Female follicular structure

There have been reports of increased incidence of urinary tract tumors and thyroid tumors in rats exposed chronically to trifluralin. Trifluralin is structurally similar to ethalfluralin, which is a known carcinogen in rats, and formulations contain N-nit-roso-di- -propylamine, an omnipresent contaminant, also a known carcinogen. Trifluralin has been classified as a group C (possible carcinogen) due to evidence of increased combined malignant and benign urinary bladder tumors in female rats and renal pelvis carcinomas in male rats. There is also evidence for an increased incidence of thyroid and follicular cell tumors in male rats. 

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