Human exposure to pesticides and thyroid cancer: a worldwide systematic review of the literatures.

Thyroid cancer is considered as one of the most prevalent cancers in the world. Some pesticides can play a role as a potentially important risk factor in thyroid cancer by affecting thyroid morphology and thyroid hormone homeostasis. The aim of present study was to systematically review the available epidemiological evidence for human exposure to pesticides and thyroid cancer. Articles were searched in PubMed, Scopus and Web of Science by suitable keywords from January 2000 to May 2021. Standard techniques for systematic reviews were followed in the current study and results reported according to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Based on the inclusion and exclusion criteria, finally seven studies including four cohort studies and three case-control studies were reviewed. Organochlorines (OCPs) in more cases, Organophosphates (OPs) and Carbamates insecticides, herbicides and fungicides were the studied pesticides. Inconsistent results were reported in the surveyed articles on the OCPs. Two articles on the Carbamates (Carbaryl and Mancozeb) showed consistently an inverse association between exposure and thyroid cancer. Increased risk of thyroid cancer due to the exposure to the Malathion was reported in one article on the OPs. Due to the limited current knowledge about the effect of pesticides on thyroid cancer in humans, human health policies must be implemented to control individual's exposure to chemicals through using of botanical pesticides in agricultural. Also, more studies must be done to fill this gap of knowledge.