The most appropriate reference to consult for information regarding the safe handling and potential hazards of a chemical substance is a:

A Drug Utilization Review (DUR) is primarily focused on evaluating prescribed medications to ensure they are used safely and effectively. While it may provide some information about drug interactions and therapeutic use, it does not address the safe handling or hazards associated with chemical substances.

A Medication Guide is a document that accompanies prescription medications and provides essential information to patients about the drug's usage, side effects, and precautions. However, it is not intended for handling or safety instructions regarding chemicals in a laboratory or industrial setting.

A Risk Evaluation and Mitigation Strategy (REMS) is a program mandated by the FDA to ensure that the benefits of certain medications outweigh their risks. While it relates to drug safety, it does not provide the detailed chemical hazard information necessary for safe handling of chemical substances.