Nijmegen environmental models allow risk assessment substances

Between 2008 and 2018 the European Union will have registered about 30,000 company-produced chemicals. More than a third of these substances have to be tested on their hazardous effects on health and environment. This new regulation on chemicals Registration, Evaluation and Authorization of Chemicals (REACH)  puts quite a burden on organizations. ‘It is impossible to test the effect of each individual substance’, said Jan Hendriks, professor of Environmental Science at Nijmegen University. ‘

Therefore we try to design models for different categories of substances. This has the added advantage that we can decrease the amount of animal experimentation.’ Recently two Nijmegen Ph D students of Hendriks’ each designed such a model.

Three criteria
For determining the effects of a particular substance three criteria are relevant. The first is persistence: how long will it take before a substance gets decomposed? ‘PCBs for instance have been forbidden for several decades now, but are still present in the environment in high concentrations’, said Hendriks.
The second criterion is bio-accumulation: what is the risk of the substance accumulating in the food chain? Bio-accumulation is often enough in itself to ban a substance, hazardous or not.

The third criterion is toxicity: will exposure to a particular substance be harmful to plant and animal life? Or the way Hendriks put it: ‘Will the creature succumb to the substance if it's exposed to it? Of crucial importance in this regard is to determine at what concentrations harmful effects do occur. Some chemicals are specially designed for killing organisms, e.g. control chemicals. In that case research is required to the selectivity of the chemical applied: does it only kill the pest or is it toxic to other organisms as well? 

Model metals
Up to now there are hardly any data available on bio-accumulation. Added to that, most studies are concerned with organic substances. In that respect the Ph D research by Karin Veltman is a major step forwards. She designed a model to predict bio-accumulation of metals in various organisms.

For this purpose she researched the general properties of various metals (amongst other properties the covalent index, which indicates to what extent metals tend to bond to bodily components like proteins) as well as species (including weight and rank in the food chain). Predictions on bio-accumulation were in agreement with the field data as far as model metals like cadmium were concerned. Organo-metals proved to be more complex, however, as they behave like a metal the one time and as an organic substance the other, making it difficult to capture them in a model.

’For pure metals the  model offers a reliable indication for the harmfulness of metals, which relieve organizations of much work’, argues Hendriks. This explains why Veltman's model is already applied by authorities to make risk assessments.

Itch
Not all organisms are equally sensitive to a substance. In the new European policy an effect in five percent of all organisms is considered acceptable. ‘We're talking about minimal effects’, Hendriks comments, ‘a creature is allowed to get itch from a particular substance, so to speak, but should not be killed by it.’

Mathijs Smit took a closer look at the in zijn proefschrift toxicity of substances released during the exploitation of oil, e.g. drilling grit. He compared effects on both individual and population level effects on cell and DNA level. Among environmental scientists there is heavy debate on what standard should be used. ‘We can distinguish between fundos en realos’, Hendriks explains. ‘The fundos believe that there should be no effect at all, not even at cell level. The realos on the other hand argue that the environment is full of stressors, including natural ones. This implies many changes on cell level.’ Hendriks deems himself a realo: ‘Ik think that the policy should focus on the effects on the level of the population. The extinction of a species is something to avoid, but the death of one single individual is perfectly ok.’

However, this is not say that Hendriks is claiming the research to effects on cell and DNA level, the so-called biomarkers, to be of no use. The value of such research is perfectly evident by Smit's doctorate thesis. He researched how biomarkers relate to effects on the organism level. On average the biomarkers turned out to be 30 to 50 times more sensitive. ‘This is valuable information for assessing the risk in case of higher substance concentrations.’ Smit's model already gets used as a basis for making risk assessments of plans for new oil platforms.

Export product
By now both Smit and Veltman are active in Norway; Smit works at STATOIL and Veltman has a position at Trondheim Technical University. Ph D students of Hendriks’ making a career abroad is the rule rather than the exception. ‘The Netherlands enjoy a worldwide repute in the

field of environmental science, which is making our scientists to major export products’, says Hendriks. ‘Being small and densely populated, the Netherlands were one of the first countries in the world faced with environmental effects. This surely accounts for the start of environmental research at an early stage.’

Characteristic of environmental science at Radboud University Nijmegen is the emphasis on theoretical-conceptual models that have predicting value and are tested by trial.
The Dutch-based expertise is applicable to every single ecosystem worldwide. Hendriks believes however that processes in arctic areas require more specific research. ‘Characteristic of arctic areas is that food chains are smaller so that these could get destroyed more easily. Furthermore it is believed that the course of processes in cold water is considerably different.’ Together with his two Ph D students in Norway Hendriks is preparing further research in the subfield of arctic environmental science.