A major worry associated with prolonged, low-level PCB exposure is:

The concern regarding prolonged, low-level exposure to polychlorinated biphenyls (PCBs) primarily relates to their association with serious health effects, particularly reproductive problems and certain types of cancer. PCBs have been classified as probable human carcinogens by multiple health and environmental agencies. This classification is based on studies indicating a link between PCB exposure and various forms of cancer, including liver cancer.

When considering health risks, the potential for PCBs to disrupt the endocrine system is significant, which can lead to reproductive issues. However, the overarching worry that emerges from long-term studies, particularly the ones involving workers exposed to high levels of PCBs, is the development of cancer, including liver cancer. The mechanism by which PCBs may contribute to cancer involves their accumulation in the body's fat tissues and their ability to induce cellular changes that can lead to malignancies.

Awareness of the carcinogenic nature of PCBs, especially in the context of occupational exposure and environmental contamination, underscores the health risks associated with both acute and chronic exposure to these compounds.