Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:6:p5
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 6 (pt 5/5)
Character Range: 1478240–1479589

in different compartments of the environment (for example, soil, water, sediment). Basically, these plot toxicity data (one value per species) as a cumulative frequency distribution against the concentration at which the toxic effect occurs. A statistical distribution is then fitted to the plot from which it can be estimated what concentration is required to protect any chosen percentage of species. In Australia, the SSD method used to derive guidelines uses the Burr type III family of distributions and is called the BurrliOZ method.
Statistically significant effects are effects (responses) in the exposed population which are different from those in the controls at a statistical probability level of p <0.05.
Steady state is the non-equilibrium state of a system in which matter flows in and out at equal rates so that all of the components remain at constant concentrations (dynamic equilibrium).
Water to soil partition coefficient (Kd) is the ratio of the concentration of a contaminant in soil pore water to that in the solid phase of soil at equilibrium. The units are L/kg. This contaminant property is affected by physicochemical properties of the contaminant and the soil. This property is usually expressed as a logarithm (that is, log Kd). In this guideline, chemicals with log Kd <3 are considered to have the potential to leach.