Daily Junction.mobi portalTechnology · August 29, 2026 · The Conversation · 5 min
The fungus appears to feed on the airborne alcohol vapours produced during whiskey maturation.
<div class="theconversation-article-body">
<span><a href="https://theconversation.com/profiles/jenny-lawler-2760862">Jenny Lawler</a>, <em><a href="https://theconversation.com/institutions/dublin-city-university-1528">Dublin City University</a></em></span>
<p>Irish whiskey is one of Ireland’s great export success stories. Exports were worth over €930 million in <a href="https://www.bordbia.ie/industry/irish-sector-profiles/alcohol-sector/">2025</a>, with the country’s much-loved spirit being sold all over the world. </p>
<p>Even amid difficult international trading conditions, with concerns around tariffs for export to the <a href="https://www.spirits.eu/media/press-releases/spiritseurope-welcomes-us-tariff-exemption-for-uk-whiskies-calls-for-extension-to-eu-spirits?">US</a>, exports to the EU have grown by more than 21% in four <a href="https://www.rte.ie/news/business/2026/0820/1588642-irish-whiskey-association-figures/">years</a>.</p>
<p>However, while thousands of barrels quietly mature in warehouses around Ireland, something else is happening outside some of them. On walls, roofs, road signs, trees and other surfaces close to some whiskey maturation facilities, a <a href="https://theconversation.com/topics/microbiology-1225?page=3">distinctive black patina</a> appears. </p>
<p>It may look like soot or air pollution, but in some cases the culprit is a fungus: <em>Baudoinia</em>, commonly known as “whiskey fungus” or “whiskey black”, and fuelled by the presence of ethanol alcohol in the air.</p>
<p>Despite the fact it has been known about for years, there has been surprisingly little research on its effects, such as whether the fungus can spread from distilleries to nearby properties, including residential homes. </p>
<p>Ethanol alcohol emissions from the industry are also <a href="https://www.gov.scot/publications/review-human-health-environmental-impacts-non-methane-volatile-organic-compound-emissions-malt-whisky-maturation-scotland-final-report-prepared-scottish-government-aether/pages/5/">thought to contribute</a> to <a href="https://cires.colorado.edu/news/airborne-ethanol-rise">ground level ozone</a>, a harmful air pollutant. But we don’t know whether the fungus has any adverse consequences for people’s health. It may not be dangerous at all, but this is something we are investigating through a project at Dublin City University.</p>
<h2>The angels’ share</h2>
<p>During maturation, ethanol and other volatile compounds evaporate and pass through the porous cask. They then enter the surrounding atmosphere around the distillery. This portion of the whiskey is often known as the “angels’ share”.</p>
<p>A <a href="https://www.gov.scot/publications/review-human-health-environmental-impacts-non-methane-volatile-organic-compound-emissions-malt-whisky-maturation-scotland-final-report-prepared-scottish-government-aether/">review</a> commissioned by the Scottish government estimated that more than 90% of non-methane volatile organic compound (NMVOC) emissions associated with whiskey production occur during maturation. </p>
<p>NMVOCs are chemicals that participate in atmospheric reactions and contribute to the formation of pollutants like ground-level ozone. Ethanol alcohol overwhelmingly dominates these emissions from whiskey production.</p>
<p>As they condense into the air moisture, these ethanol vapours also create an unusual ecological niche. Baudoinia can occur naturally at very low abundance, but exposure to this airborne alcohol can favour its growth. </p>
<p>Around maturation warehouses, this can result in conspicuous dark fungal growth on exposed surfaces. The association has been recognised for more than a century, initially around cognac maturation facilities in France, and has subsequently been documented around spirit maturation warehouses in Scotland, Canada and the US. </p>
<figure class="align-center zoomable"> <a aria-label="Zoomable image" href="https://images.theconversation.com/files/756514/original/file-20260827-50-m5ff6g.jpg?ixlib=rb-4.1.1&q=45&auto=format&w=1000&fit=clip"><img alt="Whiskey fungus" src="https://images.theconversation.com/files/756514/original/file-20260827-50-m5ff6g.jpg?ixlib=rb-4.1.1&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/756514/original/file-20260827-50-m5ff6g.jpg?ixlib=rb-4.1.1&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/756514/original/file-20260827-50-m5ff6g.jpg?ixlib=rb-4.1.1&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/756514/original/file-20260827-50-m5ff6g.jpg?ixlib=rb-4.1.1&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/756514/original/file-20260827-50-m5ff6g.jpg?ixlib=rb-4.1.1&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/756514/original/file-20260827-50-m5ff6g.jpg?ixlib=rb-4.1.1&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/756514/original/file-20260827-50-m5ff6g.jpg?ixlib=rb-4.1.1&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a> <figcaption> <span class="caption">Image of a Baudoinia lab culture.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Scotland_Baudoinia.jpg">JA Scott et al.</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span> </figcaption> </figure>
<h2>Black discolouration</h2>
<p>So can whiskey fungus spread from distilleries to nearby properties, causing unsightly dark growth in people’s homes? In 2022, following a complaint about black discolouration on houses close to the Midleton distillery in county Cork, the Irish Environmental Protection Agency (EPA) investigated whether Baudoinia was present. </p>
<p>While the fungus was <a href="https://leap.epa.ie/docs/86fb2aff-342b-4092-a763-2fb0aa28f9ff.pdf">identified</a> on a whiskey warehouse, it was not detected on any of the three nearby residential properties sampled. </p>
<p>There are still major gaps in what we know about whiskey fungus in Ireland, such as how far it travels, what controls its growth, and what, if anything, its presence tells us about ethanol concentrations in the surrounding environment. </p>
<p>A recent <a href="https://doi.org/10.1016/j.fbr.2026.100505">review</a> led by researchers at University College Cork suggests that ethanol may play several roles for the fungus. It may act as a germination signal and as a source of carbon to support the growth of the fungus. </p>
<p><a href="https://doi.org/10.1108/IJBPA-05-2021-0079">Research</a> around whiskey maturation warehouses also suggests that the extent of visible colonisation depends on factors including distance from the ethanol source, prevailing wind, moisture and the type and texture of the surface available for colonisation. </p>
<p>Ireland has commitments to <a href="https://environment.ec.europa.eu/topics/air/reducing-emissions-air-pollutants_en">reduce NMVOC emissions</a> under the EU National Emission Reduction Commitments Directive. As mentioned, these NMVOC emissions can help produce <a href="https://www.epa.ie/environment-and-you/air/faqs/">ozone</a>, a harmful air pollutant that damages vegetation and crops, reduces lung function and aggravates respiratory conditions such as asthma. It is also a greenhouse gas that contributes to climate change.</p>
<p>The difficulty is knowing precisely how much ethanol is being released. National inventories generally rely on production data and emissions factors. These are useful for estimating emissions across an industry, but they do not necessarily tell us what is happening around an individual maturation facility – how emissions change with the number and age of barrels, how ethanol disperses beyond a warehouse boundary, or how weather conditions affect local concentrations.</p>
<figure class="align-center "> <img alt="" src="https://images.theconversation.com/files/756520/original/file-20260827-50-oe7yd0.jpeg?ixlib=rb-4.1.1&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/756520/original/file-20260827-50-oe7yd0.jpeg?ixlib=rb-4.1.1&q=45&auto=format&w=600&h=346&fit=crop&dpr=1 600w, https://images.theconversation.com/files/756520/original/file-20260827-50-oe7yd0.jpeg?ixlib=rb-4.1.1&q=30&auto=format&w=600&h=346&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/756520/original/file-20260827-50-oe7yd0.jpeg?ixlib=rb-4.1.1&q=15&auto=format&w=600&h=346&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/756520/original/file-20260827-50-oe7yd0.jpeg?ixlib=rb-4.1.1&q=45&auto=format&w=754&h=435&fit=crop&dpr=1 754w, https://images.theconversation.com/files/756520/original/file-20260827-50-oe7yd0.jpeg?ixlib=rb-4.1.1&q=30&auto=format&w=754&h=435&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/756520/original/file-20260827-50-oe7yd0.jpeg?ixlib=rb-4.1.1&q=15&auto=format&w=754&h=435&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"> <figcaption> <span class="caption">Baudoinia growing on sycamore branch (top), alongside fungus free bark.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/w/index.php?curid=14934583">Rosser1954 Roger Griffith</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span> </figcaption> </figure>
<h2>Is whiskey fungus dangerous?</h2>
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