United States
Environmental Protection
Ag«" cy
Office of Water
4601
EPA811-F-95-004v-T
October 1995
National Primary Drinking
Water Regulations
Xylenes (Total)
CHEMICAL/ PHYSICAL PROPERTIES
CAS NUMBER: 1330-20-7
COLOR/ FORM/ODOR:
Clear liquid with a sweet odor; The
commercial product "mixed xylenes"
generally contains approximately 40%
m-xylene and 20% each of o-xylene, p-
xylene, and ethylbenzene, as well as
small quantities of toluene
M.P.: N/A
B.P.: 137-140° C
VAPOR PRESSURE: N/A
OCTANOL/WATER PARTITION (Kow):
Log Kow = 3.12-3.20
DENSITY/SPEC. GRAV.: 0.864 at 20" C
SOLUBILITY: N/A; Insoluble in water
HENRY'S LAW COEFFICIENT:
0.22 to 0.32 atm-cu m/mole;
ODOR/TASTE THRESHOLDS: Odor thresh-
old in air is 5x10'5 mg/L
SOIL SORPTION COEFFICIENT:
Koc = 48 -68; high to moderate mobility
in soil
BlOCONCENTRATION FACTOR:
Log BCF=2.14 in fish (calc.); not
expected to bioconcentrate in aquatic
organisms.
TRADE NAMES/SYNONYMS:
Dimethyl benzene, Xylol, Methyltoluene,
Violet 3
DRINKING WATER STANDARDS
MCLG: 10 mg/L
MCL: 10 mg/L
HAL(child): 1 day: 40 mg/L
USAGE PATTERNS
The commercial product mixed xylenes (a technical
product generally containing 20% each of o-xylene, p-
xylene and ethylbenzene, as well as small quantities of
Longer-term: 40 mg/L
HEALTH EFFECTS SUMMARY
Acufe: EPA has found xylenes to potentially cause the
following health effects from acute exposures at levels
above the MCL: disturbances in the central nervous
system, such as changes in cognitive abilities, balance,
and coordination.
Drinking water levels which are considered "safe" for
short-term exposures: Fora 10-kg (22 Ib.) child consum-
ing 1 liter of water per day: upto a 7-year exposure to 40
mg/L.
Chronic: Xylenes have the potential to cause the
following health effects from long-term exposures at
levels above the MCL: damage to the central nervous
system, liver and kidneys. Compared with benzene and
toluene, very much less is known of the human health
hazards, particularly the chronic effects of xylenes, either
as mixed xylenes, as individual isomers or in admixture
with other alkylbenzenes.
Cancer: There is inadequate evidence to state whether
">r not xylenes have the potential to cause cancer from
.retime exposures in drinking water.
Toxic RELEASE INVENTORY -
RELEASES TO WATER AND LAND: 1987
Water
TOTALS (in pounds) 875,943
Top Ten States"
TX 30,853
NJ 294,437
IL 36
IN 0
AL 34,361
CA 0
Ml 0
GA 68,310
VA 50,100
WA 27,860
Major Industries*
Petroleum refining 131,817
Metal barrels, drums 5
Textile finishing, misc. 278,454
Misc. Industrial chems. 95,706
Extruded Aluminum prod. 1,265
Furniture, fixtures 0
Cotton fabric finishing 68,310
Wood office furniture 0
Pharmaceuticals 52,285
Paper mills 52,480
* Water/Land totals only include facilities with
TO 1993
Land
3,897,738
2,099,734
280,759
206,990
145,079
59,022
91,500
86,774
15,000
33,000
52,360
2,678,958
289,542
0
69,696
138,798
91,500
15,000
67,677
3,100
2,122
releases
greater than a certain amount - usually 1 000 to 1 0,000 Ibs.
October 1995
Technical Version
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toluene) analogously to toluene is an agent of major
chemical and occupational significance.
It is produced in very large quantities and is extensively
employed in a broad spectrum of applications, primarily
as a solvent for which its use is increasing as a safe
replacement for benzene, and in gasoline as part of the
BTX component (benzene-toluene-xylene); xylenes are
also frequently used in the rubber industry with other
solvents such as toluene and benzene.
Most consumption of xylene mixtures is to produce the
individual isomers, particularly p-xylene. As individual
isomers they are extensively employed in the synthesis
of synthetic agents. For example, phthalicacid, isophthalic
acid, terephthalic acid, and diemthylterephthalate have
very broad applications in the further preparation of
phthalate ester plasticizers and components of polyester
fiber, film and fabricated items.
Production of xylenes has increased: from about 5
billion Ibs. in 1982 to 6.84 billion Ibs in 1993. In 1982 it was
estimated that industries consumed xylenes as follows:
production of ortho-xylene, 15%; production of para-
xylene, 60%; miscellaneous, 14%; exports, 11%
RELEASE PATTERNS
Major environmental releases of xylenes are due to:
emissions from petroleum refining, gasoline and diesel
engines; emissions from its use as a solvent for alkyl
resins, lacquers, enamels, rubber cement, pesticide
sprays and in organic synthesis; leaks and evaporation
losses during the transport and storage of gasoline and
otherfuels and from carburetor losses; agricultural spray-
ing. Xylenes are a natural products of many plants, and
are a component of petroleum and coal tar.
From 1987 to 1993, according to EPA's Toxic Chemi-
cal Release Inventory, xylene releases to land and water
totalled nearly 4.8 billion Ibs., of which about 81 percent
was to land. These releases were primarily from petro-
leum industries which produce xylenes as by-products of
gasoline refining. The largest releases occurred in Texas.
The largest direct releases to water occurred in New
Jersey and Georgia.
ENVIRONMENTAL FATE
Most of the xylenes are released into the atmosphere
where they may photochemically degrade by reaction
with hydroxyl radicals (half-life 1-18 hr).
The dominant removal process in water is volatiliza-
tion. Xylenes are resistant to hydrolysis, since there are
no hydrolyzable functions. Xylenes are volatile com-
pounds with relatively high Henry's Law constant (0.22
for the ortho isomer and 0.32 for the m- and p- isomers).
The half-life for evaporation from water is 3.2 hr for o-
xylene and will be 2% higher for the m- and p-xylene.
Measures of the rate of evaporation of xylenes from a
1:1000 jet fuehwater mixture found that this rate aver-
aged approximately 0.6 times the oxygen reaeration rate.
Combining this ratio with oxygen reaeration frates for
typical bodies of water, one estimates that the half-life for
evaporation of xylenes from a typical river or pond is 29
and 144 hr, respectively.
»
Xylenes are moderately mobile in soil and may leach
into groundwater where they are known to persist for
several years, despite some evidence that they biode-
grade in both soil and groundwater. This evidence in-
cludes standard biodegradability tests using various in-
ocula including sewage, activated sludge and sea water,
where mixtures are completely degraded in 8 days in
groundwater with an acclimation period of 3-4 days.
Xylenes have low to moderate adsorption to soil based
on the KOC of o-xylene(48-68) and similar chemicals.
Xylenes have been observed to pass through soil at a
dune-infiltration site on the Rhine River and to leach into
groundwater under a rapid infiltration site.
Bioconcentration is not expected to be significant.
Based on the log octanol/water partition coefficient of
3.12-3.20 for the individual isomers and using a regres-
sion relation, the log BCF forfish is calculated to be 2.14-
2.20. The log BCF for eels is 1.3.
The primary source of exposure is from air, but, xy-
lenes are a low level contaminant of both ground and
surface public water supplies.
OTHER REGULATORY INFORMATION
MONITORING:
FOR GROUND/SURFACE WATER SOURCES:
INITIAL FREQUENCY- 4 quarterly samples every 3 years
REPEAT FREQUENCY- Annually after 1 year of no detection
TRIGGERS - Return to Initial Freq. if detect at > 0.0005 mg/L
ANALYSIS:
REFERENCE SOURCE
EPA 600/4-88-039
METHOD NUMBERS
502.2; 524.2
TREATMENT:
BEST AVAILABLE TECHNOLOGIES
Granular Activated Charcoal and Packed Tower Aeration
FOR ADDITIONAL INFORMATION:
* EPA can provide further regulatory and other general information:
EPA Safe Drinking Water Hotline - 800/426-4791
* Other sources of toxicological and environmental fate data include:
Toxic Substance Control Act Information Line - 202/554-1404
• Toxics Release Inventory, National Library of Medicine - 301/496-6531 I
• Agency for Toxic Substances and Disease Registry - 404/639-6000 "
October 1995
Technical Version
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