Dealing with waste pharmaceuticals is currently something of a hot issue, for wards and clinics, for patients in their own home, for manufacturers and pharmacists, and others, and for all of those others working at the farthest end of the disposal chain.

When pharmaceutical wastes enter the disposal chain, waste processing is expected to satisfactorily destroy or otherwise minimise any likely adverse environmental impact. Dispersal and dilution and a disposal option simply will not do. Instead, the environment agency continues with its policy – something of a one-man policy – to demand ever more complex assessments of waste treatment technologies.

Regrettably, the scientific integrity that underpins those Environment Agency demands is paper thin. This has been adequately discussed on the Clinical Waste Discussion Forum on previous occasions. In summary, there is little understanding of the impact of native drug or of its perhaps many and varied thermal degradation products, nor of the other thermal degradation products of each and every compound present in waste, including the very bag or box into which it has been placed.

Further concerns must focus on the meaning of an empty syringe that in almost all other legislation is taken at face value, though the Environment Agency (England) consider that to be insufficient since there might be a few residual molecules of drug substance still present. Fortunately, we need not go far from home as Scotland takes a more enlightened view and considers an empty syringe as free of any significant residue, and does not worry unduly about the occasional tablet or capsule that might find their way into an orange waste sack.

But setting all that aside, if only temporarily, there is much research in hand to evaluate methods for the safe destruction or capture of waste pharmaceuticals. The latter is particularly important, since the real issues arise out of the excreted drug dose and capture in wastewater and sewage is the greatest necessity.

Bulk solid pharmaceutical wastes will generally be incinerated. But other technologies are available, though generally intended for processing of wastewater outflows, of untreated sewage or of sewage treatment outflow. This addresses the possible environmental impact of that part of the administered dose which is excreted in urine. At anything up to 98%, it is this massive fraction which is of significance, while a few stray capsules in an orange sack can reasonably be disregarded.

Ion-exchange resins and reed bed filtration have both proved successful in pilot and subsequently in more extensive filed trials. Now, the use of ultrasound has been investigated.

Atenolol is a β-blocker drug and an identified emerging pollutant. Advanced oxidation processes (AOPs) utilise the reaction of a highly oxidising species (hydroxyl radicals, ^•OH) for the mineralisation of emerging pollutants since conventional treatment methodologies generally fail to degrade these compounds. In the present work, degradation of atenolol was carried out using ultrasound with frequencies ranging from 200 kHz to 1 MHz as a source of hydroxyl radical. The degradation was monitored by HPLC, total organic carbon (TOC) and chemical oxygen demand (COD) reduction and ion chromatography (IC). Nearly 90 % of degradation of atenolol was observed with ultrasound having 350 kHz. Both frequency and power of ultrasound affect the efficiency of degradation. Nearly 100 % degradation was obtained at a pH of 4. Presence of various additives such as sodium dodecyl sulphate, chloride, sulphate, nitrate, phosphate and bicarbonate was found to reduce the efficiency of degradation. Although nearly 100 % degradation of atenolol was observed under various experimental conditions, only about 62 % mineralisation (from TOC and COD measurements) was obtained. Nearly eight intermediate products were identified using high-resolution mass spectrometry (LC-Q-TOF). These products were understood as the results of hydroxyl radical addition to atenolol. The degradation studies were also carried out in river water which also showed a similar degradation profile. A mechanism of degradation and mineralisation is presented.

Nejumal KK, Manoj PR, Aravind UK, Aravindakumar CT. Sonochemical degradation of a pharmaceutical waste, atenolol, in aqueous medium. Environ Sci Pollut Res 2013; DOI 10.1007/s11356-013-2301-x