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The harmful effect of a combination of Substances of Very High Concern (SVHCs or Zeer Zorgwekkende Stoffen, ZZS)) may be greater than the effect of each individual substance. Very limited consideration is given to such combination effects when issuing permits. It is also not established how many SVHCs ultimately enter the soil or water from the air. This is the result of an exploratory study by RIVM.
The precise effect of combinations on human and environmental health is mostly unknown. RIVM is recommending several ways to take this into account in the permit granting process. RIVM stresses that, aside from the combination effect, it is always important for human and environmental health to emit the lowest possible level of SVHCs into the living environment.

Scientific research shows that substances with the same toxic effect create a combination effect. Examples of substances where this is the case include polycyclic aromatic hydrocarbons (PAHs), dioxins and certain pesticides. A combination effect may also occur because substances with different effects still ultimately damage the same organ in the human body. The severity of these effects depends on the composition of the combination, the concentrations and the harmfulness of the individual substances, and may differ per location. In all cases, one fact remains the same: the lower the emission, the smaller the chance of harmful effects on humans and the environment.

Companies need a permit before they can discharge SVHCs into the water and air. This permit is usually granted per individual substance, although companies often emit a combination of hazardous substances. Another uncharted issue is how many of these substances and their combinations ultimately end up, via the air, in the soil and in surface water (deposition). To address this, RIVM is making a number of recommendations in this exploratory study.


Adjust the permit granting process
The government can make policy that reduces the chance of combination effects of SVHCs. This is in line with the European Commission’s Chemicals Strategy for Sustainability, which stresses the need to address the issue of substance combinations.
RIVM is proposing several options to take combination effects and the deposition of SVHCs and other substances into account in the permit granting process. Its advice to the government is to elaborate these options further.

Reduce SVHC emissions
The emission of SVHCs is already subject to strict conditions. By lowering the maximum emission of individual substances by a specific calculation factor, the likelihood of harmful combination effects will be reduced. This is one of the technical RIVM proposals that requires further exploration.

Map out local situations
More research is required to map out the locations in the Netherlands where SVHCs enter the air, water and soil the most. These locations can then be prioritised to prevent combination effects.

Conclude partnerships
In order to ensure that RIVM proposals are practical and workable, it is important to work together with stakeholders, such as environmental agencies.

RIVM conducted this exploratory study on behalf of the Ministry of Infrastructure and Water Management.