Implementation guidelines for Environmental Emergency Regulations: appendix 9

Appendix 9: summary of risk evaluation framework methodology for determining thresholds for environmental emergency plans

Acronyms in the risk evaluation framework

AEGL

acute exposure guideline level

B

bioaccumulation

BAF

bioaccumulation factor

BCF

bioconcentration factor

BLEVE

boiling liquid expanding vapour explosion

CEPA

Canadian Environmental Protection Act, 1999

CICADS

Concise International Chemical Assessment Documents

CRAIM / MIARC

Conseil pour la réduction des accidents industriels majeurs / Major Industrial Accidents Reduction Council

E2

environmental emergency

EPA

United States Environmental Protection Agency

ERPG-2

Emergency Response Planning Guidelines - 2

IARC

International Agency for Research on Cancer

IDLH

immediately dangerous to life or health

K_ow

octanol-water partition coefficient

LC₅₀

lethal concentration in air where 50% of test species die

LC_b

lowest reported lethal concentration in air at which death occurred

LD₅₀

median lethal dose where 50% of test species die via any exposure other than air

MIACC

Major Industrial Accidents Council of Canada, now defunct

NFPA

U.S. National Fire Protection Association

OECD

Organisation for Economic Co-operation and Development

P

persistence

PBiT

persistence, bioaccumulation and toxicity

PHAST

Process Hazard Analysis Software Tools

REF

Risk Evaluation Framework

RMP

risk management program

TRI

Toxic Release Inventory

TSMP

Toxic Substances Management Policy

Hazards evaluated by the risk evaluation framework

To decide whether a substance is potentially hazardous to humans or the environment, the Risk Evaluation Framework (REF) determines whether the substance is:

• a physical hazard, or
• a human hazard, and
• environmental hazard

In each REF category (environmental, human and physical), a trigger is assigned when certain characteristics of the substance are capable of causing harm to humans and/or the environment. A trigger is a qualifier for an E2 plan if it is accompanied by a threshold quantity. These criteria are listed in Table 1.

Before a chemical is put through the REF, it must meet the following pre-screening criteria:

• Is the chemical in commerce in Canada?
• Are the emergency plans covered by another act of Parliament?
• Are there realistic emergency pathways?

If the chemical is not in commerce in Canada, or if it is covered by another act of Parliament, or if it has no realistic emergency pathways, then the chemical is not recommended for addition to the Environmental Emergency Regulations (E2 regulations).

Descriptions of the REF criteria

1. Physical hazard ratings (Part 1 Substances)

Flammable gases and volatile flammable mixtures are included in Part 1 of Schedule 1 of the E2 Regulations based on their flash point and boiling point, also known as the flammability criteria used by the Transportation of Dangerous Goods Regulations^{Footnote 8}. Most flammable substances fulfilling these criteria will rapidly or completely vaporize at atmospheric pressure and normal ambient temperature or are easily dispersed in air and will burn readily.

Vapour cloud explosion

The volatility of a substance is taken into account by the flash point and boiling point criteria. “Flash point” is defined as the lowest temperature at which a substance gives off sufficient vapour to form an ignitable mixture with air near its surface or within a vessel.

If the chemical has a flash point less than 23°C and a boiling point less than 35°C, then the substance is capable of causing a vapour cloud explosion. If the substance does not have a flash point, or if the substance sublimes, or decomposes below the cut-off temperatures, then the substance will not be considered flammable or combustible.

According to J.P. Lacoursière (2002), the threshold quantity for a vapour cloud explosion is set at 4.5 t (10 000 lbs) because, in the event of an explosion, this quantity would result in an approximate overpressure of 3nbsp;pounds per square inch (psi) at a distance of 100 m. The calculation is performed using the TNT model with Process Hazard Analysis Software Tools (PHAST) software.

Combustibility

This category represents substances that have a flash point of less than 23°C or a boiling point of less than 35°C. The equation below calculates the quantity of substance necessary to evaporate 4.5 t within 10 minutes at ambient temperature (25°C) and 1.5 m/s wind speed.  The quantity necessary to create the evaporation rate is pooled into an area with a dike 50 cm in height.

The evaporation rate was determined by the following release equation (U.S. Environmental Protection Agency [EPA] 1999):

where: QR = evaporation rate (kg/min)
U = wind speed (m/s))
MW = molecular weight)
A = surface area of pool formed by the entire quantity of substance (m2))
VP = vapour pressure (mmHg))
T = temperature (Kelvin (K); temperature in °C plus 273)

Schedule 1, Part 1 substances that have thresholds above 4.5 t are combustible substances, with a few exceptions.

Reactivity

The current Table 2 below was slightly modified from the original data provided from the Defined Degrees of Instability Hazards of the NFPA (2002). Table 2 shows the criteria for reactivity; however, other factors may come into play such as the potential to cause a boiling liquid expanding vapour explosion (BLEVE) and accidental death histories. Table 2 below is used as a guide for expert opinion.

Table 2: reactivity

(NFPA 2002)

2. Human Hazard Ratings (Part 2 Substances)

Substances that are considered hazardous when inhaled are included in Part 2 of Schedule 1 of the E2 regulations based on their toxicity, physical state, vapour pressure and accident history.

Inhalation Toxicity

The methodology used by CRAIM (2002) when setting inhalation threshold quantities is the same as that used by the U.S. EPA when developing its RMP lists. This methodology takes into consideration the potential of toxic substances to become airborne and disperse, as well as their inhalation thresholds. The REF specifies that a chemical must have a vapour pressure greater than or equal to 10 mmHg (1.33 kPa) before it can be considered for the inhalation toxicity criteria. If a substance has a vapour pressure less than 10 mmHg (1.33 kPa), inhalation toxicity will not apply.

An index of toxicity is used to analyze the inhalation threshold. This index is derived using the physical state and volatility of a substance. By order of precedent as shown in the rationale document (J.P. Lacoursière Inc., 2002), the index of toxicity is associated with the following parameters, with the final AEGL-02 values added as the highest priority. The example shown below is with IDLH.

1. Final AEGL-02 (30 min) - data is for humans
2. IDLH (30 min) - data is for humans
3. ERPG (1 h) - data is for humans
4. Mammalian data is extrapolated back to the IDLH - data is for humans
   • LC₅₀ × 0.1 = estimated IDLH (rat 4 h - preference)
   • LC₅₀ × 0.1 = estimated IDLH (rat 4 h - preference)
   • LD₅₀ × 0.01 = estimated IDLH (rat - preference)
   • LD_Lo × 0.1 = estimated IDLH (rat - preference)

Where: MW = molecular weight
T = boiling point in °C
IDLH = immediately dangerous to life and health (g/m3)

The acute exposure guideline level (final AEGL-02 at 30 min) is the priority level for toxicity rating for humans. AEGL is the airborne concentration of a substance above which it is predicted that the general population, including susceptible individuals, could experience irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape (U.S. EPA, 2008).

The secondary toxicity value used is the immediately dangerous to life and health (IDLH) concentration developed by the National Institute of Occupational Safety and Health (NIOSH, 1994).  The IDLH is defined as the maximum airborne concentration from which one could escape within 30 minutes without any escape-impairing symptoms or any irreversible health effects.  If no IDLH is found, the Emergency Response Planning Guidelines (ERPG) -2 (AIHA, 2011) developed for Transport Canada will be used as an equivalent to the IDLH.

The values for the Index of toxicity are then correlated to the threshold quantities as shown in Table 3. The threshold quantities are based on amounts ranging from those found in a drum (≈ 0.22 t) to a tanker truck (9.1 t).

(J.P. Lacoursière Inc., 2002)

Carcinogenicity

Previously, it was concluded that 10 years was sufficient time for a carcinogenic substance to cause cancer in humans. Due to new evidence, the exposure time for a substance to cause cancer has been lowered to 5 years in accordance with the precautionary principle. It has been shown that an infant is 10 times more at risk than an adult (U.S. EPA, 2005).

The REF uses 2 sets of carcinogenicity ratings established by the International Agency for Research on Cancer (IARC, 1999) and the U.S. EPA (U.S. EPA, 2002) as shown in tables 4 and table5. The IARC or U.S. EPA classifications will only trigger an E2 plan if the substance is persistent in the environment for at least 5 years, or the substance is classified as indefinitely persistent. If these criteria are met, the substance is then assigned a threshold of 0.22 t. If the two classification systems disagree on a chemical’s rating, the most conservative assessment is used, and the chemical is rated accordingly.

Table 4: IARC human and animal carcinogenicity classifications

(IARC, 1999)

Table 5: U.S. EPA carcinogenicity classifications

(U.S. EPA, 1986 and 1999, modified)

3. Environmental hazard ratings (Part 3 Substances)

Part 3 of Schedule 1, referred to as other hazardous substances, is a new addition to the list of substances covered by the Environmental Emergency Regulations. Substances in Part 3 can be characterized as being persistent, bioaccumulative, carcinogenic to humans or toxic to aquatic organisms.

The Toxic Substances Management Policy (TSMP) of CEPA uses persistence, bioaccumulation and toxicity (PBT) criteria for determining when an organic chemical is to be considered for virtual elimination in Canada. The virtual elimination of a toxic substance released into the environment, as a result of human activity, requires the ultimate reduction of its releases to the lowest concentration that can be accurately measured, using routine sampling and analytical methods (Environment Canada 1995). TSMP virtual elimination criteria are shown in Table 6.

(Environment Canada, 1995)

Persistence

Chemical substances that degrade slowly in the environment (that is, are relatively resistant to biodegradation, hydrolysis and photolysis processes) represent potential environmental problems. Persistence is measured as a half-life, meaning the period it takes the concentration of a substance to be reduced by half, by transformation, in a medium (Environment Canada, 2000). A compound released into the environment has a tendency to partition (that is, accumulate) into one medium (air, water, soil or sediment) more than another. Partitioning, transport and transformation rates differ in each medium.

The persistence criteria with the highest scores are based on the Persistence and Bioaccumulation Regulations (Environment Canada, 2000). These are the standards set by CEPA for substances that should be virtually eliminated from the environment. Those criteria are the same as the U.S. EPA persistence, bioaccumulation and toxicity (PBT) criteria used for the Toxic Release Inventory (TRI), New Substances Evaluation and other EPA programs (U.S. EPA, 1999, 1999a). These persistence criteria can be seen in Table 7. The rest of the scale was created by estimating half of the remaining time duration.

Inorganic substances are considered infinitely persistent in the environment since the metal ion (that is, lead, arsenic) continuously separates from the original substance and forms new compounds within the environment. This implies that the metal ion within inorganic substances does not degrade. No threshold quantity exists for persistence criteria alone; this category is combined with aquatic toxicity for persistence in water.

^a Environment Canada, 1995.
^b Or evidence of atmospheric transport to remote regions such as the Arctic (Environment Canada, 1995).

Bioaccumulation (BCF/BAF/Log K_ow)

Bioaccumulation is the biological accumulation of a substance into various tissues of a living organism. Table 8 shows all three criteria can be used to determine bioaccumulation. There are different ways to estimate the bioaccumulation within an organism:

1. “bioconcentration factor” means the ratio of the concentration of a substance in an organism to the concentration in water, based only on uptake from the surrounding medium (Environment Canada, 2000);
2. “octanol-water partition coefficient” means the ratio of the concentration of a substance in an octanol phase to the concentration of the substance in the water phase of an octanol-water mixture (Environment Canada, 2000);
3. “bioaccumulation factor” means the ratio of the concentration of a substance in an organism to the concentration in water, based on uptake from the surrounding medium and food (Environment Canada, 2000).

Table 6 shows the bioaccumulation criteria used in the REF. Both the highest values for the BCF/BAF and the log K_ow are consistent with the CEPA virtual elimination clause (Environment Canada, 2000). The OECD criteria for BCF is ≥ 500, or if BCF /BAF is absent, one uses the log Kow ≥ 4 (OECD, 2001). No threshold quantity exists within the REF for bioaccumulation alone; this category is combined with aquatic toxicity.

^c (Environment Canada, 1995) (OECD 2001, modified)

Aquatic toxicity

Freshwater species toxicity data for fish in Canadian waters are collected for the REF. Acute toxicity is determined using a freshwater fish 96-h LC₅₀. The most sensitive value (lowest value) for a freshwater fish is selected and a robust study is conducted for quality control measures to determine the quality of the laboratory experiment. If the value fails the robust study, then the next most sensitive species is selected. Ground water, drainages, tributaries and rivers can all lead to contamination of a water body. Aquatic toxicity uses the persistence and bioaccumulation criteria to assist in determining the threshold quantity.

How to use Table 9

If the substance falls within the range 0.1 mg/L ≤ fish LC₅₀ value ≤ 100 mg/L, then the substance is recommended for addition under Schedule 1, Part 3 of the Environmental Emergency Regulations, after the quality control robust study has been completed.  Furthermore, if the substance meets the categories of persistence or bioaccumulation criteria set out in Table 9, then the threshold defaults to that level. For sample calculations, see Table 10.

^e Value of LC₅₀ is over 100 mg/l - considered practically non-toxic.
^f Threshold is 4.50 t, but persistence criteria drops threshold to 1.13 t.
^g Threshold is 0.22 t and persistence and bioaccumulation criteria are higher than 0.22 t, therefore take the lowest threshold.
^h Threshold is 9.10 t, but bioaccumulation data drops the threshold to 1.13 t.

Robust studies

The reliability of a data point is crucial for the evaluation. For this reason, aquatic toxicity, bioaccumulation and persistence data points are analyzed using a robust study summary created by the OECD. A robust study summary is a series of questions based on information provided in a scientific journal. Thus, for each data point selected as the most sensitive endpoint found in a book or database, the original journal is examined via a robust study summary. Each scientific journal is assigned a Klimisch rating from 1 to 4, where 1 and 2 indicate journals that are experimentally reliable, whereas 3 and 4 are scores indicative of an unacceptable data point.

Standard references that are peer-reviewed such as The Merck Index, The Condensed Chemical Dictionary, The CRC Handbook of Chemistry and Physics, the Beilstein Database, and international reviews like Concise International Chemical Assessment Documents (CICADS) and Environment Health Criteria documents should be used as much as possible for data sources.