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How to modify/add new information to inorganic substances.

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27 Jun 2018
#1
D_Avila
D_Avila's picture
How to modify/add new information to inorganic substances.

I am calculating the environmental impacts of the chemicals used in fracking. I already now from USEtox which chemicals are "missing" information. 

For instance, the following are missing information to calculate the CF at endpoint category to freshwater. 

7664-93-9
142-87-0
112-57-2
68-11-1

Reading the manuals (and from inputs from colleagues), I know that possibly the fate and exposure factors are in the database, but the effect factors not. I also know that with ECOSAR from the EPA I can get the EC50 which is necessary to calculate the EFeco (USEtox documentation p. 167 & 168).

However, the questions are:

1. How can I modify or input this information into USEtox so I can proceed with my calculations?

2. If I can modify the values, from where should I do so? From the USEtox main file or the organic database? And from which tab?

3. If I have to input a new chemical with the information from ECOSAR, will this information be "paired" with the information in USEtox?

I would appreciate a lot your input here as I am little bit stuch with these chemicals. I evaluating more than 3K different recipes and so far I am missing 104 chemicals.

Kind regards.

Daniel Avila

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29 Jun 2018
USEtox Team
USEtox Team's picture
Adding ecotoxicity effect factors in USEtox

Generally, the appraoch to obtain a log(HC50) from a set of individual EC50 data points is described in detail in Section 10.2 of the USEtox documentation. This can also be done in any version higher than USEtox 2.0 via the user interface wizard that pops up when opening the USEtox.xlsx model file.

Resulting log(HC50) values can be inserted either in the tab "Substance data" of the respective substance database file or of the USEtox model file. When using the substance database file, original values for e.g. EC50 can be inserted in the respective tabs 

When you precalculate new log(HC50), your underlying data will not be paired with existing data that were used to calculate log(HC50) that already exist in USEtox as in case of existing log(HC50) values in USEtox it is recommended to use these for comparabilty reasons.

Some additional notes regarding above-mentioned substances:

  • CAS 7664-93-9 is an inorganic acid. Inorganic substances other than metal ions can currently not be characterized by any available LCIA method including USEtox. To be able to characterize inorganic substances, chemical- and compartment-specific reaction kinetics and dynamics would need to be developed that are currently not yet avaialable/not mature enough for inclusion into USEtox.
  • CAS 112-57-2 as ionizable hygroscopic liquid substance can basically be characterized in USEtox and potentially other LCIA toxicity methods, but it is outside the appliability domain for most QSAR models implemented for estimating parameters from Kow (CAS 112-57-2 has log Kow < -3). Hence, results for this substance should always be flagged and interpreted with caution.
  • The other two CAS are strongly ionizable substances that should be carefully characterized, especially when they have more than one ionic form (as is the case for many surfactants and pharmaceuticals).
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