Even treated sewage can have substantial effects on our ecosystems [5]. Residual nutrients can cause eutrophication, resulting in algal blooms that kill fish and other aquatic life deprived of oxygen. Furthermore, pharmaceutical chemicals are known to disrupt the hormones of aquatic species. For example, co-exposure to nano-plastics and endocrine-disrupting chemicals – such as those found in pharmaceuticals and personal care products – disrupt reproductive functions in fish by altering hormone levels and impairing gamete development [6]. A study on the estuarine mummichog (Fundulus heteroclitus) found that exposure to synthetic estrogen (found in birth control pills, which enters water systems via human urine) during early development altered sex determination and feminised male fish [7].

So, what can be done to reduce our reliance on CSOs and prevent sewage discharge?

Accountability and transparency are setting the wheels in motion to ensure that water companies face consequences. CSO monitoring has increased since 2024, with every storm overflow in England now fitted with an event duration monitor [4]. Installing separated, rather than the current combined, sewage and surface water systems on new developments would also help to reduce our reliance on CSOs. Nature-based solutions – such as desealing urban areas for better drainage, reinstating wetlands, or installing sustainable urban drainage systems – would increase water storage in the soil to offload stress from the grid [2].

England’s Environment Agency is taking enforcement actions against water companies where it finds evidence of illegal dry spilling [4]. However, while recent enforcement resulted in over £6.9 million in fines for law-breaking water companies, this penalty is a drop in the ocean. To put this figure into perspective, since the privatization of the water system in 1989, a staggering £74.2 billion in dividends has been paid out to private shareholders and investment [8]. By prioritizing corporate payouts over upgrading outdated infrastructure and upholding environmental responsibility, the system is prioritizing profit over public health and environmental safety.

Figure 2: Sewage pipe on beach. By Eric Jones (2011). Licensed under CC BY 2.0.

Illegal use of CSOs is dirtying the U.K. ‘s waters. This not only threatens public health, but also aquatic life through eutrophication and the long-term effects of chemicals and plastics found in sewage.

Momentum is building to improve the situation with increased monitoring of CSOs, separate water and sewer systems for new developments, and nature-based solutions like reinstating wetlands and urban desealing. Yet, as long as corporate profits and shareholder dividends are prioritised over infrastructure upgrades, regulatory fines will remain a drop in the ocean.

Ultimately, the cleaning of the nation’s waters depends on sustained public pressure forcing corporate accountability, strict enforcement and improved infrastructure.

Cover image: Seven Sisters cliff, East Sussex, England. Photo by Luca Upper on Unsplash.