Eh, well, Handymax bulk ships (https://en.wikipedia.org/wiki/Handymax) are 200m long with 5 holds, so that's ~40m long holds, ~30m wide, and at a guess 20m deep. Contaminants picked up around the sides are likely below tolerable levels. (Heck, your bakery is probably schlepping around flour on conveyor belts exposed to greases, oils, etc. Ain't none of this stuff sterile.)
