What type of contamination occurs if a paint chip falls in soup?

The answer is chemical contamination.

The paint of the paint chip is a mixture with may chemicals that are not safe to health but hazardous, so you must inmediately think that a food contaminated with paint should be properly discarded.

Paint include voc (volatile organic solvents), chemical resins, pigments, oxides (dryers) which indeed are harmful if ingested.