| Virtually nil. Farmers (and employees certified/licensed to apply sprays) generally only spray in favourable conditions. Eg. Calm conditions where the output doesn’t go beyond a few meters of the intended swath. Given the cost, it makes little financial sense to waste it on non-target plants. And while nearly any pesticide/herbicide/fungicide will tell you to suit up and use a respirator, it’s usually because of the (often petroleum derived) volatiles used in the mixture to ensure stability and proper spreading rather than the active ingredient itself. Glyphosate (RoundUp) for example interacts with a biochemical pathway that doesn’t even exist in humans, yet still suffers from the legacy and cultural entrenchment of a paper that has since been refuted and retracted. The infamous “roundup causes cancer” paper where the author used lines of lab rats that were (intentionally, for use in cancer studies) genetically predisposed to developing tumours. The volatiles evaporate and break down rapidly, which is why a freshly sprayed field will have an odd aroma for several hours after application. Meanwhile these sprays come with a PHI (post harvest interval), whereby if a producer is following laws and regulations, the active ingredient itself is virtually undetectable at the time of harvest due to UV/heat/microbial degradation. PHIs are determined empirically by testing sprays across environments and conditions for years before certification, then still including a buffer period to account for outlier conditions where a chemical may persist beyond what was observed. |