1,4-DICHLOROBENZENE
(para-DICHLOROBENZENE)
Please Note: The main sources of information for this fact sheet are EPA's Integrated Risk Information System (IRIS), which contains information on inhalation chronic toxicity of 1,4-dichlorobenzene and the RfC, and the Agency for Toxic Substances and Disease Registry's (ATSDR's) Toxicological Profile for 1,4-Dichlorobenzene. Other secondary sources include the Hazardous Substances Data Bank (HSDB), a database of summaries of peer-reviewed literature, and the Registry of Toxic Effects of Chemical Substances (RTECS), a database of toxic effects that are not peer reviewed.
Environmental/Occupational Exposure
* The general population is mainly exposed to 1,4-dichlorobenzene through breathing vapors from 1,4-dichlorobenzene products used in the home, such as mothballs and toilet deodorizer blocks. Levels of 1,4-dichlorobenzene in some homes and public restrooms have ranged from 0.29 to 272 ppb. (1)
* Ambient air levels of 1,4-dichlorobenzene are much lower; reported levels in cities range from 0.02 to 20 ppb. (1)
* 1,4-Dichlorobenzene has been detected in drinking water at levels ranging from 0.008 to 154 ppb, and in some foods. (1)
* Occupational exposure to 1,4-dichlorobenzene may occur in factories that produce or process 1,4-dichlorobenzene products. (1)
Assessing Personal Exposure
* Exposure to 1,4-dichlorobenzene can be assessed by measuring its breakdown product, 2,5-dichlorophenol, in urine and blood. (1)
Health Hazard Information
Acute Effects:
* Acute (short-term) exposure to 1,4-dichlorobenzene via inhalation in humans results in irritation to the eyes, skin, and throat. (2)
* Animal studies have reported effects on the blood, liver, and kidneys from acute, oral exposure to 1,4-dichlorobenzene. (1)
* Tests involving acute exposure of animals, such as the LD50 test in rats and mice, have shown 1,4-dichlorobenzene to have moderate toxicity from oral exposure. (3)
Chronic Effects (Noncancer):
* Chronic (long-term) exposure to 1,4-dichlorobenzene by inhalation in humans results in effects on the liver, skin, and CNS. (1)
* Animal studies have reported effects on the respiratory system, liver, and kidneys from inhalation exposure to 1,4-dichlorobenzene, while oral studies have reported effects on the blood, liver, and kidneys. (1)
* The RfC for 1,4-dichlorobenzene is 0.8 mg/m3 based on increased liver weights in male rats. (4)
* EPA has medium confidence in the study on which the RfC was based because the critical study employed an extensive reproductive protocol including histopathologic examination of tissues of adults and offspring; medium confidence in the database because there are a number of supporting studies for the developmental and reproductive toxicology database; and, consequently, medium confidence in the RfC.
* EPA has not established an RfD for 1,4-dichlorobenzene. (4)
Reproductive/Developmental Effects:
* No information is available on the reproductive or developmental effects of 1,4-dichlorobenzene in humans. (1)
* In one animal study, exposure of pregnant rats to 1,4-dichlorobenzene via inhalation did not result in developmental effects in the offspring. In another study, an increase in the incidence of an extra rib was reported in the fetuses of pregnant rats administered 1,4-dichlorobenzene by gavage (placing the chemical experimentally in the stomach). (1,2)
Cancer Risk:
* No information is available on the carcinogenic effects of 1,4-dichlorobenzene in humans. (1)
* No animal cancer studies are available on exposure to 1,4-dichlorobenzene via inhalation, while 1,4-dichlorobenzene was found to cause kidney tumors in male rats and liver tumors in both sexes of mice when administered via gavage. (1,2)
* EPA has classified 1,4-dichlorobenzene as a Group C, possible human carcinogen. (1)
* EPA's Office of Air Quality Planning and Standards, for a hazard ranking under Section 112(g) of the Clean Air Act Amendments, has ranked 1,4-dichlorobenzene in the nonthreshold category. The 1/ED10 value is 0.13 per (mg/kg)/d and this would place it in the low category under Superfund's ranking for carcinogenic hazard. (6)
Physical Properties
* 1,4-dichlorobenzene is a white solid with a sweet taste and a strong odor. (1)
* The odor threshold for 1,4-dichlorobenzene is 0.18 ppm. (7)
* The chemical formula for 1,4-dichlorobenzene is C6H4Cl2 and the molecular weight is 147.02 g/mol. (1)
* The vapor pressure for 1,4-dichlorobenzene is 1.76 mm Hg at 25 EC, and it has a log octanol/water partition coefficient of 3.52. (1)
Uses
* 1,4-dichlorobenzene is used mainly as a fumigant for the control of moths, molds, and mildews, and as a space deodorant for toilets and refuse containers. (1)
* 1,4-dichlorobenzene is also used as an intermediate in the production of other chemicals, in the control of tree-boring insects, and in the control of mold in tobacco seeds. (1)
Health Data from Inhalation Exposure
|
Concentration (mg/m3) |
Health numbersa |
Regulatory, advisory numbersb |
Reference |
|
10,000.0 |
|||
|
_ _ _ _ 1,000.0 |
* NIOSH IDLH (6,000 mg/m3) |
1 |
|
|
_ _ _ _ 100.0 |
* OSHA STEL and ACGIH STEL (675 mg/m3) * OSHA PEL and ACGIH TLV (450 mg/m3) |
1
1 |
|
|
_ _ _ _ 10.0 |
|||
|
_ _ _ _ 1.0 |
|||
|
_ _ _ _ 0.1 |
* RfC (0.8 mg/m3) |
8 |
ACGIH STELCAmerican Conference of Governmental and Industrial Hygienists' short-term exposure limit; 15-min time-weighted-average exposure that should not be exceeded at any time during a workday even if the 8-h time-weighted-average is within the threshold limit value.
ACGIH TLVCAmerican Conference of Governmental and Industrial Hygienists' threshold limit value expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effects.
NIOSH IDLHCNational Institute of Occupational Safety and Health's immediately dangerous to life and health; NIOSH concentration representing the maximum level of a pollutant from which an individual could escape within 30 min without escape-impairing symptoms or irreversible health effects.
OSHA PELCOccupational Safety and Health Administration's permissible exposure limit expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effect averaged over a normal 8-h workday or a 40-h workweek.
OSHA STELCOccupational Safety and Health Administration's short-term exposure limit: 15-min time-weighted-average exposure that should not be exceeded at any time during a workday even if the 8-h time-weighted-average is within the threshold limit value.
RfCCReference concentration.
a
Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.b
Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers are nonregulatory values provided by the Government or other groups as advice.
References
1. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for 1,4-Dichlorobenzene. U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. 1993. National Technical Information Service PB93-182459.
2. U.S. Department of Health and Human Services. Hazardous Substances Data Bank (HSDB, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.
3. U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.
4. U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on 1,4-Dichlorobenzene. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1993.
5. U.S. Environmental Protection Agency. Health Effects Assessment for Dichlorobenzene. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1987.
6. U.S. Environmental Protection Agency. Technical Background Document to Support Rulemaking Pursuant to the Clean Air ActCSection 112(g). Ranking of Pollutants with Respect to Hazard to Human Health. EPAB450/3-92-010. Emissions Standards Division, Office of Air Quality Planning and Standards, Research Triangle Park, NC. 1994.
7. J.E. Amoore and E. Hautala. Odor as an aid to chemical safety: Odor thresholds compared with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution. Journal of Applied Toxicology, 3(6):272-290. 1983.
8. U.S. Environmental Protection Agency. Health Effects Assessment Summary Tables. Annual Update. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1993.
NOTE: THE 1,4-DICHLOROBENZENE FILE WAS LAST UPDATED 2/23/96.