Introduction

A risk assessment is the result of combining a hazard assessment with exposure scenarios – risk is a function of hazard and exposure.  To put it very simply:

Non hazardous and low exposure = low risk

Non-hazardous and high exposure = good hazard assessment required

Hazardous and low exposure = exposure management required

A hazard assessment needs to consider the physico-chemical, toxicological and ecological properties of a chemical substance and the result of this assessment leads to Classification with assignment of  ‘R Phrases’; however, this does not reflect the risk of the materials to workers, consumers or the environment and to take the hazard data to the next stage of assessment, it is necessary to understand potential exposure.

REACH requires that the hazard data are collated in the form of a Chemical Safety Assessment (CSA).  This needs to include hazard data relating to physico-chemical data, human health and environment and conclude with classification and choice of hazard phrases – currently ‘R Phrases’ but this is set to change with GHS.

Risk assessment

A full risk assessment to meet the requirements of Directive 93/67/EEC (as described in its associated technical guidance documents), is currently expected for new substances being Notified or for high-volume high-risk ‘existing’ substances being reviewed under the existing chemicals regulations.  However, REACH will lead to the need to perform a risk assessment on virtually all substances being supplied in the guise of a ‘Chemical Safety Report’ (CSR) and this is subject to guidance being developed under RIP 3. 

Even without the need to meet regulatory requirements, a basic ‘risk assessment’ is an essential part of responsible care during the production, supply or use of any chemical material.  A basic risk assessment will help determine what conditions to avoid or what protective equipment to recommend to meet other statutory requirements for handling chemicals – such as the communication or risk to customers, protection of workers and also to minimum impact on the environment through loss or accident.  The Safety data sheet itself is a product of a risk assessment in that it describes how to reduce exposure in accordance with known properties of the material.

Any type of risk assessment should include consideration of:

·        The life cycle of the product

·        Potential hazards to health and the environment

·        Physical form (solid, powder, liquid, gas etc)

·        How is the product handled (manually, automatically)

·        Is there contact with workers / consumers

·        Is there a chance of loss to the environment

·        What happens to the product after use (disposal)

The conclusions of an environmental risk assessment based, on the ratio of predicted environmental concentration (PEC) and predicted no effect level (PNEC).  Human health elements to the risk assessment are less clear-cut in their conclusions, but the principle remains the same with a comparison between the predicted level of exposure taken from the Exposure Scenario and the known or estimated degree of hazard presented as the Derived No Effect Level (DNEL) or for materials without a no effect level (eg certain carcinogens), a Derived Minimal Effect Level (DMEL). 

The requirements for risk assessment for substances reviewed under REACH follow the same concepts and the level of further control, or the need to submit more test data, may rest on the ratio between predicted exposure and the predicted no effect levels; ie. the Risk Characterisation Ratio. 

The conclusion of the Risk Assessment is the recommended Risk Management Measures – these describe what must be done to ensure Adequate Control.

Exposure Scenarios

The term ‘Exposure Scenario’ (ES) is part of the REACH terminology that is of concern to industry; however, the concept of the ES should be part of every risk assessment, whether for regulatory submission or as part of a well constructed SDS.  Under REACH, the ES will need to be part of the SDS, although the scale of the ES and logistics of including with the SDS needs further discussion.  In theory, every use of the substance or mixture will need to be described by an ES and if RIP documents are to be followed, some of these could be lengthy documents in their own right.

The ES needs to include details of exposure to workers, the general public and the environment that are specific to expected use patterns of the substance or mixture (see below for mixtures).  Generic scenarios can be used (eg. Lubricants, paints, chemical intermediates) and although should be suitably comprehensive to cover generic locations, may be site specific for Authorised substances.

It is accepted that suppliers cannot know every detail of use by their customer and likewise, customers, or Downstream Users (DU) may not want to divulge their specific uses to suppliers.  Therefore, it is possible for DUs to prepare their own ES and subsequent CSR.  This is especially applicable to mixtures in cases where such formulation details are commercially confidential.

Mixtures

Under REACH, it will be acceptable to prepare CSR or ES for mixtures of substances (preparations) where it is considered that as a result, the DU is provided with better and more relevant information.  This is especially applicable for dangerous mixtures where specific hazards of the mixture need to be considered.  However, there is still the option to prepare individual documents for each specific substance.

The environment

The Predicted Environmental Concentration (PEC) is based on models for the degradation or distribution of the substance in the environment (between water, air and solids) using physico-chemical and biodegradation data.  As well as the test data, other key factors include how the substance is manufactured, formulated or used and the dilution factors from use. 

The distribution of chemicals discharged to waste water treatment plants is described in the aptly named ‘SimpleTreat’ model.  This is a simplistic model that considers the volatility (Henry’s constant, H), the partition coefficient, adsorption coefficient and biodegradation.

Volatility                            Log H > 3                      = Significant loss to air

Partition coefficient         Log Kow > 3                 = Accumulation threat

Adsorption Coefficient   Log Koc > 3                  = Adsorption to soil / sediment

Biodegradation                  > 60%                            = Biodegradable

The model, presented in tabular form in the TGD or incorporated into the software of the risk assessment model EUSES (see below), compares each of these factors in determining the distribution of the substance in the environment.  A water soluble substance with Kow = 0, that is biodegradable, for example, is predicted to be 76% degraded with 24% lost to surface water.  But a non-biodegradable poorly water soluble material with a Log Kow of 4, may have 56% to water and 44% to sewage sludge.

Default figures are provided in the Technical Guidance Documents (TGD), describing estimated concentrations of waste in effluent, standard dilution factors, sizes of water treatment plants etc. These default values consider worse-case scenarios with, for example, 2% of material produced being lost to waste water, the position of the production unit in a small town with a small treatment works, and with final discharge going into a small stream. However, where only limited sites are involved in production, formulation or use, location-specific factors can be used, such as the size of the waste treatment works, river flow rates etc.  and this can make a big difference to the final conclusion.

The Predicted No Effect Concentration (PNEC) is based on environmental effect data, such as toxicity to fish, Daphnia or algae and is determined by applying a safety factor. For acute studies, the safety factor of 1000 is applied to the EC₅₀ value; ie. a Daphnia EC₅₀ following 48 hours exposure of 50 mg/l would lead to a PNEC of 0.05 mg/l.  Longer-term studies require a smaller safety factor, as indicated below; 

Acute EC₅₀         ÷ 1000   (Acute = short term, eg 4 days fish)

Sub-acute EC₅₀  ÷   100   (Sub-acute = medium term, eg 21 days fish)

Chronic EC₅₀      ÷    10    (Chronic = long term, pond work etc)

The ratio between PEC and PNEC is ultimately used as an indicator of risk, allowing it to be quantitatively labelled.  If the PEC is greater than the PNEC (ie. ratio > 1 ), then it can be assumed that there is a risk of effects to the environment.  The scale of the risk can therefore be crudely measured by considering this ratio – a figure of 1 to 10 is of low concern, but over 100 is of major concern, and limitation of supply could be required. 

In the absence of effects in acute studies, the PNEC is set at 1/1000 of the limit of solubility; likewise if there are no effects in longer-term studies, the PNEC will be 1/100 or even 1/10 of water solubility.

PBT / vPvB

Definitions for vPvB and PBT can be found in Annex XIII of the REACH Regulation.

To determine if a substance is PBT or vPvB, it is necessary to understand the persistence (stability) in the environment, the potential to bioaccumulate and its toxicity.   Initial assessment can be made with only three sets of test data; the ready biodegradability, partition coefficient and an acute toxicity test on an aquatic organism (eg. fish, Daphnia or algae).  Annex XIII defines PBT and vPvB, including rates of degradation in different environments; although these can be partly predicted by standard biodegradation methods, if your substance is borderline, certain expensive specialist studies may be worth performing if it keeps your substance on the market without restrictions (or Authorisation).

Bioaccumulation is initially assessed through solubility characteristics, including partition coefficient between water and octanol; substances that show a preferential solubility in octanol to water will in turn be more likely to partition into fatty tissues in animals and not be excreted in urine.  Bioaccumulation potential is more complex than simple partitioning and takes into account factors such as metabolism and ability to cross biological membranes – however, the simple and quick partition coefficient test is a good guide and if the Log Pow if less than 3 (ie. less than 1000 times more soluble in octanol than in water), the risk of bioaccumulation is considered negligible and further testing would not normally be required.

The following text is taken from Annex XIII of the REACH Regulation 2006/190

Definitions : vPvB

A substance that fulfils the criteria of the sections below is a vPvB substance.

2.1. Persistence

A substance fulfils the very persistence criterion (vP-) when:

– the half-life in marine, fresh- or estuarine water is higher than 60 days, or

– the half-life in marine, fresh- or estuarine water sediment is higher than 180 days, or

– the half-life in soil is higher than 180.

2.2. Bioaccumulation

A substance fulfils the very bioaccumulative criterion (vB-) when:

– the bioconcentration factor is greater than 5 000.

Definition  : PBT

A substance that fulfils all three of the criteria of the sections below is a PBT substance.

1.1. Persistence : A substance fulfils the persistence criterion (P-) when:

– the half-life in marine water is higher than 60 days, or

– the half-life in fresh- or estuarine water is higher than 40 days, or

– the half-life in marine sediment is higher than 180 days, or

– the half-life in fresh- or estuarine water sediment is higher than 120 days, or

– the half-life in soil is higher than 120 days.

The assessment of the persistency in the environment shall be based on available half-life

data collected under the adequate conditions, which shall be described by the registrant.

1.2. Bioaccumulation: A substance fulfils the bioaccumulation criterion (B-) when:

– the bioconcentration factor (BCF) is higher than 2 000.

The assessment of bioaccumulation shall be based on measured data on bioconcentration in aquatic species. Data from freshwater as well as marine water species can be used.

1.3. Toxicity: A substance fulfils the toxicity criterion (T-) when:

– the long-term no-observed effect concentration (NOEC) for marine or freshwater

organisms is less than 0,01 mg/l, or

– the substance is classified as carcinogenic (category 1 or 2), mutagenic (category 1

or 2), or toxic for reproduction (category 1, 2, or 3), or

– there is other evidence of chronic toxicity, as identified by the classifications:

T, R48, or Xn, R48 according to Directive 67/548/EEC.

Human exposure

A risk assessment based on human exposure should also be considered.  This will depend on the type of exposure, whether deliberate or accidental, whether repeat or one-off or whether direct (eg. factory workers) or indirect (eg. in food or drinking water).  

Although the Technical Guidance Document for Directive 93/67/EEC does devote a large proportion of its pages to human health risk assessment, there is little direct support for those preparing risk assessments and there is no simple quantitative assessment as found with environmental data.  Instead, it is necessary to make a full review of all parts of the life-cycle in which the substance can come into contact with people, including manufacture, transport, storage, formulation, use and disposal.  Parts of the life cycle may not  be obvious, such as the exposure to pigments caused by the degradation of paints.  The exposure during manufacture of a pigment or its formulation into paint may seem obvious, as is the exposure to the wet paint when applying it to a surface.  However, the exposure to the paint from weathered surfaces is less obvious, but it all needs considering.

Quantifying exposure is very difficult and models attempting to make this easier (such as the EU model, EASE) rely on inputs such as vapour pressure, temperature of the process leading to exposure, dust content etc.  Other than the rather simplistic model EASE, the finer points of human health risk assessments should be left in the hands of an expert.

REACH introduces the concept of the ‘Derived No Effect Level’ (DNEL) that tries to quantify the no effect concentration for human exposure.  This is more complex than the Environmental PNEC (see above in that it considers inter-species reliability as well as the end-points assessed.