Planetary health in practice: sensing air pollution and transforming urban environments

The paper frames air pollution as a planetary health problem that cannot be understood solely at the level of individual behaviour or population statistics, but through the infrastructures and environments that produce pollution. It positions planetary health as often focused on earth-systems overviews, and proposes a more situated, differential approach through citizen-sensing practices. The study asks three key questions: (1) How do citizens and communities document, monitor, and act upon air pollution as a problem of the health of environments? (2) How can a more situated understanding of the planetary allow attention to health practices and politics that emerge via efforts to shape environments? (3) How do citizens and communities compose more democratic, expansive possibilities for planetary health by forming and transforming environments and collectives? These questions shift focus from individual harm to environmental actions that constitute health as a planetary composition.

The article draws on science and technology studies, environmental justice, postcolonial theory, and planetary health literature. It situates citizen sensing within traditions of community-based evidence-making and challenges around achieving a "popular equality of perception" where lay experiences are often dismissed as anecdotal. Prior work shows community-generated information can improve environmental health decision-making and provoke collective action (e.g., Corburn; Bickerstaff and Walker; Epstein; Fortun et al.). It critiques planetary health framings that privilege universal systems, data gaps, and layered governance without addressing power dynamics and situated inequalities (Whitmee et al.; Hinchliffe et al.). The author engages Spivak’s re-imagining of the planetary to argue for diverse epistemes and situated struggles, highlighting how environmental injustices and governance structures shape exposure and the capacity to act (Bullard; Pulido; Sze; Walker).

Practice-based, participatory research within the Citizen Sense project in Southeast London. The team developed and deployed a low-cost DIY PM2.5 sensor (Dustbox) and a data analysis platform (Airsift). A citizen-sensing network operated for nearly 10 months (Dec 2016–Sep 2017) across up to 30 monitoring locations, collecting both sporadic and continuous data. Methods included: sensor development and calibration; co-design with communities; installation at participant-selected sites; data workshops to interpret readings; integration with mapping and contextual information; and co-authoring "Deptford Data Stories" (seven site-based narratives) that combined numerical sensor data, participant observations, planning context, and proposed actions. Three focal case locations structured analysis: (1) Deptford Park area (transport interventions); (2) Old Tidemill Wildlife Garden (green infrastructure and development conflict); (3) Pepys area (river-related emissions). The study critically examined both the capacities and limitations of low-cost sensors and how communities mobilized data to support ongoing projects and policy engagement.

• Citizen-generated data identified spatial patterns: traffic intersections and construction-adjacent areas often showed significantly higher PM levels; sheltered garden areas and pedestrianized streets showed lower levels. - Combining PM data with wind direction indicated the River Thames as a likely emissions source in some areas (Pepys), pointing to marine fuel/diesel river traffic as a significant contributor; official networks had not captured this due to siting. - Urban design and green infrastructure had a measurable mitigating effect on local PM exposure near green spaces (e.g., Old Tidemill and New Cross Gate), while nearby busy roads exhibited higher concentrations. - Citizen monitoring did not merely replicate regulatory observations; it produced distinct, situated evidence that supported community proposals and redirected attention to overlooked sources (e.g., river traffic). - Action outcomes varied: Deptford Folk and partners leveraged preliminary findings to support sustainable transport pilots and secured £2.9 million from Transport for London’s Liveable Neighbourhoods program; attempts to preserve Old Tidemill Wildlife Garden, despite evidence of air-quality benefits, were unsuccessful as housing development was approved; proposals to upgrade river vessel fuels and expand citizen monitoring faced uneven uptake due to fragmented governance (GLA vs. Port of London Authority). - Overall, environmental monitoring became enmeshed in broader struggles over urban environments, shifting health from individual behaviour change towards collective environmental interventions.

Findings show citizen sensing reconfigures air pollution and health as collective, environmental problems rather than individualized issues. Citizen-generated evidence catalyzed proposals for transport redesign, green infrastructure enhancement, and broader monitoring networks, but the translation to policy and urban change was uneven due to entrenched power dynamics, development pressures, and fragmented governance. This demonstrates that planetary health should be understood as situated, differential practices that link bodies, environments, and politics across multiple sites, rather than as a universal systems overview. Democratizing environmental evidence is entangled with democratizing environmental action; yet unequal audibility and legitimacy constrain communities’ capacity to transform environments. The work exposes frictions within prevailing planetary health framings that assume seamless integration of data and governance, illustrating instead that collective, place-based experimentation is needed to realize more just planetary inhabitations.

The paper contributes a practice-based account of planetary health that emerges through citizen-sensing engagements and collective urban interventions. It shows how participatory monitoring can surface overlooked pollution sources, support community-led design and policy proposals, and shift health from individualized metrics to environmental transformations. However, outcomes depend on power-laden urban processes and governance configurations. The study proposes rethinking the planetary as an open, democratic, and situated project that recognizes differential conditions and emphasizes collective responsibility across human and more-than-human relations. Future work should deepen integration between participatory evidence-making and responsive governance, scale and sustain community monitoring infrastructures, and develop pathways that convert situated findings into equitable, city-wide environmental health interventions.

• Site- and time-bounded study in Southeast London over ~10 months limits generalizability and seasonal coverage. - Low-cost sensors, while improved and critically engaged, may have accuracy and calibration constraints relative to regulatory monitors. - Evidence translation was constrained by fragmented and multi-level governance, limiting policy uptake (e.g., river emissions) and environmental preservation (Old Tidemill). - Outcomes depended on existing community capacity and partnerships; not all proposals could be implemented or sustained. - The research focuses on participatory processes and qualitative integration of data with context rather than providing exhaustive quantitative causal attribution across all sources.