para-Dichlorobenzene Profile

para-Dichlorobenzene Profile

QUICK SUMMARY

  • A pesticide used to repel moths, and protect against tree-boring insects
  • Associated cancers: Liver and kidney cancers (animal studies only)
  • Most important route of exposure: Inhalation
  • Uses: Moth repellant and space deodorant
  • Occupational exposures: Primarily in workers involved in its production, as well as those working in buildings where it is used to repel insects
  • Environmental exposures: Via contaminated air from industrial emissions and incinerators, and via PDCB’s use as a deodorizer and insect and animal repellant
  • Fast fact: p-Dichlorobenzene can also irritate the eyes, skin and nasal cavity, and cause shortness of breath, nausea, vomiting, and liver damage, especially at higher concentrations.

General Information

para-Dichlorobenzene is a white to colourless crystalline solid with a mothball-like odour.[1] It may also be referred to as p-dichlorobenzene, 1,4-dichlorobenzene, or PDCB.[2] There are numerous other synonyms and product names; see the Hazardous Substances Data Bank (HSDB) for more information.[2]

p-Dichlorobenzene has been classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic to humansp-Dichlorobenzene causes cancer in experimental animals. Oral administration of PDCB caused increased incidences of hepatocellular carcinomas and adenomas in mice, as well as increased incidence of renal tubular adenocarcinomas in male rats.[3,4]

Additionally, exposure to PDCB can cause painful irritation of the eyes, skin, and nasal cavity. It can also cause headache, coughing, shortness of breath, drowsiness, dizziness, nausea, vomiting, skin irritation, and liver damage.[2,4]

Regulations and Guidelines

Occupational Exposure Limits (OEL)[5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]

Canadian Jurisdictions OEL (ppm)
Canada Labour Code 10
AB, BC, MB, NB, NL, NS, ON, PE 10
SK, NT, YT, NU 10
15 [stel]
QC 20
Other Jurisdictions OEL (ppm)
ACGIH 2018 TLV 10
ppm = parts per million
stel = short term exposure limit (15 min. maximum)
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value (8 hour maximum)

Canadian Environmental Guidelines

Jurisdiction Limit Year
Health Canada’s, Ontario’s and Quebec’s Drinking Water Guidelines MAC = 0.005 mg/L 2017[20], 2017[21], 2016[22]
Ontario Ambient Air Quality Criteria 24 hour: 95 µg/m3 2016[23]
BC’s Contaminated Sites Regulation, BC Reg 375/96 Sets soil standards for the protection of human health:
Agricultural and low density residential sites: 4,500 μg/g
Urban park and high density residential sites: 9,000 μg/g
Commercial sites: 30,000 μg/g
Industrial sites: 800,000 μg/gDrinking water: 5 µg/L

 

Sets vapour standards for the protection of human health:
Agricultural, urban park, residential use standard: 800 μg/m3
Commercial use standard: 2,500 μg/m3
Industrial use standard: 7,500 μg/m3
Parkade use standard: 6,500 μg/m3
(Vapours derived from soil, sediment, or water)

2017[24]
mg/L = milligrams per litre
µg/m3 = micrograms per cubic metre
µg/g = micrograms per gram

PDCB was not included in other Canadian environmental guidelines reviewed.[25,26,27,28,29]

Canadian Agencies/Organizations

Agency Designation/Position Year
Health Canada DSL – low priority substance (already risk managed) 2006[30]
Environment Canada’s National Pollutant Release Inventory NPRI Part (Threshold Category): 1A, Reportable to NPRI if manufactured, processed, or otherwise used at quantities greater than: 10 tonnes; 5, Reportable to NPRI if released at quantities greater than: 1 tonne of 10-tonne total VOC air release. 2016[31]

p-Dichlorobenzene was not included in other Canadian government chemical listings reviewed.[32,33,34,35,36]

Main Uses

p-Dichlorobenzene is used primarily as a moth repellent and space deodorant.[1,3] It is also used as an intermediate in producing other chemicals, including polyphenylene sulphide and 1,2,4-trichlorobenzene.[1,3]

There are several other minor uses for PDCB, such as: a pesticide against certain tree-boring insects and ants; a fungicide for tobacco seeds, leather, and some fabrics; a disinfectant; an animal repellent; an intermediate chemical in producing pigment and dye; an ingredient in manufacturing certain pharmaceuticals and resin-bonded abrasives.[1,4]

There are four products listed with PDCB as an active ingredient registered with the Canadian Pest Management Regulatory Agency (PMRA).[37] Of these, three are registered for domestic use. All products listed were mothballs or air deodorizers.

Canadian Production and Trade

Canada did not import or export p-dichlorobenzene in 2015.[38]

Environmental Exposures Overview

Sources of environmental exposure to p-dichlorobenzene include industrial emissions, incinerators, and use of the chemical as a deodorizer and insect and animal repellent.[1,4] Because of its high volatility and the dispersive nature of its uses, almost all PDCB used is expected to be released into the atmosphere.[1,39]

The most significant route of exposure to PDCB for the general public is by inhaling contaminated air.[1,4] Air testing conducted in 23 locations across Canada between 1988 and 1990 found that 99% of the samples had detectable levels (>0.1 μg/m3) of PDCB.[39] The highest concentrations were found in industrial areas.[39]

Indoor air concentrations of PDCB may be one to three orders of magnitude higher than outdoor concentrations if household products containing PDCB are used.[4]

p-Dichlorobenzene has been found in various foods, including meat, fish, poultry, egg, baked goods, fruits and vegetables, butter, milk, and soft drinks.[4] Concentrations in most foods are less than 10 μg/kg.[3,4] Low levels (<1 μg/L) of PDCB have also been found in some drinking water samples in Canada.[39]

Searches of Environment Canada’s National Pollutant Release Inventory (NPRI) and the US Household Products Database yielded the following results on current potential for exposure to PDCB in Canada:

NPRI Reported Releases

NPRI 2015[40]
Substance name: ‘p-Dichlorobenzene’
Category Quantity Industry
Released into Environment 0.441 t Chemical manufacture(1 facility)
Disposed of None
Sent to off-site recycling None
US Household Products 2016[41]
Search Term Quantity Product Type
‘p-Dichlorobenzene’ 10 Pesticides, moths (9), toilet bowl deodorizer (1)
t = tonne

Occupational Exposures Overview

Inhalation is the most important route of occupational exposure to p-dichlorobenzene, although dermal exposure may also occur.[1,4]

The main occupations exposed to PDCB include workers involved in its production and processing.[1,3,4] Exposure may also occur in workplaces where PDCB is used, such as in mothball and resin-bonded abrasive wheel manufacturing plants.[4] Air concentrations were found to be higher in p-dichlorobenzene manufacturing plants compared to plants that used the chemical in their production processes.[4]

CAREX Canada has not prioritized para-Dichlorobenzen for exposure estimate development. This is because there is a lack of exposure monitoring data in the Canadian Workplace Exposure Database on which to base an estimate.

Sources

1. National Toxicology Program (NTP). 14th Report on Carcinogens for 1,4-Dichlorobenzene (2016) (PDF)
2. US National Library of Medicine. Hazardous Substances Data Bank (Search term: ‘1,4-Dichlorobenzene’)
3. International Agency for Research on Cancer (IARC). Monograph summary, Volume 73 (1999) (PDF)
4. Agency for Toxic Susbtances and Disease Registry (ATSDR). Toxicological Profile for Dichlorobenzenes (2006) (PDF)
10. Government of Newfoundland and Labrador. Regulation 5,12 Occupational Health and Safety Regulations (2012)
11. Government of the Northwest Territories. Occupational Health and Safety Regulations, R-039-2015 (2016) (PDF)
13. The Canadian Legal Information Institute (CanLII). Government of Nunavut’s Occupational Health and Safety Regulations, Nu Reg 003-2016 (2010)
15. Government of Prince Edward Island. Occupational Health and Safety Act Regulations Chapter 0-1 (2013) (PDF)
17. Government of Saskatchewan. The Occupational Health and Safety Regulations, 1996 (2016) (PDF)
18. The Canadian Legal Information Institute (CanLII). Yukon’s Occupational Health Regulations, O.I.C. 1986/164 (2012) (PDF)
19. Occupational Safety and Health Administration (OSHA). Annotated PELs (2018)
21. The Canadian Legal Information Institute (CanLII). Ontario Drinking Water Quality Standards, O Reg 169/03 (2017)
22. The Canadian Legal Information Institute (CanLII). Regulation respecting the quality of drinking water, CQLR c Q-2, r 40 (2014)
23. Ontario Ministry of the Environment and Climate Change. Ontario’s Ambient Air Quality Criteria (2016)
24. Government of British Columbia. Contaminated Sites Regulation B.C. Reg. 375/96 (2017)
26. Health Canada. Cosmetic Ingredient Hotlist (2014)
29. Alberta Environment and Parks. Ambient Air Quality Objectives (2017)
32. Environment and Climate Change Canada. Toxic Substances List – CEPA Schedule 1 (2010)
34. Canadian Council of Ministers of the Environment (CCME). National Classification System for Contaminated Sites (2008) (PDF)
35. International Joint Commission (IJC). Revised Great Lakes Water Quality Agreement of 1978 (1978) (PDF)
36. Health Canada. PMRA List of Formulants (2010) (PDF)
37. Health Canada. Pesticide Label Search (2018) (Search term: Cas number: 106-46-7.)
38. International Trade Map. TradeMap (Free subscription required)
39. Health Canada and Environment Canada. CEPA Priority Substances List assessment report for 1,4-Dichlorobenzene (1993) (PDF)
40. Environment and Climate Change Canada. National Pollutant Release Inventory (NPRI) Facility Search (Substance name: ‘p-Dichlorobenzene’)
41. US Household Products Database (HPD). Household Products (Search term: ‘p-Dichlorobenzene’)

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