Environmental emergency planning: hydroquinone risk evalution
Hydroquinone (1,4-Benzenediol)(CAS No. 123-31-9)
Risk Evaluation Conclusion:
- Threshold quantity of 0.22 tonnes (minimum concentration 10%) due to aquatic toxicity
- Is a candidate for the Environmental Emergency Regulations
The Environmental Emergency Regulations, developed under Part 8 of the CEPA 1999 (Government of Canada, 2011), establish a list of substances for which fixed facilities must notify Environment Canada that they store or use the substance on-site, by providing notices to Environment Canada, reporting when the substance is released into the environment, and developing an environmental emergency plan (E2 plan) for each substance stored or used at a fixed facility at or above specified threshold quantities.
To determine if a substance is a candidate to be added to the Environmental Emergency Regulations, Environment Canada developed a risk evaluation methodology based on the following hazard categories:
- Physical: flammable and combustible or oxidizing substances, or those having a potential to cause vapour cloud explosions or pool fires.
- Human Health: substances that are toxic by inhalation, are carcinogenic, or are corrosive.
- Environmental Health: substances that are: corrosive, persistent, bioaccumulative, or aquatically toxic.
For more information on the methodology for setting threshold quantities in the Environmental Emergency Regulations, please refer to Environment Canada (2015).
Hydroquinone (CAS No. 123-31-9) was selected for risk evaluation because it is a substance (under the Government of Canada’s Chemicals Management Plan) that, if spilled, could be immediately harmful to humans and/or the environment.
Following the risk evaluation, Environment Canada recommends that this substance be proposed for addition to Schedule 1 of the Environmental Emergency Regulations at a threshold quantity of 0.22 tonnes with a minimum concentration of 10%.
2.0 Summary of the Risk Evaluation
2.1 Physical Hazard: Flammable, Combustible or Oxidizing Substances
Because hydroquinone has a flash point of 165°C (CHEMINFO, 2007), and has a boiling point of 285°C (Lewis, 2004), this substance does not have the possibility of a vapour cloud explosion.
Therefore, no threshold is set for this substance as a result of its potential for flammability or combustibility.
2.2 Physical Hazard: Potential for Pool Fires
Environment Canada determined, via the Process Hazard Analysis Software Tools (PHAST) software, that hydroquinone is not capable of causing a pool fire.
2.3 Human Health Hazard: Inhalation Toxicity
Because hydroquinone does not have a vapour pressure greater than 10 mmHg (1.33 kPa) at 25°C (Government of Canada, 2008), the substance does not have sufficient volatility to constitute an inhalation danger.
Therefore, no threshold is set for the inhalation toxicity to humans.
2.4 Human Health Hazard: Carcinogenicity
Because hydroquinone is classified in Group 3 (not classifiable) of the International Agency for Research on Cancer (IARC, 1999), and because the substance does not have a half-life longer than five years in any medium, no threshold is set for the carcinogenicity of this substance.
2.5 Human and Environmental Health Hazard: Corrosive Substances
The measured pH is greater than 2 and less than 11.5, therefore the substance is not considered corrosive and there is no associated threshold with this category.
2.6 Environmental Health Hazard: Persistent, Bioaccumulative, or Aquatically Toxic
The acute (short-term) aquatic toxicity for hydroquinone has been determined to be extremely toxic based on studies of the most sensitive species, Fathead Minnow (Pimephales promelas), with a concentration (LC50 96 hours) of 0.044 mg/L (DeGraeve, et al., 1980).
Environment Canada determined that hydroquinone is non-persistent in water according to our risk evaluation methodology (Environment Canada, 2015).
Environment Canada determined that hydroquinone is practically non-bioaccumulative according to our risk evaluation methodology (Environment Canada, 2015).
Following the evaluation of the aquatic toxicity, the threshold is set at 0.22 tonnes.
2.7 Assigned Concentration
Hydroquinone is subject to the Environmental Emergency Regulations for aquatic toxicity. Then minimum concentration assigned in the category for aquatic toxicity is either 10% (not a carcinogen) or 1% (a carcinogen). Since hydroquinone is classified as IARC (Group 3), then the minimum concentration set for hydroquinone is 10% (Environment Canada, 2015).
2.8 Assigned Threshold
Following the risk evaluation methodology developed under section 200 of CEPA 1999, the categories (flammability, combustibility, oxidizers, inhalation toxicity, aquatic toxicity, carcinogenicity, corrosiveness, pool fires) having the lowest scientific threshold will be compared against other risk management considerations. For example, the threshold will be compared to other provincial and federal legislation or voluntary programs that may already provide adequate management of the risk from an environmental emergency. Proposed thresholds may also be modified based on policy and other considerations as assessed during the public consultation period. For more information regarding the determination of thresholds, please refer to the Implementation Guidelines for the Environmental Emergency Regulations 2011 (Environment Canada, 2011).
At this time, there are no other considerations to take into account for this substance that would result in an increase or a decrease in the calculated threshold quantity.
A proposed threshold of 0.22 tonnes with a minimum concentration of 10% is assigned for hydroquinone based on its assessed aquatic toxicity. The threshold quantity and its respective concentration will not be finalized until after public consultation.
Information concerning the quantities of hydroquinone (CAS No. 123-31-9) in use in Canada indicates that the substance exists in commerce. Following the risk evaluation of hydroquinone and taking into consideration the quantities in use in Canada, Environment Canada recommends that this substance be proposed for addition to Schedule 1 of the Environmental Emergency Regulations under CEPA 1999 at a threshold quantity of 0.22 tonnes at a minimum concentration of 10%.
Even if the quantity of a substance in use is below the threshold quantity indicated in the Environmental Emergency Regulations, Environment Canada recommends that emergency planning be applied to this substance in order to minimize, or prevent, any impacts on humans or the environment in the event of a release of the substance.
CHEMINFO. 2007. Chemical Profiles. Canadian Centre for Occupational Health and Safety (CCOHS).
DeGraeve, GM, Geiger, DL, Meyer, JS and HL Bergman. 1980. Acute and Embryo-larval Toxicity of Phenolic Compounds to Aquatic Biota. Archives of Environmental Contamination and Toxicology, 9: 557-568.
Environment Canada. 2011. Implementation Guidelines for the Environmental Emergency Regulations 2011.
Environment Canada. 2014. Summary of Risk Evaluation Framework for Determining Quantity Thresholds and Concentrations for Substances under the Environmental Emergency Regulations Set under the Canadian Environmental Protection Act, 1999 (CEPA 1999). Environment Canada.
Government of Canada. 2008. Environment Canada, Health Canada. Final Screening Assessment for 1,4-Benzenediol (CAS RN 123-31-9).
Government of Canada. 2011. Environmental Emergency Regulations, Canadian Environmental Protection Act, 1999. Environment Canada. Registered on December 8, 2011.
IARC (International Agency for Research on Cancer). 1999. Volume 71. Re-Evaluation of Some Organic Chemicals, Hydrazine and Hydrogen Peroxide- Summary of Data Reported and Evaluation. International Agency for Research on Cancer, World Health Organization.
Lewis, R.J. Sr., 2004. SAX’s Dangerous Properties of Industrial Materials, Volume 2, Eleventh Edition. Wiley-Interscience Publication, Hoboken, NJ. p. 1992-1993.
5.0 Further Reading
Ketcheson K, Shrives J. 2010. Comparison of Threshold Quantities for Substances with Final AEGL-2 and IDLH Values under CEPA’s Environmental Emergency Regulations. In: Proceedings of the Thirty-third Arctic and Marine Oilspill Program Technical Seminar on Environmental Contamination and Response. Environment Canada: Ottawa (ON). pp. 843-861.
U.S. EPA (U.S. Environmental Protection Agency). 1994. List of Regulated Toxic and Flammable Substances and Thresholds for Accidental Release Prevention. Federal Register, 59(20). Document Number 94-1556. 31. Washington (DC).
Current as of June 21st, 2016
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