Ultrafine particle emissions from 'smokeless' fuels reveal systemic gaps in indoor air quality regulation and fossil fuel transition policies

Indigenous and traditional knowledge systems often prioritize holistic health and environmental harmony, where fuel choices are embedded in cultural and ecological contexts rather than isolated technical metrics. For example, the *chulha* stoves of South Asia demonstrate how local design can mitigate smoke exposure without relying on industrial 'smokeless' fuels, yet these solutions are systematically marginalized in favor of Western-centric technological fixes. The dismissal of such knowledge reflects a deeper colonial legacy where Indigenous innovations are devalued in favor of corporate-led 'solutions.'

The reliance on solid fuels for heating and cooking has deep historical roots in industrialization and colonial resource extraction, where coal and later petroleum were positioned as 'progress' over traditional biomass. The current 'smokeless' fuel transition mirrors 20th-century campaigns to replace wood and peat with kerosene or LPG, which often exacerbated energy poverty without solving pollution. Historical parallels also include the asbestos industry's promotion of 'safe' alternatives in the 1970s, only for those to later be revealed as carcinogenic—highlighting how 'clean' labels often precede full health assessments.

Cross-culturally, the health impacts of indoor air pollution are shaped by gender roles, with women and children in many societies spending the most time near cooking fires, yet their experiences are rarely centered in policy or research. In contrast, Nordic countries have successfully reduced indoor air pollution through integrated building codes and district heating systems, demonstrating that systemic infrastructure changes can outperform individual fuel choices. Meanwhile, in East Africa, biogas programs have shown promise by leveraging local agricultural waste, but these are often underfunded compared to fossil-fuel-based 'solutions.'

Scientific evidence confirms that ultrafine particles (UFPs) from combustion penetrate deep into lung tissue, triggering oxidative stress and inflammation, with long-term exposure linked to cardiovascular and respiratory diseases. However, most studies on 'smokeless' fuels focus on particulate matter (PM2.5) rather than UFPs, creating a blind spot in regulatory standards. The lack of standardized testing for UFPs in household fuels reflects a broader gap in environmental health research, where emerging pollutants are often overlooked until their harm becomes undeniable.

Artistic and spiritual traditions often frame air as a sacred element, with pollution disrupting not just physical health but cultural and spiritual well-being. For instance, in many Indigenous cosmologies, smoke carries prayers and ancestral connections, making the replacement of traditional fuels with industrial alternatives a form of cultural erasure. Contemporary art movements, such as those in India and Nigeria, have used visual media to critique the false dichotomy of 'smoke' vs. 'clean,' instead advocating for holistic approaches to air quality that honor both health and heritage.

Future scenarios must account for the rebound effects of 'smokeless' fuels, where reduced visible smoke may lead to increased fuel consumption and UFP emissions, exacerbating overall pollution. Modeling should integrate health impacts with energy justice, ensuring that transitions do not disproportionately burden low-income households. Additionally, scenario planning must consider the role of decentralized energy systems, such as solar-powered cookstoves, which could eliminate indoor air pollution while aligning with climate goals.

Marginalized communities—particularly low-income households, Indigenous groups, and women in Global South countries—are disproportionately affected by indoor air pollution yet have the least agency in fuel choices. Their lived experiences, such as the trade-offs between cost, availability, and health risks, are rarely included in policy discussions. For example, in rural India, women often prefer traditional fuels for their affordability and cultural familiarity, despite health risks, highlighting the need for participatory solutions rather than top-down mandates.