Toxaphene distribution in the Lake Superior trout and associated sublethal ecological risk: a probabilistic approach

Toxaphene concentration in Lake Superior is increasing despite a complete ban on its usage in North America. It is speculated that it is carried through long-range transport mechanisms from the southern US fields to Lake Superior. A mathematical fate model is used to estimate the toxaphene concentration by incorporating plankton, benthos, sculpin, smelt, alewife and trout in the food web. Planktons and benthos are assumed to be in equilibrium with water and sediments, respectively. Monte Carlo (MC) simulations using Latin Hypercube Sampling (LHS) are performed to estimate toxaphene concentration and its associated uncertainties in the food web. The ecological risk is characterized based on toxaphene concentration calculated in trout tissues. The maximum acceptable toxicant concentration (MATC) is estimated from an acceptable risk of growth inhibition in trout. The one hit model is used for risk characterization and a cumulative distribution function (CDF) of risk is developed. The analysis shows a median value of risk of growth inhibition in trout is below 6%.