short time period. The data are used for the development of appropriate precautionary statements for pesticide product labels. Acute studies identify: Dermal toxicity Eye irritation Inhalation toxicity Oral toxicity Skin irritation Skin sensitization PBO has a low acute toxicity by oral, inhalation, and dermal routes in adults. It is minimally irritating to the eyes and skin. It is a not a skin sensitizer. Dermal absorption The available data indicate that less than 3% of the amount on the skin (forearm) is absorbed over an 8-hour period. Other studies with a pediculicide formulation indicate that about 2% crossed the skin and about 8% crossed the scalp. Endocrine disruption The Food Quality Protection Act (FQPA) of 1996 required the United States EPA to address the issue of endocrine disruption. Since the passage of the FQPA, the US EPA has developed a two-tiered endocrine disruptor screening program (EDSP) designed to examine potential effects of substances on the estrogenic, androgenic, and thyroid (EAT) hormone systems in both humans and wildlife. Tier 1 consists of 11 assays, and is designed to determine whether a substance has the potential to interact with the EAT hormone systems. If results indicate a relationship, the chemical progresses to Tier 2 testing. The purpose of Tier 2 is to determine whether a substance that interacts with the EAT hormone system exerts an adverse effect in humans or wildlife, and to develop a dose-response that, in association with exposure data, can be used to assess risk. PBO is one of the chemicals selected by EPA to be part of the initial effort under the EDSP. The EPA issued its first list of chemicals for EDSP testing in 2009, consisting of over 60 pesticide chemicals, including the insecticide synergist PBO. The first list of chemicals for EDSP screening is not based on a potential for endocrine activity or a potential for adverse effects. Rather, the list is based on an EPA prioritization regarding exposure potential. PBO was added to this list because of its wide use pattern (1500 products registered with US EPA), and people may be exposed to low levels of PBO in their diets, from treated surfaces in their homes (e.g., carpet), and in certain occupations (e.g., pest control operators). No evidence suggests that PBO disrupts the normal functioning of the endocrine system. This includes the recently developed data to assess the possible interaction of PBO with the endocrine system.