Office for Science & Society

Why is it that in hot countries we put salt on ice in the ice cream makers to keep the ice from melting, while in cold countries we put salt on ice to melt it?

In both cases, the answer is based on the fact that adding salt to an ice water mixture in equilibrium, lowers the freezing point (or melting point)  of the equilibrium.

Making ice cream

When  you add just ice  to the ice cream maker, the ice absorbs heat from the surrounding and starts melting. At 0C  equilibrium is reached and the temperature cannot go any lower. This is not  is not cold enough for making ice cream. When salt is added, the equilibrium will be reached, and kept at  the lower temperatures required.

Salt on the roads

When salt comes into contact with the ice on the road some  heat is released because of the solvation process. This melts the ice yielding once again an ice water equilibrium. But because of the presence of salt this mixture will re-freeze  at lower temperatures than 0C.

In both  cases the lowering of the freezing point will depend on the concentration of salt in the mixture.

Ariel Fenster

My son is taking chemistry in school and he tells me he’s grinding rocks but I’ve yet to see any rocks. Does this possess a danger?

This should be a harmless activity in that all that is happening is an automatic way to grind down minerals that often result in polished and sometime quite beautiful stones.  Be clear that some tumblers are “on” for weeks in order to polish the stones so electricity costs are a mild consideration.

David Harpp

A friend of mine is very much opposed to using a plastic kettle, for fear of  some of the toxins leaching into the water.  He therefore will use only a metal kettle.  Is there any basis for this?

In terms of the situation with plastic kettles- it is one that is answered “it depends”—some kettles can be problematic although in general the leaching of plastic materials is normally very limited and of no medical consequence.  You will find many different comments on this question on the internet and some will be good and others will be written by over-eager interpreters of the issue.

The best advice is to consult the Consumer Product Safety Directorate of the federal government.

David Harpp

Are the new Smart Meters from Hydro Quebec safe? Are they different from a cordless or cell phone when it comes to RF emissions?

Cell phones, microwave ovens, wi-fi, smart meters. What do they have in common? They all emit radiation in the radiofrequency range. And they all radiate controversy. Given that these devices are set to become as commonplace as light bulbs, it is understandable that questions arise about their possible health effects. There are all sorts of allegations that exposure can trigger ailments ranging from headaches to cancer. Allegations, however, do not amount to science. And there is a lot of science to be considered.

Let’s start with the fact that an alternating current flowing through a wire generates an electromagnetic field around it. This field can be thought of as being made up of discrete bundles of energy called “photons” that are created as the electrons in the wire flow first in one direction then in the other. Photons spread out from the wire, their energy depending on the frequency with which the current changes direction. The number of photons emitted, referred to as the ‘intensity’ or ‘power” of the radiation, depends on the voltage, the current and the efficiency of the circuit to act as an antenna.

In ordinary household circuits, the direction of the current changes sixty times a second, that is, it has a frequency of 60 Hz, the unit being named after Heinrich Rudolf Hertz, the first scientist to conclusively prove the existence of electromagnetic waves. The photons emitted by such a circuit travel through space and have the capacity to induce a 60Hz current in any conducting material they encounter. Essentially, we have a “transmitter” and a “receiver.” If special circuitry is used to produce current in the range of 10 thousand (10KHz) to 300 billion Hz (300 GHz), the photons emitted are said to be in the radiofrequency region of the electromagnetic spectrum. That’s because with appropriate modulation at the transmitter (amplitude modulation (AM), or frequency modulation (FM)) these photons can induce a current in an antenna that can be converted into sounds or images.

But what happens when photons in this energy range interact with living tissue, such as our bodies? The greatest concern would be the breaking of bonds between atoms in molecules. Disrupting the molecular framework of proteins, fats and particularly nucleic acids can lead to all sorts of problems, including cancer. However, photons associated with radiofrequencies do not have enough energy to do this, no matter what their intensity. An analogy may be in order.

Consider a weather vane sitting on a roof. It is mounted on a sturdy metal rod, but of course can spin. You decide you want to knock it off the roof, but all you have are tennis balls. You start throwing the balls, but even if you hit the support, nothing happens. You just can’t impart enough energy to the ball to have it break a metal rod. And it doesn’t matter if you gather all your friends, and they all throw balls at the same time. You may have increased the “intensity” of your efforts, but it doesn’t matter, because no ball has enough energy. Of course if you had a cannon, you could knock down the target with one shot. That’s why high energy photons such as generated by very high frequency currents, as in x-rays, are dangerous. They can break chemical bonds! While you are not going to damage the weather vane with the tennis balls, you can surely make it spin, and the friction generated will heat up the base, the extent depending on how many balls are thrown.

Now, back to our photons. In the radiofrequency region, no photon has enough energy to break chemical bonds, but they can make molecules move around, generating heat. The more photons released, the greater the heating effect. This is exactly how microwave ovens work. They operate at radiofrequencies, but at a very high intensity or “power” level, meaning they bombard the food with lots of photons causing the food to heat up. You certainly wouldn’t want to crawl into a working microwave oven and close the door behind you. Similarly, you wouldn’t want to stand right next to a high power radio transmitting antenna, such as used by radio or TV stations, because you could get burned very badly. But the number of photons encountered drops very quickly with distance as they spread out in all directions, so that even standing a few meters from the base of such an antenna would not cause any sensation of heat. Just think of how quickly the heat released by a light bulb drops off with distance.

The “smart meters” that are being installed by electrical utilities monitor the use of electricity and relay the information via a built-in radio transmitter. But the radiation to which people are exposed from these meters quickly drops off with distance, as with the light bulb, and is way below established safety limits. Furthermore, the smart meters only transmit for a few milliseconds at a time for a grand total of a few minutes a day! Cordless phones, cell phones, routers, baby monitors, video game controls and especially operating microwave ovens expose us to similar radiation, usually at far higher levels. Smart meters are responsible for a very small drop in the radiofrequency photon bucket.

It must be pointed out, though, that safety standards are essentially based on the heating of tissues. But what about the possibility of “non-thermal” effects? What if radiofrequency photons cause damage by some other mysterious mechanism? Over the last 30 years more than 25,000 peer-reviewed papers have been published on electromagnetic fields and health, many devoted to non-thermal effects. Health agencies do not find present evidence persuasive of a hazard at ordinary exposure levels, and given the extent of research that has been carried out, it is unlikely that one will be identified in the future.

Although an overwhelming number of studies on cell phones and brain cancer have shown no effect, admittedly some have suggested a barely detectable link. Despite the weak evidence, the International Agency for Research on Cancer has classified electromagnetic fields associated with radiofrequencies as “possibly carcinogenic,” indicating a level of suspicion without any implication that the fields actually cause cancer. This notion pertains to cell phone use and has nothing to do with the far weaker fields associated with wi-fi and smart meters. I would have no issue with a smart meter in my house.

What then about those consumers who claim they have developed symptoms after smart meters were installed? I think it is appropriate to consider John Milton’s poetic view of the power of imagination: “The mind is its own place, and in itself can make a heaven of hell and a hell of heaven.”

 Joe Schwarcz

Your question is way to inclusive to accurately answer —the answer is “it depends”—-some fish can  be perfectly safe to eat and other imports can be quite problematic.

Here is a recent short article produced by ABC news in the U.S. I believe that this piece provides one with the appropriate caution.  If you are absolutely sure of the store’s policies where you shop, go ahead and consume but with the warnings out there–be careful.  Here is a statement that can give one pause:

“Also this week, (March, 2013) regulators in China closed 180 food plants after uncovering more than 23,000 food safety violations. Despite the crackdown, China denies that its food exports are dangerous.”

This is a classic case of “caveat emptor” (let the buyer beware) but China is a major exporter of fish so checking the internet for warnings would be wise.

It is simply impossible to make a blanket statement about the safety of all fish from China.

David Harpp

My question is regarding the treatment of ADHD. I’m a psychologist in private practice on the West Island, specializing in assessments for ADHD and learning disabilities, etc. I usually talk about the most effective treatment being a combination of medication and behavioral interventions, etc. However, I’m wondering what you’ve found in your research regarding the use of Omega 3 for the treatment of ADHD. Everything I’ve read about dietary changes (and many other types of treatments) has indicated that they don’t help. However, there seem to be promising results with the use of Omega 3. What do you think? And if it is effective, at what dosages? Thanks very much! 

ADHD is a complex condition with no simple solution. Fish oil supplements as well as omega-3 fatty acid pills are aggressively marketed as a solution but the evidence is very thin. It is possible that dietary alterations may help, but there is no universal formula. The always reliable Dr. Ben Goldacre has discussed this issue and I’ve also provided two other discussions that might be of interest – The Omega Wave and a document on Nutrition and ADD/ADHD. I think the bottom line is that the jury is still out on fish oil supplements as they relate to ADHD but much of the promotional material is, let us say, fishy.

Joe Schwarcz

The walls of refrigerators have to be heavily insulated in order to maintain efficient cooling. Polyurethane foam insulation has been the classic material used for this purpose and guess what it used to be “blown” with? Chlorofluorocarbons! Foams are created by blowing a gas into an appropriate substance to form bubbles. Of course the gas must not react with the material, and in the case of insulation, should not transmit heat. CFCs, the same substances used as refrigerants, were ideal, at least until their environmental consequences were discovered. Legislation was then introduced that called for the removal of the refrigerant from any discarded refrigerator. But, surely surprising to most people, far more CFCs were used for foam blowing than for refrigeration. A typical fridge may have a couple of hundred grams of refrigerant but can hold twice as much blowing agent captive in its insulation. And “captive” is the appropriate expression because studies have shown that more than 90% of the original blowing agent is still present in a refrigerator fifteen years after it has been discarded. Unless special methods are employed, when such fridges are recycled for their metal content, the blowing agent is released to the atmosphere. Shredding the fridge into small pieces in an airtight chamber allows the blowing agent to be recovered. This technique is expensive but can offer huge environmental benefits. Currently manufactured refrigerators do not present this problem. The insulation gas now used is cyclopentane which has no effect on ozone depletion and has a negligible global warming effect. CFCs as refrigerants were replaced in the 1990s by HFCs (hydrofluorocarbons) which do not damage the ozone layer but still contribute to the greenhouse effect. Some manufacturers are now switching to isobutane as refrigerant, because like cyclopentane, it has a minimal impact on the environment. Given that millions and millions of discarded fridges are stockpiled around the world, the problem associated with the CFC content of their polyurethane foam insulation is not a trivial one.

Joe Schwarcz

Black cohosh. This plant native to North America has traditionally been used to treat menopausal symptoms with mostly anecdotal evidence for efficacy. Dr. Katherine Newton of the Group Health Cooperative in Seattle decided to put black cohosh to a scientific test and enlisted 351 menopausal women between the ages of 45-55 who experienced at least two hot flashes a night. The women were randomly assigned to one of five treatment groups: 160 milligrams of black cohosh daily; a multi-botanical supplement containing 200 milligrams black cohosh and 9 other herbal ingredients including alfalfa, pomegranate and Siberian ginseng; a multi-botanical supplement plus increased soy consumption; hormone therapy; or placebo capsules. After 3, 6, and 12 months, black cohosh was no better than placebo in reducing the frequency or severity of hot flashes or night sweats. The same was true for the other herbal products. Women who were given hormone therapy had significantly fewer hot flashes and night sweats than women given placebo. Another issue with black cohosh is its potential to interfere with the effectiveness of drugs used in cancer therapy. And then there is the problem that women relying on black cohosh may not be getting what they think they are getting. When researchers analyzed 11 of the most popular black cohosh tablets and capsules available in New York City using a process called high-performance liquid chromatography, they identified hundreds of different compounds within each black cohosh sample. Three of the products didn’t have black cohosh at all, but instead contained an Asian species of Actaea, a Chinese herb related to black cohosh but without any proven effects in easing menopausal symptoms. Supplement manufacturers substitute Actaea for black cohosh, because it is less expensive to produce. What about women who are happy with black cohosh? Any concern here? There is in the UK where health authorities want a warning label on black cohosh products because of the possibility of liver damage. This problem isn’t particularly well documented but certainly any physician finding liver dysfunction should ask the patient about the use of black cohosh, or indeed, of any herbal remedy.

Joe Schwarcz