Spores are everywhere, particularly in soil, so they can be present in crops in particular, especially root veg. Whilst washing removes gross debris, you'll never wash all the bacteria from the surface. To a greater or lesser degree all primary foods have a low level of contamination. Whether that contamination becomes an issue depends upon handling, storage and processing conditions (and processing includes what happens in the home).
Consider what comes in with harvest from fields, all kinds of stuff, dirt, rodents, insects, metal, stones etc. etc. The processing of rice is fairly crude too and so there will be present in the processing plant environment and in the final product some B.cereus organisms which could potentially cause harm down the line.
Other pathogens such as E.coli and Salmonella which are indicators of feacal contamination can also be present in vegeatables from cow poo (or other animal faeces). There have been many classic food poisoning outbreaks from salad, one from Parsley, unpasteurised apple juice where river/flood water from cow-fields have contaminated either the water courses/supply of the veg itself, washing won't remove sufficient contamination and hence people/kids get sick. The miracle is that the incidence of harm for the amounts consumed round the world are pretty low indeed!