How to extrapolate across 100,000+ substances, sites and species with SSDs ?

Jan Hendriks
Radboud University, the Netherlands

Each second, 1 new chemical is added to the more than 65,000,000 already registered. In the EU, 100,000+ compounds are awaiting assessment while 1,500,000 contaminated sites potentially require clean-up. Worldwide, 8,000,000+ species, of which 10,000+ endangered, need protection (Hendriks, 2013).

At the same time, empirical research is severely limited by financial, practical and ethical constraints. Assessing 100,000+ substances at 100,000+ sites threatening 100,000+ species obviously cannot be achieved by toxicological testing only. As an alternative, I suggest that we focus on simple models. Instead of going for statistical regressions with the highest explained variability, we might attach more value to meaningful equations of which the coefficients and exponents can be interpreted physically.

We have derived and collected SSDs on toxic and non-toxic stressors to discern patterns across stressors, species and endpoints. In this contribution, some examples were discussed. We looked at (1) intra-species and inter-species variability, (2) the number of species included in an SSD, (3) SSDs across modes of action, (4) the combined use of SSDs for toxic and non-toxic stressors, (5) ‘field’-based SSDs (PNOFs) and (6) in vitro biomarker SSDs to in vivo bioassay SSDs (Azevedo et al, 2014; De Hoop et al, 2011; Elshout et al, 2013; Fedorenkova et al, 2010, 2012, 2013; Golsteijn et al, 2012, 2013; Hendriks, 2013, Hendricks et al, 2013; Smit et al, 2009.