Abstract
BACKGROUND: Many pesticide products are mixtures of multiple chemicals. These include active ingredients intended to kill pests, and so-called inert ingredients intended to improve the physical characteristics of the product. In addition, shortly before applying a pesticide product, applicators often mix adjuvants into the sprayer tank. Adjuvants are products designed to improve the performance or physical properties of a pesticide spray mixture. Manufacturers may use a particular chemical compound both as an inert ingredient within pesticide products and as a component of adjuvant products. Nonetheless, regulations dictate that data on use are publicly available only for the portion used in adjuvants. Adjuvants are exempt from federal registration, but are defined as pesticides in California. Based on that definition, California has identified α-(p-nonylphenyl)-ω-hydroxypoly(oxyethylene) (APNOHO) as the most widely used pesticide in the state, applied to more than 10 million acres annually. That quantified use includes only agricultural acres treated with adjuvants containing APNOHO. Total APNOHO use is likely higher because manufacturers also use the chemical as an inert ingredient within pesticide products, although data on such use are shielded by regulation. OBJECTIVES: We use APNOHO as a case study to demonstrate that the use of adjuvants and inert ingredients is difficult to track because relevant information is not publicly available. We synthesize information that suggests widespread agricultural use of alkylphenol ethoxylates, such as APNOHO, may pose significant human and environmental health risks. We then make recommendations for future research and policy. METHODS: We used information from California's pesticide use reporting system and the U.S. Environmental Protection Agency (EPA) to estimate use of APNOHO. We used U.S. EPA and European databases, as well as published research, to identify human and environmental health hazards of APNOHO. We focused on research showing that APNOHO is an endocrine-disrupting chemical. DISCUSSION: Within California, APNOHO is applied in more than 150 adjuvant products. Nationwide, it is used as an inert ingredient in at least 650 pesticide products. Exposure to APNOHO is associated with endocrine disruption, birth defects, and aquatic toxicity. We suggest that the case of APNOHO illustrates the larger problem of a lack of publicly available data on use and toxicity of many adjuvants and pesticide inert ingredients. We recommend that researchers and regulators include adjuvants and inert ingredients when evaluating pesticide hazards, including endocrine disruption. We also recommend regulatory requirements to identify all ingredients on product labels. https://doi.org/10.1289/EHP10634.