(Pictured Above) Dr Amrit Kaur Purba, Assistant Professor and Wellcome Fellow, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine
In the 19th century, our politicians woke up to the dangers of unclean water. London’s aptly named ‘Great Stink’ of 1858 forced MPs to revolutionise the sewer network, and then the 1875 Public Health Act was passed, fuelled by new understanding of germs and disease, tackling cholera with regulations to ensure safe drinking water.
That combination of crisis and new research being turned into government policy lay behind what remains one of the biggest changes to public health regulation in our history.
Now we stand on the threshold of a new era in public health: online safety. We must take it just as seriously as polluted water, and address it in the same way – through regulation that protects the public, grounded in a clear understanding of how harms spread and affect behaviour.
Unregulated social media platforms such as TikTok, X, and Instagram, are increasingly becoming environments where harmful content, such as violence, disinformation and hate speech, can spread rapidly.
This is why I’m pleased to have launched the Digital Determinants of Health Hub [AP1] at the London School of Hygiene and Tropical Medicine[AP2] , funded by the Wellcome Trust. Its purpose is to bridge the gap between research and policy by generating actionable causal evidence on digital harms and how to prevent them. The Hub is supported by a Youth Advisory Group to ensure young people’s voices are central, and a Policy Advisory Group, including the Scottish Violence Reduction Unit, drawing on Scotland’s track record of leading the way in violence prevention. I recently spoke at their conference on this issue, where it was clear that the same leadership must extend to digital environments.
Exposure to harmful content may have significant impacts on young people, particularly during critical stages of development. While the comparison is not exact, there are important parallels with earlier public health challenges, where risks were initially poorly understood but carried substantial consequences if left unaddressed. In the same way that polluted water once spread harm invisibly through communities, harmful digital content may now be shaping behaviours in ways we are only beginning to understand.
There is growing concern that social media may contribute to violence among young people, including knife crime. While the pathways are complex, online environments can influence the norms and expectations that underpin real-world interactions.
Social media platforms are driven by algorithms designed to maximise engagement. In practice, this can prioritise content that provokes strong emotional reactions. For some young users, this may include repeated exposure to content that normalises or glorifies violence, conflict and retaliation – a form of “digital pollution” that is difficult to see, measure or regulate.
Over time, this may influence how violence is perceived – not as exceptional, but as routine or even acceptable. In some cases, online disputes can escalate into offline conflict, with digital interactions acting as a catalyst rather than a separate space.
These risks are particularly relevant during adolescence, a critical developmental period in which identities, values and social norms are still forming. Just as exposure to polluted water once had disproportionate effects on vulnerable populations, repeated exposure to harmful content may have lasting implications for young people.
Recent legal cases reflect growing recognition of these issues. This week, a Los Angeles court ruled in favour of a young woman who argued that social media platforms contributed to harms to her mental health. While such cases are complex, they signal increasing scrutiny of the environments platforms create.
If left unaddressed, these patterns may contribute not only to individual harm, but to wider societal challenges, including pressure on criminal justice systems and communities already disproportionately affected by violence.
History offers a useful parallel. Efforts to clean up the water supply were met with resistance from vested interests. Today, parts of the technology industry raise similar concerns about the impact of regulation on innovation. Yet just as unregulated water systems once posed risks to public health, unregulated digital environments may now be contributing to harm at scale.
In the UK, the Online Safety Act (2023) represents an important step forward. However, significant gaps remain. Content related to violence and knife crime often operates through coded language, imagery and cultural references, making it harder to detect, much like early public health threats that were not immediately visible but no less harmful. At the same time, changes in platform governance may influence digital environments globally. As with water systems, what happens in one place can have consequences elsewhere.
Addressing these challenges will require a coordinated public health response. Technology companies hold significant power, and their priorities do not always align with violence prevention. Greater transparency and accountability are therefore essential.
A key priority is improving independent access to platform data. At present, researchers and policymakers see only fragments of the digital environment, while the systems shaping exposure remain largely opaque. Without this visibility, it is difficult to identify where risks are concentrated or how harms spread. The rapid development of generative AI adds further complexity, increasing both the volume and speed at which content can be produced and shared. But technology can also form part of the solution, helping to detect harmful content, monitor digital environments in real time, and support more transparent oversight.
This will require independent regulation, meaningful access to data, and collaboration between governments, researchers and organisations such as the Scottish Violence Reduction Unit.
The public health community now faces a familiar challenge: how to act on emerging evidence before harms become fully entrenched.
Social media is now deeply embedded in young people’s lives. We cannot remove it, but we can improve the safety of the environments it creates. Like water, digital spaces are something we rely on every day – and their quality matters.
The lesson from history is not just that we acted, but that we acted before the full scale of harm was understood. The question now is whether we are prepared to treat harmful online content as a form of pollution that requires intervention, or whether we will wait until the consequences become impossible to ignore.
By Dr Amrit Kaur Purba, Assistant Professor and Wellcome Fellow, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine
Digital-determinants-of-health-hub@lshtm.ac.uk
www.linkedin.com/company/digital-determinants-of-health