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Forget Homeopathic Arsenic for Stress Reduction

stressDuring a recent talk on the relation between the body and the mind, I mentioned the newest anxiety-relieving craze, colouring books. Aimed at adults, these feature intricate patterns that provide quite a challenge for staying inside the lines. The contention is that focusing on the special patterns distracts the mind from anxiety and stress. Evidence is sketchy, but millions of colouring books are flying off the shelves, topping best-seller lists. That in itself says something about our society.

After my talk I was approached by a lady who claimed she had something better than colouring books to relieve anxiety and slipped a vial full of pills into my hand. She didn’t seem like a clandestine drug pusher so I thought I would look down and find some pills of lorezapam or maybe St. John’s Wort. Such was not the case. The label on the vial read “Arsenicum album 30C.”

No, she was not trying to poison me. These were homeopathic arsenic pills based on the curious notion that a substance that in large doses causes certain symptoms can, in homeopathic potency, repel the same symptoms. Since arsenic poisoning is associated with anxiety and restlessness, a person suffering such symptoms should find relief in a homeopathic dose of arsenic. In the bizarre world of homeopathy, potency increases with greater dilution, and a dose of 30C is said to be extremely potent. Such a pill is made by sequentially diluting a solution of arsenic a hundred fold thirty times and then impregnating a sugar pill with a drop of the final solution. At a dilution of 30C, not only is there no trace of arsenic left, there isn’t even a water molecule that has ever encountered any of the original arsenic.

Homeopathy is a scientifically bankrupt practice that was invented over two hundred years ago by German physician Samuel Hahnemann who was disenchanted with bloodletting and purging, common medical procedures at the time. He was a good man who searched for kinder and gentler treatments and homeopathy fit that rubric. Since knowledge of molecules was almost non-existent at the time, Hahnemann could not have realized that his diluted solutions contained nothing. Actually, the truth is that they did contain something. A hefty dose of placebo!

Now here is the kicker to this story. Hahnemann was quite accomplished in chemistry and actually developed the first chemical test for arsenic. In 1787 he found that arsenic in an unknown sample was converted to an insoluble yellow precipitate of arsenic trisulfide on treatment with hydrogen sulfide gas. When in 1832 John Bodle in England was accused of poisoning his grandfather by putting arsenic in his coffee, John Marsh, a chemist at the Royal Arsenal, was asked to test a sample of the coffee. While he was able to detect arsenic in the coffee using Hahnemann’s test, the experiment could not be reproduced to the satisfaction of the jury and Bodle was acquitted. Knowing that he could not be tried for the same crime again, he later admitted to killing his grandfather.

The confession infuriated Marsh and motivated him to develop a better test for arsenic. By 1836 he had discovered that treating a sample of body fluid or tissue with zinc and an acid converted any arsenic to arsine gas, AsH3, which could then be passed through a flame to yield metallic arsenic and water. The arsenic would then form a silvery-black deposit on a cold ceramic bowl held in the jet of the flame and the amount of arsenic in the original sample could be determined by comparing the intensity of the deposit with that produced with known amounts of arsenic.

The Marsh test received a great deal of publicity in 1840 when Marie LaFarge in France was accused of murdering her husband by putting arsenic into his food. Marie was known to have bought arsenic from a local chemist which she claimed was to kill rats that had infested the house. A maid swore that she has seen her mistress pour a white powder into her husband’s drink and Marie had also sent a cake to her husband who was travelling on business just prior to his becoming ill. The dead husband’s family suspected that Marie had poisoned him and somehow got hold of remnants of food to which she had supposedly added arsenic. The Marsh test revealed the presence of arsenic in the food and in a sample of egg nog, but when the victim’s body was exhumed the investigating chemist was unable to detect arsenic.

To help prove Marie’s innocence by corroborating the results of the investigation of the exhumed body, the defense enlisted Mathieu Orfila, a chemist acknowledged to be an authority on the Marsh test. Much to the defense’s chagrin, Orfila showed that the test had been carried out incorrectly and used the Marsh test to conclusively prove the presence of arsenic in LaFarge’s exhumed body. Marie was found guilty and sentenced to life in prison. The controversial case captured the imagination of the public and was closely followed through newspaper accounts making Marie LeFarge into a celebrity. It would also go down in the annals of history as the first case in which a conviction was secured based on direct forensic toxicological evidence. Because of Mathieu Orfila’s role in the case, he is often deemed to be the “founder of the science of toxicology.” The Marsh test became the subject of everyday conversations and even became a popular demonstration at fairgrounds and in public lectures. This had an interesting spin off. Poisonings by arsenic decreased significantly since the existence of a proven, reliable test served as a deterrent.

As far as claims about relieving anxiety with homeopathic arsenic go, well, they cause me anxiety. I think I’ll flush those homeopathic tablets down the drain (no worry about arsenic pollution here) and buy a colouring book.

Dr. Joe Schwarcz


antimonyPicture this. You swallow a little pill, wait until it irritates your intestines enough to expel its contents and then hunt through the expelled excrement to retrieve the pill. Why? So you can use it next time to get rid of the bad humours in your body that are making you sick. How can a pill survive passage through the digestive tract? It can, if it is made of metal, in this case, antimony. Now, don’t go asking the pharmacist for antimony pills. The scenario just described isn’t current, it was plucked out of the Middle Ages when the cure for disease was to expel “bad humours” from the body. Actually, that was not unlike the current craze of expelling unnamed toxins from the body with a variety of “cleanses,” many of which have a laxative effect.

Hopefully nobody today would be silly enough to use antimony or its compounds, because here we are talking about real toxicity. Of course they didn’t realize that in the Middle Ages; all they knew was that antimony was pretty good at evacuating the body. And not only through the rear portals. One method involved drinking wine that had been left standing overnight in a cup made of antimony. This resulted in the antimony reacting with tartaric acid in the wine to form antimony tartrate, a compound that induces vomiting. The idea of purging the body to treat illness persisted into the late stages of the 18th century. When Mozart came down with a mysterious illness, he was treated with “tartar emetic,” as antimony tartrate was commonly called. What ailment he suffered from isn’t clear, but he died within two weeks. His symptoms of intense vomiting, fever, swollen abdomen and swollen limbs are consistent with antimony poisoning. Of course, we cannot prove that antimony was responsible for Mozart’s death, he also suffered from rheumatic fever since childhood, a condition that may have led to his demise at a young age.

Mozart had always been sickly and it is well known that he had been often treated with antimony compounds by his physicians and that he even dosed himself when he didn’t feel well. It is interesting that Mozart actually believed he was being poisoned, but not by himself. He thought his musical rival Antonio Salieri was trying to do him in. Although the famous movie “Amadeus” alludes to this possibility, historical facts do not corroborate the poisoning story. Contrary to the portrayal, Salieri did not confess at the end of his life to having tried to kill Mozart.

Back in the 1990s a volatile compound of antimony known as stibine (SbH3) was accused of being responsible for crib death. The theory was that it was produced from antimony oxide added as a flame retardant to polyvinylchloride sheets. A fungus found in mattresses supposedly made this conversion possible, at least under laboratory conditions. The theory has now been dismissed because neither the fungus, nor levels of antimony in babies’ blood could be correlated with crib death.

More recently Greenpeace created a stir with a booklet entitled “A Little Story About The Monsters In Your Closet.” What sort of “monsters?” The subtitle brings them out of the closet: “Study finds hazardous chemicals in children’s clothing.” Yup, the monsters are chemicals. One that the Greenpeace study detected was antimony trioxide, present in all fabrics that have polyester as a component. No great surprise here since antimony trioxide is used as a catalyst in the production of polyester as well as a flame retardant. And it is true that antimony trioxide can be described as presenting a hazard. But hazard is not the same as risk.

Hazard is the innate potential of a substance to cause harm without taking into account extent or type of exposure. Inhalation of antimony compounds in an occupational setting can be a problem, and it is correct that antimony trioxide has been classified as “suspected of causing cancer via inhalation.” But this is not relevant for the trace amounts found in fabrics. Here the issue would be migration out of the fabric and subsequent absorption. This has been extensively investigated and the amounts that are encountered are well below the established migration limits. The same applies to the trace amounts that leach out of the polyester bottles that are widely used for water and other beverages. Concentrations are less than the 5 parts per billion safety limit.

Antimony does not occur in nature in its metallic form, so where did Middle Age physicians get it? Like most metals, antimony has to be smelted from its ore, in this case antimony sulfide, also known as stibnite, a substance that has been known for thousands of years. Jezebel, the Biblical temptress is said to have used it to darken her eyebrows and stibnite was the main ingredient in “kohl” used by ancient Egyptian women in a type of mascara. Exactly who figured out that heating antimony sulfide converts it to antimony oxide, which yields metallic antimony when fired with carbon, is unknown, but if you visit the Louvre, you can see a 5000 year old vase that is made of almost pure antimony.

Today, neither metallic antimony nor its compounds have a medical use, although up to the 1970s, antimony compounds were used to treat parasitic infections like schistosomiasis. These preparations did kill the parasites, but sometimes they also dispatched the patient. Up to the early twentieth century, tartar emetic was used as a remedy, albeit an ineffective one, for alcohol abuse. The New England Journal of Medicine once reported a case of a man whose wife tried to cure him of his alcoholic habit by secretly putting tartar emetic into his orange juice. The result was a trip to the hospital with chest pains and liver toxicity. Two years later the man reported complete abstinence from alcohol. Seems antimony had taught him a lesson.

Joe Schwarcz PhD

Chemistry Lesson for The Food Babe…and everyone else #13

vani hariYikes-There’s Cyanide in My Salt!

Is it true that they add cyanide to salt,” was the question tossed at me via an email. The answer is yes, sort of. Some commercial varieties of salt have small amounts of sodium ferrocyanide added to prevent caking. When humidity is high, a thin layer of moisture forms on the surface of the salt crystals, and some of the salt dissolves in this layer to form brine. If the relative humidity then drops, the water evaporates and the brine solution recrystallizes between the salt crystals, causing them to aggregate into clumps. Ferrocyanide decreases the solubility of salt in water so the salt is less likely to dissolve in the moisture that coats the crystals and that in turn reduces the amount of recrystallization.

Any mention of cyanide conjures up images of poison so the presence of ferrocyanide in salt sounds scary. That’s why producers would rather list it on a label as “yellow prussiate of soda,” an old-fashioned term first coined in reference to Prussia, the country where it was originally synthesized. There is, however, no need to be terrified of ferrocyanide because the cyanide in this compound is tightly bound to an iron atom and is not released in the body. Even if it were, it would be irrelevant because the amount would be way too little to cause any harm. And ferrocyanide itself is remarkably non-toxic.

Other anti-caking agents are available. Regular Windsor salt, for example, uses calcium silicate, whereas its kosher salt version uses yellow prussiate of soda. Kosher salt should really be called “koshering salt” because it is used to draw blood out of meat based on the biblical reference that consuming blood should be avoided. It is not blessed by a rabbi nor is it healthier than any other salt. The difference is that it is composed of large irregular shaped flakes that can cover the surface of the meat easily and then can be washed off. The large flakes gather moisture more easily from the air and apparently ferrocyanide is better at reducing the solubility of the salt in the moisture layer that other anticaking agents.

The only nutritional difference between regular salt and kosher salt is that kosher salt has no added iodide. The addition of iodide to salt began in the 1920s to remedy the increased incidence of goiter, a swelling of the thyroid gland caused by a lack of iodine in the diet. Back then many people had a very limited diet and lacked iodine, but that is not the case today in North America. Using kosher salt is not going to lead to iodine deficiency. Many chefs prefer to use kosher salt because regular salt is comprised of tiny cube-shaped crystals that allow for very tight packing while the irregularly shaped flakes of kosher salt don’t pack so easily, leaving lots of air space between the crystals. The large grains of kosher salt are therefore easier to pick up with a pinch of the fingers, making it easier to gauge the amount of salt to be added to food. Because of the space between the grains of kosher salt, a spoonful of regular salt will have about twice the salting power of kosher salt. This has to be taken into account when recipes that call for salt by volume are followed.

Joe Schwarcz PhD

Are Chemists Suffering from Chemophobiaphobia?

principleMost chemistry conferences these days feature a session on the “public understanding of chemistry.” Usually speakers express frustration about equating the term “chemical” with “toxin” or “poison,” about consumers looking for “chemical-free” products, and about the extent of scientific illiteracy. There tends to be a collective bemoaning of the lack of appreciation of the contributions that chemistry has made to life and of the eyebrows raised when a chemist reveals his profession in some social setting. Annoyance surfaces about synthetic chemicals being seen as the culprits responsible for a host of human ailments whereas natural substances are judged to be unquestionably safe.

Often there is criticism of bloggers who maintain that if you can’t pronounce the chemical name of a food ingredient you shouldn’t be eating it and of the bothersome image of the frizzy-haired “mad scientist” who is bent on brewing up some nasty carcinogen to unleash on an unsuspecting public. There’s lots of lamenting the demonization of “petroleum-derived” chemicals by scientifically uneducated, self-appointed protectors of the public good.

Speaker after speaker expresses concern that the public is being unduly alarmed by ill-informed pundits who inflate the risks of non-stick cookware, fluoride, pesticide residues, preservatives, plasticizers, GMOs and various chemicals found in cosmetics and cleaning agents. There is also concern that chemists are unfairly maligned, mistrusted and uncaring about the long term consequences of their actions. All of this is usually followed by a call to arms to change the public’s attitude toward chemistry, and vigorous discussions ensue about how to go about curing what is seen as widespread “chemophobia.” I know, because I’ve been there and have taken an active role in such dialogues.

Now, though, it seems that our worries may have been overblown, at least judging by the largest survey ever carried out about the public’s attitude toward chemistry by the U.K.’s Royal Society of Chemistry. A qualifier has to be mentioned here though. In the U.K. pharmacists are also called chemists and this likely skewed the statistics since health professionals tends to be regarded in a positive fashion.

The survey featured interviews with over 2000 randomly selected people and discussions with a number of focus groups. While there were concerns about chemicals, chemistry as a profession was viewed positively. Sixty percent of the subjects interviewed said they believed that the benefits of chemistry outweigh any harmful effect, and eighty four percent agreed that chemists make a valuable contribution to society. Interestingly, only twelve percent of chemists interviewed thought the public would have such a high appraisal of their profession.

When it comes to chemicals, seventy percent agreed that everything can be toxic at a certain dose, but only sixty percent knew that everything is made of chemicals. On the positive side, less than twenty percent thought that all chemicals are dangerous. So chemophobia does not seem to be as extensive as we think it is.

Chemists have a knee-jerk reaction every time we see the word “chemical” used in what we consider to be an inappropriate fashion. We bristle when someone says they do not want to eat food that contains chemicals or when we hear that consumers are looking for a cleaning agent without chemicals. What ignorance, we think! But it seems that when people use “chemical” in this fashion, they refer to substances that they believe are potentially toxic, not to all chemicals in general. It’s a matter of semantics. Maybe we are wasting our time by trying to set the record straight every time we see the word chemical used in a way that strays from our scientific definition. Perhaps it is time to accept that words can have different meanings depending on their context, and that when lay people talk about “chemicals” they are using the term to mean substances that are potentially harmful.

Ridiculing the misuse of the word as a synonym for “toxic”, as those of us in the chemistry field often tend to do, can have an undesired consequence. It can give the impression that we think that all chemicals are safe. In fact no one knows the potential harm that can be caused by some chemicals better than chemists.

An unreasonable attack mounted against some chemical by a chemically illiterate person is sometimes interpreted by chemists as an attack on their profession and prompts a vigorous rebuttal. Even if scientifically warranted, it tends to project an image of being a defender of all chemicals.

As scientists, chemists are gung-ho on evidence and are wary of anecdote. Yet, it appears that our belief that chemists are considered as societal pariahs because they produce chemicals, that is, “toxins,” is purely anecdotal. The U.K. survey actually revealed that seventy-five percent of people think that chemistry has a positive impact on our wellbeing.

Admittedly, I was surprised by that statistic, probably having been misled by my personal anecdotal evidence. Because of the business I’m in, I tend to take note of any chemical nonsense I come across. I see it in my emails and on posts on my Facebook page. And I guess I forget that the vast majority of people who have a reasonable view of chemicals and chemists are not vocal about their beliefs. It’s the squeaky wheel that we hear.

Thanks to the Royal Society of Chemistry’s survey, we can now move from anecdote to science. It is comforting to note that chemophobia is not rampant and that only twenty-five percent of people are confused, bored, shocked, saddened or angered by chemistry. But there is another noteworthy statistic. More than half the people do not know what chemists actually do, and do not feel confident enough to talk about chemistry. So instead of worrying about the misuse of the word “chemical,” we should focus on educating the public about the role of chemistry in our lives.

Joe Schwarcz PhD

Phthalates and microwave ovens

phthalateIt always pays to read the study! It really does, because popular accounts often misinterpret what researchers actually found and end up raising undue alarm. Of course it is raising the red flag of alarm that gets attention, and these days, with all sorts of bloggers scooting around to popularize their websites hoping to recruit advertisers, getting attention is what it is all about. Let’s get down to a study that generated the headline: “Don’t Microwave Those Vegetables; It Could Lead to Diabetes.” As one would expect, that headline ricocheted around the Internet spawning all sorts of comments about the evils of microwave ovens and plastic dishes. First of all, the study referred to was not about microwaving leftovers, and second, the word diabetes was never mentioned. What researches did was to take some data about phthalate metabolites found in urine as measured on a single occasion to see if there was any association with blood pressure. They did find an association, albeit a weak one. There was a difference of 1-2 mm Hg in systolic blood pressure between low and high levels of phthalate metabolites, which is essentially insignificant for an individual but could have significance across a population.
Where do the phthalates come from? These chemicals are used extensively as “plasticizers” to soften hard plastics such as polyvinyl chloride (PVC) which is commonly used in food production equipment, floor tiles, blinds, furniture and packaging. So given the ubiquitous nature of PVC, it isn’t surprising that trace amounts of phthalates end up in the urine. But microwave containers are not made of PVC; they are made of polyethylene or polypropylene which contain no phthalates. While some commercial plastic wraps are made of PVC, home plastic wraps and sandwich bags are usually made of polyethylene with no phthalates in sight.
There are other issues here too. Associations cannot prove cause and effect. Indeed, there may actually be reverse causation. People may have higher blood pressure because they eat a lot of processed foods which may harbour phthalates, but the increase in blood pressure may be due to other components such as salt or fat. Phthalates may be just a marker for processed food consumption. Furthermore, there are many kinds of phthalates and they have very different properties. Also, single measurements of substances in urine are always a problem because they may not be reflective of average values.
The bottom line here is that this study has nothing to do with microwave dishes or with diabetes. The only way any connection can be made to diabetes is through suggesting that high blood pressure can increase the risk of diabetes. But most assuredly, in spite of the headlines it generated, this study does not show that using plastics in a microwave oven could lead to diabetes.
Dr. Joe Schwarcz

You Asked: Should we be concerned about parabens in cosmetics?

parabensNot if you look at the numbers. Many cosmetics now advertise “no parabens,” as they cater to chemical paranoia. Parabens are very effective preservatives and prevent bacterial growth in creams and lotions. The reason that they have made news is that they have estrogenic activity. But the fact is that this activity by comparison to the body’s natural estrogen is essentially insignificant, some 10,000 times less. Based on studies carried out with animals, the no observed adverse effect level (NOAEL) has been determined to be about 800 mgs per kg of body mass. The NOAEL is the maximum amount that can be given on a regular basis without causing any effect. This means that a 70 kg person would have to apply 55 grams of parabens regularly to have an adverse effect, assuming that it is all absorbed when applied to the skin, which of course is not the case. And how much cream does this translate to? Given that the most parabens used as a preservative makes up about 0.8% of the weight of a lotion, a quick calculation shows that about 70 bottles each containing 100 mL each would have to be applied to the skin every day to approach the NOAEL. Basically, parabens “toxicity” is a non-issue. And not that this is of any relevance, but parabens occur in nature. They are found in blueberries as well as in the secretions female dogs use to attract males.

Joe Schwarcz

You Asked: Is it true that dogs are being poisoned by propylene glycol in some dogfoods?

dog foodNumerous Internet posts attempt to scare dog owners with questions like “Is It a Dog Food Aide or Automotive Antifreeze?” The reference is to propylene glycol, a chemical added to some dog foods to help retain moisture. Of course being an antifreeze component and serving as a food additive are not mutually exclusive. After all nobody worries about eating salt because it is also used in enemas. The potential risk of a substance is determined by studying it, not by making specious associations.

So what do the studies say? Unfortunately when it comes to dogs, not a whole lot. In humans, propylene glycol when ingested is pretty innocuous. Toxicity occurs when blood concentration reach 4 grams per liter, which is unachievable by consuming foods or beverages that contain the chemical. And yes, it is used in human food, mostly to retain moisture, although it also serves as a solvent for flavours. The pharmaceutical industry uses propylene glycol as a solvent in formulations of drugs that are insoluble in water. In beer it can stabilize head foam, in soft drinks and flavoured coffees it carries flavour, it stabilizes whipped cream and prevents the formation of crystals in ice cream.

Canada attaches no numerical value to the maximum amount of propylene glycol that can be used as long as it conforms to “good manufacturing practices.” In the U.S., it can be used up to 50 grams per kilogram of food or beverage. Europe allows maximum of 3 grams per kilogram. The reason for the discrepancy is not clear since there is no evidence that amounts greater than the European limit cause any problem. But this difference between amounts allowed in Europe and the U.S. did cause quite a kerfuffle when Fireball Whisky was recalled in Norway, Sweden and Finland. It seems the American version of the product found its way across the ocean with levels of propylene glycol above those acceptable in Europe.

This precipitated a public outcry in Europe where people recalled with horror the 1985 episode when some Austrian wines were adulterated with diethylene glycol, another chemical that can be used in antifreeze, to make the wines sweeter and more full-bodied in the style of late harvest wines. Nobody was hurt except the Austrian wine industry which suffered an almost complete collapse.

The publicity about the Fireball recall in Europe bounced back to the U.S. where this whisky is a popular choice among the college set due to its low cost and relatively high alcohol content. Rumors that a Fireball recall was underway sent ripples of upset across social sites.There was no recall, but as expected the chemophobes rallied around the “they’re putting antifreeze into our food” battle cry. The fact is that someone would perish from alcohol poisoning long before enough alcohol were consumed to cause a problem with propylene glycol.

Exactly why propylene glycol is found in Fireball whisky isn’t clear. The company goes no further than to say that “the secret to Fireball is buried in the depths of our souls and it’s so damn special that we just can’t share it. Although we’d love to talk Fireball, we have a strict policy that we let our whisky speak for itself.” In all likelihood propylene glycol is used as a solvent for some flavour that is added to the whisky.

While there is no issue with propylene glycol in human food, dogs may be a different case. They often eat the same food for all their meals and the continued ingestion of propylene glycol even in small doses may conceivably be a problem. That is just what a class action lawsuit launched by a California pet owner contends. He claims that two of his dogs got sick and one died after he began to feed his pets with “Beneful” produced by Nestle Purina Dog Care. The lawsuit describes over 3000 complaints on line about dogs developing liver problems, kidney failure, seizures and diarrhea due either to propylene glycol or ochratoxin, a fungal metabolite found in the food.

The manufacturer dismisses the notion that Beneful is the cause of the ailments. Dogs get sick, and owners then look for a cause, with food being a prime suspect, they say. And Beneful is not associated with symptoms any more than any other dog food, whether it contains propylene glycol or not. However, whether that is indeed the case is hard to know. Nobody it seems has actually done a study. Given that propylene glycol is known to be toxic to cats, causing “Heinz body anemia,” and since questions have been raised about its effects on dogs, it may be prudent to choose varieties of dog food that do not contain the chemical.

Joe Schwarcz PhD

The turf may be artificial but the issues are real

artificial turfThe women’s World Cup provided us with some hot soccer but it also brought the simmering controversy about the safety of playing on artificial turf to a boil. That’s an apt term because these surfaces heat up in the sun much more than natural grass and players complain of greater risk of heat exhaustion. They also complain of carpet burns and blisters on the feet. But the bigger concern is potential toxicity.

The first synthetic playing surface was developed by Monsanto in the 1960s. Named “ChemGrass,” at a time when it was still acceptable to use a chemical connection in a positive way, it was made by melting together nylon pellets and a pigment, and then extruding the hot mix through spinnerets to produce ribbons which could be woven into a fabric. It was durable enough, but falling on it was no fun even though the nylon carpet was supported by a soft foam layer of polyurethane. When it was installed in Houston’s Astrodome as “AstroTurf,” ballplayers had to add “carpet burn” and “turf toe” to their vocabulary.

“Field Turf,” a Canadian company took the complaints to heart and came up with an improved version. Out went the stiff nylon fibers, in came soft, elastic polyethylene fibers lubricated with silicone oil. These were tufted into a rubberized plastic mat, just like a giant shag rug. The “tour de force,” though, was the “infill” composed of sand and granules of “crumb rubber” which kept the fibers upright and provided shock absorbency. Old rubber tires and athletic shoe soles were frozen and ground up to make the pellets that would eventually become the subject of heated debate.

The issue is that tires are made of a mix of natural and synthetic rubbers and contain an incredibly complex array of chemicals ranging from natural contaminants such as lead to zinc oxide used in the vulcanization process and polycyclic aromatic hydrocarbons in the oil blended with the rubber to provide proper texture. There are vulcanization accelerators like benzothiazole, amines added as antioxidants and butadiene and styrene residues from the synthetic rubber component. Many of these are known, probable or possible carcinogens. Carbon black, used as a reinforcing filler, can harbour “nanoparticles” which some researchers claim are carcinogenic and can penetrate cells, even finding their way to the brain. Lead-based pigments, now phased out, but once used to colour the grass, are another worry. There is also concern that dust from the rubber pellets can trigger allergies and asthma.

Of course the major question is extent of exposure. That can come from the inhalation of volatiles or dust released as the crumb rubber crumbles further under stress. There is also the possibility of swallowing any particles that are kicked up by action on the field, a special concern to goalkeepers who often dive to make a save and end up stirring up the rubber pellets. Can this be of any consequence? A preliminary collection of data by a soccer coach in the US suggests an unusual number of cancer cases among athletes who have spent a lot of time playing on artificial surfaces, and in the case of soccer, a greater incidence among goalkeepers than other players. So far this evidence is anecdotal, but science often starts with someone noting such a relationship and saying, “hmmm, isn’t that interesting?”

Given that the sporting landscape is dotted with artificial turf, and that thousands and thousands of children, who are more prone to the effects of toxins, play on such surfaces, further investigation is in order. Solid epidemiological data are needed to determine if there is indeed a link between artificial turf and cancer incidence, and we need experimental data about the extent and effects of exposure. The latter can be addressed by sampling the air above artificial fields for chemicals wafting out and by immersing samples of turf in fluids that simulate sweat, lung mucus and digestive juices. So far, the few experiments that have been carried out along these lines found that the chemicals detected were below what is considered to be hazardous, but there is great variation between turfs produced by different companies, so that small surveys cannot yield conclusive results. Furthermore, such studies do not address the possible cumulative effect that may be proportional to the time spent playing on artificial turf.

At this point it is impossible to quantify the toxicological risk, if any, of playing on artificial turf that may look like grass, and even feel like grass, but doesn’t behave like grass.


Dr. Joe Schwarcz

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