Pendimethalin is not registered as a herbicide for rice crops. The crop can be affected if you use that herbicide

Pendimethalin can be used as pre-emergent herbicide in rice fields at 3-5 days after transplanting in transplanted rice / 5-8 days after sowing in direct seeded rice 

Pendymethalin is used mixed with propanil 8-12 days after sowing as pre-emergent for weeds (post emergent for directed seeded rice). Could be a small affectation of rice (in not covered seeds), especially in roots (wider tips) but easily recuperated. Pendimethalin have poor solubility in water, in a normal application it remain in the soil surface and not reach the root area (position´s selectivity). Also can be used as pre-emergent in rice. In Central America is registered for rice.