This study used semipermeable membrane devices (SPMDs) to identify industrial effluents that induce mixed function oxidase (MFO) activity in fish cell lines. Investigators deployed SPMDs for two weeks at three pulp mills and one oil sands facility, and at two tributaries near Fort McMurray, Alberta. SPMDs provided samples of known exposure time in effluents and river waters by simultaneously sampling the effluent stream and the river upstream and downstream of the mixing zone at each site. In addition, the investigators conducted laboratory experiments with rainbow trout to quantify the MFO response in fish exposed to various concentrations of the oil sands effluent.