Introduction
Sources of indoor nanoparticle pollution
Exposure pathways
Health risks of nanoparticle exposure
Regulatory and safety considerations
Mitigation and alternatives
Future directions
Conclusions
References
Further reading
Fragranced candles, sprays, and cleaners may smell pleasant, but new science shows they generate harmful nanoparticles that linger in the air and affect your health.
Image Credit: New Africa / Shutterstock.com
Introduction
Fragranced consumer products, such as air fresheners, cleaning sprays, candles, and personal care items, emit numerous volatile organic compounds (VOCs) that can generate secondary pollutants, including formaldehyde. Exposure to these chemicals increases the risk of migraine headaches, asthma attacks, respiratory and mucosal symptoms, skin reactions, and neurological complaints.1
Recent studies also show that non-combustion products, such as scented wax melts, release terpenes that react with ozone to form new nanoparticles, challenging the assumption that flame-free fragranced products are harmless.2
This article explains how fragranced consumer products contribute to indoor air nanoparticle pollution through various exposure pathways while offering practical ways to reduce individual exposure to these chemicals.
Sources of indoor nanoparticle pollution
Fragranced products emit VOCs, including monoterpene mixtures from scented wax melts, that react rapidly with indoor ozone to form highly oxygenated molecules and secondary organic aerosols. This process leads to intense particle nucleation and growth, with sizes increasing from under 3 nm up to hundreds of nanometers in the sub-micron range.2
Primary nanoparticles are subsequently released into the environment by combustion and spraying. Whereas burning candles and incense generate ultrafine soot and ash, aerosolized cleaners and personal-care products create droplets that dry into particles.1
Under low nitrogen oxide conditions common indoors, terpene ozonolysis generates peroxy radicals that sustain nanocluster growth, resulting in particle number concentrations above 106 cm-3, comparable to those from gas stoves or combustion sources.2
Exposure pathways
Indoor environments, particularly those with high levels of dust, fibers, or combustion byproducts, can be polluted with fragrance-derived ultrafine particles in addition to microplastics. The deposition of particles into the lungs depends on size, with larger ones trapped in the upper respiratory tract and nanoparticles capable of reaching the bronchioles and alveoli.5
Dermal exposure to fragrance ingredients and plasticizers, such as phthalates, occurs following the use of personal care products, including cosmetics, shampoos, sunscreens, nail polishes, and skin emollients. Evidence also shows that solvents and nanoparticles can penetrate damaged or hydrated skin, increasing systemic absorption.3
Ingestion may occur when chemicals from packaging materials migrate into food. Settling VOC-derived particles and phthalates on surfaces may lead to hand-to-mouth transfer, especially in children.1
Health risks of nanoparticle exposure
Nanoparticles generate a high number of reactive oxygen species (ROS) due to their large surface area, which leads to oxidative stress, inflammation, and genotoxicity. Oxidative damage to deoxyribonucleic acid (DNA) and histones has been observed in human and animal studies, with higher DNA-damage markers present in polluted settings.5
Nanoparticles are mainly related to the mechanism of toxicity induced by the accumulation of ROS.4
The inhalation of nanoparticles can cause oxidative stress and inflammation, which can irritate the bronchi and reduce lung function. These effects are particularly severe among individuals with preexisting respiratory diseases, such as asthma or chronic obstructive pulmonary disease (COPD). Several nanoparticles can cross the blood-brain barrier (BBB), with experimental evidence of oxidative-stress-mediated neurotoxicity and other neurodegenerative processes.4,5
When particles traverse the air-blood barrier, systemic effects include endothelial dysfunction, cardiotoxicity, and immune disruption. Nanoparticles such as silica and certain metal oxides exacerbate vascular damage and alter lipid metabolism.4
Children, pregnant women, and older adults are particularly sensitive to nanotoxicity, as well as individuals with chronic conditions. Overall, prudent exposure reduction and stronger safety evaluation are warranted.4
Toxic effects of nanoparticles on health.4
Regulatory and safety considerations
In the United States, there is no law requiring full disclosure of fragrance ingredients. In fact, labels and safety data sheets may list ‘fragrance’ as an ingredient, despite a single fragrance possibly containing dozens to hundreds of chemicals.
Previous studies have reported that hundreds of VOCs, including hazardous air pollutants, are emitted from everyday fragranced products, with only a small fraction disclosed. Both conventional and "green" fragranced products have been shown to release hazardous compounds, with little difference between them.1
Risk assessment is further complicated by complex, proprietary mixtures, which lead to wide variability across product categories and use settings. Additional challenges include frequent second-hand exposures in workplaces and public venues, as well as the limited ability to identify which specific chemicals or combinations are responsible for observed health effects.1
Mitigation and alternatives
Local exhaust systems that capture emissions at the point of generation, or well-designed general ventilation systems, are effective methods for reducing indoor concentrations. Even natural ventilation, such as opening windows, reduces nanoparticle levels, although less effectively than engineered solutions.
Mechanical filtration (e.g., HEPA filters) and substitution with lower-emission products are especially effective in home and workplace environments. In occupational labs, enclosed or sealed equipment has been shown to cut particulate matter levels dramatically, an approach that can be adapted to consumer and office use.6
Administrative controls, task planning, training, posted warnings, and good housekeeping further limit exposure. When other measures are constrained, properly fitted respirators provide temporary protection.6
When consumers are provided with the information needed to identify potential sources of nanoparticles and elect for low-emission tools, labs, and suppliers will be forced to prioritize safer formulations. Together, source control, ventilation, smarter purchasing, and informed users provide a practical roadmap for reducing indoor particles.
Future directions
There remains an urgent need to establish standardized and transparent test methods for characterizing emissions, including ultrafine and nanoparticle fractions, across various product categories and use conditions, such as spraying, heating, and venting. Protocols should quantify and report primary VOCs, secondary reaction products like formaldehyde, and particle number concentrations for public disclosure.1
Longitudinal studies and emerging 3D organoid models are needed to clarify dose-response and multi-organ effects of nanoparticle exposure, as highlighted by recent toxicology reviews.4
Policymakers are also encouraged to require companies to provide complete ingredient disclosures for fragrances, regulate indoor emissions with parity to outdoor hazardous air pollutants, incorporate fragrance chemicals into health-protective indoor air quality standards, and encourage fragrance-free policies in offices, healthcare facilities, hotels, and transportation.1
Conclusions
Fragranced consumer products are a significant and often underrecognized source of indoor nanoparticles that arise from primary emissions and secondary reactions of VOCs. Evidence across epidemiology, toxicology, and indoor monitoring studies has confirmed that nanoparticle exposure leads to respiratory irritation and asthma exacerbations, systemic inflammation and vascular dysfunction, as well as potential neurotoxic effects, with children, older adults, pregnant people, and those with chronic disease at greater risk.1,2,4,5
Limited ingredient transparency and federal regulations emphasize the importance of precautionary reduction to prevent excessive exposure to nanoparticles. These measures should prioritize ventilation and high-efficiency filtration, as well as fragrance-free or low-emission substitutions, labeling standards, and education, to minimize involuntary exposure and protect health in homes, workplaces, and public settings.
References
- Steinemann, A. (2016). Fragranced consumer products: exposures and effects from emissions. Air Quality, Atmosphere & Health. 9(8), 861-866. DOI:10.1007/s11869-016-0442-z, https://link.springer.com/article/10.1007/s11869-016-0442-z
- Patra, S. S., Jiang, J., Liu, J., et al. (2025). Flame-Free Candles Are Not Pollution-Free: Scented Wax Melts as a Significant Source of Atmospheric Nanoparticles. Environmental Science & Technology Letters 12(2), 175-182. DOI:10.1021/acs.estlett.4c00986, https://pubs.acs.org/doi/10.1021/acs.estlett.4c00986
- Anderson, S. E. & Meade, B. J. (2014). Potential health effects associated with dermal exposure to occupational chemicals. Environmental Health Insights 8, 1-15. DOI:10.4137/EHI.S15258, https://journals.sagepub.com/doi/10.4137/EHI.S15258
- Xuan, L., Ju, Z., Skonieczna, M., et al. (2023). Nanoparticles‐induced potential toxicity on human health: applications, toxicity mechanisms, and evaluation models. MedComm 4(4), e327. DOI:10.1002/mco2.327, https://onlinelibrary.wiley.com/doi/10.1002/mco2.327
- Buzea, C., Pacheco, I. I., & Robbie, K. (2007). Nanomaterials and nanoparticles: sources and toxicity. Biointerphases 2(4), MR17–MR71. DOI:10.1116/1.2815690, https://avs.scitation.org/doi/10.1116/1.2815690
- Zumrut, I. B., Kale, O. A., Tetik, Y. O., & Baradan, S. (2024). Mitigation strategies to reduce particulate matter concentrations in civil engineering laboratories. Environmental Science and Pollution Research 31(8), 12340-12350. DOI:10.1007/s11356-024-31926-w, https://link.springer.com/article/10.1007/s11356-024-31926-w
Further Reading
Last Updated: Sep 25, 2025