What you should know about the cancer-causing chemical found in recalled dry shampoo

Health Canada issued a mass recall on Tuesday of Unilever hair products containing the cancer-causing chemical benzene.

This time, the listed products were dry shampoos sold over the last two years by Unilever brands Bed Head TIGI, Dove and Tresemmé. But other hair and skin products have also been subject to recalls in recent years due to the presence of benzene.

Most recently, Edgewell Personal Care Company issued a voluntary recall of its Banana Boat scalp and hair sunscreens containing benzene in July. In April, the U.S. Food and Drug administration issued a recall of several Disney-branded hand sanitizers over the same chemical. Benzene also led to the recall of several Procter & Gamble Company spray antiperspirants in 2021.

Benzene is a petrochemical often found in vehicle emissions. So why is it sometimes found in dry shampoos, hand sanitizers and aerosol sunscreen, and what are the risks to consumers' health?

To better understand, CTVNews.ca takes a look at what benzene is and how it's used in manufacturing.

WHAT IS BENZENE?

Benzene is a clear liquid chemical found in gasoline. It's also used in the synthesis of other chemicals and as a solvent in the chemical and pharmaceutical industries. It's a natural component of crude oil, and is produced by both natural and human-made processes.

Although liquid at room temperature, it evaporates and becomes gaseous very quickly. For that reason, most humans are exposed to it through the air they breathe. It can also be absorbed through skin contact. According to Health Canada, vehicle emissions are the major source of benzene released into the environment, but other sources include cigarette smoke and emissions from volcanoes and forest fires.

WHAT ARE THE DANGERS?

Paul Demers has spent years of his career studying the effects of harmful chemicals like benzene on human health.

Demers is director of the Occupational Cancer Research Centre, a senior scientist with Ontario Health and a professor with the occupational and environmental health division of the University of Toronto's Dalla Lana School of Public Health.

While exposure to high levels of benzene can cause temporary symptoms such as anemia, memory loss, skin irritation and even unconsciousness, Demers said benzene is also classified as a carcinogen – a cancer-causing agent.

"It's not an uncommon thing to encounter out there," Demers said in a phone interview with CTVNews.ca on Thursday. "The problem is, we've known it's a cause of cancer since around 1979 or 1980. So (for) over 40 years it's been classified as a human carcinogen internationally."

Health Canada warns exposure to benzene can result in cancers including leukemia and blood cancer of the bone marrow, as well as other potentially life-threatening blood disorders.

The agency wrote in its recall notice on Tuesday that the concentration of benzene found in the affected shampoos "would not be expected to cause adverse health consequences," but Demers said there's reason to be concerned about the cumulative effects of even trace amounts of benzene found in personal care products.

"When we think about the low levels in consumer products we're really concerned about the long-term effects that might be in there, and that's why cancer comes up," he said. "If it's personal care products that you're aiming at your body, whatever's in there – even if it's a small amount – we would probably be concerned about it."

WHY IS BENZENE FOUND IN CONSUMER PRODUCTS?

Because benzene is released in combustion and used in heavy industry, most dangerous exposure to benzene takes place in occupational settings. Firefighters and people who work in printing, in factories where rubber or steel are processed or in gas stations face some of the highest risks of workplace exposure.

As far as Demers knows, benzene is not used to produce consumer goods such as dry shampoos and conditioners, aerosol sunscreen, antiperspirant or hand sanitizer. But because it's used to make so many other chemicals and industrial products, there's always a chance of contamination. In the case of the Oct. 18 Unilever recall, an internal investigation found the aerosol propellant in the spray cans was the source of contamination.

That's why quality control is such an important component of manufacturing. When benzene shows up in a consumer good, Demers said it's likely because something in the manufacturing or quality control process has gone wrong.

"It's a good thing we pay attention to consumer products in this way," he said. "It seems like periodically we've got toxic metals showing up in products, or different types of chemicals showing up in products, so this is something we've always got to be vigilant about."

For information about what to do if you think you've purchased a recalled product, visit recalls.canada.ca.