Pharmaceutical drugs are becoming more ubiquitous as access to medicines improves worldwide and millions of tonnes are produced annually. Active ingredients found in prescription medications, over-the-counter remedies and veterinary treatments have led to significant advancements in human and animal health. The growing accessibility of these drugs across diverse populations promises to save countless lives and enhance overall well-being. However, a less positive aspect of their widespread use is their discharge into the environment. Pharmaceuticals have been found in wastewater, surface water, sediments, groundwater and drinking water as a consequence of inappropriate disposal, treatment and management—and all of these contaminated waters inevitably reach the ocean, contributing further to the global problem of ocean pollution.

Over the last few decades, pharmaceuticals have emerged as a major group of environmental contaminants. One study measured the presence of 61 different pharmaceuticals, including antihistamines, antibiotics and heart medicines, across 258 rivers including the Thames in London and the Amazon in Brazil. Results revealed contamination on every continent, and more concerningly that a quarter of the sites contained potentially harmful concentrations of certain drugs. They also showed strong correlations between socioeconomic factors and polluted rivers, with older residents, unemployment and poverty rates all associated with higher levels of pharmaceutical pollution. While areas with more people discharge more drugs, the interconnectedness of the global water cycle means that similar pollutants have been found in the polar regions, reaching as far as Antarctica.

Although the largest global source of pharmaceutical pollution is patient excretion following the use of a medicine, many municipal sewage treatment plants were not designed to eliminate medicinal waste. Professor Kenneth Leung, director of the State Key Laboratory of Marine Pollution in Hong Kong, explained the scale of the problem. “We have found that many of these chemicals could not be removed by conventional sewage treatment and they accumulate in the environment, eventually reaching a concentration that can trigger a negative impact on wildlife,” he said.

Most of these chemicals are not highly persistent, with their degradation rates ranging from almost complete to limited. The problem is that their continuous addition to the environment in small amounts will make them “pseudo-persistent”—persisting in the environment not due to their chemical qualities, but due to endless replenishment from their source.

As some of these compounds demonstrate toxicity even at very low levels of exposure, there are mounting concerns about their impact on marine life as they become increasingly prevalent in bodies of water. The effects of chemical exposure on marine animals during the early stages of life may not be observed until adulthood, making correlation difficult to establish. Some documented effects include the feminisation of fish and amphibians when exposed to traces of oral contraceptives, and altered fish behaviour after exposure to residues of psychiatric drugs – these altered behaviours include increased risk-taking and disordered movement patterns and migration, which negatively impact the animal’s responses to predators.

Until recently, pharmaceutical pollution in waterways was thought to be a greater threat to aquatic life than human health. However, the consumption of water contaminated with trace amounts of active ingredients has caused adverse effects in humans. One of the most concerning possibilities is antibiotics in the environment contributing to antimicrobial resistance. These risks have resulted in more widespread recognition of a need for monitoring and stewardship of medicines in order to minimise environmental exposure.

Although the chemical and pharmaceutical industries have taken steps to reduce the environmental consequences of their products through the principles of green chemistry, the nature of pharmaceuticals means they will always present some risk of harm. A range of strategies are required to reduce pharmaceutical waste.

“If a pharmaceutical is effective, it will probably also be toxic to the environment. In these circumstances we need to optimise or reduce their use,” explained Professor Leung. “We have to use a risk management-based approach; it depends on how much is being used, how much is discharged, the persistence and toxicity, and the potential for accumulation.”

Examples of risk management strategies include prescribing antibiotics only when needed, and disposing of expired or unused medicines correctly rather than flushing them. Some countries have voluntary disposal systems, like Australia and the US, where patients may return unused medicines for proper disposal. Additionally, advanced wastewater treatment processes like ozonation, nanofiltration or reverse osmosis can remove most pharmaceuticals effectively. These are more expensive than conventional treatment processes and remain rare, particularly in low-income countries and regions, which are the most vulnerable to pollution. Still, some countries, such as Switzerland, have successfully upgraded their wastewater treatment systems to incorporate some of these processes.

Pharmaceutical contaminants are only a part of the problem with healthcare waste. The healthcare industry is heavily reliant on single-use plastics, making it a major contributor to the plastic pollution problem. As the industry expands with increasing sophistication and more medical products are delivered across the world, more waste is being created and improved disposal methods are required.

Large amounts of plastic waste are generated at healthcare facilities worldwide, but only a small share is recycled. Much of it ends up in marine ecosystems and eventually become microplastics. The covid-19 pandemic contributed to an increased demand for plastic, much of it mismanaged, which reached the ocean and affected marine life. One report estimated that 1.56 million facemasks entered the ocean in 2020, leading to cases of marine organisms becoming entangled in or ingesting the covid-19 waste. This produced tragic images of seabirds and marine mammals helplessly trapped in plastic, often resulting in their death. While medical-grade plastic is vital for protecting human health, it cannot simply be thrown away and forgotten about.

As single-use plastics remain the cleanest, most efficient way to facilitate health and hygiene in healthcare facilities, it is difficult to cut down on plastic use in the medical field. However, ongoing discussions around sustainability in medical plastics include experimenting with bioplastics such as polylactic acid, which can be recycled to produce lactic acid, and polyhydroxyalkanoates, which are biodegradable.

Although human health rightfully remains the primary focus of the medical field, mounting evidence suggests that potentially harmful pharmaceutical residues are accumulating in our water supplies. The long-term effects of these contaminants may not become apparent for years or even decades. Consequently, the healthcare industry must now broaden its perspective to consider the environmental impact of its products. A more holistic approach is essential to safeguard human health in the long term, as environmental and human well-being are inextricably linked.