Chapter 2

Risk assessment of chemicals

Test your skills as a risk assessor: We want to do a hazard assessment according to REACH for a simple industrial chemical that acts as baseline toxicant (i.e. has no specific modes of toxic action). The dimensionless air-water partition coefficient of the chemical is Kaw = 0.1, the octanol water partition coefficient is 100, the rate constant for degradation in air is ka = 0.5 d–1 and that for biodegradation in water is kw = 0.05 d–1. Is the chemical a PBT chemical? If you lack parameters, make an educated guess. Which additional parameters are needed to decide if the chemical is PBT (persistent, bioaccumulative and toxic)?

In probabilistic risk assessment you compare the distribution of exposure concentrations with the distribution of safe effect concentrations, e.g., NOEC values for chronic toxicity. These distributions are called species sensitivity distributions. Would it also be possible to use in vitro data for constructing effect distributions for human health risk assessment? Can you just take the measure in vitro effect data or do you need a specific extrapolation step before you can use them?
Could in vitro data be useful for application of the precautionary principle?