Bloodborne pathogens are microorganisms that can cause disease in humans and are carried by which of the following?

Bloodborne pathogens are specifically defined as microorganisms that are present in human blood and can lead to diseases if transmitted through blood. These pathogens, which include viruses such as hepatitis B, hepatitis C, and HIV, thrive and are spread via the bloodstream. This close association with blood is what classifies them as "bloodborne."

The other options, while potentially involved in transmission of certain other diseases, do not align with the definition and characteristics that define bloodborne pathogens. Saliva, air, and sweat can be vectors for pathogen transmission in general, but they are not the primary mediums for bloodborne pathogens, which rely specifically on blood for their transmission and harm. Therefore, recognizing that blood is the medium through which these particular pathogens are carried provides clarity on the nature of bloodborne diseases and the importance of safety measures to prevent exposure, such as in healthcare and other environments where contact with blood is possible.