Over the years, Varanasi's research demonstrated how marine organisms accumulate and process environmental contaminants such as hydrocarbons, the toxic components of petroleum products. She and her team studied the health of fish in the Puget Sound near Seattle, and acquired expertise in oil spill detection and rapid analysis. Those methods were used during NOAA's seafood safety response after environmental catastrophes, including Exxon Valdez oil spill in Alaska, the Persian Gulf War, Hurricane Katrina and Deepwater Horizon disaster in the Gulf of Mexico.