Household air pollution and health: rethinking indoor exposure in the places we call home

Abstract

Household air pollution has long been overlooked in environmental health policy, yet the evidence now makes clear that our homes, particularly in low and middle-income countries, are often the most significant sites of exposure to airborne pollutants. This “Household Air Pollution” collection brings together six recent studies that investigate emissions from common household activities, characterize pollutant concentrations in domestic environments, and assess associated health risks. This multidisciplinary research – spanning environmental engineering, aerosol science, epidemiology, and public health – demonstrates that improving household air quality is both necessary and feasible. Together, they highlight the urgent need for integrated strategies, policies and standards that prioritize indoor environments as a key determinant of health and developing health-centered design, source control, and public awareness to improve indoor air quality where it matters most: in our homes. We are grateful to the authors for their insightful contributions, the reviewers for their expertise, and the Scientific Reports editorial team for their support. We hope this Collection serves as a valuable resource and a call to action for scientists, public health officials, architects, and policymakers alike.

Introduction

In recent decades, our understanding of air pollution and its impacts on health has deepened considerably, but household air pollution (HAP) remains an underappreciated frontier in environmental health. Individuals in developed countries spend approximately 90% of their time indoors, with over two-thirds of that within their homes¹. Indoor air can contain a complex mixture of pollutants, including particulate matter, volatile organic compounds (VOCs), carbon monoxide, nitrogen dioxide, and biological agents, often at concentrations exceeding those found outdoors^2–4. Despite this, indoor exposures are still insufficiently represented in environmental policy and health risk assessments⁵. This oversight is especially concerning given the well-established health effects associated with indoor air pollutants. Numerous studies have linked indoor exposure to increased risks of asthma, chronic obstructive pulmonary disease (COPD), cardiovascular disease, and lung cancer^6–9. Vulnerable populations (children, the elderly, and individuals with pre-existing conditions) are particularly at risk, as their exposure tends to be higher and their physiological defenses weaker^10,11. Furthermore, the COVID-19 pandemic has renewed attention on indoor environments, revealing how poor ventilation and prolonged indoor occupancy can exacerbate airborne transmission risks^12,13.

This Special Collection in Scientific Reports presents six original contributions that shed light on multiple dimensions of indoor pollution in residential settings. Collectively, these studies advance our knowledge of emission sources, exposure profiles, health associations, and methodological innovations for assessing and mitigating HAP.

Caracci et al.¹⁴ conduct a detailed characterization of particles emitted from everyday combustion-based practices – such as grilling, incense burning, and mosquito coils, revealing that ultrafine particles (≤ 0.1 μm) often carry toxic metals like cadmium and chromium (VI), as well as carcinogenic PAHs. Their findings highlight the inadequacy of traditional exposure models that overlook particle size and chemical speciation, a critique echoed by broader indoor exposure literature^15,16.

Choi et al.¹⁷ analyzed PM₂.₅ (≤ 2.5 μm) levels in Korean households across seasons, identifying higher winter concentrations in homes using combustion-based heating. These findings align with prior research on how space heating and ventilation practices vary globally, altering indoor pollution burdens^18,19. López de Paz et al.²⁰, studying households in Bogotá, link cooking-related emissions and insufficient ventilation to increased pollutant concentrations and respiratory symptoms, adding to growing evidence from Latin American and low-to-middle-income countries where indoor exposure is often exacerbated by structural inequities²¹.

Children’s unique vulnerability to air pollution is addressed in the study by Chatzidiakou et al.²², who employs GPS-linked personal monitors to track ultrafine particle exposure across multiple indoor and transit environments. This microenvironmental approach reflects a shift in exposure science toward individualized and temporally resolved assessments^23,24. Their work confirms that indoor microenvironments (including homes and vehicles) dominate children’s daily exposures, in line with previous research showing that ambient monitoring alone underestimates true exposure burdens in youth²⁵.

In another contribution, Vianello et al.²⁶ examine the emission of VOCs from commonly used cleaning products, demonstrating how even products marketed as “eco-friendly” may emit compounds exceeding health-based thresholds. These findings reinforce earlier warnings about secondary organic aerosol formation from terpenes and the lack of consumer awareness regarding chemical exposure indoors^27,28. They call for stronger regulation and clearer labeling, long-standing recommendations from the indoor chemistry research community²⁹.

Addressing the need for practical tools, Di Gilio et al.³⁰ proposes an indoor air quality (IAQ) index that combines pollutant concentrations with behavioral and ventilation metrics. Such integrative approaches are increasingly recommended to capture the dynamic nature of indoor environments and support decision-making by occupants, designers, and regulators alike^31–34.

Contribution by Kuye and Kumar³⁵ assessed four solid fuels (wood briquettes, smokeless coal, kiln-dried and seasoned wood) in UK homes, testing four types of stoves (eco-design, multifuel, Clear Skies Stage V, open fireplace) during winter. They measured indoor ultrafine particles, PM_2.5, PM₁₀ (≤ 10 μm), black carbon, and carbon monoxide, showing IAQ was significantly affected by fuel type, room size, stove design, and burn duration, and was further worsened by poor ventilation. They concluded that burning solid fuels, whether for heating or leisure, raises exposure to harmful pollutants, including ultrafine particles, irrespective of stove or fuel efficiency. Despite rising energy costs driving reliance on fires, even ‘eco’ stoves impair IAQ, highlighting persistent health risks.

The evidence synthesized across these six studies highlights the need to reframe how we conceptualize and manage air pollution. Indoor sources such as cooking, cleaning, heating, and material off-gassing are deeply embedded in cultural and domestic routines, often escaping regulatory oversight. Building codes in many regions continue to prioritize energy efficiency over IAQ, leading to airtight environments with limited ventilation³⁶. Furthermore, disparities in housing quality, occupant awareness, and access to mitigation technologies reinforce health inequalities tied to indoor pollution³⁷.

To ensure that the places we call home are truly safe, a paradigm shift is required: one that places indoor environmental quality at the center of healthy building design, public health planning, and environmental justice. This includes advancing real-time IAQ monitoring, promoting low-emission materials and appliances, updating building ventilation standards, and fostering behavioral change through targeted communication and education. Future research should focus on chronic exposures, synergies with outdoor pollution, and the development of policies that integrate health, energy, and housing goals in a unified framework.

The studies in this Collection mark an important step toward that vision. By advancing measurement techniques, exposure science, and health linkage, they provide a robust foundation for rethinking IAQ in the places we inhabit most intimately, i.e. our homes.

Declarations

Competing interests

The authors declare no competing interests.