Which of the following is not a part of standard precautions?

Standard precautions are infection control practices used in healthcare settings to prevent the transmission of infectious agents. They are designed to protect both the healthcare worker and the patient.

The correct choice here is "isolation precautions." Isolation precautions refer to specific measures taken to prevent the spread of infections that are known or suspected to be contagious. They are applied to patients with certain infections that require additional measures beyond standard precautions, such as contact, droplet, or airborne precautions.

On the other hand, the other options are foundational elements of standard precautions. Hand hygiene involves thorough washing or sanitizing of the hands to reduce the risk of spreading pathogens. Personal protective equipment (PPE) consists of barriers such as gloves, masks, gowns, and eye protection to help prevent transmission when there is potential exposure to blood or bodily fluids. Environmental cleaning refers to the routine cleaning and disinfection of surfaces and equipment in healthcare settings to reduce the risk of infection.

Thus, "isolation precautions" stands apart from standard precautions, as it involves additional measures tailored for specific situations rather than the broader application aimed at all patients.