Creosote is genuinely harmful to humans. It is classified as a probable human carcinogen by multiple health agencies, and direct contact with it can cause everything from severe skin burns to organ damage. The substance is not a single chemical but a complex mixture of hundreds of compounds, many of which are individually toxic. How dangerous it is to any one person depends on the type of creosote, the route of exposure, and how long that exposure lasts, but the overall picture from occupational studies and case reports is clear: avoiding unnecessary contact is well-justified.
What Creosote Actually Contains
The word “creosote” refers to more than one product, which is part of why conversations about its safety can get confusing. Coal tar creosote, the dark oily liquid used to preserve railroad ties, utility poles, and marine pilings, is the form most people encounter and the one most studied for health effects. It is produced by distilling coal tar at high temperatures, and the result is a thick mixture that can contain over 300 different chemical compounds. A smaller category, wood creosote (derived from beechwood), has historically been used in some traditional medicines and has a different chemical profile, though it is not without risks of its own.
The compounds that make coal tar creosote particularly dangerous are polycyclic aromatic hydrocarbons, commonly abbreviated as PAHs. PAHs are a family of chemicals formed when organic material is burned or heated. Several of them are known or probable carcinogens. Laboratory analysis of creosote has detected the mutagenic PAHs benzo[a]pyrene and benz[a]anthracene at concentrations of about 0.18% and 1.1%, respectively.1PubMed. The presence of the mutagenic polycyclic aromatic hydrocarbons benzo[a]pyrene and benz[a]anthracene in creosote P1 Those percentages might sound small, but benzo[a]pyrene is one of the most potent carcinogens known, and creosote-treated structures can leach these compounds into surrounding soil and water for decades. Beyond PAHs, creosote also contains phenols, cresols, and heterocyclic compounds containing nitrogen, sulfur, and oxygen, each contributing their own toxic effects.
How People Get Exposed
You do not need to drink creosote for it to cause harm. The three main routes into the body are skin contact, inhalation of vapors or mists, and ingestion, and the first two are far more common in practice. Workers in wood preservation plants, railroad maintenance crews, and utility workers face the highest exposures, but homeowners who reuse old railroad ties for landscaping or gardening also come into contact with creosote regularly.
For workers, the balance between skin and lung exposure matters. A study measuring both inhalation and dermal exposure during timber impregnation found that cooling the vacuum vessel before unloading reduced inhalation exposure to roughly one-third of what it would otherwise be. Interestingly, some structural safety measures intended to reduce exposure did not always work as planned and in certain configurations actually increased exposure. Dermal exposure varied widely depending on the specific work procedures, and workers assembling pre-treated railroad sleepers experienced lower inhalation exposure than impregnation workers but similar levels of skin contact.2PubMed. Inhalation and dermal exposure of workers during timber impregnation with creosote and subsequent processing of impregnated wood In other words, you do not have to be breathing in heavy fumes to absorb a significant dose. The skin is a surprisingly efficient gateway for these chemicals.
For the general public, casual exposure usually involves touching old creosote-treated wood, inhaling its distinctive smoky-tar odor on warm days when the wood sweats out oils, or consuming food grown in soil that has been contaminated by leaching. Children are especially vulnerable because they are more likely to touch treated wood and put their hands in their mouths.
What Happens with Acute Exposure
The immediate effects of creosote depend on how you come into contact with it. Skin contact with the oily liquid, especially in sunlight, can produce chemical burns, blistering, and a rash that resembles a severe sunburn. This phototoxic reaction happens because certain PAHs in creosote absorb ultraviolet light and release energy that damages skin cells. Workers who get creosote on their skin and then go out into the sun often develop far worse irritation than those who stay indoors.
Inhaling concentrated creosote vapors causes irritation of the nose, throat, and lungs. Symptoms can range from coughing and wheezing to more serious respiratory distress with heavier exposures. Eye exposure produces stinging, tearing, and in some cases lasting sensitivity to light.
Ingestion is rarer but far more dangerous. A documented fatal case of creosote poisoning described extensive ulceration of the mouth and throat upon presentation. Post-mortem examination revealed that the esophagus and stomach were intact, suggesting the corrosive damage concentrated in the oropharynx.3Postgraduate Medical Journal. A fatal case of creosote poisoning Reviews of creosote toxicity describe a broader range of potential internal effects from significant exposure, including loss of consciousness, convulsions, mental impairment, and kidney and liver damage.4Environment. Technology. Resources. Review of Creosote Pollution Toxicity and Possibilities of Bioremediation These severe outcomes are associated with substantial doses, not incidental contact, but they underscore why creosote should never be treated casually.
The Cancer Evidence
The long-term risk that concerns public health agencies most is cancer, and the evidence points in one direction. A study tracking cancer incidence among workers exposed to creosote in wood impregnation plants in Norway and Sweden found elevated risks for several cancers. Skin cancer showed a statistically significant increase, with an observed rate roughly 2.4 times higher than expected. Lip cancer and malignant lymphoma were also elevated, though the numbers were too small for firm conclusions on those specific types. The researchers noted that occupational sun exposure may have contributed to the lip and skin cancer rates, since outdoor workers face UV radiation on top of their chemical exposure. Still, the findings pointed to creosote itself as a contributor.5PubMed. Cancer incidence among creosote-exposed workers
Case reports have reinforced the connection between prolonged creosote exposure and skin cancer specifically. One well-documented case involved a railroad worker who developed squamous cell carcinoma linked to decades of coal tar creosote exposure on the job.6PubMed Central. Squamous cell carcinoma of the skin and coal tar creosote exposure in a railroad worker The pattern across studies is consistent with what toxicologists would expect given the known carcinogenicity of the PAHs in creosote. Benzo[a]pyrene, the compound detected at 0.18% in creosote, is classified as carcinogenic to humans based on strong evidence from both animal studies and human epidemiology.
The cancer risk is not limited to the skin. Research into the molecular effects of occupational PAH exposure found that creosote workers and chimney sweeps had reduced DNA methylation at two specific genes, F2RL3 and AHRR, both of which are associated with lung cancer risk. The PAH exposure from creosote oil appeared to drive these epigenetic changes, meaning creosote may be influencing cancer risk through mechanisms that go beyond direct DNA damage.7PubMed Central. DNA methylation of the cancer-related genes F2RL3 and AHRR is associated with occupational exposure to polycyclic aromatic hydrocarbons Epigenetic modifications like these do not change the DNA sequence itself but alter how genes are read, and these particular changes have been independently linked to increased cancer susceptibility.
Measuring Exposure in the Body
One of the practical challenges with creosote exposure is that you cannot always tell how much you have absorbed just from the smell or appearance of your work environment. Researchers have settled on a useful biomarker: a metabolite called 1-hydroxypyrene, measured in urine. When the body processes pyrene, one of the PAHs common in creosote, it produces this metabolite, and urine concentrations correlate well with overall PAH exposure. Studies of creosote workers have confirmed that urinary 1-hydroxypyrene reliably tracks exposure to the medium- and large-ring PAHs that cause the most concern, though it does not capture exposure to smaller molecules like naphthalene as effectively.8PubMed Central. Significance of dermal and respiratory uptake in creosote workers: exposure to polycyclic aromatic hydrocarbons and urinary excretion of 1-hydroxypyrene
In occupational settings, both pre-shift and post-shift urine samples are collected to gauge how much PAH a worker has absorbed during a single work period.2PubMed. Inhalation and dermal exposure of workers during timber impregnation with creosote and subsequent processing of impregnated wood This kind of monitoring is critical because, as mentioned earlier, skin absorption can be as significant as inhalation, and a worker who feels no respiratory symptoms may still be absorbing substantial amounts through their hands and forearms. The biomarker approach captures all routes of exposure at once, which makes it a better gauge than air sampling alone.
Railroad Ties in Gardens and Landscaping
The most common way non-workers encounter creosote is through old railroad ties. They are cheap, durable, and widely available, so people use them as garden bed borders, retaining walls, and landscape edging. This is where the residential risk lives, and the evidence suggests it deserves more attention than most gardeners give it.
Research on community gardens that used railroad ties as plot dividers found that total PAH concentrations in soil within 18 inches of the creosote-treated timbers were on average four times higher than concentrations in the center of garden plots and more than five times higher than background PAH levels. Concentrations dropped with distance from the timbers and approached background levels around 18 inches away.9PubMed Central. Characterization and Low-Cost Remediation of Soils Contaminated by Timbers in Community Gardens That means plants grown right up against a railroad tie border are rooted in substantially contaminated soil, and root vegetables planted close to the timbers are the most concerning.
The contamination is not a one-time event. Railroad ties continue leaching PAHs into surrounding soil for years. On hot days, the oily sheen that appears on the surface of old ties is creosote migrating out of the wood, and rain washes it into the surrounding earth. If you already have railroad ties in your garden, growing edible plants at least two feet away from them reduces exposure considerably based on the concentration gradient the research documents. Replacing them with untreated stone, concrete blocks, or naturally rot-resistant woods like cedar eliminates the concern entirely.
Groundwater and Soil Contamination
Beyond the immediate area around treated wood, creosote poses a broader environmental issue. Former wood treatment sites, old rail yards, and areas where creosote-treated poles have been stored can have deeply contaminated soil and groundwater. Creosote does not dissolve easily in water, but its lighter compounds, particularly phenols and some smaller PAHs, are mobile enough to reach aquifers. Once there, they can persist for a long time.
Remediation efforts have shown some promise. Column experiments simulating a permeable barrier made of peat and sand demonstrated that the material could remove between 94% and 100% of PAHs and 93% to 98% of nitrogen-, sulfur-, and oxygen-containing heterocyclic compounds from creosote-contaminated water. Phenol removal was more variable, ranging from 44% to 97%.10PubMed. Treatment of creosote-contaminated groundwater in a peat/sand permeable barrier–a column study These results suggest affordable, low-tech approaches can be effective, but they also highlight the scale of the contamination problem that develops when creosote enters the water supply.
For homeowners near former industrial sites, this matters because well water can be affected. If you know your property is near a site that historically handled creosote-treated materials and you draw water from a private well, testing for PAHs is a reasonable precaution. Municipal water systems test for these contaminants as part of their regulatory requirements, but private wells are the owner’s responsibility.
Regulations and Restrictions on Use
The regulatory landscape around creosote reflects its hazard profile. In the European Union, creosote has been heavily restricted since 2003. Consumer use is banned outright, and industrial use requires authorization under the Biocidal Products Regulation, with strict conditions on worker protection. The restrictions were tightened further in subsequent reviews, and several member states have pushed for a complete ban. In the United States, creosote remains registered as a restricted-use pesticide, meaning only certified applicators can purchase and apply it. You cannot buy it at a hardware store. The Environmental Protection Agency has evaluated it multiple times and maintained its availability for industrial wood preservation based on the argument that it prevents decay in critical infrastructure like railroad ties and utility poles, where alternatives have historically had performance limitations.
Several countries, including Germany and Sweden, have gone further with restrictions or outright bans for certain applications. Australia and New Zealand have also tightened rules around handling and disposal. The trend across the developed world is toward fewer uses and tighter controls, driven largely by the cancer data and environmental persistence.
For practical purposes, this means the average person should not be treating their own wood with creosote, and in many jurisdictions, doing so is illegal. The main exposure risk for non-workers comes from old treated materials already in place, particularly railroad ties in residential settings and aged utility poles on or near private property.
Common Misconceptions About Creosote Safety
A persistent belief is that once creosote-treated wood has aged and dried out, it becomes safe. The research on soil contamination near railroad ties directly contradicts this. Old ties continue leaching PAHs, and the process accelerates in warm weather. The “dried out” appearance is somewhat misleading; the interior of the wood typically remains saturated, and heat draws the oils to the surface.
Another misconception confuses chimney creosote with coal tar creosote. The soot and tar buildup inside chimneys is often called “creosote” colloquially, and while it does contain PAHs from incomplete wood combustion, it is chemically distinct from the industrial product used for wood preservation. Both are health hazards, but chimney buildup is primarily a fire risk and a source of indoor air pollution, whereas coal tar creosote is a concentrated industrial chemical with well-documented carcinogenicity.
Some people also assume that sealing or painting over creosote-treated wood makes it safe for garden or playground use. Sealants can reduce surface leaching in the short term, but they degrade over time, especially in outdoor conditions, and do not address the contamination already present in adjacent soil. If the wood is in contact with the ground, moisture migration through the bottom of the timber continues regardless of what you have applied to the top.
Wood Creosote in Traditional Medicine
An entirely separate product called wood creosote, derived from the distillation of beechwood tar, has a long history in Japanese traditional medicine. The best-known use is in Seirogan, an over-the-counter gastrointestinal remedy that has been sold in Japan for well over a century. Wood creosote contains primarily guaiacol and creosol, which have antiseptic and antidiarrheal properties, and its chemical composition is quite different from coal tar creosote. The PAH content is much lower, and the compounds that dominate are simpler phenolic molecules rather than the large, multi-ring hydrocarbons that make coal tar creosote carcinogenic.
That said, wood creosote is not without controversy. Some toxicologists have raised concerns about its long-term safety, and the fact that it shares a name with coal tar creosote has caused confusion in both the public and the regulatory sphere. The two products should be thought of as entirely different substances that happen to share a label. The health risks discussed throughout the rest of this article apply to coal tar creosote, which is the form found in railroad ties, utility poles, and industrial wood preservation.