Studies at the University of Massachusetts showed that pesticides sprayed on apples penetrate 20% deep into the skin of the apple.
"So again, it turns out studies at UMass, University of Massachusetts, have studied if you take regular pesticides, spray them on an apple like in a conventional farm, basically the pesticides will penetrate 20% deep into the skin of the apple." (said at 0:20:11)
A 2017 study conducted at the University of Massachusetts Amherst (Yang et al.) evaluated the penetration of pesticides into apples and the efficacy of various washing agents. The researchers found that after 24 hours of exposure, 20% of the applied amount of the systemic fungicide thiabendazole (and 4.4% of the non-systemic insecticide phosmet) had penetrated into the apples. The speaker slightly mischaracterizes the metric by describing the 20% figure as a depth percentage ('penetrate 20% deep into the skin') rather than the fraction of applied pesticide quantity that entered the fruit tissue.
- context: Effectiveness of Commercial and Homemade Washing Agents in Removing Pesticide Residues on … (Journal of agricultural and food chemistry 2017)
"LC-MS/MS results showed, however, that 20% of applied thiabendazole and 4.4% of applied phosmet had penetrated into the apples following the 24 h exposure. Thiabendazole, a systemic pesticide, penetrated 4-fold deeper into the apple peel than did phosmet, a non-systemic pesticide, which led to more thiabendazole residues inside the apples, which could not be washed away using the NaHCO 3 washing solution." (abstract, results, passage verified)
pubmedfull study (doi)