| Chemical Abstract Number (CAS #) |
106423
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| Synonyms | p-Xylene |
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1,4-Dimethylbenzene |
| Analytical Methods |
EPA Method 502.2 |
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EPA Method 503.1 |
EPA Method 524.1 |
EPA Method 524.2 |
EPA Method 602 |
EPA Method 624 |
EPA Method 8020A |
EPA Method 8021A |
EPA Method 8260A |
| Molecular Formula | C8H10 |
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| Use | Synthesis of terephthalic acid for polyester resins and fibers ("Dacron," "Mylar,"
"Terylene"); pharmaceutical synthesis; insecticides
CHEM INTERMED FOR DIMETHYL TEREPHTHALATE & TEREPHTHALIC ACID
CHEM INTERMED FOR DIMETHYL TETRACHLOROTEREPHTHALATE-HERBICIDE
SOLVENT
p-Xylene frequently used for paints or in the printing trade.
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| Consumption Patterns | Dimethyl terephthalate and terephthalic acid for saturated polyester production, 100%
(except negligible amounts used as solvents, coating 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. Demand: 1985: 4.5 billion lb; 1986: 4.7 billion lb; 1990
/projected/: 5.23 billion lb.
CHEMICAL PROFILE: Paraxylene. Dimethyl terephthalate and terephthalic acid, 85%; exports,
15%. (Domestically, negligible amounts are used in solvents, coatings and pesticides).
CHEMICAL PROFILE: Paraxylene. Demand: 1988: 5,600 million lb; 1989: 5,800 million lb;
1993 projected/: 7,000 million lb. (Includes exports, but not imports, which totaled 220 million lb
last year).
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| Apparent Color | Colorless plates or prisms at low temp ; Colorless liquid ; Color: Saybolt units 30
(research, pure & technical grades)
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| Odor | Sweet
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| Boiling Point | 138.37 deg C
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| Melting Point | 13.3 deg C
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| Molecular Weight | 106.17
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| Density | 0.86104 @ 20 deg C/4 deg C
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| Odor Threshold Concentration | Detection in air at 0.05 ppm.
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| Sensitivity Data | 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
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| Environmental Impact | p-Xylene will enter into the atmosphere primarily from fugitive emissions and exhaust
connected with its use in gasoline. Industrial sources include emissions from petroleum refining
and its use as a solvent and chemical intermediate. Discharges and spills on land and waterways
result from its use in diesel fuel and gasoline and the storage and transport of petroleum products.
Most of the p-xylene is released into the atmosphere where it may photochemically degrade by
reaction with hydroxyl radicals (half-life 1.7-18 hr). The dominant removal process in water is
volatilization. p-Xylene is moderately mobile in soil and may leach into groundwater where it is
known to persist for several years despite some evidence that it biodegrades in both soil and
groundwater. Bioconcentration is not expected to be significant. The primary source of exposure
is from air, especially in areas with high traffic.
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| Environmental Fate | TERRESTRIAL FATE: When spilled on land, p-xylene will volatilize and leach into the
ground. p-Xylene may be degraded during its passage through soil. The extent of the degradation
will depend on its concentration, residence time in the soil, the nature of the soil, and whether
resident microbial populations have been acclimated.
AQUATIC FATE: In surface waters, volatilization appears to be the dominant removal process
(half-life 1-5.5 days(1,SRC)). Some adsorption to sediment will occur. Although p-xylene is
biodegradable and has been observed to degrade in seawater, there is insufficient data to access
the rate of this process in surface waters. Although it has been observed to degrade in
groundwater in one study, it is known to persist for many years in groundwater, at least at sites
where the concentration might have been quite high.
ATMOSPHERIC FATE: When released into the atmosphere, p-xylene may degrade by reaction
with photochemically produced hydroxyl radicals (half-life 1.7 hr in summer and 18 hr in
winter ). However, ambient levels are detected because of large emission .
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| Drinking Water Impact | DRINKING WATER: In a survey of 30 Canadian water treatment facilities, the avg
value of p-xylene combined with ethyl benzene was (1 ppb with a maxium value of 10 ppb and
30% of the supplies pos . The raw water for the supplies had a lower max concn of <1 ppb .
p-Xylene has been qualitatively detected in the municipal drinking water supplies of Cleveland,
OH , Philadelphia, PA , Washington, DC , Tuscaloosa, AL and Houston, TX .
DRINKING WATER: In a survey of organics in drinking water derived from groundwater
sources, p- and o-xylene combined were found in 2.1% of 280 sample sites suppyling <10,000
persons and 1.1% of 186 sites supplying >10,000 persons. The max combined concn were 0.59
and 0.91 ppb, respectively . The max combined amount of m- and p-xylene in bank filtered
Rhine R water in the Netherlands was 0.1 ppb . In 6 drinking water wells near a landfill, 0.3-2.1
ppb of p-xylene was found . Detected in all 14 drinking water studies in the lowland of Great
Britian, 10 from surface water sources and 4 from ground supplies .
GROUNDWATER: In groundwater under a landfill in Norman, OK - 0.9 ppb and under a
rapid infiltration site in Phoenix, AZ - 0.10-49 ppb ; under a coal gasification site in Wyoming
15 months after gasification complete - 240-830 ppb . In a recovery well from a landfill 7 years
after closing - 2.9 ppb p-xylene .
SURFACE WATER: In the raw water supplies for 30 Canadian treatment facilities, 23%
contained a combination of p-xylene and ethyl benzene which averaged <1 ppb and whose max
value was <1 ppb in summer and 2 ppb in winter . Detected, not quantified in the Black Warrior
River in Tuscaloosa, AL and the Glatt River in Switzerland .
SEAWATER: In Vineland Sound, MA, samples taken over 15 months ranged from 4.5-66 parts
per trillion for the p- and m-xylene combined . In open and coastal sections of the Gulf of
Mexico, 2.7-24.4 parts per trillion for the p- and m-isomers, combined .
RAIN/SNOW: West Los Angeles, CA, 9 parts per trillion .
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