Priority Existing Chemical Assessment Reports -

ortho -Dichlorobenzene

 

CHEMICAL IDENTITY

Chemical name (IUPAC)

• 1,2-Dichlorobenzene

Registry numbers

ortho-Dichlorobenzene is listed on the Australian Inventory of Chemical Substances (AICS).

• CAS number 95-50-1

• EINECS number 202-425-9

Other names

• ortho-Dichlorobenzene

• o-Dichlorobenzene

• o-DCB

• 1,2-DCB

Trade names

• CHLOROBEN

• DICHLOROBENZENE, -ORTHO, -LIQUID

• O-DICHLOR

• ORTHODICHLOROBENZENE

APPLICANTS

Australian Manufacturing Workers Union
3/440 Elizabeth Street
MELBOURNE
VIC 3000

Bio-Scientific Pty Ltd
PO Box 78
GYMEA
NSW 2227

Merck Pty Ltd
207 Colchester Road
Kilsyth
VIC 3137

Recochem Inc
PO Box 478
WYNNUM
QLD 4178

Redox Chemicals Pty Ltd
30-32 Redfern Street
Locked Bag No. 60
WETHERILL PARK
NSW 2164

ORTHO-DICHLOROBENZENE OVERVIEW

ortho-Dichlorobenzene (o-DCB; CAS No. 95-50-1) was declared a Priority Existing Chemical on the 7 April 1998. The declaration of o-DCB was in response to health and environmental concerns due to its widespread use as a degreasing agent.

Industrial uses in Australia include formulations as paint removers, as a degreaser (for grease traps, drains and automotive parts) and as a decarboniser in the automotive and marine industries.

The manufacture of o-DCB does not occur in Australia, consequently, all of the material used is imported. Current imports amount to less than 100 metric tonnes per annum. Approximately 10 tonnes are for industrial uses and the remainder for agricultural/veterinary uses which are not assessed in this report.

o-DCB is well absorbed by inhalation and oral routes. The target tissues and organs are adipose tissue, liver, kidneys and plasma proteins. Metabolism of o-DCB is by aromatic hydroxylation to give dichlorophenol. Further metabolism by conjugation with glutathione, sulfate or glucuronate can occur. The parent compound and its derivatives are rapidly excreted in the urine with minor amounts lost in faeces. Due to its volatile nature, traces of o-DCB may be found in expired air.

In humans, acute exposure to o-DCB can result in headache, malaise, nausea, vomiting and vertigo. Dermal exposure to o-DCB can result in painful irritation with reddening and blistering of the skin while the vapour may cause eye irritation. In animals, acute high dose exposure may induce central nervous system depression resulting in respiratory distress and death. Liver damage can result from chronic exposure to o-DCB.

In several microbial assays o-DCB has been found to be without mutagenic or clastogenic effects. Similarly, in mammalian test systems o-DCB has shown no evidence of genotoxicity. Long-term studies with animals have shown no evidence of carcinogenicity.

Based on the assessment of health effects, o-DCB should be classified in accordance with the ASCC Approved Criteria for Classifying Workplace Hazardous Substances (ASCC, 1999a), as ‘Harmful if swallowed’ (risk phrase R22) and ‘Irritating to the eyes, respiratory system and skin’ (risk phrases R36/37/38).

Occupational exposure to o-DCB in Australia can occur during product formulation or end-use of such products. However, exposure to o-DCB is expected to be low due to the enclosed nature of some operations, limited exposure duration and the relatively small quantities of material used.

The occupational risk assessment for o-DCB concluded that, for known Australian work situations, potential atmospheric concentrations of o-DCB are unlikely to reach levels that may cause acute effects. In addition, it is unlikely that workers in these situations will be at risk from chronic adverse health effects related to o-DCB exposure, as margins of exposure are likely to be high after taking into account the intermittent nature of the exposure, the small quantities involved and the dilute nature of the products.

The chemical is biodegradable under aerobic conditions and relatively soluble in water. Its removal from aqueous systems occurs significantly from volatilisation, and at equilibrium, around 98% of the chemical would be expected to partition to the atmosphere where it will break down through reaction with hydroxyl radicals. Large discharges to relatively small water volumes could constitute a hazard to the aquatic environment. However, concentrations likely to occur in aquatic systems are expected to be generally of low concern, and this expectation is supported by monitoring data from Australia and overseas. A relatively low aquatic risk is predicted.

The relatively short atmospheric lifetime of o-DCB indicates concentrations will not occur at levels harmful to the atmosphere. While widespread transport within the troposphere is likely, the chemical is not expected to reach the stratosphere and therefore not expected to have an influence on global warming or ozone depletion.

Under present conditions of use, there are no significant risks to the public from the appropriate use o-DCB or products containing o-DCB.

It is recommended that, for the protection of the environment, o-DCB should be sent to licenced liquid waste disposal contractors where possible.

It is further recommended that the exposure standard for o-DCB be reviewed by the National Occupational Health and Safety Commission.