In order to study the purity of recycled fibre‐based materials, products containing recycled fibre as well as recycled pulp were examined with regard to their chemical impurities, toxicity and microbiological quality. The study was carried out to clarify both qualitatively and quantitatively the variations in microbiological quality. The levels of several classes of chemical substances were analysed and semi‐volatile and volatile substances identified. The toxicity and mutagenicity of virgin fibre and recycled fibre materials were screened using the Photobacter toxicity test and the Ames Salmonella mutagenicity test. Preliminary chemical characterization of the mutagens was carried out. Identification of the compounds found in the mutagenic fractions was performed by gas chromatography/mass spectrometry (GC/MS). The concentration of various substances analysed was found to be low, although the variety of substances present appeared to be very broad. Preliminary chemical characterization revealed that some samples contained compounds known to have mutagenic or other toxic activity. Also, the recycled fibre pulps contained large amounts of various microbes, the microbial load consisting mainly of aerobic spore‐forming bacteria. The paper‐making process was found to clearly have reduced the total microbial counts.