Which type of chemicals are not required to be disclosed according to safety regulations?

The correct choice is proprietary chemicals. These are substances that a company has developed and wishes to keep confidential for competitive reasons. Proprietary chemicals may include formulations that are not disclosed to the public, even if they present health or safety concerns. Regulatory agencies often provide exceptions for proprietary information to protect intellectual property, meaning that specific details about these chemicals do not have to be disclosed as part of safety regulations.

This understanding contrasts with the other types of chemicals listed in the question. For instance, hazardous chemicals must be disclosed according to safety regulations to ensure that individuals and organizations are informed about potential risks and can take appropriate safety measures. Similarly, organic and common chemicals may also fall under regulations requiring disclosure for safety and health considerations. Hence, proprietary chemicals are unique in that they are often exempt from mandatory disclosure, thus making this answer the best fit for the question.