Caution: Do Not Touch, Eat, or Inhale

A new government report adds four more industrial chemicals to a growing number of carcinogens.

We already know cigarette smoke can cause cancer. Flame retardants in our couches, too. But I bet you didn’t know fence posts and telephone poles can be a cancer risk. That’s because they’re often treated with a wood preservative that just made the government’s watch list of substances that might cause cancer in humans.

That list is now 243 items long, after the Department of Health and Human Services added four more this week: ortho-toluidine, 1-bromopropane, the aforementioned roadside hazard pentachlorophenol, and cumene, a chemical that oil-and-gas drillers inject deep into the earth for hydraulic fracturing, which could contaminate groundwater. Whether you can pronounce those substances or not, you should at least know about them—especially if you live or work around industries where they are prevalent.

“If you can identify things that cause cancer,” says Ruth Lunn, director of the Office of the Report on Carcinogens, “that’s the first step in hopefully preventing those cancers.”

Good advice, so it’s too bad the Environmental Protection Agency doesn’t require companies to ensure that industrial chemicals are safe before putting them on the market. Reformers, including NRDC (which publishes onEarth), are pushing for legislation to change that. But for now, we potentially come into contact with thousands of new, untested substances every year, and it's up to us to make sure they're safe: Anyone who suspects a chemical might cause cancer can nominate it for review by the National Toxicology Program. That interagency group then reviews the scientific literature to evaluate the substance’s risk to human health.

The most recent report categorizes only one new substance, ortho-toluidine, as a known carcinogen. The other three additions, at this stage in the research, are “reasonably anticipated” to cause cancer.

Unfortunately, once a chemical makes it on the government’s list, the companies making or using it don’t have to do much beyond informing their employees of the workplace hazard. (Take it off the market, you say? Nah.) Consumers outside of California—the only state that requires labeling on products containing carcinogens—are largely on their own.

With that in mind, below are some details on your four latest reasons to worry.


The Department of Health and Human Services first listed this substance as a potential carcinogen in 1983. But after reviewing more recent studies showing that it causes bladder cancer in humans, the department elevated its status. Ortho-toluidine is a synthetic chemical produced abroad to make rubber chemicals, herbicides, and textile dyes. Rubber chemical and dye manufacturers have the highest risk of exposure, because they may touch or inhale the chemical at work. It’s also found in tobacco smoke and prilocaine, a local numbing agent applied before medical and dental procedures and tattoo application.

HOW TO AVOID: At-risk workers should wear protective clothing and keep their workspaces well ventilated. Everyone else should limit exposure to products containing ortho-toluidine and check herbicides and dye labels. You might also want to stop smoking and rethink that dolphin tat.


Dry cleaners often use this smelly, colorless (or pale) liquid as a “green alternative” to perchloroethylene, which is also on the carcinogen list. It's also used to clean optics, electronics, and metals, and can be found in glue for foam cushions. People who are most likely to inhale this substance are those who use chemical sprays in the adhesive, asphalt, aircraft maintenance, synthetic fiber, and furniture industries. Although there are no studies showing 1-bromopropane causes cancer, it has been linked to neurological illnesses in humans. It also has led to skin, lung, and intestinal tumors in rats.

HOW TO AVOID: Again, if you work in any of those industries, make sure that you wear the right protective gear, your space is well ventilated, and that your employers follow safety guidelines.


This flammable liquid smells like gasoline and lingers in coal tar and petroleum fuels. As mentioned above, the natural gas industry injects cumene into the ground during drilling operations, along with many other toxic substances. A 2011 congressional report found that between 2005 and 2009, energy companies were using 95 products that contained 13 carcinogens. Cumene is also found in tobacco smoke and used to make plastics and acetone, a solvent used to dissolve varnishes and paints, such as nail polish. There’s no research on human health and cumene, but it causes lung and liver tumors in mice.

HOW TO AVOID: People can inhale cumene via tobacco smoke and automobile fumes or be exposed if they work somewhere that uses or produces the volatile liquid. Do your best to not breathe in car exhaust, and seriously, quit smoking already.

Pentachlorophenol (and its byproducts)

Research shows that workers who treat lumber (utility poles, fence posts, wood pilings) with this wood preservative have a higher risk of developing non-Hodgkins lymphoma, a cancer of the immune system. Living near wood-treatment facilities can also increase exposure to this mixture of chlorinated dioxin compounds that also causes tumors in mice.

HOW TO AVOID: Stay away from treated wood and any surrounding soil, which can become polluted with the compounds as the wood breaks down. In other words, only hug trees that are still alive. And if you work in the wood-treatment industry, wear protective clothing, work in a well-ventilated area, and limit the amount of time working with the product.

Curious about the other 239 substances on the government’s watch list? Check out the 13th Report on Carcinogens, and be careful out there.

This article was originally published on onEarth, which is no longer in publication. onEarth was founded in 1979 as the Amicus Journal, an independent magazine of thought and opinion on the environment. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. This article is available for online republication by news media outlets or nonprofits under these conditions: The writer(s) must be credited with a byline; you must note prominently that the article was originally published by and link to the original; the article cannot be edited (beyond simple things such grammar); you can’t resell the article in any form or grant republishing rights to other outlets; you can’t republish our material wholesale or automatically—you need to select articles individually; you can’t republish the photos or graphics on our site without specific permission; you should drop us a note to let us know when you’ve used one of our articles.

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