The ETX software program calculates a (log) normal distribution through toxicity data entered by the user.

This gives a species sensitivity distribution (SSD). This distribution is subsequently tested for statistical criteria on normality. The estimated 5th percentile and median of the calculated distribution are presented, each with their respective two-sided 90% confidence interval. With the calculated SSD the fraction of affected species at a given environmental concentration can be estimated, or an expected ecological risk (EER expected ecological risk (expected ecological risk )) at a series of environmental concentrations. The program also offers the opportunity to estimate the 5th percentile of very small data sets using the so called small sample method.


Recurring error messages about 'Microsoft's Data Acess Components (MDAC)' and 'Microsoft.ACE.OLEDB registration' prompted us to update the software. With the present version (2.3, August 2020) these issues are solved.


The techniques offered with ETX are used in risk assessment and in derivation of environmental quality standards (EQS Environmental Quality Standards (Environmental Quality Standards )) in the Netherlands and Europe. The techniques are frequently used in the field of ecotoxicology. The purpose of ETX 2.3 is to offer the user the calculation methods as described in the scientific literature. You can find an overview of the underlying literature in the Manual.

Download ETX

Download the program ETX 2.3

Download the file named ETX 2.3.msi onto your computer. Double clicking the file will invoke the program installer, which takes you through the installation process in just a few steps.

Software requirements

The Microsoft .NET framework is a prerequisite for installing ETX 2.3. This software package is already preinstalled when using Windows as operating system. In case it is not, the .NET framework version can be downloaded for free from the Microsoft website.

Make sure the Microsoft Access Database Engine 2010 Redistributable is installed on your computer. It can be downloaded from the following Microsoft website: After clicking on Download, two files can be selected. Select AccessDatabaseEngine.exe (do not select: AccessDatabaseEngine_X64.exe). The selected file is the 32 bit version of this software component. You should select this file, even if you have 64 bit computer. The reason is that ETX is a 32 bit program. After downloading, install the Access Database Engine by double clicking it and running the installation process.


Download the Manual

The manual was written for ETX version 2.0. The technical and scientific description in the manual still apply to ETX 2.3 as the content of the software was not changed.  Only the section of the manual pertaining to the installation procedure described in the manual of ETX 2.0 is outdated.

Citing ETX

The current version of ETX can be cited as ETX 2.3. The preferred citation can be found in the manual.


The current version (ETX 2.3) of this program was released in August 2020. The previous version (2.2) was released in September 2017;  ETX 2.1 was released in February 2015 and the first version (ETX 2.0) was released in 2004. The current update does not concern any technical, scientific changes.


There is no helpdesk to answer questions of users. However, we welcome your comments on the program and its functioning at