How to Calculate German Water Hazard Class (WGK)

Little Pro on 2016-01-08 Views:  Update:2018-10-17

German Water Hazard Class (WGK) sometimes is also called German Water Endangerment Class (WGK). This is often included in the section 15 of SDSs. German's Federal Water Act requires that facilities handling substances that are hazardous to waters must be built and operated in a way that water bodies are protected from pollutions. To this end, the Water Hazard Class (WGK) of a substance or mixture has to be determined based on the Administrative Regulation on the Classification of Substances Hazardous to Waters (VwVwS; amended in 2005), communicated and documented.

There are three water hazard classes (WGK) for chemicals under the German Federal Water Act. Non-hazardous to waters can only be claimed if there is sufficient data to support it.

  • 1: low hazard to waters;
  • 2: hazard to waters;
  • 3: severe hazard to waters;

In this article, we will show you how to determine the Water Hazard Class (WGK) for substances and mixtures and how to document them in a compliant way. To start with, you need to be aware that there are 4 important annexes attached to the VwVwS. We will need to refer to them frequently.

  • German Water Hazard Class Substance List 1 (Annex I): List of substances already classified as non-hazardous to waters by German authority;
  • German Water Hazard Class Substance List 2 (Annex II): List of substances for which the Water Hazard Class (WGK) has already been determined and published by German authority;
  • Annex III: Guidelines on the Classification of Substances and Mixtures into Water Hazard Classes;
  • Annex IV: Recommended template for the documentation of the Water Hazard Class (WGK) for a substance or a mixture.

Determination of German Water Hazard Class (WGK) for Substances

For substances listed in annex I or II, you could directly refer to the WGK given in annex I or II. For substances that are not listed in annex I or II, you need to carry out your own classifications, document them and submit the documentation-form (annex VI) to the Office of Documentation and Information on Substances Hazardous to Waters at the Federal Environment Agency.

For an unlisted substance, you could easily determine its WGK in three steps:

Step I: Obtain the following hazard data at least:

  • Acute oral or dermal toxicity to mammals (e.g. LD50 in rats) and other chronic effects;
  • One piece of data on aquatic toxicity - fishes (acute), daphnia (acute) or algae);
  • Biodegradability;
  • Potential for bioaccumulation.

Step II: Determine evaluation points for the substance's health hazards and environmental hazards according to table 1 and table 2.

How to Calculate German Water Endangerment Class (WGK) How to Calculate German Water Hazard Class (WGK)

  • Low solubility in water (less than 100 mg/l in the case of gases and solids, less than 10 mg/l in the case of liquids);
  • No toxicity at saturation levels (tested with at least two organisms: fishes, daphnia or algae);
  • Ready biodegradability in the case of organic liquids;

Please note that if any data is missing, conservative default value shall be used. You shall always use the most sensitive value.

Determination of Water Hazard Class (WGK) for Mixture

All mixtures have to be self-classified. The WGK of a mixture should be determined either by using a calculating rule and the WGK of each component of the mixture or on the basis of experimental test data generated with the mixture.

To determine the WGK for a mixture, you need to obtain its composition info and determine the WGK for each component first. Then the mass fractions of the individual components are added up by their WGK, and the WGK of the mixture is then determined according to the table below.

Mixture German Water Hazard Class (WGK)

Example 1: If a mixture contains less than 5% of WGK 2 components and no WGK 3 components, this will classify the mixture as WGK 1;

Example 2: If a WGK 3 component with a concentration of 0.05% is added to a substance non-hazardous to waters, the mixture is classified as WGK 1. If the substance contains this component as an impurity resulting from the production process, then it will be classified as "non-hazardous to waters".

Components are taken into account if their fraction exceeds the following thresholds:

  • 0.1% in the case of carcinogenic substances
  • 0.2% in the case of all other substances;
  • If carcinogenic substances are actively added to a mixture and their fraction is less than 0.1%, the mixture is classified at least into WGK 1;
  • the same applies when the fraction of WGK 3 additives is less than 0.2%.

Reminder 1: The self-classifications of mixtures do not need to be submitted to the Federal Environment Agency. However, the documentation (recommended template) of the said classifications must be made available to the local competent authority of the federal state of Germany where the facility is located.

Reminder 2: An important difference between WGK-classification and other classification systems is that substances currently insufficiently investigated, not jet classified or not chemically identified are regarded as highly hazardous to waters (WGK 3) for reasons of precaution.

Now go and calculate your own WGK!! Share this page if you like it.


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