Submitted to: Archives of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2007
Publication Date: 1/5/2008
Citation: Moore, M.T., Greenway, S.L., Farris, J.L., Guerra, B. 2008. Assessing Caffeine as an Emerging Environmental Concern Using Conventional Approaches. Archives of Environmental Contamination and Toxicology. 54:31-35. Interpretive Summary: Caffeine has been suggested as a novel rice seed treatment for deterrent of blackbirds, but its effects on aquatic non-target organisms has not been thoroughly examined. A suite of 48 h and 7 d toxicity assessments using US EPA-approved standardized organisms were conducted examining lethal and sub-lethal (growth and reproduction) effects of caffeine. Caffeine concentrations eliciting lethal and sub-lethal responses were above concentrations typically seen in streams across the U.S. Use of caffeine as a rice seed treatment should pose negligible risk for most aquatic non-target organisms, should runoff occur.
Technical Abstract: Organic wastewater contaminants, including pharmaceuticals, caffeine, and nicotine, have received increased scrutiny because of their detection in water bodies receiving wastewater discharge. Despite recent measurement in US streams, caffeine’s effect on freshwater organisms is not well documented. The present study measured caffeine’s lethal and sub-lethal effects upon the freshwater species, Ceriodaphnia dubia, Pimephales promelas, and Chironomus dilutus. These organisms used in standard testing or effluent monitoring were exposed to aqueous caffeine solutions under static exposure for 48 hours and daily renewed static exposure for seven days. Averaged responses of 48-h acute endpoints indicated C. dubia was more sensitive to caffeine exposures (LC50 = 60 mg/L) than either P. promelas (LC50 = 100 mg/L) or C. dilutus (LC50 = 1230 mg/L). Exposure-response slopes confirmed these findings (3% mortality / mg/L for C. dubia; 0.5% mortality / mg/L for P. promelas; and 0.07% mortality / mg/L for C. dilutus). Comparative seven-day responses between C. dubia and P. promelas (LC50 = 46 and 55 mg/L, respectively) were more similar than the broad range of acute values. Sub-lethal effects measured for caffeine exposure included impaired C. dubia reproduction (IC50 = 44 mg/L) and inhibited P. promelas growth (IC50 = 71 mg/L). Caffeine should pose negligible risk for most aquatic vertebrate and invertebrate organisms when results of this study are combined with earlier studies reporting environmental concentrations and product half-lives.