Chemical Exposures as Risk Factors for the Development of Thyroid Cancer

Area of Science:

• Environmental Health
• Oncology
• Toxicology

Background:

• Thyroid cancer (TC) incidence has increased globally in recent decades.
• Traditional risk factors do not fully explain this rise, necessitating research into environmental influences.
• Investigating environmental chemical exposures is crucial for understanding TC etiology.

Purpose of the Study:

• To review the scientific literature on the association between environmental chemical exposures and thyroid cancer.
• To identify specific chemicals linked to increased thyroid cancer risk.
• To evaluate the strength of evidence and identify research gaps.

Main Methods:

• A narrative review of existing scientific studies.
• Inclusion of research on per- and polyfluoroalkyl substances (PFAS), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), phthalates, phenols, nitrates, and polycyclic aromatic hydrocarbons (PAHs).
• Synthesis of findings regarding the association between these chemicals and thyroid cancer.

Main Results:

• Evidence suggests an association between per- and polyfluoroalkyl substances (PFAS) and polychlorinated biphenyls (PCBs) exposure and thyroid cancer, especially papillary thyroid cancer.
• Nitrate exposure, even at accepted safe levels, has also been linked to thyroid cancer.
• Associations for phthalates, PBDEs, phenols, and PAHs are less consistent and require further study.

Conclusions:

• A link exists between certain chemical exposures and thyroid cancer development.
• Current evidence is insufficient to establish a causal relationship due to study limitations.
• Further research is essential to inform public health policies and clinical guidance regarding environmental risk factors for thyroid cancer.