The primary route of entry of PCBs into humans is:

PCBs, or polychlorinated biphenyls, are a group of man-made organic chemicals that were widely used in industrial and commercial applications before their harmful environmental and health effects were recognized. The primary route through which PCBs enter the human body is ingestion.

This occurs when individuals consume contaminated food or water. PCBs can bioaccumulate in the fatty tissue of animals and fish in aquatic environments, and as humans often consume these contaminated food sources, ingestion becomes the main pathway for exposure. When PCBs enter the digestive system, they can be absorbed into the bloodstream and distributed throughout the body, leading to potential health issues.

While inhalation and absorption can contribute to exposure in certain scenarios, such as occupational settings or through skin contact with contaminated substances, the most significant and common route for the general population is through the ingestion of contaminated food and liquids. Inoculation is not relevant in this context, as PCBs are not transmitted through vaccination or other means of direct injection. This highlights why ingestion is the primary concern when evaluating routes of exposure to PCBs.