Cunningham C, Li S, Vizeacoumar F, Bhanumathy K, Lee J, Parameswaran S, et al ivermectin side effects For example, for chemicals with short biological half lives, such as bisphenol A BPA, urine concentrations from one person can vary over the course of a single day because exposure occurs at meals and the compound is rapidly metabolized and excreted Teeguarden et al