There is a one in five chance that a packet of coffee beans sold in Europe contains residues of pesticides thought to have been erased during roasting, and in some cases include banned sprays that cause cancer, according to new research.

There is a “systemic pattern” of pesticides showing up again and again in beans from most major production regions, says Coffee Watch, a US-based non-profit organisation seeking to reform the global coffee industry.

Coffee Watch partnered with Pesticide Action Network (PAN) UK and German development groups Inkota-network and Deutsche Umwelthilfe to compile a report on “the hidden cost of coffee”, warning that “pesticides applied to coffee farms thousands of kilometres away travel to your cup far more often than consumers realise”.

The report, published on Tuesday, set out a warning to coffee drinkers that the “standard reassurance” given by companies – that residues are destroyed by roasting – is not always the case.

“Scientific evidence tells a more complicated, less comfortable story,” according to Coffee Watch, which said that some pesticides – those of “high thermal stability” – can bind themselves to a bean and emerge intact after roasting.