Environmental emergency planning: phosphoric acid, tributyl ester risk evaluation
Phosphoric acid, tributyl ester(CAS No. 126-73-8)
Risk Evaluation Conclusion:
- Threshold quantity of 4.5 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).
Phosphoric acid, tributyl ester (CAS No. 126-73-8) 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 4.5 tonnes with a minimum concentration of 10%.
2.0 Summary of the Risk Evaluation
2.1 Physical Hazard: Flammable, Combustible or Oxidizing Substances
Because phosphoric acid, tributyl ester has a flash point of 146°C (CHEMINFO, 2006) and has a boiling point of 289°C (HSDB, 2006; Government of Canada, 2009), 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
Phosphoric acid, tributyl ester has not been modeled for pool fire risks. Therefore, it is not known whether it is capable of causing a pool fire.
2.3 Human Health Hazard: Inhalation Toxicity
Because phosphoric acid, tributyl ester does not have a vapour pressure greater than 10 mmHg (1.33 kPa) at 25°C (Genium, 2006), 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 phosphoric acid, tributyl ester is not classified in any group of the International Agency for Research on Cancer (IARC, 2014) or the U.S. Environmental Protection Agency (U.S. EPA, 2005), 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 phosphoric acid, tributyl ester has been determined to be moderately toxic based on studies of the most sensitive species, Fathead minnow (Pimephales promelas), with a concentration (LC50 96 hours) of 8.18 mg/L (Geiger et al., 1986).
Environment Canada determined that phosphoric acid, tributyl ester is practically non-persistent in water according to our risk evaluation methodology (Environment Canada, 2015).
Environment Canada determined that phosphoric acid, tributyl ester is slightly bioaccumulative according to our risk evaluation methodology (Environment Canada, 2015).
Following the evaluation of the aquatic toxicity, the threshold is set at 4.5 tonnes.
2.7 Assigned Concentration
Phosphoric acid, tributyl ester is subject to the Environmental Emergency Regulations for aquatic toxicity. The minimum concentration assigned in the category for aquatic toxicity is either 10% (not a carcinogen) or 1% (a carcinogen). Since phosphoric acid, tributyl ester is not carcinogenic, then the minimum concentration set for phosphoric acid, tributyl ester 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 4.5 tonnes with a minimum concentration of 10% is assigned for phosphoric acid, tributyl ester 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 phosphoric acid, tributyl ester (CAS No. 126-73-8) in use in Canada indicates that the substance exists in commerce. Following the risk evaluation and policy considerations of phosphoric acid, tributyl ester 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 4.5 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 Database. 2006. Phosphoric Acid, Tributyl Ester. Canadian Centre for Occupational Health and Safety.
Environment Canada. 2011. Implementation Guidelines for the Environmental Emergency Regulations 2011.
Environment Canada. 2015. 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.
Genium Group Inc. 2006. Material Safety Data Sheet Collection. Tributyl Phosphate. Genium Group., Amsterdam NY, U.S. TRI1720.
Geiger, DL, SH Poirier, LT Brooke, and DJ Call. 1986. Acute Toxicities of Organic Chemicals to Fatheaded Minnows (Pimephales promelas). Volume III. Ctr. for Lake Superior Environ. Stud., Univ. of Wisconsin-Superior, Superior, WI :328
Government of Canada. 2009. Environment Canada, Health Canada. Screening Assessment for the Challenge Phosphoric Acid, Tributyl Ester (CAS RN 126-73-8).
Government of Canada. 2011. Environmental Emergency Regulations, Canadian Environmental Protection Act, 1999. Environment Canada. Registered on December 8, 2011
HSDB (Hazardous Substances Data Bank). 2006. Phosphoric Acid, Tributyl Ester (CAS#126-73-8). National Library of Medicine. Toxnet Home.
IARC (International Agency for Research on Cancer). 2014. IARC Monographs Database on Cancer Risks to Humans. International Agency for Research on Cancer, World Health Organization.
U.S. EPA (United States Environmental Protection Agency). 2005. Guidelines for Carcinogenic Risk Assessment.
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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