Looking into this, it's hard to say since there are contamination issues at every point between preharvest and the moment you put it into your mouth: https://ww

Looking into this, it's hard to say since there are contamination issues at every point between preharvest and the moment you put it into your mouth: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6899298/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6899298/ It doesn't seem to rank the causes it lists, but googling it suggests widespread contamination caused by fecal matter runoff from animal ag finding its way into irrigation water.