Application Code
Application Type
Applicant
Application Received
Submission Period
Consideration date
Considered by
14 July 2008
HRC07004
To reassess a hazardous substance under section 63 of the
Hazardous Substances and New Organisms Act 1996 (“the
Act”)
Chief Executive of ERMA New Zealand (“the Chief
Executive”)
11 April 2008
14 April - 27 May 2008
18 June 2008
Purpose of the Application
A Committee of the Authority (“the Committee”)
Pentachlorophenol: a reassessment of pentachlorophenol
(PCP) and its sodium salt.
1.1
Following consideration of the application for reassessment, the Committee has revoked the approvals for the importation or manufacture of PCP (HSR003042) and the sodium salt of PCP (HSR007163).
2.1
An application was lodged by the Chief Executive pursuant to section 63 following grounds for reassessment having been established under section 62 by the
Authority in its decision dated 29 June 2007. This reassessment decision was determined in accordance with section 29, taking into account additional matters to be considered in that section and matters relevant to the purpose of the Act, as specified under Part II of the Act. Unless otherwise stated, references to section numbers in this decision refer to sections of the Act.
2.2
Consideration of the application followed the relevant provisions of the Hazardous
Substances and New Organisms (Methodology) Order 1998 (“the Methodology”).
Unless otherwise stated, references to clauses in this decision refer to clauses of the
Methodology.
3.1
The application was formally received on 11 April 2008. In the application, the
Agency reviewed the hazard classifications of pentachlorophenol and its sodium salt. The Agency also evaluated the risks, costs and benefits associated with the

availability of the substances and recommended that the Authority revoke the existing approvals for the substance.
3.2
In accordance with sections 53(1) and 53A, and clauses 2(2)(b) and 7, public notification was made on 14 April 2008 (on ERMA New Zealand’s web site) and the application was advertised in the four main newspapers (New Zealand Herald,
Dominion Post, Christchurch Press and Otago Daily Times).
3.3
Submissions closed on 27 May 2008, 30 working days after public notification.
3.4
Various Government departments, Crown Entities and interested parties, including the New Zealand Food Safety Authority (Agricultural Compounds and Veterinary
Medicines (ACVM) Group), the Ministry of Health and the Department of Labour
Work Place Group, which in the opinion of the Authority would be likely to have an interest in the application, were notified of the receipt of the application
(sections 53(4) and 58(1)(c), and clauses 2(2)(e) and 5) and provided with an opportunity to comment or make a public submission on the application.
3.5
The Agency received no submissions on this application.
3.6
No external experts were used in the consideration of this application (clause 17).
3.7
The following members of the Authority’s Hearings Committee considered the application as a fax back in accordance with a delegation under section 19(2)(b): Dr
Max Suckling (Chair), Dr Manuka Henare and Dr Deborah Read.
4.1
4.2
The purpose of the application was to reassess the existing approvals for pentachlorophenol (PCP) and its sodium salt.
In accordance with clause 24, the Committee’s approach to the consideration was to:
 review the available information;
 establish the hazard classifications for (PCP) and its sodium salt and derive the controls that are prescribed under section 77 for each classification;
 identify potentially non-negligible risks, costs, and benefits;
 assess the potentially non-negligible risks and costs ( according to the qualitative descriptors detailed in Appednix1);
 determine whether the default controls, prescribed under section 77, and the additional controls, prescribed under section 77a, mitigate any unacceptable risks;
 undertake a combined consideration of all the risks and costs and determine whether the combined risks and costs are negligible or non-negligible;
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 taking into account the risk characteristics established under clause 33, evaluate the risks, costs and benefits in accordance with clause 34 and determine whether the application should be approved or declined under clauses 26, 27 and section 29;
 confirm and set the controls or revoke the previous approval.
4.3
In the risk assessment, risks were assessed in accordance with clause 12, costs in accordance with clause 13 and benefits in accordance with clauses 9, 11, 13 and 14
4.4
and section 6(e).
In the application, the Agency concluded that on the weight of the evidence, the information available to it constituted an adequate and appropriate basis for assessing the risks costs and benefits associated with PCP and its sodium salt. In the absence of quantitative exposure information, the Agency used qualitative exposure assessment models to determine the levels of risk to human health and the environment. The Agency noted that there was uncertainty inherent in these assessments.
4.5
The risk management framework used by the Authority requires consideration of uncertainty. Clause 8 requires the Authority to be mindful of the scale and significance of the risks, costs and benefits when reviewing the information available. In addition, according to clause 29, when there is scientific and technical uncertainty or disputed information, the Authority must determine the materiality and relevance of that uncertainty. If such uncertainty cannot be resolved, clause 30 requires the Authority to take into account the need for caution in managing the adverse effects of the substance.
4.6
The Committee has reviewed the available information and is satisfied that the available information is relevant and appropriate and is sufficient to demonstrate that the effects are of a sufficient magnitude to warrant attention under the Act.
4.7
The Committee noted that the Agency classified PCP and its sodium salt as follows in Table 1:
Table 1: Summary of Hazard Classifications for PCP and its sodium salt.
Substance
Classification
Acute Oral Toxicity
Pentachlorophenol
6.1B (very toxic if swallowed)
Acute Dermal Toxicity 6.1B (very toxic in contact with skin)
Acute Inhalation Toxicity 6.1B (very toxic if inhaled)
Pentachlorophenol, sodium salt
6.1B (very toxic if swallowed)
6.1B (very toxic in contact with skin)
6.1B (very toxic if inhaled)
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Overall Acute Toxicity 6.1B
Skin Irritation 6.3A (causes skin irritation)
Eye Irritation
Skin Sensitisation
6.4A (causes eye irritation)
6.5B
(skin sensitiser)
6.1B
6.3A (causes skin irritation)
6.4A (causes eye irritation)
6.5B
(skin sensitiser)
Carcinogenicity
Reproductive Toxicity
Target Organ Systemic
Toxicity
6.7B (suspected carcinogen)
6.8B
(reproductive/developmental toxicant) – may cause harm to the unborn child
6.9B (target organ systemic toxicant) – liver, kidney and CNS effects.
6.7B (suspected carcinogen)
6.8B
(reproductive/developmenta l toxicant) – may cause harm to the unborn child
6.9B (target organ systemic toxicant) – liver, kidney and
CNS effects.
Aquatic ecotoxicity
Terrestrial vertebrate ecotoxicity
4.8
9.1A (very toxic to aquatic life) 9.1A (very toxic to aquatic life)
9.3A (very toxic to terrestrial vertebrates)
9.3A (very toxic to terrestrial vertebrates)
The Committee noted that these classifications for PCP and its sodium salt differ from that of the previously approved substances. The revised classifications are
4.9
based on a more thorough review by the Agency of the available toxicological and ecotoxicological data.
In the application, the Agency used the controls assigned as part of the approval.
These controls were based on the substances hazardous properties as set out in the
HSNO Regulations. These controls were used as a reference for evaluation in the application and are listed in Section 3.4.2 and 3.4.3 of the application and have not been reproduced here.
4.10
The Committee notes that PCP and its sodium salt were used in the timber preserving industry in New Zealand until 1988 when its use ceased. It was previously used to treat timber, fibres and textiles to enhance their natural durability and increase their resistance to fungal or insect attack.
4.11
PCP and its salt were deregistered by the Pesticides Board in 1991 and there are no current approvals under the Act for the use of any PCP-containing products in
New Zealand. However PCP and its sodium salt were given deemed approvals upon transfer into the HSNO regime in July 2006 via the Hazardous Substances
(Chemicals) Transfer Notice 2006 and therefore are currently approved under
HSNO for manufacture in or importation into New Zealand
4.12
The Committee notes that, in New Zealand, PCP and its sodium salt have been replaced by other chemical agents for all of their former uses.
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4.13
Based on their hazardous properties and their lifecycles PCP and its sodium salt have the potential to cause adverse effects to:
 workers involved in the manufacture of the substances;
 workers and bystanders should an incident occur in transportation or storage of the substances;
 users of the substances in the timber preserving industry and textile industries;
 the public who use any of the woods or fibres that have been treated;
 the environment from spillage, seepage or by the substances release from treated material;
 the relationship of Māori to the environment through exposure of water, soil and native flora and fauna to the substances.
4.14
In June 2007, the Authority decided that there were grounds for reassessment of
PCP and its sodium salt, because:
 other substances with similar or improved beneficial effects and reduced adverse effects were available (section 62(2)(b)); and
 information showing a significant change of use or a significant change in the quantity manufactured, imported, or developed had become available.
(section 62 (2)(c)).
4.15
In the reassessment of substances containing PCP and its sodium salt, the Agency prepared an application for the Committee which took into account the effects arising from the hazardous properties of:
 PCP and its sodium salt;
 by-products produced during the manufacture of PCP and its sodium salt that remain present in the substances as impurities. These include dioxins
(for example, tetra-, hexa- and octachlorodibenzo-p-dioxin) and hexachlorobenzene; and
 timber or fibres treated with PCP or its sodium salt will have.
4.16
In its application for PCP and its sodium salt the Agency identified potentially significant and therefore non-negligible risks to the environment, to human health and safety, to the relationship of Māori with the environment, to society and the community and to the market economy.
Identification of potentially non-negligible risks and costs (adverse effects)
4.17
The Committee considers the potentially non-negligible risks and costs associated with PCP and its sodium salt relate to the substances’ toxic and ecotoxic properties.
These risks arise during all stages of the substances lifecycle including the life of the timber or fibres that have been treated with PCP or its sodium salt.
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Identification of potential benefits
4.18
The Committee considers that the following potential benefits are relevant to availability of PCP and its sodium salt:
(1) when applied to timber or wood by one of a number of processes such as pressure, dip or spray, the substances enhance the natural durability of that timber or wood against fungal or insect attack; and
(2) fibres and textiles impregnated with PCP or its sodium salt have an increased resistance to fungal or insect attack.
4.19
The Committee noted the availability of alternatives to PCP and its sodium salt for the uses listed in 4.18 and noted that PCP and its sodium salt have been replaced by these alternatives for all uses in New Zealand. Accordingly PCP and its sodium salt do not have any particular characteristics that result in any unique benefit.
Assessment of potentially non-negligible risks and costs to the Environment and human health and safety (adverse effects)
4.20
Taking into account the Agency’s assessment of the potentially non-negligible risks and costs with PCP and its sodium salt in New Zealand, the Committee assessed the impact for the environment and to human health and safety. The assessments were conducted assuming that the controls identified by the Agency are in place and best practice guides are used by all those involved with the substances.
4.21
With regard to the environment, the Committee considers that PCP and its sodium salt will pose a non-negligible risk to the aquatic environment and to terrestrial vertebrates. Specifically, the Committee notes that :
1) PCP and its sodium salt are highly ecotoxic to different organisms in the environment and may persist in the environment for a long time. The manufacturing by-products identified in paragraph 4.15 are found in all environmental compartments, are persistent and tend to accumulate in higher animals. Their resistance to degradation and semi-volatility means that they may be transported over long distances. Even very small concentrations of dioxins can cause adverse effects on the environment.
2) The Committee notes that historically the management and disposal of
PCP and its sodium salt was poor, leading to a large number of contaminated sites around New Zealand. Controls were added during approval to minimise their effects during the use to treat timber and fibres in conjunction with the use of best practice guides these controls would decrease the likelihood that these effects would occur. However due to the potential magnitude of these effects the resulting level of risk to the environment remains between a low and medium level during manufacture, packaging, importation, transportation, storage, use and disposal.
3) An additional environmental concern is the risk posed by the in-service use, end use and disposal of treated timber or fibres. The Agency notes that there is a risk of discharge, leaching or volatilisation of PCP and its
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sodium salt from treated timber or fibres into the environment. The resistance of PCP, its sodium salt and impurities to degradation and its high ecotoxicity means that there is the potential for long-term adverse effects where the substances have leached or volatilised from treated timber or fibres that are in contact with the ground (for example, timber buried in landfills, exposed timber at timber yards, timber used for rural fencing etc).
4) There are no suitable controls available to the Committee to reduce the likelihood of these processes occurring or to mitigate their effects. As a consequence of the magnitude of the environmental effects caused by this contamination and the likelihood that such contamination would occur, the level of risk to the environment posed by PCP and its sodium salt will continue to be high.
4.22
With regard to the effect of PCP and its sodium salt to human health and safety there are a range of potential chronic and toxic effects (table 1) that have been identified by the Agency. The Committee considers that the level of risk associated with these effects range from negligible to high. Specifically, the Committee notes that:
1) Historically chronic exposure, to PCP and its sodium salt, of workers has occurred and this has been blamed for a number of chronic heath conditions suffered by those workers. This was a factor in the timber industries voluntary withdrawal of PCP- based products from New
Zealand timber treatment in 1988.
2) The adherence to HSNO controls would substantially reduce the likelihood (to between unlikely and highly improbable) that the potential acute and chronic effects would have on the health of workers and bystanders during the treatment of timbers and fibres. Due to the potential magnitude of these risks, however, the resulting level of risk remains between a low and medium level for acute oral toxicity, acute dermal toxicity, acute inhalation toxicity and skin sensitisation, while a
high level of risk remains for the chronic adverse effects of carcinogenicity, reproductive toxicity and target organ toxicity.
3) Of particular concern with regard to human health and safety, is the risk posed from the in-service use, end use and disposal of treated timbers and fibres. There are risks associated with the discharge, leaching and volatilisation of PCP and its sodium salt into the environment and the risks that this present to human health. There is also an additional risk associated with people being exposed to the substances via direct contact with timber surfaces which may release timber preservative residues.
These risks are particularly high in the case of “wet” timber that has been prematurely released form a timber treatment site. As with the environmental effects the Committee lacks suitable controls to mitigate these effects and the level of risk to human health must be regarded as
high.
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Assessment of potentially non-negligible benefits to the environment and human health and safety
4.23
Potential benefits are listed in 4.18. However, since there are many alternative products available in New Zealand that provide the same or better benefits, and that PCP and its sodium salt are not permitted preservatives under NZS 3640:2003 and there is no desire by the industry to have the substances reinstated, the
Committee considers that negligible benefits accrue from the approval of PCP or its sodium salt.
Assessment of any risks, costs or benefits which arise from the relationship of Māori to the environment
4.24
Taking into account the Agency’s assessment of the potentially non-negligible risks and costs with PCP and its sodium salt in New Zealand, the Committee assessed the level of risk of PCP and its sodium salt to the relationship of Māori to the environment to range from low to high given adherence to HSNO controls.
4.25
The Committee recognises that the historical practice and management of timber treatment chemicals has contributed to a large number of contaminated sites around New Zealand. The condition of these sites is offensive to Māori because they affect the relationship of Māori with the environment with regard to:
 the erosion of tikanga and mātauranaga Māori through the poisoning of the environment;
 limiting their ability to perform their role as Kaitiaki by potentially limiting the productivity and life-sustaining quality of both land and water; and
 damaging tah hauroa by disrupting both their physical wellbeing and spiritual wellbeing.
4.26
The Committee considers however that full compliance with the HSNO controls and the Best Practice Guidelines would prevent this situation occurring to the same extent in the future. This would substantially reduce the likelihood of these effects to between unlikely and highly improbable. However, due to the potential magnitude of these effects, the resulting level of risk remains low with regard to tikanga and mātauranaga Māori, medium with regard to Kaitiakitanga and high for factors associated with taha hauroa.
4.27
The Committee considers there are negligible benefits associated with the approval of PCP or its sodium salt for the relationship of Māori to the environment.
Assessment of any risks costs or benefits to New Zealand’s international relationships
4.28
The continued approval of PCP and its sodium salt presents a significant risk to a number of New Zealand’s international obligations:
 While not specifically listed, PCP and its sodium salt can potentially be captured under the Stockholm Convention for Persistent Organic
Pollutants (POPs), due to its potential contamination with dioxins (which are listed in the Convention);
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 PCP and its sodium salt are listed under the Rotterdam Convention as chemicals that have been banned or severely restricted for health or environmental reasons and are subject to the ‘Prior Informed Consent’ provisions of the Convention;
 Both the Stockholm and Rotterdam Conventions have been ratified by
New Zealand.
Likely effects of the substances being unavailable
4.29
The Committee notes that there are a number of alternative products available for the treatment of timber and fibres and notes that in New Zealand, PCP and its sodium salt have been replaced by other chemical agents for all of its former uses.
The industries that formerly used the substances have expressed no desire to use the substances now or in the future.
4.30
Thus, the Committee considers that there are no adverse effects associated with the substances being unavailable.
5.1
In summary, the Committee considers the risks of PCP and its sodium salt to the environment and human health to be high.
5.2
The Committee considers there are significant risks to Maori cultural wellbeing, society and the community and to New Zealand’s international obligations.
5.3
The Committee considers that there are no significant benefits associated with the availability of PCP and its sodium salt.
5.4
Thus, the Committee considers that it is evident the risks and costs associated with the approval of PCP and its sodium salt outweigh the benefits.
Conclusions
5.5
Taking into account, the approach to risk, the precautionary approach and the effects of the substances being unavailable, the Committee considers that the high level of adverse effects (risks and costs) to the environment, human health, the relationship of Māori to the environment and New Zealand’s international relationships outweigh any positive effects (benefits) associated with the availability
5.7
of PCP and its sodium salt in New Zealand.
5.6
Accordingly, the Committee declines to approve the continued manufacture or importation of the PCP or its sodium salt in New Zealand.
Revocation
The approvals to manufacture or import PCP and its sodium salt are revoked.
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5.8
Since PCP and its sodium salt was removed from the market and not been used since 1988 this revocation takes effect immediately.
6.1
6.2
6.3
Chair
The Committee determines that, pursuant to section 29 and clause 27 the adverse effects of PCP and its sodium salt outweigh the positive effects.
Accordingly, the Committee revokes the approvals for the importation or manufacture of the approvals for PCP (HSR003042) and the sodium salt of PCP
(HSR007163). This revocation takes effect from the date of this decision.
In accordance with clause 36(2) (b), the Committee records that, in reaching these conclusions, it has applied the balancing tests in section 29 and clauses 26 and 27.
6.4
Dr Max Suckling
It has also applied the following criteria in the Methodology:
 clause 9 – equivalent of sections 5, 6 and 8;
 clause 11 – characteristics of substance;
 clause 12 – evaluation of assessment of risks;
 clause 13 – evaluation of assessment of costs and benefits;
 clause 14 – costs and benefits accruing to New Zealand;
 clause 21 – the decision accords with the requirements and regulations;
 clause 22 – the evaluation of risks, costs and benefits – relevant considerations;
 clause 24 – the use of recognised risk identification, assessment, evaluation and management techniques;
 clause 25 – the evaluation of risks;
 clause 33 – risk characteristics;
 clause 34 – the aggregation and comparison of risks, costs and benefits;
 clause 35 – the costs and benefits of varying the default controls.
Date: 14 July 2008
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Qualitative descriptors are indicative only and they are primarily intended to be used to rank risks and benefits for the purposes of balancing risks and costs against benefits, and so that risks can be prioritised for management. The ‘descriptor’ words should not be seen in any absolute senses
– they are simply a means of differentiating levels of significance.
This section describes how the Agency staff and the Authority address the qualitative assessment of risks, costs and benefits.
Risks and benefits are assessed by estimating the magnitude and nature of the possible effects and the likelihood of their occurrence. For each effect, the combination of these two components determines the level of the risk associated with that effect, which is a two dimensional concept.
Because of a lack of data, risks are often presented as singular results. In reality, they are better represented by ‘families’ of data which link probability with different levels of outcome (magnitude).
The magnitude of effect is described in terms of the element that might be affected. The qualitative descriptors for magnitude of effect are surrogate measures that should be used to gauge the end effect or the ‘what if’ element.
Tables A3.1 and A3.2 contain generic descriptors for magnitude of adverse and beneficial effect. These descriptors are examples only, and their generic nature means that it may be difficult to use them in some particular circumstances. They are included here to illustrate how qualitative tables may be used to represent levels of adverse and beneficial effect.
The sample qualitative descriptors for effects on the market economy listed in the ERMA
New Zealand technical guide to decision making 1 include representative numbers. These
‘economic’ descriptors were developed prior to the publication of the technical guide on identification and assessment of effects on the market economy, 2 which refines the approach that ERMA New Zealand applies to identifying and assessing economic effects.
These numbers do not align well with the qualitative descriptors in the other categories
(effects on the environment, effects on human health, and effects on society and communities), as they relate more to an event than an effect. In particular the numbers are unclear about how they take account of time (are they annual, or over the life of the activity) and they do not have a local, regional or national context.
ERMA New Zealand has adopted a revised set of qualitative descriptors for the magnitude of effect on the market economy, as shown below
.
1 ERMA New Zealand. 2004. Decision Making: A Technical Guide to Identifying, Assessing and Evaluating Risks,
Costs and Benefits, ER-TG-05-01. Wellington: Environmental Risk Management Authority.
2 ERMA New Zealand. 2005. Assessment of Economic Risks, Costs and Benefits: Consideration of Impacts on the
Market Economy, ER-TG-06-01. Wellington: Environmental Risk Management Authority.
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Table A3.1: Magnitude of adverse effect (risks and costs).
Descriptor Examples of descriptions: ADVERSE
Minimal Mild reversible short term adverse health effects to individuals in highly localised area
Highly localised and contained environmental impact, affecting a few (less than ten) individuals members of communities of flora or fauna, no discernible ecosystem impact
Local/regional short-term adverse economic effects on small organisations (businesses, individuals), temporary job losses
No social disruption
Minor
Moderate Minor irreversible health effects to individuals and/or reversible medium term adverse health effects to larger (but surrounding) community (requiring hospitalisation)
Measurable long term damage to local plant and animal communities, but no obvious spread beyond defined boundaries, medium term individual ecosystem damage, no species damage
Medium term (one to five years) regional adverse economic effects with some national implications, medium term job losses
Some social disruption (e.g. people delayed)
Major
Mild reversible short term adverse health effects to identified and isolated groups
Localised and contained reversible environmental impact, some local plant or animal communities temporarily damaged, no discernible ecosystem impact or species damage
Regional adverse economic effects on small organisations (businesses, individuals) lasting le ss than six months, temporary job losses
Potential social disruption (community placed on alert)
Massive
Significant irreversible adverse health effects affecting individuals and requiring hospitalisation and/or reversible adverse health effects reaching beyond the immediate community
Long term/irreversible damage to localised ecosystem but no species loss
Measurable adverse effect on GDP, some long term (more than five years) job losses
Social disruption to surrounding community, including some evacuations
Significant irreversible adverse health effects reaching beyond the immediate community and/or deaths
Extensive irreversible ecosystem damage, including species loss
Significant on-going adverse effect on GDP, long term job losses on a national basis
Major social disruption with entire surrounding area evacuated and impacts on wider community
Table A3.2: Magnitude of beneficial effect (benefits).
Descriptor Examples of descriptions: BENEFICIAL
Minimal Mild short term positive health effects to individuals in highly localised area
Highly localised and contained environmental impact, affecting a few (less than ten) individuals members of communities of flora or fauna, no discernible ecosystem impact
Local/regional short-term beneficial economic effects on small organisations (businesses, individuals), temporary job creation
No social effect
Minor Mild short term beneficial health effects to identified and isolated groups
Localised and contained beneficial environmental impact, no discernible ecosystem impact
Regional beneficial economic effects on small organisations (businesses, individuals) lasting less than six months, temporary job creation
Minor localised community benefit
Moderate Minor health benefits to individuals and/or medium term health impacts on larger (but surrounding) community and health status groups
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Descriptor Examples of descriptions: BENEFICIAL
Major
Massive
Measurable benefit to localised plant and animal communities expected to pertain to medium term.
Medium term (one to five years) regional beneficial economic effects with some national implications, medium term job creation
Local community and some individuals beyond immediate community receive social benefit.
Significant beneficial health effects to localised community and specific groups in wider community
Long term benefit to localised ecosystem(s)
Measurable beneficial effect on GDP, some long term (more than five years) job creation
Substantial social benefit to surrounding community, and individuals in wider community.
Significant long term beneficial health effects to the wider community
Long term, wide spread benefits to species and/or ecosystems
Significant on-going effect beneficial on GDP, long term job creation on a national basis
Major social benefit affecting wider community
Likelihood in this context applies to the composite likelihood of the end effect, and not either to the initiating event, or any one of the intermediary events. It includes:
 the concept of an initiating event (triggering the hazard), and
 the exposure pathway that links the source (hazard) and the area of impact (public health, environment, economy, or community).
Thus, the likelihood is the likelihood of the specified adverse effect initiating event. It will be a combination of the likelihood of the initiating event and several intermediary likelihoods 4
3 resulting from that
. The best way to determine the likelihood is to specify and analyse the complete pathway from source to impact.
Likelihood may be expressed as a frequency or a probability. While frequency is often expressed as a number of events within a given time period, it may also be expressed as the number of events per head of (exposed) population. As a probability, the likelihood is dimensionless and refers to the number of events of interest divided by the total number of events (range 0–1). (See Table A3.3.)
Table A3.3: Likelihood.
1
2
3
4
Descriptor Description
Highly improbable Almost certainly not occurring but cannot be totally ruled out
Improbable
(remote)
Very unlikely
Unlikely
(occasional)
Only occurring in very exceptional circumstances.
Considered only to occur in very unusual circumstances
Could occur, but is not expected to occur under normal operating conditions.
3 The specified effect refers to scenarios established in order to establish the representative risk, and may be as specific as x people suffering adverse health effects, or y% of a bird population being adversely affected. The risks included in the analysis may be those related to a single scenario, or may be defined as a combination of several scenarios.
4 Qualitative event tree analysis may be a useful way of ensuring that all aspects are included.
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5
6
7
Descriptor
Likely
Very likely
Extremely likely
Description
A good chance that it may occur under normal operating conditions.
Expected to occur if all conditions met
Almost certain
Using the magnitude and likelihood tables a matrix representing a level of effect can be constructed (Table A3.4).
Table A3.4: Level of risk.
Magnitude of effect
Likelihood Minimal Minor Moderate Major Massive
Highly improbable
Improbable
Very unlikely
Unlikely
Likely
A
A
B
C
D
A
B
C
D
E
B
C
D
E
E
C
D
E
E
F
D
E
E
F
F
Very likely E E F F F
Extremely likely E F F F F
The Agency considers that, for this substance, the level of risk/benefit can be assigned as follows in Table A3.5.
Table A3.5: Assignment of level of risk/benefit.
Code
A & B
C
D
E
F
Level of risk/benefit
Negligible
Low
Medium
High
Extreme
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