In today’s age, plastic waste is a major problem for our environment. The decomposition of plastic waste causes widespread contamination in all types of ecosystems worldwide. Micro-plastics in the lower micrometer size range and especially nano-plastics can become internalized by cells and thus become a threat to human health. To investigate the effects of internalized micro- and nano-plastics on human gene transcription, we used an in vitro assay to quantify CREB (cAMP response element binding protein) mediated transcription. Here we show that CREB mediated gene expression was mainly but not exclusively induced by phosphorylation. In addition, the amount of CREB affected transcription was also studied. We were also able to show that the strong CREB mediated stimulation of transcription was diminished by micro- and nano-plastics in any chosen setting. This indicates a threat to human health via the deregulation of transcription induced by internalized micro- and nano-plastics. However, this established quantifiable in vitro transcription test system could help to screen for toxic substances and non-toxic alternatives.