The environmental fate characteristics of industrial biocides used in oil and gas applications are of increasing concern due to the industry’s drive for sustainable best practices and regulatory pressure on water use and disposal. A detailed understanding of the environmental impact of biocides is critical to their safe use and requires extensive testing. This paper will review current data on the environmental fate and ecotoxicity of commonly used oxidizing and non-oxidizing biocides in oil and gas applications. All of the biocides have some level of inherent toxicity to non-target aquatic species. Ecotox profiles versus aquatic invertebrates fish and algae will be presented. Environmental toxicity may be reduced or eliminated following degradation of the biocide active ingredients under environment conditions. Key elements of the efate profile include biodegradability bioaccumulation end-product formation and chemical stability (hydrolysis photolysis). The specific pathways of biotic and abiotic decomposition and current methods for deactivation of the biocides will be reviewed.