Pesticides as risk factors for head and neck cancer: A review.

Humans may be exposed to pesticides such as fungicides, herbicides, and insecticides, during occupational and non-occupational activities. Pesticides could be related to cancer development mainly because of their effects on the endocrine and immune systems and their cumulative effect. The present review evaluated in current literature evidence of an association between exposure to pesticides and the occurrence of head and neck cancer (HNC). A literature search for cohort studies was conducted in the PubMed, Web of science, and Cochrane databases. Methodological quality of each study was rated with the Scottish Intercollegiate Guidelines Network (SIGN) checklist. One thousand one hundred and thirty-two studies were identified. Thirty-two were included. Most of the studies found addressed occupational exposure to pesticides and were conducted in Europe and North America. Eleven high-quality studies were found. Most of them found no association between exposure to pesticides and increased risk of HNC. Two studies found some evidence of a positive association between pesticide (malathion and atrazine) exposure and thyroid cancer. The literature review does not support a clear evidence for association between pesticides exposure and HNC. Only limited evidence points to a positive association between exposure to some pesticides and thyroid cancer. Further standardized studies based on appropriate designs are required to clarify the effect of pesticides on the genesis of HNC, considering dose, length of exposure, and type of pesticide.