Not all of the information that you need for this project will be found in the scholarly literature. Instead, you will have to investigate applied resources to find certain types of information. For example, if you need official environmental sampling data collected by a government agency, you will want to search for that agency's publications rather than scholarly literature.
The repositories below are good places to look for raw sample data on health-related topics. Video demonstrations of several of them are embedded at the bottom of this page.