Pharmaceuticals

Pharmaceuticals can enter the environment via a number of channels including domestic waste, veterinary services, landfill leachate, animal husbandry, hospitals and healthcare facilities, and treated wastewater. While the UK is regarded as having a robust water management infrastructure, the compositional complexity of water makes the elimination of residuals difficult. Wastewater treatment plants follow a similar formula; 1) screen contents for large items (nappies, bricks etc), 2) sedimentation tanks allow organic solid matter to separate and settle in the form of slude, 3) aeration tanks pump water, air and bacteria through the wastewater, removing smaller sludge particles and harmful bacteria 4) finally, waster is moved to a second settlement tank, where useful bacteria and remaining sludge sink the bottom to be recycled back into the treatment process. This multi-staged operation may be harnessing various advanced technologies, but the fact remains, that trace quantities of pharmaceuticals are still detectable in both sludge and water downstream of treatment facilities.

In Kaspryzk-Hordern et al (2021) measured the presence of carbamazepine, a common anti-epileptic medication, in river catchments downstream of five WWTPs in South-West England. They found that on average, 3.4g day-1 of carbamazepine could be detected in receiving downstream waters. However, a weekly peak of 20.9g day-1 was noted across all sites. The authors attribute this anomaly to the existence of consumption-only and down-the-drain days. In the former, the population served by the WWTP is believed to be consuming their medications. In the latter, the population is thought to be improperly disposing of unused medication down sinks and toilets. The down-the-drain days create a spike in pharmaceutical concentrations that exceeds the capacities of WWTPs. Diclofenac, recently on the surface water watch list, was detected in 97% of Thames samples and above the proposed EQS of 0.1 mg/l in 12 samples. 

Pharmaceutical products in wastewater may result in the proliferation of antibiotic-resistant bacteria. Where wastewater containing these resistant bacteria is released directly into the environment, a serious problem arises. These water bodies can provide a hotbed for exchanging resistance genes between bacteria species. In the interest of mitigating the antibiotic-resistant public health crisis, wastewaters must receive effective treatment. Even with sophisticated water-treatment technologies, the problem of residual pharmaceuticals - those in trace but not negligible quantities - remains. These residual pharmaceuticals journey from treatment plants to rivers, oceans, and lakes, disrupting aquatic ecosystems with a cornucopia of toxicologically complex compounds. 

The precise effects of residual pharmaceuticals in ecosystems and on human health are not well understood.  Understanding the physio-chemical interactions of pharmaceuticals and environments would require knowledge of the quantities, substances, biotic communities, water pH, and temperature. Given that environments, particularly water bodies, are changing constantly, the task of quantifying the toxicodynamics would be exceedingly difficult. In areas of the world where water treatment standards are low and vulnerable communities are regularly exposed to high concentrations of pharmaceuticals, the impact is clear. Among the known effects are antibiotic resistance, symptoms of endocrine disruption, and infertility. However, in areas where water treatment is highly regulated, but pharmaceuticals are constantly drip-fed into water bodies causing low-level chronic exposure, a knowledge gap exists. What is known is that pharmaceuticals can accumulate in river sediments, soils, fish tissue, and crops. From there, pharmaceuticals can circulate back into food chains, disrupt ecosystems, derail microbial balance in soil and water, and deplete oxygen availability in water. 

Eamples of species known to be affected by pharmaceuticals.