Oxygen consumption is indicative of an organism's metabolic state, whereby alterations in respiration rate can result from the presence of different stimuli. Here, we develop a novel approach based on quenched fluorescence oxygen sensing and respirometry method for toxicity screening assays using the nematode Caenorhabditis elegans. Previously, C. elegans was established as a useful model in soil and aquatic toxicology studies. For existing toxicology screening approaches with C. elegans, however, the endpoint is lethality. In addition, the assay time frame for the existing approaches is considerably longer than that for the approach described here. We present a sensitive, robust, high-throughput platform using standard laboratory equipment for toxicological studies by measuring respiration rate in C. elegans animals using a phosphorescent probe.