When people get ill, we mostly take medicines, get better, and by and large that’s the end of the story. For scientists studying our waste water however, it’s only the beginning. What’s often overlooked is that humans will then excrete pharmaceuticals such as antibiotics and antidepressants, with much of this waste ending up in the wild. Water treatment plants can filter out some of these drugs, but studies have demonstrated that persistent pharmaceutical residues are still sneaking through the metaphorical net.
What happens when these drugs enter our waterways? Diana Aga, a professor in the chemistry department at the University at Buffalo has been trying to answer this question. She explains that the results can be both varied and alarming. ‘Antibiotics are most interesting because at very low levels they encourage the development of antimicrobial resistance,’ she says. ‘Some major drugs are no longer effective in killing pathogens and that’s because pathogens have developed resistance.’ When it comes to human health this is certainly the most dangerous consequence. However, as Aga explains, there are also many other surprising consequences when it comes to fish and wildlife.
‘Two years ago, we showed that antidepressants that are excreted by humans end up in rivers and lakes, with fish then accumulating them in the brain,’ says Aga. ‘You have this effect – we call it “happy fish” because they’re under the influence of antidepressants. We haven’t yet shown it in the wild, but in lab experiments the fish don’t avoid predators anymore. The long-term effect might be a collapse in biodiversity.’
Other drugs can also have dramatic effects on ecosystems. Release of birth control pills into the wild has long been linked to endocrine disruption in fish. This can lead to males producing eggs or females no longer producing eggs. Some fish have even been shown to develop both female and male sex organs.
Aga and her team have been analysing how wastewater treatment plants could be adapted to avoid this problem. The most common method at such plants is called ‘activated sludge’, which involves microorganisms breaking down organic contaminants. But this is only partly effective when it comes to pharmaceuticals. Aga has demonstrated that adding two more processes known as ‘granular activated carbon’ and ‘ozonation’ can reduce the concentration of escaped residues by more than 95 per cent. These processes increase the cost of treatment considerably, but Aga emphasises that it’s a good investment. In particular, as populations grow and more and more cities worldwide consider recycling wastewater into drinking water, it could prove essential in preventing the drugs we take to cure us causing more harm than good.