Which of the following is the best example of secondary contamination?

Secondary contamination occurs when a person, object, or area becomes contaminated as a result of something or someone that has already been contaminated. This can happen through various means, such as indirect contact or through the environment becoming contaminated.

In this context, contact with runoff from firefighting operations on ignited material exemplifies secondary contamination because the runoff may carry hazardous materials away from the original source, affecting people or the environment that were not in direct contact with the initial contamination. This situation illustrates how an individual can be exposed to hazardous materials without being in direct contact with the source, which is the essential characteristic of secondary contamination.

The other scenarios do not fit the definition of secondary contamination effectively. Direct contact with a toxic substance represents primary contamination, where an individual is directly exposed to the hazardous material. Inhalation of hazardous vapors is also a form of direct exposure and primary contamination, as is absorption through the skin from a chemical spill. These actions involve directly interacting with the contaminants, not through indirect means like runoff or the environment.