Urban Streams Have Higher Levels of Contaminants (image) Cary Institute of Ecosystem Studies Share Print E-Mail Caption The type and abundance of pharmaceutical contaminants vary along an urban-to-rural gradient. More developed, urban streams have higher levels of contaminants, and the microbial communities in these streams reflect that history of exposure. Credit AJ Reisinger Usage Restrictions To promote this press release. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.