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You Asked: What are “oxo-biodegradable plastic” shopping bags?

question markPolyethylene shopping bags are a big convenience but they also present a big problem. While they can be recycled, many just get carelessly discarded and end up in the environment not only as an eyesore but as a danger to wildlife. Estimates are that only about 3% of plastics that can be recycled actually are. Polyethylene does not degrade easily in the environment and the bags can end up as pollutants for decades. Some clever chemistry can, however, help the situation.

If certain salts of iron, manganese, nickel or cobalt are incorporated into the polyethylene, polypropylene or polystyrenene molecular chains during manufacture, they will catalyze the breakdown of the polymers. But the breakdown requires the presence of oxygen because the mechanism of the degradation involves “oxidation,” which means forming bonds between some of the carbon atoms in the polymer and oxygen atoms supplied by oxygen in the atmosphere. Exposure to ultraviolet light speeds up the reaction

Once the chain has been “oxidized,” the bonds between the oxygen bearing carbons and their neighbours are significantly weakened and begin to break apart. The resulting short chains are then biodegraded by microbes basically to carbon dioxide and water. Depending on the extent of UV and oxygen exposure, and ambient temperature, oxo-biodegradable plastics visually disappear in as little as two months, although the process can take up to a year and a half. These bags will not degrade in a landfill and therefore will not generate methane, a potent greenhouse gas. They cannot be composted, but they can be recycled just like other polyethylene bags. The big advantage is a reduction in all those bags that end up fluttering from trees or floating in the ocean. Of course, until the plastic breaks down, it can still pose a risk to wildlife but there is no doubt that the oxo-biodegradable plastic is preferable to the conventional variety in terms of impact on the environment.

 

Dr. Joe Schwarcz

The U.S. Toxic Substances Control Act (TSCA)

dangerAmidst the cacophony of jingoist, vacuous blather at the Republican Convention there were some noteworthy phrases that probably slipped by most viewers. A number of speakers talked about the need to reign in the activities of the Environmental Protection Agency, the “EPA.” That is something one would expect from Republicans who want as little government interference in their life as possible. But these are the same Republicans who voted to update the 1976 Toxic Substances Control Act that finally was passed in June by Congress with bipartisan approval after ten years of debate. This update was very much needed because significant information has been accumulated since 1976 about exposure to chemicals in the environment and their potential effect on health.

The old law required companies to register new chemicals that would enter commerce with the EPA but there was no requirement to furnish any safety data, and there was no provision for EPA to tackle the risks associated with chemicals already on the market at the time. The assumption was that chemicals are safe unless shown to be otherwise. The EPA did have the power to ban a chemical, but the burden of proof of harm was on the agency. Also, the economic downsides had to be factored in before the use of any chemical was limited. With companies introducing about 700 chemicals every year, and the EPA inventory building up to some 85,000 substances, the task of ferreting out dangerous ones is overwhelming. While determining risk when exposure is high, such as in an occupational setting, is relatively easy, determining risk to consumers who may be exposed to some chemical in tiny amounts over a long period is daunting.

But under the new law, EPA has to examine a chemical before it is put on the market and make a decision about safety. The risk assessment will take into account how a chemical is used. For example, a fluorinated compound may be deemed to be fine for use in airplane fire extinguishers, but not as an oil repellant in pizza boxes. An important new feature is that the agency will now have the authority to ask for information from producers about studies that have been carried out and can even ask for further studies. Another new facet is that EPA does not have to consider the economic implications of declaring a substance to be toxic. Furthermore, it is going to be much tougher for a company to withhold information claiming trade secrecy.

There are also 90 chemicals that have been identified as meriting investigation and possible regulation with EPA having to adhere to mandatory deadlines. The new bill has the support of the chemical industry because it should reduce consumer angst given that EPA will now be charged with examining the safety of chemicals before they go on the market. But here is the issue. While Republicans in the House voted for the bill, they also voted to cut the EPA’s funding and staffing for 2017. If EPA is going to carry out its new duties effectively, it will need more, not less funding. The plan is that some of the shortfall will be offset by charging companies fees for submitting chemicals for EPA to review. That may not sit well with Republicans.

Joe Schwarcz PhD

There ain’t no cure for the summertime buzz!

cicadas
There’s a buzz in the air these days, a loud one. I’m sure you’ve heard it but it could have easily been mistaken for a malfunctioning drone plane stuck in the trees. The sounds of summer are slowly becoming dominated by the mating songs of male Cicadas, as their relatively long lives culminate in a grand finale. And it sure is noisy.

You may have seen the recent headlines from the media outlets that announced the imminence of a “Cicadapocalypse”, but I can assure you that it will be significantly less dramatic than that. As usual, however, there is some truth behind the warning, only that there may be many more Cicadas around this year than in others, due to the strange periodicity of the Cicada lifecycle.

Cicadas are large-bodied insects, closely related to aphids and plant hoppers, who spend most of their lives as larvae eating roots underground before they pupate to adulthood and crawl up the nearest tree to mate and lay eggs before dying. In Eastern North America there are seven kinds, which are known as Periodical Cicadas, four species of which have 13-year lifecycles and the other three have 17-year cycles.

If you are surprised, either by the length or by the periodicity of these insects’ lifecycles, it would not be an unreasonable reaction, firstly because most insects do not live for much more than a year.  Secondly, the odd association with prime numbers is otherwise uncommon among animals, and that is the point. The irregular timing of the mass emergences is the key to its success, as it makes it near impossible for predatory animal populations to track and enjoy the bounty of crunchy and nutritious Cicadas when they become available.

You see, usually predator-prey lifecycles mirror one another to some degree, in that when there is more prey in one year, there can be more predators in the next (more food for them). But as the number of prey decreases, so will the number of predators that can be supported, and so on, leading to a slightly out-of-phase oscillation of predator populations with prey over time. This interaction between the number of predators and the number of prey over time leads to the classic ebb and flow of their populations, as they closely track each other throughout the years.

However, the thing about prime numbers is that they are only divisible by themselves and therefore, prey populations that peak in 13 or 17-year cycles will not overlap with any other peaks in predator cycles, other than during the one rare occurrence of their own mass emergence. This has the effect of preventing a build-up of predator populations in the years prior to the mass emergence and as a consequence, the adult Cicadas find themselves in an environment that is relatively devoid of threats to their survival. As such, many more Cicadas will survive to reproduce than can possibly be consumed. The irregularity of their mass appearances successfully allows the majority of the Cicadas to overwhelm their predators and survive long enough to reproduce.

So if this is all about predator avoidance, what’s with all the noise then? As it happens, the brief duration of adult Cicada lives is occupied by one goal before kicking the bucket, either as predator food or from old age: to attract a mate and to reproduce. It is the male Cicadas who are making the noise and they are doing it to attract and seduce the females into choosing them as a mate based on the quality of his noisy buzz.

The mating call is produced by vibrating two membranes, which are located under the males’ wings and are known as tympanic membranes, resonating at specific frequencies to create the loud buzz. This concept is the same as the one that allows us to make music from a speaker, wherein the speaker’s cone (membrane) is forced to vibrate and the effect is a projection of a loud sound outwards. The Cicadas’ concert may not be music to our ears but it certainly has a charming effect on the females of their species.

Many animals use sound to seduce: crickets and grasshoppers produce a stridulation from scraping ridged combs on their legs or wings, songbirds sing complex melodies, frogs croak and even humans use speech, song and intonation to court and woo one another. In all cases, the underlying principle in the attractiveness relates to the ability of the individual making the sounds.

In nature, courtship behaviours among the animal kingdom typically involve the evaluation of tasks that are not easy to accomplish, therefore a strong performance will tend to imply that it is being made by a strong and healthy individual. These are the qualities that will make the difference between producing average offspring and creating kin that will be inherently more successful at surviving and reproducing in the next generation. Evolution favours those that do better than others and animal reproduction is largely about honing in on those signals that give us hints about the quality of a potential mate’s genes.

Perhaps you don’t think that making a loud and persistent sound really can represent a skill that makes one sexy to others but I dare you to try it. You’ll quickly find that screaming about your sexiness at full volume is really tiring…. I’m sure your neighbours will agree too! The point is easily made though: if you are a big male Cicada, who can make a big and loud noise at the right frequency, all while avoiding the myriad of predators out there, you must have the right stuff for survival and a female Cicada will find that to be irresistible.

So as we sit around the lake, sipping on a cold beverage and try to make the most of our last days of summer, let’s listen to the chorus coming from the trees and acknowledge that the symphony of sound is a remarkable marvel of nature, one marked by a unique time signature and an impressive reed section.

Dr. Adam Oliver Brown

Cats and catnip

catWhat do we know about cats? You show them a litter box and they will from that moment on never make anywhere else in the house. Try that with a dog. Cats don’t have receptors for sweets, so you can’t train them by offering them sweet treats. In fact, you can’t train  them at all. That’s supposedly because they are too smart to cater to human whims. I don’t know about that; after all, they will chase the beam of a laser pointer ad nauseum, never learning that they cannot catch it.

If you think your cat is affectionate towards you because he or she rubs up against your leg, think again. They are just marking you as their territory, so that if they find themselves in danger, they’ll know where to run for protection. Cats do have a remarkable ability to land on all fours if you toss them into the air, and they are pretty good at catching mice and birds that they will then offer as a present to the household where they happen to be living. If you want to reciprocate to this kindness, you can offer them a little catnip. They’ll immediately turn on their back and wait for some tummy rubbing. Why they respond to the scent of this flowering plant is a mystery since it doesn’t seem to offer any evolutionary advantage. Actually, not all cats are attracted, but roughly three quarters of them are. Some sort of genetic trait is likely involved. Furthermore, only mature cats are attracted, kittens are actually repelled by the scent.

The chemical in the scent of catnip that produces cat euphoria is nepetalactone. The plant does not produce this compound to attract cats. Since cats do not pollinate, and do not eat insects, there is no advantage to the catnip plant to attract felines. So we have to look elsewhere for any advantage offered to the plant by nepetalactone. It turns out that this compound happens to be a pheromone, or sex attractant, for aphids, the tiny sap-sucking insects that can sap the life out of a plant.

Obviously there is no advantage to the plant in attracting aphids. But there is an advantage in attracting aphid predators. The lacewing fly and creepy wasp find that aphids provide just the right environment for laying their eggs and have learned to hunt down aphids by going after the pheromone they produce. The catnip plant takes advantage of this phenomenon and churns out nepetalactone to attract the aphid predators that then lay their eggs inside the live aphids and end up killing them.

While cats love catnip, cockroaches do not. The scent of nepetalactone sends them skittering away.  Removing the roaches’ antennae renders them indifferent to nepetalactone, revealing that it is receptors on these rather than on the feet or in the mouth that respond. Nepetalactone also repels a variety of biting insects, including the mosquito. But it’s not a good idea to use an insect repellant based on this chemical if you are on safari. Catnip attracts big cats too. Like lions, tigers and leopards. I don’t think you want these guys rubbing against your leg.

Joe Schwarcz PhD

You Asked: Does the Magnetic Laundry System work?

question markMagnets are fascinating. Imagine the amazement of the ancient Greeks who discovered that some naturally occurring stones, later named magnetite because they were found in a region of Greece called Magnesia, attracted iron. The stones also quickly attracted superstitious beliefs. Magnetite was said to have had magical powers, the ability to heal the sick and frighten away evil spirits. Archimedes, in an undoubtedly apocryphal story, is said to have used magnetite to remove nails from enemy ships and sink them. Magnets never sank ships, but they were used to guide them. We are talking about the compass.

Thousands of years ago the Chinese also noted the properties of naturally occurring magnetite. When made into the shape of a needle and floated on water, the magnetite always lined up in a north south direction! By about 1000 AD, the Chinese had developed the compass that became the key to navigation. But magnets have also been used to navigate people away from reality. In the 1800s physician Anton Mesmer had people hold onto magnetized rods to attract disease out of their body. Mesmerism, as his antics came to be called, often worked. The success of the treatment had nothing to do with the magnets, rather it was based on the belief of the patient. Magnets are great placebos. Today, magnetized bracelets can be purchased to energize the gullible. And you can buy magnetic laundry disks for insertion into washing machines to allow laundry to be done without the use of detergents. The claim is that the magnets ionize water and thereby increase its cleaning ability. Nonsense.

Advertising for these products often attacks commercial detergents accusing them of containing cancer causing chemicals and hormone disruptors. The claim is that the magnetic disks reduce health risks by eliminating exposure to these substances while also saving money since there is no need to purchase detergents. Furthermore, use of the disks prevents the release of toxic substances into the environment. That all sounds very “green.” References are given to a patent for the laundry disks, as well as to a study supposedly demonstrating their cleaning efficacy.

It is important to understand that the only requirement for obtaining a patent is novelty. In this case, since nobody before had the idea of putting magnets into a washing machine, the patent was not hard to get. When it comes to the patent, there is no need to show that the magnets actually do anything, just that their use in this context is novel. How about the study carried out by a testing lab that examined the cleaning efficacy? Technicians actually took bundles of clothes, washed them in a magnet equipped washing machine and demonstrated they came out cleaner than they went in. Surprise, surprise! Water is an excellent solvent and cleans remarkably well even without any detergent. The “study” had no control. That is, there was no comparison between laundering with just water and laundering with the magnetized water.

Is there any rationale that the magnets can actually do something? Water is diamagnetic, which means that it will be repelled by a magnet. But the effect is very, very, small. If a vial of water is placed on a piece of floating Styrofoam and a strong magnet is brought close, it will slowly move away from the magnet. An interesting phenomenon, but nothing to do with cleaning ability. But there is something about the advertising for the laundry disks that is not contestable. They are guaranteed to last for fifty years, a guarantee that is indeed safe since magnets do not rot. That is more than what can be said about the claims of their miraculous cleaning properties.

Joe Schwarcz PhD

DEET Me Up: How Best to Repel a Mosquito

mosquito

When it comes to protection from mosquitoes, opinions are abuzz.  Burn citronella candles.  Wear repellant bracelets.  Douse yourself with Avon’s Skin-So-Soft.  Eat garlic.  Take vitamin B1 supplements.  Use concentrated DEET.  Use dilute DEET.  People are confused.  Needlessly.  There are many questions science cannot readily answer, but the question of what is the most effective mosquito repellant is not one of them.  That’s because it doesn’t take rocket science to design an appropriate study.  You don’t need sophisticated equipment and you don’t have to extrapolate from rat studies.  All you need are some human volunteers who are willing to stick their bare arms into a cage of hungry female mosquitoes.  And that is exactly what researchers had fifteen volunteers do at the University of Florida in a study reported in the New England Journal of Medicine.  And now we know what works and what does not.

This study was very carefully done.  Temperature, humidity, density of the mosquito population and state of hunger of the insects were all controlled.  Sixteen popular products were purchased and tested repeatedly with the time until first bite being accurately measured.  Lets’ start with what doesn’t work.  You can forget about any of the “repellant” wristbands.  They kept mosquitoes away for the stunning time of about twenty seconds.  Avon’s “Skin-So-Soft” may make your skin feel soft but will only keep the bugs away for about twenty minutes.  After that your skin will get pretty bumpy from all the bites. Other citronella preparations fared even worse.  So unless you are willing to walk around constantly spraying yourself, forget the citronella products.  So what works?  N,N-diethyl-m-toluamide or “DEET.”

Some people worry about DEET because they’ve heard reports of toxic reactions and are suspicious of the substance because it is a synthetic chemical.  Whether a substance is synthetic or not has nothing to do with its safety profile.  Indeed DEET has a remarkable safety record.  It is estimated that since its introduction around 1960, about 8 billion doses have been applied to humans.  And this has resulted in fewer than 50 serious toxic effects of which more than 75% resolved with any further problems.  In the handful of cases where there were residual effects, there was heavy, frequent application over the whole body.  The New England Journal study has now shown that such applications are not necessary.  A DEET concentration of 24% provided five hours of protection.  Even a 5% concentration, which can be used on children, kept the mosquitoes away for an hour and a half.  DEET should not be used under clothing, on an open cut or with sunscreen.  So there it is.  Look for a product that has between 25 and 30% DEET for adults and apply it every four hours or so.  For young children use the 5% stuff.  If you really want something “natural,” although I don’t know why that should be appealing, “Bite Blocker” made with soy oil offers about ninety minutes of protection as do products made with eucalyptus oil.  And if you think that citronella has a pleasant smell, you’re not alone.  Mosquitoes like it too.

A recent study by Consumers Union corroborated these results.  “Off Deep Woods” with 98% DEET kept mosquitoes and ticks away for over ten hours.  Products with 20-34% DEET worked for at least five hours.  The best non-DEET product was Repel Plant Based Lemon Eucalyptus which contains p-menthane-3,8-diol.  It worked for about three and a half hours.  Products with picaridin did not work well, neither did a shirt treated with permethrin.

 

Joe Schwarcz

 

Toxic chemicals in the environment

photosynthesisVirtually no day goes by without an alert from the media about some chemical in the environment that is suspected of harming our health. It may do this by disrupting our hormones, triggering cancer, causing heart disease, affecting brain development, or any combination of these. Among numerous other substances it might be oxybenzone in sunscreens, tetrachloroethylene residue in dry cleaned clothes, caramel colouring in cola drinks, arsenic in rice or phthalates in plastics. The allegations are generally backed up by references to the scientific literature but interpreting the data in practical terms is very challenging. It has been said that our ability to collect data has outstripped our ability to analyze what the data means.

Take endocrine disruptors for example. These are chemicals that can in some way interfere with the chemical messengers we call hormones. Such interference can cause cancer, developmental issues, learning disabilities, attention deficit disorder, obesity and reproduction problems, especially if exposure is during the critical period of development between a fertilized egg and a full formed baby. This is the time when cells multiply quickly and take on their individual characteristics. Exposure to chemicals that would be innocuous in an adult can at this point have serious consequences. It stands to reason that effort should be made to reduce exposure to endocrine disruptors particularly during pregnancy.

But here’s the rub. We are awash in endocrine disruptors, both natural and synthetic. There are dozens and dozens of chemicals that when tested on cell cultures in the lab or in animals have hormone disruptive effects. Yes, there are the usual suspects like bisphenol A, phthalates and parabens, but numerous others don’t get much play in the press because they occur in nature. Naringenin in oranges and grapefruit, genistein and daidzen in soy, hops in beer, nicotine in tobacco caffeine in coffee and indole in corn can all be shown to have the ability to disrupt hormonal activity. The same goes for resveratrol in red wine, as well as for ethanol which is the alcohol in alcoholic beverages. Of course the effects of all of these are dose dependent and route of exposure dependent. Inhalation, ingestion or dermal exposure can have very different effects.

I am certainly not saying that we should have no worries about chemicals to which we are exposed. We do need to be concerned about alcohol, lead, smoke, mercury, some pesticides and some flame retardants, but we also need to understand that just because some substance in a pure form causes an adverse effect in a test tube or in an animal doesn’t mean that its presence in a consumer product presents a risk. There are thousands of chemical reactions going on in our body all the time including numerous ones that break down potential toxins. The human body and its interaction with chemicals is far too complex to yield simple answers.

 

Joe Schwarcz

Plastics

plastic bottles“I hate plastics. We should get rid of them.” So began an email I received. The correspondent went on to talk about how plastics are a plague on the environment, how they contain chemicals that contaminate our food supply, disrupt our hormones, cause autism and ADHD and use up valuable petroleum deposits. What prompted the email was some comments I made about different plastics having different properties and how there were some concerns with some but not with others. The disturbing part of the message was the insinuation that I must be in the pockets of the plastic industry since I did not agree that plastics were substances forged in hell. That allegation is easy to answer. I get zero funding from the petroleum or plastics industries. My allegiance is to the scientific method. Where that path leads, I go.

It is true that plastics can be an environmental plague. But plastic shopping bags don’t jump into rivers or trees by themselves, and empty bottles that should be recycled don’t leap into garbage cans unaided. People are the problem. As far as using up petroleum resources, only about 5% of oil goes towards plastic manufacture, and in North America the prime raw material is actually not petroleum but natural gas. I should add that while plastics are mostly made from fossil fuels, this is not the case exclusively. Polylactic acid, widely used today, is made from corn and there is extensive research in the area of “green chemistry” to produce a variety of polymers from plant products.

What about the bit about contamination of our food supply? Anytime two surfaces come into contact, there is an exchange of chemicals. Indeed, it is possible that trace amounts of plastic chemicals with endocrine disruptive properties may end up in our food supply, but the dose is so small that any sort of harmful effect is very unlikely. Heat increases the release of chemicals, so it is better to use glass or ceramic for warming up food, although plastics labeled as microwave safe contain no easily leached components. As far as ADHD and autism go, the fact is that nobody knows the cause. There is much speculation ranging from genetics and microbiome imbalances to environmental contaminants but plastic ingredients would come way down the list. It is true that we can definitely live without plastic microbeads in cosmetics and even without synthetic fabrics, although resorting to cotton poses a whole range of other problems. But the suggestion to get rid of plastics is simple-minded nonsense that amounts to lack of seeing the forest for the trees.

Our life today depends on plastics. They are vital components of our airplanes, our cars, our buildings, our TV sets, our food production and drug manufacturing equipment, as well as numerous consumer goods ranging from shampoo bottles to shower curtains and toothbrushes. Yes, you could make toothbrushes from wood and pig bristles, but nylon is a lot better. Modern medicine could not function without plastics. Intravenous tubing, blood bags, burn dressings, artificial limbs, heart-lung machines, artificial joints, pacemakers, MRI machines, CAT scanners and x-ray equipment and white dental fillings rely on plastics. And just try to make a computer without plastics. Right now you are reading this on a computer or cell phone that could not function without plastics. Mr. McGuire in the Graduate was right: “I want to say one word to you. Just one word. Benjamin: Yes, sir. Mr. McGuire: Are you listening? Benjamin: Yes, I am. Mr. McGuire: Plastics!”

 

Joe Schwarcz

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