Types of literature

A description of the types of literature.

A primary study produces results by creating new data and analysing it, whereas a secondary study makes use of already published data to combine and synthesize it in a larger dataset, to give a broader overview of the scientific evidence. In summary, both primary and secondary literature produce new scientific results but differ in their data source.

Primary scientific literature

Primary scientific literature is reports on studies that collected and analysed data either from the field, the lab or through statistical modelling. We did not perform primary scientific research in any of our projects presented on this website. However, we collected primary scientific articles for two of our projects: Burdens in wildlife and Cooking. In the example of Cooking, we collated primary scientific literature that performed lab experiments to investigate if cooking reduces the PFAS concentrations in seafood and fish. In our project Burdens in wildlife, we compiled primary scientific literature that collected data on the PFAS exposure of wildlife in the field.

Secondary scientific literature

Secondary scientific literature, or reviews, are studies that do not report on data directly from the field, the lab or statistical models. Instead, reviews compile relevant primary or secondary articles, extract and re-analyse or synthesize the data, and/or provide a narrative summary. There are many types of reviews. Refer to About research synthesis to learn more about the different types of reviews. All projects presented on this website are secondary studies/reviews. In the example of Cooking, we reviewed primary scientific literature on the reduction of PFAS concentrations in seafood and fish via cooking. We extracted the data produced by these primary studies and re-analysed them in a meta-analysis that produced a new overall outcome. In the example of our project Umbrella Review, we compiled secondary scientific literature on PFAS exposure and its consequences in humans, animals and the environment. We extracted relevant data and presented it as a Systematic Evidence Map.