Swedish researchers are sounding the alarm about bisphenol A, which is a very common plastic chemical but which, if released, can damage people's ability to have children.
Tomas Östberg, an environmental chemist at the Jegrelius Institute, says that there could be a "hidden flood" of a dangerous substance.
He also says that what is important is that there are alternatives, so that the problem has a solution.
Swedish supermarket chains are already saying that they'll go over to receipts that are free of bisphenol A, but the substance is used in all sorts of tickets and receipts, says Tomas Östberg.
"It is everything from train, plane and bus tickets, to betting slips, parking tickets, queue slips in shops - and we have found bisphenol A in all receipts."
The reason is they all are made from so-called 'thermopaper', which is useful because it changes colour by being heated - which means a clear print without using toner.
In the summer there were fears because of bisphenol A being present in the plastic used to make some baby bottles - but researchers say that the amounts found in receipts are 1000 higher, and that they are spred far more easily.
The European Food Safety Authority is considering sharper laws on the use of bisphenol A, but also claims that the current limits are safe.
Sweden has demanded that the limit be raised, and is considering a national ban.