Follow-up to ecological risk assessment of organotin substances on domestic substances list: chapter 6

6. Sources of Uncertainty

Predicted concentrations of organotins in water and sediments, based on estimated usage, release rates and treatment efficiency, are considerably higher than those reported in the 1994 survey. It must be recognized, however, that the survey focused on harbours, marinas and shipping lanes, and it is quite possible that sampling was not done in the areas of highest industrial releases of organotins.

Experimental K_ow values are lacking for most organotins, making estimates of bioaccumulation and partitioning to sediments uncertain. K_ow values can be extremely difficult or impossible to determine for organotin substances that are practically insoluble in water, because the presence of even a small amount of a more water-soluble impurity (i.e., <<1%) significantly increases the amount of tin in the water phase (IUCLID, 2002b). Estimations of K_ow may not be accurate for organotin substances that hydrolyze quickly, and the hydrolysis of organotins is controversial (Environment Canada, 2006).

Several subcategories of organotins have been detected in sediments, but sediment toxicity studies have been carried out only with tributyltin.