Priority Existing Chemical Assessment Reports -

para-Dichlorobenzene

 

CHEMICAL IDENTITY

Chemical name (IUPAC)

• 1,4-Dichlorobenzene

Registry numbers

p-DCB is listed on the Australian Inventory of Chemical Substances (AICS).

• CAS number 106-46-7

• EINECS number 203-400-5

Other names

• para-Dichlorobenzene

• p-Dichlorobenzene

• p-DCB

• 1,4-DCB

Trade names

• Di-Chloricide

• Evola

• Globol

• Para Crystals

• Paracide

• Paradow

• Paramoth

Applicants

Amtrade International Pty Ltd
PO Box 6421
St. Kilda Road Central PO
MELBOURNE
VIC 3004

Bio-Scientific Pty Ltd
PO Box 78
GYMEA
NSW 2227

Crown Scientific Pty Ltd
144 Moorebank Ave
MOOREBANK
NSW 2170

Recochem Inc
PO Box 478
WYNNUM
QLD 4178

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

Sigma Aldrich Pty Ltd
PO Box 970
CASTLE HILL
NSW 2154

Unipuns International Pty Ltd
PO Box 1109
FERNTREE GULLY
VIC 3128

PARA-DICHLOROBENZENE OVERVIEW

Para-dichlorobenzene (p-DCB; CAS No. 106-46-7) was declared a Priority Existing Chemical on 7 April 1998. The declaration of p-DCB was in response to concerns relating to possible human health risks and environmental hazards associated with the widespread use of the material in school and public toilet blocks and urinals and as an air freshener.

Up to 1000 tonnes of p-DCB are imported and used annually in Australia. p-DCB is primarily used as a deodoriser in toilet blocks, in household toilet bowls and as a room freshener. It has some minor uses in the agricultural and pharmaceutical industries.

Occupational exposure to p-DCB in Australia is primarily due to operations involved in the handling and processing of imported material. Exposure during such procedures may result from inhalation of dust when opening bags of raw material and of vapour, produced by sublimation or during melting and recasting operations. Exposure of the general public to p-DCB is from the use of several consumer products that contain p-DCB.

p-DCB is adsorbed well by inhalation and oral routes and less well by dermal contact. Target organs for p-DCB are adipose tissue, liver, kidneys and lungs. Metabolism of p-DCB is by aromatic hydroxylation and, depending on the species involved, results in the formation of epoxides which are converted to their corresponding dichlorophenols. Further metabolism by conjugation with sulfate or glucuronate can occur. The parent compound and its derivatives are rapidly excreted in the urine. There is no evidence that p-DCB bioaccumulates in any tissue.

Acute exposure to p-DCB vapour within the range of 30 to 60 ppm in air is associated with irritation to the nose, eyes and upper respiratory tract. Exposure to vapour of 80 to 160 ppm results in acute discomfort, painful irritation of the nose and eyes and may induce breathing difficulties. Ingestion of large doses of p-DCB have been associated with vomiting, vertigo, disorientation, tiredness and oedema. Chronic exposure to large doses of p-DCB may result in headache, nausea, vertigo, ataxia, dysarthria, hyporeflexia, paresthesia, behavioural and haematological changes including anaemia.

Genotoxicity studies of p-DCB have produced negative results. However, p-DCB does induce the formation of kidney tumours in male rats and liver tumours in both sexes of mice after prolonged exposure. The formation of kidney tumours in male rats is thought to be due to the presence of the protein, a2m-globulin. As a2m-globulin is specific to the mature male rat, p-DCB is not considered to present a carcinogenic risk to humans by this mechanism. The tumours observed in mice after prolonged exposure to p-DCB are also considered to be irrelevant to humans. There are significant differences in the metabolism of p-DCB in the liver of mice and humans and it has been further observed that the mouse strains used demonstrate a high natural rate for liver tumour formation.

Exposure of pregnant rats to p-DCB vapour produced no evidence of maternal toxicity or embryo- or foetotoxicity. There have been no teratogenic effects observed in animals or humans as a result of acute or chronic exposure.

Environmental exposure to p-DCB can occur due to the use of the product in toilets from which it may be washed into the sewer system or enter the atmosphere by virtue of its volatile nature. p-DCB does not persist in air or surface water but accumulates in anaerobic sediments. p-DCB has a medium acute toxicity for aquatic life and may impair the reproduction of aquatic life. However, based on current patterns of p-DCB use within Australia, the risk to the environment is expected to be low.

The occupational risk assessment for p-DCB concluded that, for known Australian work situations, potential atmospheric concentrations of p-DCB are unlikely to reach levels likely to cause acute effects, including eye or respiratory irritation. In addition, it is unlikely that workers in these occupations will be at risk from chronic adverse health effects related to p-DCB exposure, as margins of exposure are generally high for inhalation exposure. In the absence of any monitoring data for workers involved in the hygiene sector estimates for p-DCB exposure were obtained using the UK EASE model. Results from this modelling indicate that the risk to workers is expected to be low.

Recommendations for reducing potential occupational health and safety risks for p-DCB include the monitoring of airborne p-DCB to be undertaken and a review of the current occupational exposure standard for p-DCB by the National Occupational Health and Safety Commission.

The hazard classification should be amended to include the follows safety phrases, S23 ( Do not breath vapour), S24 (Avoid contact with skin), S25 (Avoid contact with eyes) and S51 (Use only in well ventilated areas).