Nonlyphenol ethoxylates are industrial compounds (often surfactants) used as detergents, emulsifiers and foaming agents in a long list of household products including toilet paper, plastics, pest sprays and personal care products. In the aquatic environment, they degrade into compounds that include 4-nonylphenol (4-NP), an endocrine disruptor that has been detected at elevated levels in marine organisms in California estuaries. The scientists leading this project suspect that septic tanks and toilet paper are a main source of 4-NP in the coastal environment and in this project will examine the consequences of the compound on the Pacific oyster, focusing on how (or if) the chemical alters the shellfish’s immune system. In experiments, oysters will be injected with the bacterium Vibrio campbellii (nonpathogenic in oysters) and V. harveyi (pathogenic in oysters). Scientists will then monitor the animals’ immune response vis-à- vis total hemocyte counts, superoxide anion production levels and hemocyte lysozyme activity. Changes in protein production in gonadal tissues and hemocyctes will be examined, and there will be an effort to detect changes in the transcription profiles (number of copies of mRNA from a specific segment of DNA) for genes involved with antimicrobial defense. Results will be shared with the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment, which has identified a critical need for targeted studies of 4- NP toxicity on marine organisms.