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Mold in Tobacco, Cigars and Cigarettes

Mar 10, 2026 | Uncategorized | 0 comments

We all know that smoking can cause cancer. But did you know that mold also causes cancer and researchers are starting to link the mycotoxins found in moldy tobacco to cancer as well?

If you are a smoker, you might want to know that tobacco is notorious for being infected with mold and mycotoxins.

A pack of cigarettes can look dry, clean, and uniform on the outside while harboring a complex community of fungi and their toxins on the inside. In one classic multi-country survey, researchers isolated “hundreds of strains of fungi” from commercial cigarettes, concluding more than fifty years ago that “cigarettes are contaminated with various fungi.”

The mycotoxins found in mold are not destroyed when tobacco is burned.

They will transfer into the smoke, and the person smoking this mold infected tobacco will ingest these harmful, and potentially deadly toxins into their lungs where it will then enter their blood stream. Even temperature treatments, such as cooking and freezing, do not destroy mold mycotoxins.

More recent work has confirmed that tobacco—whether for cigarettes, cigars, or smokeless products—regularly carries species of Aspergillus, Penicillium, Fusarium, and other molds that can survive curing, storage, and even the burning process.

In controlled storage experiments, cigarettes kept at high humidity for just over a week showed pronounced fungal overgrowth in the tobacco column. Studies of cured and stored tobacco leaf routinely recover Aspergillus niger, Aspergillus flavus, Penicillium species, and Rhizopus, the same genera responsible for visible mildew, off-odors, and mycotoxin contamination in other stored agricultural products.

These findings have significant implications for consumers already concerned about tar, nicotine, and combustion byproducts because mold contamination adds an additional, often overlooked layer of biological and chemical exposure risk.

How Mold Gets Into Tobacco

Mold reaches tobacco at multiple points: in the field, during curing, in storage and manufacturing, and later in a smoker’s home or workplace.

Major contamination pathways include:

  • Field and harvest exposure. Tobacco plants provide nutrients and moisture that support fungal colonization, particularly by Aspergillus and Penicillium species, both in the soil and on plant surfaces.

  • Curing and fermentation. Air-curing and flue-curing create warm, humid environments where molds can proliferate and alter the leaf’s chemical composition. In moldy cigar tobacco, Aspergillus species have been identified as the dominant mold, representing more than 90 percent of the fungal load in visibly affected leaves.

  • Storage and distribution. Cured tobacco leaves and finished products sit in warehouses, factories, and transport containers where even minor moisture excursions can trigger mildew events. Surveys of flue-cured tobacco show a “constant association” between stored leaf and common storage molds like Aspergillus and Penicillium.

  • Retail and end-user environments. Research on commercial cigarettes has demonstrated that storage at very high relative humidity for eight days or longer leads to pronounced fungal growth in the tobacco itself. In practice, that risk increases in damp retail back rooms, humidors used incorrectly, and homes with elevated indoor humidity.​

Because tobacco is an organic, nutrient-rich matrix, it behaves like other stored agricultural commodities. When temperature and moisture cross key thresholds, molds quickly colonize available surfaces, consume starches and proteins, and generate volatile organic compounds and mycotoxins.

From an environmental health perspective, the tobacco supply chain is a serial opportunity for fungal contamination.

What Happens When Moldy Tobacco Is Smoked

Burning and inhaling a biological material that contains fungi and mycotoxins raises two distinct questions: whether viable organisms or fragments enter the smoke stream, and whether mycotoxins survive combustion or pyrolysis in ways that matter for human health.

Studies examining the microbiology of commercial cigarettes confirm that the tobacco rod contains both bacterial and fungal components under typical storage conditions. When these cigarettes are exposed to high humidity, fungal overgrowth becomes more pronounced, with visible growth and higher counts in culture.

Experimental work on cigarette smoke and microbial toxins indicates that burning contaminated tobacco can generate a mixture of:

  • Fungal spores and fragments drawn into mainstream smoke or released into sidestream smoke as particles.

  • Microbial cell wall components and toxins that can be carried on particulate matter or in the gas phase.

Smokers as vectors of contaminants

From an indoor environmental standpoint, smokers and smokeless tobacco users can act as vectors, bringing fungal spores, fragments, and mycotoxins into homes, vehicles, and workplaces on:

  • Opened packs, loose tobacco, pouches, and cigars.

  • Clothing, hands, and surfaces contaminated by handling moldy or dusty tobacco products.

Occupants who do not smoke but share the same environment may therefore be indirectly exposed not only to secondhand smoke but also to trace amounts of mold and mycotoxins associated with tobacco products and their dust.

Indoor Environments, Moldy Tobacco, and Inspection Strategy

For a building science–focused firm, mold in tobacco is relevant because it intersects with indoor air quality, occupant complaints, and source identification.

Rooms and materials impacted by tobacco use

Spaces with heavy or chronic tobacco use often show a predictable pattern:

  • Nicotine staining and odor on walls, ceilings, HVAC components, and contents.

  • Embedded smoke residue and particulate within carpets, soft furnishings, and dust reservoirs.

  • Elevated background particle levels when occupants smoke indoors, especially in smaller or poorly ventilated rooms.

If tobacco itself is mold-contaminated, two additional dynamics can appear:

  • Localized mold and odor around storage areas (drawers, cabinets, humidors, closets) where humidity, off-gassing, and tobacco dust combine.

  • Increased fungal biomass and mycotoxins in settled dust, especially in areas near storage or frequent use, further complicating efforts to distinguish building-source mold from imported sources.

From an assessment perspective, it becomes important to differentiate between mold arising from building moisture issues and mold introduced via occupant behaviors and products such as tobacco.

Conclusion

Mold in tobacco is not an abstract or rare phenomenon. Decades of research show that cigarettes, cigars, and smokeless tobacco frequently carry Aspergillus, Penicillium, and related storage molds, along with their mycotoxins, including aflatoxins and ochratoxin A.

For environmental and mold professionals, tobacco products represent both a direct exposure medium and a confounding factor when investigating indoor air quality complaints.

References

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