Ecological Analysis of the Association Between 2,4-Dichlorophenoxyacetic Acid (2,4-D) Exposure and Thyroid Cancer Incidence in the United States

Background/Objectives: The increasing incidence of thyroid cancer in the United States suggests a possible role for environmental exposures that potentially alter thyroid hormone regulation through cellular toxicity. 2,4-Dichlorophenoxyacetic acid (2,4-D) is a commonly used herbicide that can act as an endocrine disruptor and may be toxic to the thyroid gland. This ecological study examined county-level associations of 2,4-D use and age-adjusted incidence of thyroid cancer in the United States.