Which incident would constitute an exposure to bloodborne pathogens?

A needle stick injury constitutes an exposure to bloodborne pathogens because it involves a direct puncture of the skin by a needle that may be contaminated with blood. Bloodborne pathogens are infectious microorganisms present in human blood and can cause diseases such as hepatitis B, hepatitis C, and HIV. When a needle, which may have been used on an infected patient, penetrates the skin of a healthcare worker, pathogenic blood can enter the worker's bloodstream, leading to potential infection.

In contrast, while a patient coughing or droplets of saliva may pose a risk for airborne or droplet transmission of infections, they are not considered direct exposure to bloodborne pathogens. Using contaminated dental tools could lead to other forms of infection, but it does not involve direct exposure in the same way that a needle stick does.