Cigarette smoke contains more than 9,000 chemicals, including more than 60 carcinogens. According to the U.S. Food and Drug Administration, there are 93 harmful and potentially harmful chemicals found in tobacco products.

But, when asked, adults in the U.S. can name only a few, such as tar and nicotine. How can we ensure that more smokers are aware of the risks? My team’s research suggests that we can look to other countries for an answer.

Labels around the world

To increase the public awareness of toxic chemicals in tobacco products, the World Health Organization (WHO) recommends that countries warn the public about toxic ingredients in tobacco products through large warnings with pictures.

According to a study with a U.S. national sample of adults, health warning labels on cigarette packs are the primary way consumers prefer to obtain information on chemicals in tobacco products. Warning labels can inform consumers – both current smokers and susceptible nonsmokers – at a minimum cost.

Pictorial warnings are superior to text-only warnings, because they catch consumers’ attention and increase their attempts to quit. For example, in a randomized clinical trial, 40 percent of adult smokers who received pictorial warnings attempted to quit smoking, compared to 34 percent of those who received text-only warnings. While this appears to be a small difference, the difference is still meaningful given that warnings can reach a large number of people.

As such, more than 100 countries in the world have implemented pictorial warnings, consistent with the WHO recommendations. Among the over 100 countries, Nepal, Vanuatu, India, Thailand and Australia are leading other countries in terms of the size of the warnings.

Despite these benefits – and the fact that consumers want to know more in learning about toxic chemicals in cigarette smoke – the U.S. has not introduced graphic warnings. The U.S. has also not introduced any novel warning message on harmful and potentially harmful chemicals in cigarette smoke. In fact, its four required warnings have not changed since 1984. Of those four, there’s only one message about toxic chemicals: “Cigarette smoke contains carbon monoxide.”

Other countries, meanwhile, are making efforts to present consumers with graphical information about toxic chemicals other than carbon monoxide.

Mexico, for example, introduced pictorial warnings on cigarette packs with specific statements about the dangers of toxins in 2010. Their warnings describe where toxic chemicals can be found in products other than cigarettes: “Contains Formaldehyde: a toxin that is used to preserve dead bodies.” Mexico also changes its warnings more frequently than any other country in the world, rotating new warnings every three months.

Since 2012, Australia has also required large pictorial warnings that cover over 80 percent of the cigarette pack. Meanwhile, U.S. warnings on average cover very little of the total cigarette pack.

Australia also standardized the size and color of cigarette packs and introduced descriptive warning messages in yellow color about toxic chemicals. The warnings describe how toxic chemicals in tobacco smoke cause disease: “Inhaling tobacco smoke releases benzene into your body. Benzene causes leukemia, increases the risk of other cancers and is believed to be dangerous at any level of exposure.”

In 2012, Canada replaced warnings about the quantitative levels of toxic chemicals with short statements about the presence of those chemicals. This followed a study showing that the numerical amount of tar and nicotine emission displayed on cigarette packs in many countries was misleading. While smokers often believe that “light” cigarettes are safer than others due to their low nicotine quantities, they are likely to inhale the same amount of chemicals from light cigarettes as regular cigarettes. This is because the amount of chemicals inhaled by a smoker depends on the individual smoker’s puffing behavior.

International comparisons

Our new study looks at online survey data from more than 4,000 adult smokers in Australia, Canada, Mexico and the U.S. We found that smokers’ knowledge of toxic chemicals described on each country’s warnings significantly increased between 2012 and 2014 in all countries but the U.S., after the countries added information about toxic chemicals to cigarette packs.

For example, as of September 2012, the average smoker in Mexico did not know that any of the three chemicals listed on cigarette packs – cyanide, formaldehyde and radioactive polonium 210 – was in cigarette smoke. However, in January 2014, smokers on average knew at least one, our study found.

Our results suggest that descriptive information about toxic chemicals can enhance smokers’ understanding of smoking-related risks. In our study, smokers’ perceptions of their risk of smoking-related conditions listed on packs – such as heart disease – increased over time in Australia, Canada and Mexico - but not in the U.S.

Moreover, smokers who knew more toxic chemicals and took a closer look at the warnings were also more likely to know about related health risks and believe that they were at a higher risk than nonsmokers – with the U.S. again the exception.

Moving forward

There is more we can do to identify communication strategies that discourage smoking and maximize public understanding of toxic chemicals. For example, we do not know whether it is more effective to describe how chemicals lead to disease or to note where toxic chemicals can be found in daily products.

Still, it appears clear that there’s plenty of room for improvement on U.S. cigarette pack warnings.

Given the effectiveness of pack warnings and the public desire to learn more about toxic chemicals, our research shows it would be beneficial to include more descriptive information about toxic chemicals in cigarette smoke in U.S. warnings. Large, graphic and often-rotated warnings would be ideal, as we have learned from other countries.