Yes, creosote is carcinogenic. Coal tar creosote, the dark, oily substance used to preserve railroad ties, utility poles, and marine pilings, is classified as a “probable human carcinogen” (Group 2A) by the International Agency for Research on Cancer. The closely related process of coal tar distillation that produces creosote holds an even stronger classification: Group 1, meaning it is definitively carcinogenic to humans based on clear evidence of skin cancer. The U.S. National Toxicology Program has listed coal tars and coal tar pitches as “known human carcinogens” since 1980.
But the story is more nuanced than a simple yes. There are different types of creosote with very different risk profiles, and your actual danger depends on the type, duration, and route of exposure.
Coal Tar Creosote vs. Wood Creosote
The word “creosote” refers to two chemically distinct substances, and only one poses a serious cancer risk. Coal tar creosote is an industrial product distilled from coal tar. At least 75% of its chemical makeup consists of polycyclic aromatic hydrocarbons (PAHs), a family of compounds with well-documented links to cancer. This is the creosote used to treat wood for outdoor industrial use.
Wood creosote is a different product entirely, derived from beechwood or the creosote bush. It consists mainly of phenols, cresols, and related compounds rather than PAHs. Animal studies evaluating cancer after oral exposure to wood creosote have not found a tumor-promoting response. Wood creosote has historically been used in some pharmaceutical products, and its primary health concern is liver effects rather than cancer. When people ask whether creosote causes cancer, they’re almost always asking about the coal tar variety.
Which Cancers Are Linked to Creosote
Studies of workers exposed to coal tar in industrial settings have found increased cancer risk across a surprisingly wide range of tissues: skin, lung, bladder, kidney, pancreas, prostate, rectum, scrotum, and the central nervous system. Skin cancer is the most historically documented. Reports of creosote-related skin disease go back to 1898, when a case of scrotal tumors in a creosote worker was published in the British Journal of Dermatology.
A cohort study of 922 creosote-exposed workers found a skin cancer rate 2.37 times higher than in unexposed people. One notable case involved a 50-year-old railroad worker who developed squamous cell carcinoma on his knee, an area shielded from sunlight but repeatedly soaked with creosote that filtered through his work clothing over 30 years. That detail matters because it helps separate the creosote effect from sun exposure, which has been a confounding factor in earlier studies where cancers appeared on sun-exposed skin.
Lung and bladder cancers are also strongly linked. Exposure to coal tar pitch among roofers and pavers carries a Group 1 classification specifically for these two cancer types.
How Creosote Causes Cancer
The cancer-causing mechanism centers on those PAHs that make up the bulk of coal tar creosote. On their own, some PAHs are only weakly carcinogenic. The real damage happens after your body tries to break them down. During metabolism, PAHs are converted into intermediate compounds called diol epoxides. These reactive molecules bind directly to DNA, forming what scientists call “adducts,” essentially chemical attachments that distort the DNA’s normal structure.
When a cell with damaged DNA replicates before the damage is repaired, the result is a permanent mutation. If that mutation hits a gene responsible for controlling cell growth or differentiation, it can set a cell on the path toward becoming cancerous. One well-studied example: a PAH metabolite from benzo(a)pyrene binds to specific spots on the p53 gene, the same tumor-suppressing gene that cigarette smoke targets. Coal tar creosote compounds have also shown both tumor-initiating and tumor-promoting activity in animal skin studies, meaning they can start the cancer process and accelerate it.
Risks for People Living Near Contaminated Sites
You don’t have to work directly with creosote to be affected. Residents living near former wood treatment plants or on land previously used for creosote operations show measurably higher rates of several health problems. In Texarkana, Texas, 214 residents of a housing development built on a former creosote wood treatment site had skin rash rates of 27.9%, compared to 4.9% in a nearby comparison neighborhood. They also showed elevated rates of chronic bronchitis.
A separate study of 199 long-term residents near a wood treatment plant found bronchitis rates three times higher than controls (17.8% vs. 5.8%) and asthma rates nearly four times higher (40.5% vs. 11%). These residents also reported more skin rashes after sun exposure (29% vs. 5%) and more neurological symptoms, including irritability, light-headedness, and extreme fatigue. Testing confirmed measurable differences in reaction time, visual field function, and grip strength.
Some components of coal tar creosote dissolve in water and can migrate through soil to groundwater, which is why the EPA lists coal tar creosote as a hazardous constituent of waste. If your home is near a site that once housed a wood preservation facility or gas manufacturing plant, avoiding areas of known soil contamination is a practical precaution.
Skin Contact and Dermal Absorption
Direct skin contact is one of the most important exposure routes. Creosote penetrates clothing and absorbs through skin, as the railroad worker case illustrates. Beyond cancer, non-cancer effects of skin contact include dermatitis, photosensitivity (increased vulnerability to sunburn and skin reactions), irritation of mucous membranes, and conjunctivitis. Workers handling creosote-treated wood commonly notice skin discoloration on their hands and any area where creosote soaks through protective gear.
Animal experiments reinforce the skin cancer connection. Mice housed in creosote-impregnated wooden boxes developed unexpectedly high numbers of skin tumors. Separate experiments documented skin carcinomas in mice directly exposed to creosote oils.
Current Regulations and Restrictions
Creosote has no registered residential uses in the United States. The EPA restricts it to commercial and industrial outdoor applications like railroad ties, utility poles, and marine pilings. Indoor applications are prohibited, as is any use on wood that will contact food, animal feed, or drinking water. It is classified as a restricted-use pesticide, meaning only certified applicators can handle it.
In 2021, the EPA proposed additional worker protection measures for employees at wood treatment facilities. OSHA sets a workplace exposure limit of 0.2 milligrams per cubic meter for coal tar pitch volatiles, reflecting the seriousness of inhalation risk in occupational settings.
For the general public, the main exposure scenarios are contact with old creosote-treated wood (such as repurposed railroad ties used as garden borders), living near contaminated former industrial sites, or handling creosote-treated materials during demolition or construction. Using creosote-treated railroad ties in home gardens or landscaping is not recommended, particularly around areas where food is grown.