He learned that 70% of produce items contain pesticide residues that are linked to possible health problems like cancer and Alzheimer’s—and washing only removes part of the contamination.

“If we could detect them, we could avoid consuming them, and reduce the risk of those health issues.”

His device, called PestiSCAND, employs spectrophotometry, which involves measuring the light that is reflected off the surface of fruits and vegetables. In his experiments he tested over 12,000 samples of apples, spinach, strawberries, and tomatoes. Different materials reflect and absorb different wavelengths of light, and PestiSCAND can look for the specific wavelengths related to the pesticide residues.