Indoor Air Pollution – A Relevant Threat to Fertility

Relevance for Reproductive Medicine and Pregnancy – Focus on Printer-Emitted Particles (PEPs)

Indoor Air Pollution – Overlooked Sources

Indoor air pollution is often underestimated, yet one of its most overlooked sources is the everyday laser printer. During operation, laser printers emit engineered nanoparticles—so-called printer-emitted particles, or PEPs—from nano-enabled toners. These emissions are not trivial. Studies show that in offices and even in homes, particle concentrations can reach levels comparable to those near heavily trafficked urban roads or cigarette smoke in enclosed spaces [1,2].

Laser Printer: Billions of Ultrafine Particle Emissions

Laser printers release billions of ultrafine particles per printed page—particles smaller than 100 nanometers—along with volatile organic compounds, polycyclic aromatic hydrocarbons, and metals [3,4,16].

Due to their small size, ultrafine particles can penetrate deep into the respitory tract and may translocate into the bloodstream. [5]. Research confirms that such emissions occur reproducibly during printer operation and may accumulate in insufficiently ventilated indoor environments [1,2].

Biological Effects of Ultrafine Particles

Ultrafine particles are of concern because they can induce oxidative stress and inflammatory responses, mechanisms associated with cellular injury and tissue damage [5,6]. Epidemiological studies suggest that exposure to airborne particulate pollution during pregnancy is associated with oxidative DNA damage, inflammation, and adverse reproductive outcomes [6,7].

Recent research on micro‑ and nanoplastics (MNPs) has shown that such particles can distribute widely throughout the body after inhalation or ingestion. Experimental studies detected particles in organs including lung, liver, spleen, brain, reproductive organs, and blood [8]. Some studies further suggest that nanoscale particles may cross biological barriers including the blood‑brain barrier, placenta, and blood‑testis barrier under experimental conditions [8,9].

Although the toxicological properties of MNPs and printer‑emitted ultrafine particles are not identical, the findings contribute to broader concerns regarding nanoscale particle exposure and reproductive health.

Short‑term exposure to airborne particles has been associated with respiratory irritation and cardiovascular stress, whereas long‑term exposure has been linked to systemic inflammation, genotoxicity, oxidative stress, and DNA damage [5,10]. These biological pathways are also discussed in fertility and reproductive health research [11].

Air Pollution, Epigenetics and Reproductive Health

Increasing evidence suggests that air pollution may influence epigenetic regulation, including altered DNA methylation patterns in placental tissue and reproductive cells [12]. Such changes are being investigated for possible effects on embryo development and long‑term health outcomes.

There is also evidence linking air pollution exposure to sperm DNA fragmentation and altered epigenetic programming [13].

Direct causal links between laser printer emissions and infertility have not yet been conclusively demonstrated. Nevertheless, the underlying biological mechanisms, including oxidative stress, inflammation, endocrine disruption, and genotoxic effects—are well established in environmental health science.

Historical Context

Concerns regarding environmental pollutants and fertility have been discussed for decades. In the early 2000s, environmental and political debates in Germany – mentioning the laser printers – increasingly focused on endocrine‑disrupting chemicals and declining sperm quality. Although such discussions were often speculative at the time, subsequent scientific research has strengthened interest in possible links between environmental exposures and reproductive health.

Findings from German Research Groups

University of Duisburg-Essen

Investigations during laparoscopic procedures identified carbon nanoparticle aggregates in peritoneal tissue samples. Electron microscopy revealed nanoscale carbon particles in affected tissue [14].

University of Rostock

Electron microscopic analyses reportedly identified carbonaceous particles in lung tissue samples from a deceased printer service technician with long‑term occupational toner exposure. This finding was discussed in occupational exposure debates but remains limited to case‑based evidence.

University of Freiburg (IUK)

Experimental studies involving toner particle exposure demonstrated inflammatory and immunological cellular responses in exposed subjects and cell systems [15].

In vitro studies further demonstrated cytotoxic and genotoxic effects of printer‑emitted particles in A549 lung epithelial cells [15].

Current Research

In 2020 research groups led by Nancy Lan Guo at West Virginia University have since investigated the genomic changes, first of rats, later of Singaporean printing company workers have experienced. In many respects, the workers’ genomes changed the same ways the rats’ genomes did. [17]. Guo said:

There is one group that I think should know: pregnant women. Because once many of these genes are altered, they are passed down through the generations. It’s not just about you.

The relevance of air quality control in reproductive medicine has recently gained increasing attention. Dr. Nahed Hammadieh discussed the question of whether air filtration systems may improve assisted reproductive technology (ART) outcomes at the Filtration and Fertility Symposium, Climate Control Middle East Webinar 14.05.2026.

Background

Ultrafine laser printer emissions are particularly critical because they are invisible, odourless and highly respirable – in poorly ventilated indoor spaces long-term exposure in particular poses a considerable health risk.

Laser printer emissions are therefore classified as anthropogenic organic aerosols – they contain carbon, are produced by humans and are distributed in the air as aerosols.

Composition of laser printer emissions

Only approx. 1-10 % of the emissions are toner. The majority are ultrafine and nanoparticles. The majority are produced secondarily – through thermally induced processes and reactions within the printer housing (Birmili, 2020).

Typical components of ultrafine laser printer emissions:

• solid micro- and nanoplastic particles and chemicals
• condensed organic compounds
• organic compounds, e.g. VOCs, polycyclic aromatic hydrocarbons (PAHs) and PFAS
• Carbon black and metal-containing nanoparticles (2-8 %)

Ultrafine particles (UFP) – characteristics and effects

• Size: < 100 nanometres – smallest fine dust fraction
• Source: combustion processes, abrasion, secondary formation in the ambient air / atmosphere
• Properties: high reactivity, large surface area with low volume

Possible Health effects:

• deep penetration into the alveoli (pulmonary alveoli)
• transmission into the bloodstream
• overcoming the blood-lung / blood-brain barrier
• triggering of inflammation and oxidative stress
• disorders of the immune system
• PAHs in particular are highly carcinogenic
• involvement in neurodegenerative disease

Special feature: in addition to the blood, UFP can reach the brain and the central nervous system via the olfactory nerve, where, similar to the Trojan horse, they bring possible accumulated toxins with them.

Scherrer Institute (PSI) from March 2025 emphasises the importance of secondary aerosols:

A large proportion of particle pollution is not produced directly at the source, but through chemical reactions in the atmosphere. Secondary aerosols are formed when gaseous precursors such as toluene, benzene or volatile organic compounds react with each other in the air.

With laser printing, on the other hand, substances that are solid at ambient temperature vaporise at the high temperature. If the temperature drops again, the vapour pressure also drops and nucleation (or condensation if there is sufficient surface area) can take place without chemicals being involved.

This significantly increases the relevance of low-emission source materials.

Measurement of UFP: 2.34 billion particles per printed page

Laser printers emit an average of 1.6 to 15 billion tiny particles per printed page, known as particulate matter (Barthel et al. 2011).

Detection of ultrafine particles: via number concentrations, e.g. with condensation particle counters, electrical mobility analysers (particles per cm³), not via mass

Unsuitable: optical or gravimetric standard methods (e.g. PM₁₀/PM_2.5)

Myth:

Printer particles disappear by themselves

Common misconception: assumption that printer emissions „disappear“ quickly, similar to fog.

The electrostatically charged, toxic substances, which are invisible to us, can remain in the room air for a long time and are visibly deposited in large numbers on surfaces or filters. The very tiny particles possibly are inhaled and can break through human barriers. Due to their large surface area, they can act as a „Trojan horse“, taking a lot of material with them – possibly more toxic than the core particle – deep into the organism – right into the brain

Effect on health – evaluation of 2,000 reports from those affected (Abimbola Ojo et al. 2024)

• Acute consequences: Respiratory tract (90 %), allergies (70 %)
• Long-term: chronic respiratory (15 %) and cardiovascular and neurological diseases, metal allergies, gastrointestinal diseases and cancer
• „visible toner“: chronic fatigue, bronchial hyperreactivity, asthma/COPD and cardiovascular diseases

Special risks:
the ability to cross the blood-brain barrier makes UFP particularly dangerous (Oberdörster et al., 2004).

Recommendations for laser printers + copiers

• Device replacement Print safely with ink instead of toner
• Count particles Make the invisible visible!
• Retrofit filters Laser printers never without filters!
• Separate room installation with independent supply and exhaust air!
• Room air purifier Reduce the amount of UFP!
• Print less You protect the environment, your health and your wallet!

Conclusion

Air pollution is a silent epidemic, and PM0.1 is perhaps the quietest of all pollutants (Schraufnagel 2020).

Laser printers are not merely harmless office devices. They are measurable sources of indoor air pollution with scientifically documented emissions and plausible possibly long-term health implications. The broader evidence demonstrates clear biological pathways linking such exposure to fertility impairment, DNA damage, and heritable epigenetic changes—suggesting that the risks may extend beyond immediate health to future generations.

The good news is that there are already simple and cost-effective solutions for reducing or even eliminating exposure that can be implemented easily and on a large scale. Preventive, mandatory, limiting rules indoors for the ultrafine particles that are invisible to us are urgently needed

Author

Heike Krüger, Chair of the Board
nano-Control, International Foundation