Maximum expected environmental concentration

This gives an example of fate modeling in which the risks of an insect growth inhibitor, CGA-72662, in aquatic environments were assessed using a combination of the SWRRB and EXAMS mathematical models.. Runoff of CGA-72662 from agricultural watersheds was estimated using the SWRRB model. The runoff data were then used to estimate the loading of CGA-72662 into the EXAMS model for aquatic environments. EXAMS was used to estimate the maximum concentrations of CGA-72662 that would occur in various compartments of the defined ponds and lakes. The maximum expected environmental concentrations of CGA-72662 in water were then compared with acute and chronic toxicity data for CGA-72662 in fish and aquatic invertebrates in order to establish a safety factor for CGA-72662 in aquatic environments. 

The toxicity of CGA-72662 to fish and daphnids was determined from aquatic laboratory tests. The LC5Q was then compared to the maximum environmental concentration of CGA-72662 expected (from EXAMS) in ponds and lakes. The ratio of LC. /MEC is... 

SCCPs are persistent and bioaccumulative, and thus concentrations in the environment and biota are expected to increase with continued release to the environment. Standard risk assessment methods comparing effect levels to environmental concentrations may underestimate the risk of persistent and bioaccumulative substances, such as SCCPs. Persistent substances can take decades to reach a maximum steady state concentration in the environment, resulting in an underestimation of the potential exposure to these compounds if steady-state has not been achieved, and releases into the environment continue. Similarly, it can take a long time for persistent and bioaccumulative substances to reach a maximum steady-state concentration within an organism this is supported by the observations of Sochova et al., [62] who noted an increase in toxicity of SCCPs for longer exposure duration with nematodes. The durations of standard toxicity tests may be insufficient to achieve the maximum tissue concentration, resulting in an underestimation of the effect threshold. 

In general, concentrations of PCDDs/DFs have decreased in all media (Fig. 2.13). Decrease in ambient air was significant with annual incremental decreases observed. For instance, the declines in all of arithmetic mean, median, and maximum concentrations were significantly correlated with those in annual emission of individual years presented in Fig. 2.5a (r>0.7, / <0.05). An eight-fold decrease was observed over a period of 6 yr. This decline in concentrations of PCDDs/ DFs is related to regulation of emissions in South Korea. Because most of environmental release occurs primarily into air, residues in other media would also be expected to follow the same declining trend observed in air. 

Some tertiary containment assessments have considered the environmental receptors surrounding the installation and potential pathways for pollution flows. However, many concentrated solely on assessing the maximum practical use of installed containment capacity, and determining the consequent fire-fighting attack duration. Buncefield showed that consequences might be much more extensive than expected. 

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