Using cold running water to wash fruit and vegetables may not be enough to remove pesticides, a new paper published in the American Chemical Society’s journal Nano Letters has found. The report states that “the risk of pesticide ingestion from fruits cannot be avoided by simple washing other than peeling.”

Authors Dongdong Ye, Ke Zheng, Shaobo Han and colleagues developed a high-tech imaging method to detect low levels of common pesticides. Their findings suggest that removing agricultural chemicals may take more than a rinse and that pesticide contamination goes further than skin-deep.