American Dental Association Improves Mouth Cancer and Smokeless Tobacco Brochures

I have been critical of the American Dental Association’s distribution of misinformation about smokeless tobacco and tobacco harm reduction (discussed here and here).  New ADA brochures on mouth cancer and smokeless tobacco show significant improvement  over their past publications.

The new pamphlet on mouth (and throat) cancer (here) accurately describes the disease as occurring “…most often in people who smoke cigarettes, cigars, or pipes and drink heavily (30 drinks or more per week).  That combination is estimated to cause the majority of mouth and throat cancers diagnosed in the United States.  Here are some additional risk factors:

• “Current research shows that some types of human papillomavirus (HPV) can cause throat cancer, which affects the base of the tongue and tonsils. HPV is very common— many people have the virus in their bodies and don’t even know it.

• “People who often spend long periods of time in the sun are at higher risk for lip cancer.” (emphasis in the original)

The brochure mentions one other risk factor, “a diet with too few fruits and vegetables,” but this is relevant mainly for people in developing countries, not in the U.S.

The new brochure on smokeless tobacco (here) drops many of the unscientific allegations that appeared in earlier versions and focuses a good deal on cessation.  Mouth cancer goes unmentioned, which is appropriate, given that the risk is so low. 

Still, the brochure is flawed.  Here are some questionable statements:

1.  “One can of smokeless tobacco has as much nicotine as 60 cigarettes or three packs.”  This is about as meaningless as claiming that one bottle of bourbon has as much alcohol as 19 cans of beer.  Just as responsible drinkers modulate their alcohol intake when using different products, smokeless users and smokers modulate their nicotine intake based on the products they use, attaining nearly the same peak nicotine blood level regardless of the source.  In comparing product nicotine levels, the ADA demonizes nicotine, which, while addictive, is not a major factor in any smoking-related illness.

2.  “Smokeless tobacco … has over 3,000 chemicals, including 28 cancer-causing substances.”  This is technically accurate but meaningless. One could also make the factual statement: “Coffee has over 1,000 chemicals, including 21 cancer-causing substances.” (here)  Any food or drink is composed of thousands of chemicals, some of which are or may be carcinogens.  Focusing on these is a scare tactic, described by renowned biochemist Bruce Ames as “hysteria over tiny traces of chemicals that may or may not cause cancer.” (here). 

3.  “People may think that smokeless means harmless, but nothing could be further from the truth.”  No credible tobacco harm reduction scientist or advocate claims that any tobacco product is absolutely safe; suggesting otherwise is nothing but a straw-man argument. 

The truth about smokeless is readily apparent: A wealth of scientific data show that smokeless means almost no measurable health risk.

Low Trace Metal Levels in American Smokeless Tobacco Products Mean No Significant Health Risk

I previously discussed a comprehensive chemical analysis of smokeless tobacco products conducted by M.F. Borgerding and colleagues at RJ Reynolds Tobacco Company and published in Regulatory Toxicology and Pharmacology (abstract here).  I focused on the results for tobacco-specific nitrosamines in that post (link here). 

Borgerding and colleagues analyzed many other agents, including trace metals.  As they write, “Human exposure to toxic trace metals occurs from a variety of sources that include diet, the environment, vitamin and dietary supplements, tobacco and tobacco smoke, among others.”  They measured levels of cadmium, arsenic, nickel, chromium and lead.

The diet is a prominent source of trace metals, so it is reasonable to compare the exposures to these metals from smokeless tobacco to those from the diet.  I will use a series of reports from the European Food Safety Authority (EFSA) for these comparisons.  I will report the metal levels in smokeless tobacco products as micrograms (ug) per gram (g) of tobacco, in dry weight.  I will compare the exposure from using one can of moist snuff per day (about 15 g of tobacco, dry) with daily dietary exposure.

It is important to note that this discussion will deal only with exposure, which is the amount of a substance that is contained in food or other products that we consume.  The other factor is uptake, which is the amount that we absorb.  Substances have a broad range of absorption rates; the absorption rate from food traveling through the gastrointestinal tract may be different from that of a smokeless tobacco product held in the lip. 

The absorption rate of trace metals from smokeless tobacco is not known, but a general idea is provided by studies that have estimated the percentage of nicotine absorbed from these products.  A study that I discussed recently (here) estimated that one-quarter to one-third of the nicotine in Swedish snus is delivered to the user.  That is a good place to start with respect to the potential absorption of other agents.  

Cadmium

Cadmium occurs naturally in the environment; for nonsmokers, the diet is the dominant source of this contaminant.  It is potentially toxic to the kidneys, and is listed by the International Agency for Research on Cancer (IARC) as a carcinogen, primarily based on lung cancer after inhalation by workers in high-exposure industries (here).   

The EFSA reports that dietary exposure is 19.5 ug (here).  Borgerding reports that moist snuff contains cadmium at a level of 1.05 ug/g.  Thus, a user of one can per day is exposed to 15.8 ug of cadmium, or about 80% of the dietary level.  This combined exposure is only one-half of the 70 ug that the World Health Organization suggests as a safe daily cadmium intake (reported in this article). 

A recent analysis of federal data revealed that smokeless tobacco users do not have elevated blood or urine cadmium levels compared with nonusers of tobacco (abstract here).  In that study cigarette smokers have elevated cadmium levels.

Arsenic

Arsenic also occurs naturally in the environment, and is present in a variety of forms (here).  IARC lists arsenic as a cause of urinary bladder, lung and skin cancers, based on studies of high levels of the metal in drinking water (hundreds to thousands of ug per liter)(here).  The World Health Organization guideline recommends that level of arsenic in drinking water not exceed 10 ug per liter.   

The EFSA reports that dietary exposure is 56 ug per day (here).  Borgerding reports that moist snuff contains arsenic at a level of 0.21 ug/g, meaning that a one-can-per-day user is exposed to 3.2 ug of arsenic, or about 6% of the dietary exposure. 

Nickel

Nickel alloys and compounds have been produced commercially for over 100 years. IARC lists some nickel compounds as a cause of lung and nasal cancers, based on workers in these industries who were exposed to massive quantities by inhalation (here).  In comparison, everyone else is exposed to vanishingly small quantities of nickel, mainly from food and water, and there is no evidence of health risks at this level.

The EFSA reports that dietary exposure to nickel is 150 ug/day (here).  Borgerding observes that moist snuff contains nickel at a concentration of 2.05 ug/g.  Thus, a one-can-per-day user is exposed to about 31 g, or roughly 21% of the dietary exposure.       

Chromium

As with nickel, metal workers who were exposed to massive quantities of some chromium compounds developed lung cancer, resulting in IARC classification of chromium as a carcinogen (here).  However, there is little evidence that much lower exposure from food and water is problematic. 

Chromium is, in fact, an essential micronutrient. The recommended daily allowance is 35 ug for adult men and 25 ug for adult women (here).  Borgerding advises that moist snuff contains chromium at a concentration of 1.6 ug/g, so one can provides about 24 ug.

Lead

Lead occurs naturally in the environment, but exposures were elevated in the last century due to its use in water pipes, paint and gasoline.  However, lead is no longer used for these purposes, making diet the primary source for most people.  Because lead affects the developing nerve system, exposure among children is of particular concern.  Although numerous studies have focused on workers exposed to massive quantities of lead, links to cancer are not conclusive; IARC lists lead as a probable carcinogen (here).

The EFSA reports that dietary exposure to lead is 41 ug/day (here).  Borgerding notes that moist snuff contains lead at a concentration of 0.32 ug/g.  A one-can-per-day user is exposed to about 6.1 ug, or 21% of the dietary exposure.      

In summary, exposure to cadmium, arsenic, nickel, chromium and lead from moist snuff is much lower than that from a typical diet.  Although all of these metals cause cancer in workers and others with massive exposures, levels from the diet and moist snuff are vastly lower and present no significant health risks.

Carcinogens in Coffee and Smokeless Tobacco: Truths & Half-Truths

If a health official announced, “The use of coffee, which contains 21 known human carcinogens, is not harmless,” she would be correct... but not entirely so.

A leading expert in carcinogenesis, Bruce Ames, authored a scientific manuscript in 2000 reporting that 21 known carcinogens are found in coffee (abstract here). Roasted coffee contains thousands of chemicals in addition to addictive caffeine. Some of these agents have been shown in laboratory experiments to cause cancer. Professor Ames also reported that humans consume carcinogens every day in foods and beverages that are considered “safe”; the carcinogens are present in such minuscule quantities that they play no significant role in the development of human cancer. He wrote:

“Naturally occurring pesticides that are rodent carcinogens are ubiquitous in fruits, vegetables, herbs, and spices. Cooking foods produces about 2000 milligrams per person per day of burnt material that contains many rodent carcinogens and many mutagens… In a single cup of coffee, the natural chemicals that are known rodent carcinogens are about equal in weight to a year’s worth of synthetic pesticide residues that are rodent carcinogens, even though only 3% of the natural chemicals in roasted coffee have been adequately tested for carcinogenicity.”

Here are some of the cancer-causing agents in coffee: Acetaldehyde, benzaldehyde, benzene, benzofuran, benzo(a)pyrene, caffeic acid, catechol, 1,2,5,6-dibenzanthracene, ethanol, ethylbenzene, formaldehyde, furan, furfural, hydrogen peroxide, hydroquinone, isoprene, limonene, 4-methylcatechol, styrene, toluene, xylene. And there are still about a thousand chemicals that haven’t been tested.

While this is a scary list, health officials are not calling for a ban on coffee. They know that epidemiologic studies show that coffee, while not absolutely harmless, is quite safe to consume.

Let’s get back to that statement at the beginning of this entry. In fact, a Daviess County (Kentucky) health department official was quoted in a news report, saying, “The use of smokeless tobacco, which contains 28 human carcinogens, is not harmless.” She was commenting on Switch and Quit Owensboro, a public health campaign that tells smokers the truth about vastly safer smoke-free cigarette substitutes (here).

The health department official was parroting a commonly used but almost meaningless factoid about smokeless tobacco. It is used by the CDC (here), the National Cancer Institute (here), the American Lung Association (here), and many state agencies (example here ).

The factoid is essentially meaningless because numerous epidemiologic studies have established that cancer risks associated with smokeless tobacco are so low that they are barely measurable.

Coffee contains 21 carcinogens and smokeless tobacco contains 28; both have high levels of an addictive drug (caffeine and nicotine, respectively). Neither coffee nor smokeless tobacco is absolutely safe, but informed public health practitioners know that the health risks with either are minimal. The real risk is in misleading smokers with partial truths.