Little Pro on 2016-10-14
We hope you have enjoyed learning how to calculate predicted no-effect concentration (PNECs) for a specific environment compartment (water, soil, sediment, etc) from our previous tutorial. To determine the risk of a substance to a given environmental compartment, we still need to compare PNEC values with predicted environmental concentrations (PECs). Quite often measured exposure data is not available, in which case we need to reply on exposure assessment models to estimate environmental exposure levels. In this tutorial, we will teach you how to use EUSES to calculate predicted environmental concentrations (PECs).
The European Union System for the Evaluation of Substances (EUSES) is a free tool developed by the European Commission to assist authorities, research institutes and companies to estimate environmental exposure levels of industrial chemicals and biocides. EUSES is easy to use. Only a few data on substance properties are needed to calculate PECs for tier 1 assessment. If the use of default exposure estimates and tier 1 assessment do not lead to PEC/PNEC<1, a refined assessment is possible in EUSES by including more specific information on releases.
Click here to download EUSES.
Once you have downloaded EUSES, unzip it and run it, you will see the following screen. The first thing you should do is to create a "new study". The next thing you should do is to select "assessment types" and then click "start".
When you run EUSES for a new study for the first time, you will need to choose EUSES assessment models and run mode (See screenshot below).
Different models are available. In this tutorial, we will choose type I environmental assessment for both local scale and regional scale. Usually both local scale and regional scale are chosen to calculate both the regional concentration (PECregional) and the local concentration (PEClocal). In addition, continental PEC values are derived in EUSES, but they are not used in the risk assessment. For new substances, only local scale is selected.
The local concentration is calculated for each local point source. The regional concentration mainly serves as estimates for background levels, and the estimates of these are so-called steady-state concentration, i.e. the concentration obtained at releases and fate processes taking place over infinite time within 10% of the size of the EU.
Three types of run mode is available: direct, interactive and outline. In this tutorial, we recommend interactive mode because you can see intermediate results such as predicted environmental concentrations (PECs).
The following information needs to be input to EUSES to estimate predicted environmental concentrations (PECs). It is also the minimum information you need to gather before you run EUSES. In addition, if you would like to use EUSES to calculate PNECs and risk characterization result, you should also collect various eco-tox endpoints such as LC50/EC50/NOEC.
|Substance Identification||Chemical name, description, CAS no.||-|
|MP||Melting Point||Celsius Degrees|
|BP||Boiling Point||Celsius Degrees|
|LogKow||octanol-water partition coefficient||-|
|Biodegradability||Screening results of biodegradability study||-|
|Tonnage||Production tonnage, import and export tonnage||-|
|Use pattern||Use title, use category, industry category and life cycle stage (production, formulation, industrial use, professional use, consumer use, service life, waste treatment).||See REACH use descriptors|
Release fractions based on environmental release categories (ERC) or SPERC and emission days.
Please note that default release percentage and emmission days in EUSES shall not be used.
|Read: How to calculate environmental emissions of chemical substances.|
The picture below is the user input interface of EUSES.
You may have noticed that each field is followed by a letter u, s, d, o. Those letters mean undefined, user input, default value and output value respectively. If you have changed some output values or default values, you can simply type "??" to get the original values back.
After you have input physio-chemical properties, you will be required to provide tonnage information and use patterns. Then click "next" and "next" until you see PECs calculated by EUSES (please refer to later example).
Tip 1: If you enter the number first and then the unit, EUSES assumes that you want to enter the value in the given unit and does not convert the number. However, if you change the unit and not the number, EUSES assumes that you want to convert the number to this unit and recalculates it according to its new unit.
Tip 2: For your first assessment, please do not change any EUSES output values in the following pop-up screens. They are calculated by EUSES by using the information you have provided.
However, if you have actual data on partition coefficients (for example, organic matter-water partition co-efficient Koc), bio-concentration factors, or degradation data (DT50), you are recommended to input them to EUSES to do a refined assessment. Please refer to refined EUSES assessment at the end of this article.
EUSES output data includes all of the following:
Note: As a Tier 1 exposure estimation model, EUSES is simple to use and is specifically developed to quickly evaluate substances. However, EUSES is inherently conservative. Refined assessment or higher level models may be needed if a substance does not pass tier 1 risk assessment.
Let's assume that you need to calculate predicted environmental concentrations for substance A. The substance is to be imported to EU to formulate cosmetics. Its physio-chemical properties, tonnage information and use pattern is listed as follows. The selected assessment type is type I enviromental exposure (local scale and regional scale). The run mode is "interactive".
|Molecular Weight||240 g/mol|
|Melting point||105 Celsius Degrees|
|Boiling Point||210 Celsius Degrees|
|Vapor Pressure||0.0008 Pa|
|Water solubility||38mg/L (Qsar class: hydrophobics)|
|Tonnage info||Import 99t/y to EU, no production in EU|
|Emission fraction and emission days||
Here are the screenshots of inputting above values in EUSES step by step. User input values are marked in orange.
In absence of more specific emission fractions, default values based on ERCs can be used in EUSES to derive environmental exposure estimates(PECs).
Please note that the final PEC values are equal to the sum of regional PEC values and local PEC values. After you have obtained above PEC values, you can compare them with PNEC values to do risk characterization.
Instead of relying on the minimum info required by EUSES to calculate PECs, you can input more actual values (see table below) or replace some EUSES output values to do a refined assessment.
|Parameter||Default assessment||Refined assessment|
|Partition co-efficient and bio-concentration factors||They are calculated by QSAR models based on substance structure, melting point, vapor pressure and logKow.||Reliable measured data (e.g. organic carbon -water partition co-efficient Koc values, BCF value) should be used in preference to QSAR outputs.|
|Degradation in various compartments||They are estimated from bio-degradability screening study.||
Reliable measured degradation data (e.g. DT50 values ) should be used.
Lower DT50 values lead to lower PECs.
|Release factors or rates (before STP)||Default release factors based on the enviromental release categories of a use.||
The default release factor can be refined by taking into account i) release preventing techniques or ii) onsite RMM with set effectiveness. Release factors from industry-specific SPERCs can also be used.
Lower release factors lead to lower PECs
|Discharge rate of the biological sewage treatment plant (STP)||2 000 m3 /day||
For site-specific assessment, the flow rate can be changed according to the site-specific data.
Higher rate leads to lower PECs.
|Receiving surface water flow rate||18 000 m3 /day (corresponding to a dilution factor of 10)||
For site-specific assessments, the flow rate or the dilution factor can be changed according to the site-specific data.
Higher flow rate leads to lower PECs.
|Biological sewage treatment plant (STP)||By default, the releases to fresh and marine water are expected to be treated in a standard biological STP for all uses||
Choose use STP or by-pass STP based on actual situation.
Using STP lowers PECs.
|Application to agricultural soil of the sludge of the biological sewage treatment plant (STP)||The sludge is by default assumed to be applied to agricultural soil||
For site-specific assessments, if incineration or other waste treatment of the sludge is foreseen, then agricultural application of sludge does not take place.
Incineration lowers soil PECs significantly.
|Daily use amount at a site Annual use amount at the site||They are calculated from the “tonnage per use”||
The daily and annual use amount at a site for a use can be overwritten by the registrant based on actual situation.
Lower use amount leads to lower PECs.
|Daily widespread use amount in standard town||It is calculated from the “tonnage per use”, corresponding to the consumption in a standard town of 10 000 inhabitants, multiplied by a safety factor of 4||Registrants can overwrite this value, for example, if they have sufficient information to demonstrate that the use of the substance is evenly distributed in space and time. In this case, it is possible to divide the default tonnage by a factor of maximum 4.|
|Time pattern of release to water||Continuous||The pattern of release to water can be changed to intermittent (i.e. if the releases take place less than once per month and for no more than 24 hours).|
Good job. You have learned what EUSES and PECs are and how to use EUSES to calculate predicted environmental concentrations (PECs). Please subscribe our newsletter to keep updated of our new articles.
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