What Is Anthrene (Anthracene) and Is It Dangerous?

Anthracene, sometimes called anthrene in older chemical literature, is a solid polycyclic aromatic hydrocarbon (PAH) made of three fused benzene rings, with the molecular formula C₁₄H₁₀. It shows up wherever organic material burns incompletely, from coal tar to wood smoke to vehicle exhaust. On its own, anthracene is not classified as a human carcinogen by major health agencies, which sets it apart from several of its more notorious PAH relatives. But “not carcinogenic” does not mean “not dangerous.” Anthracene has a peculiar and underappreciated capacity to become toxic when exposed to sunlight, and its effects on aquatic life are significant enough to keep it on the U.S. EPA’s priority pollutant list.

What Anthracene Actually Is

Anthracene is a white to pale-yellow crystalline solid that forms naturally during the incomplete combustion of organic matter. It was first discovered in coal-tar distillation products in 1832 and gained industrial importance a few decades later when chemists realized that alizarin, the prized red dye previously extracted from madder root, could be synthesized from anthraquinone, which is derived from anthracene.¹ That dye connection drove early commercial interest and remains one of anthracene’s main industrial uses today, alongside its role in manufacturing plastics, insecticides, and wood preservatives.

Structurally, anthracene belongs to a family called acenes, which are linearly fused aromatic rings. Its three-ring “straight line” shape gives it different electronic and physical properties compared to phenanthrene, its angular isomer. Phenanthrene is actually the more thermodynamically stable of the two in the gas phase, largely because its bent shape allows greater aromatic stabilization of the electron system.² The practical consequence is that anthracene is somewhat more reactive than phenanthrene, particularly at the center ring’s 9 and 10 positions, and this reactivity matters for both its industrial chemistry and its behavior in the environment.

Anthracene’s crystal structure has attracted research interest because the way its molecules stack, through a mix of edge-to-face and face-to-face arrangements, affects the stability of different solid forms.³ This may sound academic, but it matters for anyone working with anthracene-based materials in electronics or organic semiconductors, where crystal packing directly influences how well the material conducts charge.

Where You Encounter It

Anthracene is one of the most common PAHs in the environment. PAHs as a group are widespread contaminants produced by incomplete combustion of organic materials, and the dominant sources include fossil fuel burning, motor vehicle emissions, waste incineration, oil refining, and coke and asphalt production.⁴ Diesel exhaust, coal combustion, agricultural waste burning, and wood and cow-dung-cake burning are also significant contributors to PAH levels in breathable air particles.⁵

For people who do not live near industrial sites, the most relevant exposure pathway is often the home. Wood-burning stoves and fireplaces substantially increase indoor PAH levels. In homes that use wood-burning appliances, 24-hour indoor concentrations of anthracene and several other PAHs have been measured at roughly three to five times the levels found in homes without them.⁶ Chemical analysis of birch wood combustion has shown that anthracene, along with fluorene, phenanthrene, fluoranthene, and pyrene, makes up more than 70% of the total PAH mass emitted.⁷ So if you heat with wood, anthracene is a significant component of what you are breathing indoors.

Food is another route. PAHs are common contaminants of processed food, typically at trace levels. Smoked foods, charcoal-broiled meats, and anything exposed to direct combustion during cooking will contain PAHs. The most closely monitored compound in food is benzo[a]pyrene, a known carcinogen, which has been found at concentrations up to 50 micrograms per kilogram in charcoal-broiled steaks.⁸ Anthracene accompanies benzo[a]pyrene in these settings, though at varying concentrations and without the same carcinogenic profile.

Is Anthracene a Carcinogen?

This is the question most people are really asking, and the answer is more nuanced than a simple yes or no. Anthracene itself is not classified as carcinogenic to humans by the International Agency for Research on Cancer (IARC), the U.S. EPA, or other major regulatory bodies. In laboratory genotoxicity testing, anthracene did not cause DNA strand breaks, even without external metabolic activation, placing it in the “inactive” category alongside naphthalene and phenanthrene. By contrast, eleven other PAHs tested in the same study, including benzo[a]pyrene and benz[a]anthracene, did cause DNA damage.⁹

That finding is consistent with the general pattern in PAH toxicology: the larger, heavier PAHs with four or more rings tend to be the carcinogenic ones. Anthracene, with its three rings, lacks the structural complexity that allows those heavier compounds to form DNA-damaging metabolites inside the body. So in the narrow question of whether anthracene causes cancer the way benzo[a]pyrene does, the current evidence says no.

However, this creates a false sense of safety if you stop reading here. Anthracene sits on the EPA’s priority pollutant list not because of cancer but because of other forms of toxicity, particularly its behavior in the presence of light.

The Phototoxicity Problem

Anthracene’s most striking hazard is phototoxicity, the ability to become significantly more harmful when exposed to ultraviolet light or sunlight. This is where the compound goes from relatively benign to genuinely concerning.

When anthracene absorbs UV light, it enters an excited electronic state. In that state, it can generate reactive oxygen species, essentially aggressive molecules that damage cells by attacking their membranes and other structures. In studies on human skin cells (keratinocytes), anthracene stood out as an exception among three-ring PAHs: while other compounds of similar size were not phototoxic, anthracene was. After a 24-hour incubation period following light exposure, more than 80% of skin cells exposed to anthracene at relatively low concentrations lost viability.¹⁰

The mechanism involves anthracene’s triplet excited state, which interacts with oxygen dissolved in tissue. Chloride ions, which are present in human sweat and in marine environments, can actually influence this process. Chloride appears to strike a balance between increasing the yield of the reactive triplet state and allowing it to live long enough to interact with oxygen, making it a more effective phototoxic agent than in pure fresh water.¹¹ This has practical implications: workers with anthracene on their skin who then go into sunlight, or aquatic organisms in salty or brackish water, face amplified toxicity.

What makes this worse is that anthracene’s breakdown products can be even more phototoxic than the parent compound. When anthracene degrades in sunlight, it produces intermediates like 9,10-anthraquinone and phthalic acid. Research has found that these photodegradation products actually enhance the toxic effect on skin rather than reducing it.¹² So the intuition that “sunlight will break it down and make it safe” gets the answer partly backward: yes, sunlight destroys anthracene rapidly, but the stuff it turns into can be nastier than what you started with.

Damage to Aquatic Ecosystems

The phototoxicity story becomes especially important in water. Anthracene enters rivers, lakes, and oceans through industrial discharge, stormwater runoff, and atmospheric deposition. Once in the water and exposed to sunlight, it poses a genuine threat to aquatic organisms.

Tiny water fleas (Daphnia magna), which are a staple test species for water toxicity, show strong sensitivity to the combination of anthracene and UV radiation. At an anthracene concentration of just 8.2 micrograms per liter with no UV light, the number of offspring produced dropped by about 14%. But when both anthracene and UV-A radiation were present, mortality reached 70% and reproduction dropped by 69%.¹³ The damage was proportional to both the anthracene concentration and the UV intensity, meaning even modest amounts of each can compound into serious harm.

Algae are affected as well. In a freshwater flagellate alga, the concentration that halved growth was measured at about 4.3 milligrams per liter.¹⁴ Aquatic plants suffer through a more specific mechanism: photomodified anthracene (the products formed when anthracene is altered by sunlight) blocks electron transport in photosynthesis, first at one key site and then cascading to a second, effectively shutting down the plant’s ability to use light energy.¹⁵

Fish are not spared either. In cell-based studies using fish cells, exposure to anthracene plus UV light increased levels of reactive oxygen radicals and products of lipid damage, suggesting that oxidative stress to cell membranes is a primary mechanism of harm.¹⁶ Across the board, anthracene’s toxicity in aquatic systems is dramatically amplified by sunlight in ways that standard dark-exposure tests would miss entirely.

Does Anthracene Build Up in the Food Chain?

One piece of relatively good news: anthracene does not biomagnify efficiently in the way that some persistent organic pollutants do. Studies on shrimp (Penaeus monodon) found that the animals cleared anthracene from their tissues roughly a thousand times faster than they accumulated it. At low dietary concentrations, the shrimp took up only about 0.1% of the anthracene in their feed. At higher concentrations, the animals simply stopped eating as much, and at very high levels, tissue damage appeared at the tail end of the body.¹⁷

That said, the bioaccumulation potential of PAHs in general does increase with molecular weight. Research on Daphnia pulex showed that heavier PAHs concentrate much more dramatically in organism tissues, and the octanol-water partition coefficient (a measure of how much a chemical prefers fats over water) is a strong predictor of that tendency.¹⁸ Anthracene, being a mid-weight PAH, falls somewhere in the middle. It does accumulate, but organisms that can metabolize it tend to flush it out relatively quickly.

How Anthracene Breaks Down

Anthracene is not particularly persistent once it reaches the surface environment, because two powerful forces work to degrade it: sunlight and microorganisms.

Photodegradation is fast. Under simulated sunlight, over 99.99% of anthracene was degraded within 24 hours, producing intermediates including 9,10-anthraquinone and phthalic acid.¹² In salty water, the photodegradation rate roughly doubles compared to deionized water, owing to a complex interplay between salting-out effects and changes to anthracene’s excited-state chemistry.¹⁹ With a photocatalyst like titanium dioxide, the process can be pushed even harder under controlled conditions.²⁰

Biodegradation in soil is also effective. Bacteria isolated from plant root zones, such as Bacillus cereus strains, have been shown to break down more than 82% of anthracene within 120 hours under favorable conditions, converting it into intermediates like dihydroxyanthracene and anthraquinone.²¹ Among PAHs, anthracene’s relatively low molecular weight makes it one of the faster ones to degrade; heavier PAHs like benzo[a]pyrene break down considerably more slowly.²²

The catch is that breakdown speed depends heavily on the specific environment. In deep soil without light or microbial activity, anthracene can persist for much longer. And as noted earlier, the breakdown products themselves are not necessarily safe.

Cleaning Up Anthracene-Contaminated Soil

For contaminated sites, the research on remediation offers some surprisingly low-tech options. Simply mixing soil at regular intervals, which increases oxygen availability and contact between soil microorganisms and the contaminant, was the fastest approach in one study, eliminating detectable anthracene from both arable and pasture soils within 56 days of weekly mixing.²³ Adding earthworms was the second-fastest approach, clearing the contaminant within 112 days. Counterintuitively, adding a non-ionic surfactant, which you might expect to help dissolve and mobilize the anthracene for easier degradation, actually inhibited removal. Only 37% of the spiked anthracene disappeared with surfactant treatment, compared to 62% in untreated soil over the same period.

More engineered approaches using bio-slurry reactors with alternating oxygen conditions have also shown promise, with performance depending on how quickly new anthracene is loaded and whether additional microorganisms are introduced.²⁴ Compost amendments have shown a positive effect as well, likely because the added organic material feeds soil fungi and bacteria that participate in degradation.²²

How Scientists Detect Anthracene in the Environment

Anthracene fluoresces under UV light, a property that makes it useful as a tracer compound in research but also provides a basis for analytical detection. The standard method for identifying and quantifying anthracene in water and soil is gas chromatography coupled with mass spectrometry (GC-MS), which can measure PAHs like anthracene, naphthalene, phenanthrene, and fluorene at very low concentrations in environmental samples.²⁵

For field applications where you need a fast answer, immunoassay-based methods have been developed. One technique uses antibodies coupled to an enzyme-linked assay to detect anthracene in water samples at concentrations as low as about 2.4 nanograms per milliliter.²⁶ An even more sensitive approach, combining immunoassay with PCR amplification, has pushed detection limits down to the femtogram-per-milliliter range, making it suitable for finding trace amounts in soil.²⁷ These rapid-test methods are increasingly useful for environmental decision-making at contaminated sites, where waiting days for laboratory GC-MS results is not always practical.

Practical Takeaways for Everyday Exposure

For most people, anthracene exposure comes in small doses from sources like wood smoke, grilled food, and ambient air pollution. These levels are unlikely to cause acute harm, but they add to the overall PAH burden your body handles. A few common-sense measures help reduce that burden: ensuring good ventilation if you heat with wood, limiting charring when you grill, and avoiding prolonged skin contact with coal-tar-based products like certain old-fashioned driveway sealants.

If you work in an occupation where anthracene contact is more direct, such as coal-tar processing, aluminum smelting, or creosote treatment of wood, the phototoxicity risk is the one to take seriously. Getting anthracene on your skin and then working in sunlight can lead to irritation, redness, and over time, skin damage that standard dark-exposure risk assessments would not predict. Protective clothing, prompt washing, and limiting UV exposure after contact are the standard recommendations in occupational health settings. The evidence suggests that even at fairly low concentrations, the interaction between anthracene, its breakdown products, and sunlight is potent enough to warrant genuine caution.