What product was produced at the same plant as PBB and contributed to contamination?

• A. Magnesium oxide
• B. DDT
• C. Formaldehyde
• D. Mercury

Answer: (A)

Cross-contamination from a multi-product facility is the key idea. When a single plant runs different products on shared equipment, residues from one product can end up in the next batch if cleaning isn’t thorough. In this historical case, the plant that produced polybrominated biphenyls (PBB) also manufactured magnesium oxide. The shared processing lines and inadequate separation allowed PBB residues to contaminate cattle feed made at the same site, so the contamination could spread into dairy animals and their milk. The other substances listed were not produced at that plant in this incident, so they don’t fit the contamination source. This example shows why strict controls and dedicated equipment are crucial in feed mills to protect milk safety.