HSDB record page.

4-Xylene was detected in expired breath samples of residents in Bayonne, NJ (3.0-3.2 ug/cu m), Los Angeles, CA (1.4-2.3 ug/cu m), and Pittsburgh, PA (1.1 ug/cu m)(1). 4-Xylene was detected in expired breath samples in Los Angeles, CA (2.43-3.46 ug/cu m)(2). Combined 3-/4-xylene was detected in expired breath samples in Bayonne, NJ at average concentrations of 4.7-10 ug/cu m(3). Based on a sample of 355 persons, it was determined that 95% of the population of Bayonne and Elizabeth, NJ had detectable levels of combined 3-/4-xylene in expired breath(4).

The mean concentration of 3-/4-xylene was 0.21 ng/mL in the blood of 134 school-age children that participated in the School Health Initiative: Environment, Learning, Disease (SHIELD) study in Minneapolis, MN(1). The mean concentration of 3-/4-xylene was 0.32 ng/mL in the blood of 43 children living in an inner city neighborhood of Minneapolis, MN(2).

The reported mean concentration of 3-/4-xylene measured in the personal air of 36 high school students in New York City participating in the TEACH study was 10.9 ug/cu m in the summer and 6.71 ug/cu m in the winter(1). A median measured personal 3-/4-xylene concentration of 4.4 ug/cu m was determined for participants of the BEAM study which included 55 individuals employed in non-manufacturing workplaces, including schools and offices, and living in suburban or urban locations in the greater Boston, MA area(2).

If the compound has been ingested, rapid gastric lavage should be performed using 5% sodium bicarbonate. For skin contact, the skin should be washed with soap and water. If the compound has entered the eyes, they should be washed with large quantities of isotonic saline or water. In serious cases, atropine and/or pralidoxime should be administered. Anti-cholinergic drugs work to counteract the effects of excess acetylcholine and reactivate AChE. Atropine can be used as an antidote in conjunction with pralidoxime or other pyridinium oximes (such as trimedoxime or obidoxime), though the use of '-oximes' has been found to be of no benefit, or possibly harmful, in at least two meta-analyses. Atropine is a muscarinic antagonist, and thus blocks the action of acetylcholine peripherally.

Sixteen men were studied in an exposure chamber to assess the effect of four hr exposure to toluene (3.25 mmol/cu m), p-xylene (2.84 mmol/cu m) a mixture of toluene and p-xylene (2.20 + 0.94 mmol/cu m) and a control condition. With the aid of microcomputers subjects performed tests of simple reaction time, short term memory, and choice reaction time immediately after entering the chamber, after two, and after four hours of exposure. The results indicate that the performance on the tests was unaffected by exposure. In the light of this result, the risk of an acute effect on central nervous functions after exposure for four hours at these concn was considered to be minimal.

Eight male subjects were experimentally exposed to toluene, p-xylene, and a combination of toluene and p-xylene to study the influence of coexposure and exposure to different levels of each solvent on their uptake and elimination. The exposures were performed for 4 hr at exposure levels equivalent to or lower than the Swedish threshold limit value for toluene, 300 mg/cu m (3.2 mmol/cu m). During and after the exposure, solvent concentrations were measured in blood and in expired air. In addition, the pulmonary ventilation rate was measured during the exposure. Decreases in the blood/end exhaled air concentration ratio were found for both toluene and p-xylene when given in combination compared with separate exposure. The total solvent uptake relative to the exposure level was decreased after exposure to the higher solvent concentration, and the apparent clearance was also decreased after exposure to the higher concentration of solvent. Finally, the blood solvent concentration were lower at the end of the exposure compared with the maximal concentration during each exposure condition. In the kinetics of toluene and p-xylene, the total amount of toluene or p-xylene, or both, seems to be of major importance. The change in blood/end exhaled air concentration ratio may indicate an effect of coexposure.

It is unclear whether the pneumotoxicity observed with bromobenzene in phenobarbital-induced rats is related to bromobenzene bioactivation in lung, liver or both. To help differentiate pulmonary from hepatic bioactivation, bromobenzene was admin alone and in combination with p-xylene, which inhibits pulmonary but induces hepatic cytochrome P450. Exposure to p-xylene alone (3400 ppm for 4 hr) produced no changes in bronchoalveolar lavage fluid measurements ... or serum sorbitol dehydrogenase. p-Xylene incr hepatic microsomal benzyloxy-, pentoxy-, and ethoxy-resorufin O-dealkylase activities but decr pulmonary microsomal benzyloxy- and pentoxy-resorufin O-dealkylase activities. Immunoblot analysis revealed an induction of hepatic but not pulmonary microsomal P450IIB apoprotein. When rats were exposed to p-xylene (2800 ppm) or room air for 4 hr, treated 12 hr later with bromobenzene (0.5 mL/kg, ip) or corn oil, and killed after 12 hr, p-xylene incr hepatic P450IIB (27-fold) concomitant with a similar incr in benzyloxy-resorufin O-dealkylase activity. p-Xylene also incr hepatic P450IA apoprotein (3 to 4-fold) with a complimentary incr in ethoxy-resorufin O-dealkylase activity. p-Xylene potentiated bromobenzene-induced hepatotoxicity. In pulmonary microsomes p-xylene and bromobenzene each produced similar decr in both ethoxy- and benzyloxy-resorufin O-dealkylase activities. The combination of p-xylene and bromobenzene had an additive effect on pulmonary P450IA1 reduction. Bronchoalveolar lavage fluid analysis and histopathology revealed no pneumotoxicity with any treatment. p-Xylene potentiation of bromobenzene-induced hepatotoxicity without pneumotoxicity suggests that the liver does not produced metabolites of bromobenzene which are directly involved in pulmonary damage.

The effects of p-xylene and ethanol on the lung metabolism of benzo(a)pyrene were studied. p-Xylene was admin by ip injection at doses ranging from 0.1 to 1.0 g/kg (1:1 in soybean oil). Ethanol was admin po at 5 g/kg (40% w/v). Rats given p-xylene, ethanol, or p-xylene and ethanol were sacrificed 1 hr after treatment. Additional time points of 15 min, 30 min, 4 hr, and 24 hr after p-xylene (1 g/kg) were examined. 3-Hydroxy-benzo(a)pyrene (3-OH) formation was measured fluorometrically as aryl hydrocarbon hydroxylase activity in lung microsomes. p-Xylene (1 g/kg) inhibited the formation of 3-OH benzo(a)pyrene 40% at 15 min, 27% at 30 min, 43% at 1 hr, and 39% at 4 hr after treatment. Inhibition of aryl hydrocarbon hydroxylase activity was still present 24 hr after dosing (41%). Aryl hydrocarbon hydroxylase activity was inhibited 27% and 46% at 0.5 mg/kg and 1.0 mg/kg p-xylene (1 hr), respectively, while the lowest dose (0.1 mg/kg) did not change activity. Analysis of the major metabolites of benzo(a)pyrene by HPLC demonstrated that the formation of 3-OH and 4,5-diol benzo(a)pyrene were inhibited 32% and 50%, respectively, in lung microsomes prepared 24 hr after a single injection of p-xylene (1 g/kg). None of the other metabolites analyzed were changed by p-xylene. Ethanol had no effect on 3-OH benzo(a)pyrene formation during a 1-hr treatment. A combined dose of ethanol and p-xylene moderately inhibited 3-OH benzo(a)pyrene formation. These findings indicate that benzo(a)pyrene detoxication (i.e., 3-OH formation) in rat lung is selectively inhibited by p-xylene but not ethanol. Ethanol appears to modify the inhibitory effect of p-xylene.

For more Interactions (Complete) data for 4-XYLENE (6 total), please visit the HSDB record page.

Acute exposure to cholinesterase inhibitors can cause a cholinergic crisis characterized by severe nausea/vomiting, salivation, sweating, bradycardia, hypotension, collapse, and convulsions. Increasing muscle weakness is a possibility and may result in death if respiratory muscles are involved. Accumulation of ACh at motor nerves causes overstimulation of nicotinic expression at the neuromuscular junction. When this occurs symptoms such as muscle weakness, fatigue, muscle cramps, fasciculation, and paralysis can be seen. When there is an accumulation of ACh at autonomic ganglia this causes overstimulation of nicotinic expression in the sympathetic system. Symptoms associated with this are hypertension, and hypoglycemia. Overstimulation of nicotinic acetylcholine receptors in the central nervous system, due to accumulation of ACh, results in anxiety, headache, convulsions, ataxia, depression of respiration and circulation, tremor, general weakness, and potentially coma. When there is expression of muscarinic overstimulation due to excess acetylcholine at muscarinic acetylcholine receptors symptoms of visual disturbances, tightness in chest, wheezing due to bronchoconstriction, increased bronchial secretions, increased salivation, lacrimation, sweating, peristalsis, and urination can occur. Certain reproductive effects in fertility, growth, and development for males and females have been linked specifically to organophosphate pesticide exposure. Most of the research on reproductive effects has been conducted on farmers working with pesticides and insecticdes in rural areas. In females menstrual cycle disturbances, longer pregnancies, spontaneous abortions, stillbirths, and some developmental effects in offspring have been linked to organophosphate pesticide exposure. Prenatal exposure has been linked to impaired fetal growth and development. Neurotoxic effects have also been linked to poisoning with OP pesticides causing four neurotoxic effects in humans: cholinergic syndrome, intermediate syndrome, organophosphate-induced delayed polyneuropathy (OPIDP), and chronic organophosphate-induced neuropsychiatric disorder (COPIND). These syndromes result after acute and chronic exposure to OP pesticides.

LC100; Species: Tetrahymena pyriformis (Ciliate); Concentration: 3.77 mmole/L for 24 hr /Conditions of bioassay not specified/

LC50; Species: Crangon franciscorum (Shrimp); Concentration: 2.0 ppm for 96 hr /Conditions of bioassay not specified/

EC50; Species: Chlamydomonas angulosa (Green algae) age 72-96 hr exponential growth phase, 5X10+4 cells/mL; Conditions: static, 19 °C, pH 6.5; Concentration: 430 mmol/cu m for 3 hr; Effect: physiology, photosynthesis /formulated product/

EC50; Species: Chlorella vulgaris (Green algae) age 3-4 days exponential growth phase, 20X10+4 cells/mL; Conditions: static, 19 °C, pH 6.5; Concentration: 990 mmol/cu m for 3 hr; Effect: physiology, photosynthesis /formulated product/

For more Ecotoxicity Values (Complete) data for 4-XYLENE (16 total), please visit the HSDB record page.

TERRESTRIAL FATE: Based on a classification scheme(1), Koc values ranging from of 204-540(2-4), indicate that 4-xylene is expected to have moderate to low mobility in soil(SRC). Volatilization of 4-xylene from moist soil surfaces is expected to be an important fate process(SRC) given an estimated Henry's Law constant of 6.90X10-3 atm-cu m/mole(5). 4-Xylene is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 8.84 mm Hg at 25 °C(6). Biodegradation is an important fate process under acclimated conditions(7) and in subsurface soils and groundwater where volatilization is hindered(8). 4-Xylene is expected to biodegrade in soil under both aerobic and anaerobic conditions(8) and has been observed to biodegrade in standard biodegradability tests using various inocula(9). For example, using OECD Guideline 301F (Ready Biodegradability: Manometric Respirometry Test) with a mixture of sewage, soil and natural water inoculum, 4-xylene reached 90% of its O2 consumption in 28 days which classified 4-xylene as readily biodegradable(9). Biodegradation proceeds more slowly under anaerobic conditions as is evidenced by about 50% removal of 4-xylene after several months using nitrate-amended soil column(10). Under anaerobic conditions, a long lag period may be required before xylene degradation commences(11).

AQUATIC FATE: Based on a classification scheme(1), Koc values ranging from 204-540(2-4), indicate that 4-xylene may adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(5) based upon a Henry's Law constant of 6.90X10-3 atm-cu m/mole(6). Using this Henry's Law constant and an estimation method(5), volatilization half-lives for a model river and model lake are 3.1 hours and 4.1 days, respectively(SRC). According to a classification scheme(7), a BCF values of 15(8)and 19(9), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Biodegradation is an important process in groundwater where volatilization is hindered(10). 4-Xylene has been observed to biodegrade in standard biodegradability tests using various inocula(11). For example, using OECD Guideline 301F (Ready Biodegradability: Manometric Respirometry Test) with a mixture of sewage, soil and natural water inoculum, 4-xylene reached 90% of its O2 consumption in 28 days which classified 4-xylene as readily biodegradable(11). However, under anaerobic conditions, a long lag period may be required before xylene degradation commences(12). Hydrolysis is not expected to be an important environmental fate process since this compound lacks functional groups that hydrolyze under environmental conditions(5). Irradiation studies using humic substances(13) suggest photooxidation of xylene may have some environmental importance in natural surface waters exposed to sunlight(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 4-xylene, which has a vapor pressure of 8.84 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase 4-xylene is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 26 hours(SRC), calculated from its rate constant of 1.43X10-11 cu cm/molecule-sec at 25 °C(3). Vapor-phase 4-xylene is degraded slowly in the atmosphere by reaction with night-time nitrate radicals(SRC); the half-life for this reaction in air is estimated to be 65 days(SRC), calculated from its rate constant of 4.53X10-16 cu cm/molecule-sec at 25 °C(4). 4-Xylene has been detected in rainwater and snow(5,6), and therefore, it may be removed from the air by wet deposition(SRC). 4-Xylene does not absorb at wavelengths >290 nm(7) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC).

Combined 3-/4-xylene was detected in the volatiles of several table ready foods at concentrations of 10-114 ppb(1). 4-Xylene was detected in the volatiles of roasted duck at concentrations of 0.7-21.2 ppb(2). Unspecified concentrations of 4-xylene were detected in California nectarines(3). Unspecified concentrations of 4-xylene were detected in eggs from the US(4). Unspecified concentrations of 4-xylene were detected in the volatiles of meat products in the US(5).

As part of the US FDA Total Diet Program, monitoring of 70 foods between 1996 and 2000 detected 3-/4-xylene in the following food items(1):[Table#428]

The substance can be absorbed into the body by inhalation, through the skin and by ingestion.

inhalation, skin absorption, ingestion, skin and/or eye contact

Oral (L165) ; inhalation (L165) ; dermal (L165)

IDENTIFICATION AND USE: 4-Xylene (p-xylene) is a colorless liquid (Note: A solid below 56 degrees F). It is used for synthesis of terephthalic acid for polyester resins and fibers; pharmaceutical synthesis; insecticides. p-Xylene is also frequently used for paints or in the printing trade. HUMAN EXPOSURE AND TOXICITY: Three women exposed to p-xylene at 100 ppm for 1 to 7.5 hours/day, for 5 days, showed no effects on electroencephalograms, evoked potentials, or cognitive performance, but frequently reported headache and dizziness as a result of exposure. In contrast, four men exposed at concentrations of up to 150 ppm p-xylene under the same exposure conditions reported no increase in headaches or dizziness. Slight impairment of vestibular and visual function and reaction time was noted at exposure levels from 200 to 300 ppm. There was adaption to the impairment over five successive daily exposures. Human data indicate that acute inhalation exposures to 460 ppm mixed xylene and 100 ppm p-xylene vapors produce mild and transient eye irritation. p-Xylene is possibly ototoxic at concentrations that are relevant to the occupational setting. Levels of blood xylenes reflect recent exposure. The m-and p-xylene isomers usually are measured together and reported as m/p-xylene. ANIMAL STUDIES: Increased hepatic cytochrome p450 concentrations and reduced nicotinamide adenine dinucleotide cytochrome C reductase activity occurred in rats exposed 3 days to 2000 ppm of p-xylene. In lung microsomes, cytochrome p450 content was decreased. Marked activation and tremor were observed at concentrations between 400 and 1500 ppm p-xylene in rats. The CNS depressant threshold was 1940 ppm. In a study of levels of noradrenaline and dopamine in the forebrain and hypothalamus, rats (six males/group) were exposed to 0 or 2000 ppm p-xylene 6 hr/day for 3 days. The animals were killed 16-18 hr after the last exposure. In exposed animals there was a significant increase in catecholamine levels and turnover in various parts of the hypothalamus. There was no effect on dopamine levels or turnover in the forebrain. Histological damage to the outer hair cells of the organ of Corti provided evidence of ototoxicity in rats exposed by oral gavage to p-xylene, but not m- or o-xylene, at a dose of 900 mg/kg/day, 5 days/week for 2 weeks. The losses of hair cells occurred in the area of the cochlea responsive to medium frequencies (10-25 kHz). Mice were exposed to p-xylene at 150, 1500, or 3000 mg/cu m, 24 hr/day from days 7-14 of gestation. Toxic effects were decr weight of fetuses, increased incidence of skeletal retardation, and decrease in activity of enzymes, succinic dehydrogenase, alkaline, acid phosphatase, glucose 6-phosphatase and changed characteristic features of functional maturity of the nephron, retardation of fetus was dose related. In other experiment, increased incidence of malformations mostly cleft palates, were observed only with m- or p-xylene. Malformations (ie cleft palate) associated with mixed or individual isomers were primarily reported at maternally toxic doses. Each xylene isomer was administered to male rats intraperitoneally in 2 similar doses, 24 hours apart over a range of concentrations from 0, 0.12-0.75 mL/kg (105-650 mg/kg) and evaluated femoral bone marrow 30 hours after the first injection. No increase in micronucleated polychromatic erythrocytes was observed for any xylene isomer. p-Xylene was nonmutagenic using the Ames assay. It did not revert Salmonella typhimurium strains TA1535, TA1537, TA1538, TA98, & TA100 either with or without metabolic activation. ECOTOXICITY STUDIES: The xylene isomers have a similar degree of toxicity as mixed xylenes to estuarine/marine invertebrates. For m-xylene and p-xylene, the respective 48-hour LC50 values are 19.3 and 24.5 mg/L in brine shrimp, suggesting that the m-xylene and p-xylene isomers are slightly toxic to estuarine/marine invertebrates on an acute basis.

p-Xylene is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death. Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.

F003; When xylene is a spent solvent, it is classified as a hazardous waste from a nonspecific source (F003), as stated in 40 CFR 261.31, and must be managed according to State and/or Federal hazardous waste regulations. /Xylenes/.

U239; As stipulated in 40 CFR 261.33, when xylene, as a commercial chemical product or manufacturing chemical intermediate or an off-specification commercial chemical product or a manufacturing chemical intermediate, becomes a waste, it must be managed according to Federal and/or State hazardous waste regulations. Also defined as a hazardous waste is any residue, contaminated soil, water, or other debris resulting from the cleanup of a spill, into water or on dry land, of this waste. Generators of small quantities of this waste may qualify for partial exclusion from hazardous waste regulations (40 CFR 261.5). /Xylenes/

Pursuant to section 8(d) of TSCA, EPA promulgated a model Health and Safety Data Reporting Rule. The section 8(d) model rule requires manufacturers, importers, and processors of listed chemical substances and mixtures to submit to EPA copies and lists of unpublished health and safety studies. p-Xylene is included on this list. Effective date 10/4/82; Sunset date: 10/4/92.

Section 8(a) of TSCA requires manufacturers of this chemical substance to report preliminary assessment information concerned with production, exposure, and use to EPA as cited in the preamble in 51 FR 41329. Effective date 1/26/94; Reporting date: 3/28/94.

This action promulgates standards of performance for equipment leaks of Volatile Organic Compounds (VOC) in the Synthetic Organic Chemical Manufacturing Industry (SOCMI). The intended effect of these standards is to require all newly constructed, modified, and reconstructed SOCMI process units to use the best demonstrated system of continuous emission reduction for equipment leaks of VOC, considering costs, non air quality health and environmental impact and energy requirements. p-Xylene is produced, as an intermediate or a final product, by process units covered under this subpart.

Listed as a hazardous air pollutant (HAP) generally known or suspected to cause serious health problems. The Clean Air Act, as amended in 1990, directs EPA to set standards requiring major sources to sharply reduce routine emissions of toxic pollutants. EPA is required to establish and phase in specific performance based standards for all air emission sources that emit one or more of the listed pollutants. 4-Xylene is included on this list.

Persons in charge of vessels or facilities are required to notify the National Response Center (NRC) immediately, when there is a release of this designated hazardous substance, in an amount equal to or greater than its reportable quantity of 100 lb or 45.4 kg. The toll free number of the NRC is (800) 424-8802. The rule for determining when notification is required is stated in 40 CFR 302.4 (section IV. D.3.b).

p-Xylene is designated as a hazardous substance under section 311(b)(2)(A) of the Federal Water Pollution Control Act and further regulated by the Clean Water Act Amendments of 1977 and 1978. These regulations apply to discharges of this substance. This designation includes any isomers and hydrates, as well as any solutions and mixtures containing this substance.

/When administered to rabbit, rat, and guinea pig/ p-xylene was excreted as p-toluic acid derivative, but a 2,5-dimethylphenol glucuronide was also isolated ... .

Metab of p-xylene (100 umol) studied in isolated, perfused rabbit livers and lungs. Release of p-tolualdehyde into circulation did not occur in perfused rabbit livers. P-toluric acid (n-p-toluylglycine) was major hepatic metabolite, with smaller amt of toluic acid & p-methylbenzyl alcohol. Rabbit livers did not produce detectable amt of p-tolualdehyde, 2,5-dimethylphenol or any glucuronide conjugates. One major pulmonary metab was p-methylbenzyl alc. Predominance of this metab reflects deficiency of lung tissue in alc dehydrogenase. Perfused lung also produced 2,5-dimethylphenol a derivative not produced in the liver. During p-xylene metab in perfused lungs, derivatives which became covalently bound to lung proteins were formed which suggests that p-xylene metab might proceed at least partially through reactive intermediate(s) causing destruction of pulmonary cytochrome P450. Metab was also characterized using reconstituted monooxygenase systems containing purified rabbit pulmonary lung cytochrome P450 (i) & (ii).

The involvement of sequential side-chain oxidn, sulfation, & glutathione conjugation in formation of mercapturic acids from xylenes was investigated. The position of methyl groups attached to the aromatic nucleus affected metabolism. Factors that are involved in high yield of mercapturic acids after admin of o-xylene as compared to m-xylene & p-xylene incl relatively low apparent affinity of o-methylbenzyl alcohol for cytosolic alcohol dehydrogenase, the relatively high apparent affinity of o-methylbenzyl alc for cytosolic sulfotransferase, & the high electrophilic reactivity of the o-methylbenzyl sulfate.

Meta & para isomers are ... extensively oxidized to toluic acids (about 90% of the dose), & these are conjugated mostly with glycine. Hydroxylation to corresponding xylenols also occurs to a small extent.

For more Metabolism/Metabolites (Complete) data for 4-XYLENE (14 total), please visit the HSDB record page.

P-xylene has known human metabolites that include 2,5-dimethylphenol and 4-Methylbenzylalcohol.

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.

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 incr ventilation rate retained less xylene.

In rats exposed to 208 mg/cu m methyl-(14)C para-xylene for 1 hour, distribution of radioactivity immediately after termination of the exposure was highest in the kidneys, followed by subcutaneous fat, ischiatic nerve, blood, liver and lungs. Activity was 1/5 to 1/30 of these levels 6 hours after the end of exposure.

Pregnant mice were exposed by inhalation to (14)C para-xylene (theoretical concentration, 2000 ppm (8680 mg/cu m)) for 10 min on days 11, 14 or 17 of gestation, and distribution of the label was determined 0, 0.5, 1 and 4 hours after exposure. The label quickly entered the embryo, but uptake was low relative to maternal tissues. All fetal activity was extractable, indicating that no firmly bound metabolite was present.

For more Absorption, Distribution and Excretion (Complete) data for 4-XYLENE (10 total), please visit the HSDB record page.

Permitted for use as an inert ingredient in non-food pesticide products; [EPA] Found in coal tar; Commercial xylene is a mixture of the o-, m-, and p- isomers; Used as a solvent, raw material, catgut sterilant, and in microscopy; [Merck Index] Used predominately to make purified terephthalic acid (PTA) and dimethyl terephthalate (DMT) which are used in polyester production; Also used as a solvent, for paints, in the printing trade, and in the production of di-paraxylene and herbicides; [HSBD]

Painting (Solvents) [Category: Paint]

Synthesis of terephthalic acid for polyester resins and fibers and in the manufacture of vitamins, pharmaceuticals, and insecticides

PX /4-xylene/ is the most important commercial isomer. Almost all of the PX is converted to terephthalic acid and dimethylterephthalate, and then to poly(ethylene terephthalate) for ultimate use in fibers, films, and resins. Miscellaneous uses include as solvent, production of di-paraxylene, and as a herbicide.

p-Xylene ... frequently ... used for paints or in the printing trade.

Used as a chemical intermediate for the synthesis of 1,4-bis(chloromethyl)benzene; dimethyl terephthalate; poly-p-xylylene; terephthalic acid; 4-(tri-fluoromethyl)benzaldehyde; 4-(trifluoromethyl)benzyl alcohol; 2,5-xylidine.

19.7% of total 1980 xylene market.

(1978) 3.19X10+11 G

(1983) 3.23X10+11 G

(1985) 5.03X10+11 g

For more U.S. Exports (Complete) data for 4-XYLENE (10 total), please visit the HSDB record page.

(1978) 9.53X10+9 G

(1983) 3.18X10+10 G

(1985) 6.53X10+10 g

(1986) 3.71X10+7 gal

For more U.S. Imports (Complete) data for 4-XYLENE (9 total), please visit the HSDB record page.

2023: 5,500,000,000 - <7,000,000,000 lb

(1976) 1.32x10+12 g

(1977) 1.44X10+12 G

(1980) 1.9X10+12 G

(1981) 2.06x10+12 g

For more U.S. Production (Complete) data for 4-XYLENE (26 total), please visit the HSDB record page.

CHEMICAL PROFILE: Paraxylene. Dimethyl terephthalate and terephthalic acid for saturated polyester production, 100% (except negligible amounts used as solvents, coatings or pesticides) (1985)

CHEMICAL PROFILE: Paraxylene. Dimethyl terephthalate and terephthalic acid for saturated polyester production, 100% (except negligible amounts for use as solvents, coating or pesticides). This includes 75% for domestic consumption and 25% for export.

CHEMICAL PROFILE: Paraxylene. US Demand: 1985: 4.5 billion pounds; 1986: 4.7 billion pounds; 1990: 5.23 billion pounds /projected/

CHEMICAL PROFILE: Paraxylene. Dimethyl terephthalate and terephthalic acid, 85%; exports, 15%. (Domestically, negligible amounts are used in solvents, coatings and pesticides).

For more Consumption Patterns (Complete) data for 4-XYLENE (12 total), please visit the HSDB record page.

Low temperature fractional crystallization was the first and for many years the only commercial technique for separating PX /4-xylene/ from mixed xylenes. ... PX has a much higher freezing point than the other xylene isomers. Thus, upon cooling, a pure solid phase of PX crystallizes first. Eventually, upon further cooling, a temperature is reached where solid crystals of another isomer also form. This is called the eutectic point. PX crystals usually form at about -4 °C and the PX-MX /4-xylene-3-xylene/ eutectic is reached at about -68 °C. In commercial practice, PX crystallization is carried out at a temperature just above the eutectic point. At all temperatures above the eutectic point, PX is still soluble in the remaining C8 aromatics liquid solution, called mother liquor. This limits the efficiency of crystallization processes to a per pass PX recovery of about 60-65%. The solid PX crystals are typically separated from the mother liquor by filtration or centrifugation.

Currently about 60% of the p-xylene produced worldwide is by adsorption technology. ... In this process, adsorbents such as molecular sieves are used to produce high purity PX /4-xylene/ by preferentially removing PX from mixed xylene streams. Separation is accomplished by exploiting the differences in affinity of the adsorbent for PX, relative to the other C8 isomers. The adsorbed PX is subsequently removed from the adsorbent by displacement with a desorbent. Typical PX recovery per pass is over 95%, compared to only 60-65% for crystallization. Thus recycle rates to the separation and isomerization units are much smaller where adsorption is used.

Selective crystallization or solvent extraction of meta-, para-mixture; separation from mixed-xylene feedstocks by adsorption.

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.

Petroleum Refineries

Benzene, 1,4-dimethyl-: ACTIVE

The commercial product "mixed xylenes" is a technical product generally containing approximately 40% m-xylene and 20% each of o-xylene, p-xylene, and ethylbenzene, as well as small quantities of toluene.

Xylenes will enter the atmosphere primarily from fugitive emissions and exhaust connected with their use in gasoline. Industrial sources include emissions from petroleum refining and their use as solvents and chemical intermediates ... The primary source of exposure is from air, especially at occupational sites where xylenes are used and in areas with high traffic. /xylenes/

Concentration of 4-xylene in gasoline: 5.6% wt