People in the United States took more prescription drugs than ever last year, with the number of prescriptions increasing from 3.99 billion (with a cost of $308.6 billion) in 2010 to 4.02 billion (with a cost of $319.9 billion) in 2011. Those numbers and others appear in an annual profile of top prescription medicines published in the journal ACS Chemical Neuroscience.

Make what you will of the fact that antipsychotic drugs were the 5th most common by type. And these are only the prescription drugs, the amount of non-prescription pharmaceuticals and pharmaceuticals for veterinary and husbandry purposes would be hugely more.

Whatever the amount of drugs prescribed, it is the fate of those drugs that will concern us. Some part will not be taken by the patients, stored for some time and then disposed directly. Fortunately, many US towns have regular drop-off schemes which are hugely successful in capturing waste pharmaceuticals that would otherwise go down the drain or into domestic waste. Most waste pharmaceutical capture schemes do not promote the collection for disposal of empty drug containers, only unused and unwanted drugs, so although individually tiny the cumulative burden of the trace amounts of drug residue in those empty containers may by significant and in this area more work is required.

And the rest, that fraction that is taken as prescribed. Some is metabolised in the body and some excreted unchanged. But whether it is a range of metabolites or the unchanged drug, out it will come, in tears and saliva, skin and hair, and perhaps even on the breath of patients though these are just relatively trivial routes for excretion applicable to only some small range of drugs. The majority however will appear in faeces and urine, particularly the latter. Down the drain and along the foul sewer, or even pissed up against a lamppost, it makes massive contribution to the environmental burden of pharmaceuticals, making other lesser escape or release routes effectively trivial.

Do we deal with these trivial contributions? Yes, of course, they must not be overlooked, but there is much to do first to consider the fate of excreted and waste pharmaceuticals, and to develop suitable interventions to assure environmental protection.