Correlation between blood ethylenethiourea and thyroid gland disorders among banana plantation workers in the Philippines.

Ethylenebisdithiocarbamates (EBDCs) are metabolized into ethylenethiourea (ETU), a possible human carcinogen and an antithyroid compound. In this study our goal was to correlate ETU levels with the incidence of thyroid gland disorders among banana plantation workers exposed to EBDC. We randomly selected 57 directly exposed workers and 31 indirectly exposed workers from four banana plantations and 43 workers from an organic farm; all subjects underwent complete medical examinations and laboratory tests. Results showed a higher mean thyroid-stimulating hormone measurement among exposed workers compared with the control group, although the levels were well within normal range. Nine of the exposed farmers had abnormal thyroid ultrasound findings, consisting mostly of solitary nodules, compared with three among the control group. Analysis of variance showed significantly different blood ETU levels among the directly exposed, indirectly exposed, and control groups (p < 0.001), but ETU levels in urine were not significantly different (p = 0.10). Environmental ETU levels were below the U.S. Environmental Protection Agency remediation levels. Among farmers with solitary thyroid nodules, we found a very good direct correlation between the size of the nodule and blood ETU level. In this study we showed that blood ETU is a more reliable biomarker for EBDC exposure than urinary ETU; therefore, the determination of blood ETU should be part of medical surveillance efforts among workers exposed to EBDC to detect occurrences of thyroid gland disorders.