Most chipsealing in New Zealand is carried out using bitumen cutback (i.e. diluted) with kerosene. Under the new regulatory framework established by the Hazardous Substances and New Organisms (HSNO) Act (1996), bitumen with the addition of kerosene between 2.5–20% by weight has been classified as a 9.1C substance that is ‘ecotoxic to the aquatic environment’. Other (non-ecotoxicity related) classifications also apply. Cutback bitumens with more than 20% kerosene are not classified.
The 9.1C ecotoxicity classification is derived from a calculation based on the aquatic toxicity of kerosene. Implicit in this classification is the assumption that the kerosene in cutback bitumen has the same bioavailability as pure kerosene. The object of this research was to establish whether this assumption is valid and whether the 9.1C classification for cutback bitumens is warranted. The research focused solely on aquatic ecotoxicity; other possible environmental affects of cutbacks in the atmosphere or terrestrial environment caused by toxicity or mechanical fouling were outside its scope.
As a review of the literature failed to find any experimental data on the aquatic ecotoxicity of cutbacks, an experimental programme was undertaken.
Keywords: aquatic ecotoxicity, bioaccumulation, bioavailability, bitumen, classification, cutback bitumen, ecotoxicity, environment, hazardous substance, kerosene