Monthly Archives: February 2014

What is the gambler’s fallacy?

gamblerImagine you are in a casino at a roulette table waiting to gamble. You have been following the game for a while and you’ve noticed that the last six outcomes were black. Well, it is quite remarkable, isn’t it? The probability to get six outcomes of the same color at the roulette is 1/64, approximately 1,6%. The chance to get seven consecutive blacks is the half, 1/128 or better 0,8%. Figures never lie! You must be very unlucky to obtain seven black shots. Therefore you put all your paycheck on red. But… wait a second. Is that right?

Obviously not! What you are missing is something fundamental which is the fact that consecutive outcomes at the roulette table are independent events which means that knowing the outcome of one provides no useful information about the outcome of the other. This involves that the probability to get seven consecutive blacks is truly 1/128 but the probability to obtain a seventh black after the first six ones is no more that 1/2, as there is nothing preventing the ball to stop either on a red or a black spot.

Unsuspecting gamblers may convince themselves that the odds are in their favor whilstroulette1 they are not! So, be careful!

That’s the gambler’s fallacy.  That’s it! Cool, isn’t it?


by Francesco Pochetti

Endocrine Disruptors: how we are poisoned by everyday chemicals

How many chemicals do we get in touch with every day? Are they safe? In which doses? What kinds of chemicals are they?

If you have ever tried to find an answer to the previous questions probably this is the right place to check it out. In order to be as rigorous as possible I report the transcript of the first part of a very interesting and together frightening video I found on the net on Earth Focus web page, which you can find here and which I embed hereafter. Therefore I limited myself to simply watching the video and carefully writing down what I heard.


The topic dealt is crucial and is about Endocrine Disruptors (ED), a class of compounds, well known to science, which tend to interfere with the biological processes at the base of hormonal control. Basically,  ED have a molecular structure which resembles very closely the one of the most important human hormones (testosterone, progesterone, estrogens…) ; this feature gives them the ability to deceive cellular receptors which cannot recognize the real hormones from the fake ones. The result is that even at very tiny doses these chemicals might be very dangerous, altering irreversibly the most basic physiological human processes.

The above video (which I highly recommend) has been built gluing together pieces of interviews from the highest world experts in this field, whom I list below, before pasting the transcript, and whom I report within the transcript itself in order to clarify the respective contributes.

  • Andy Igrejas (National Campaign Director/ Safer Chemicals, Healthy Families)
  • Theo Colborn, Phd (President & Founder, The Endocrine Disrupting Exchange)
  • Erin Switalski (Executive Director, Women’s voices for the Earth)
  • Cecil Corbin-Mark (Deputy Director, WE ACT)
  • Sean G. Palfrey, MD (Clinical Professor of Pediatrics & Public Health/ Boston University School of Medicine, MA)
  • Heather White (Executive Director, Environmental Working Group)
  • Judith Robinson (Executive Director, Coming Clean)
  • Mia Davis (Vice President of Health & Safety, Beauty Counter)
  • Johanna Congleton, Phd (Senior Scientist,  Environmental Working Group)
  • Linda S. Birnbaum, Phd (Director, National Inst of Environmental Health Sciences/ National Toxicology Program, NH)
  • Julia Brody, Phd (Executive Director, Silent Spring Institute)
  • Tracey Woodruff, Phd, MPH (Director, Program on Reproductive Health in the Environment/ University of California, San Francisco)




“They are everywhere in our environment, in the air we breath, the water we drink, the food we eat, they are in everyday products we use for personal care and cleaning, they are in our furniture, our children toys and the products we use in gardening and agriculture and almost all of us have them inside our bodies.

Andy Igrejas “Chemicals right now according to the best evidence we have are contributing to the chronic disease burden in this country in ways that are substantial.”

Sean G. Palfrey “We are seeing increases clearly in certain kinds of illnesses, asthma is one, autism in another, ADHD (Attention Deficit Hyperactivity Disorder) is a third”

endo5Theo Colborn “One out of every third child born today is going to have diabetes and if you are a minority it’s one out of two”

Andy Igrejas “Chemicals contribute to the incidents of leukemia”

Mia Davis “breast cancer, infertility”

Theo Colborn “alzhaimer’s and parkinson’s”

Tracey Woodruff “People are more obese […] than they were up to 20 years ago”

Judith Robinson “Child’s cancers are going on”

Linda S. Birnbaum “We’re seeing effects on sperm count in men […]”

Andy Igrejas “They are more of these bizarre heart effects particularly around male reproductive development”

Theo Colborn “If I were a parent I would be very concerned”

endo2They were meant to make life easier and they do. Chemicals fight diseases […] and support manufacturing. They’re big business, a key stone of the us economy from consumer goods to high technology almost all aspects of modern life depend on the chemical industry. Chemical production in the US has grown 25 fold since World War II. It sales above 763 billion dollars in 2011. The chemical industry supports over 3 million US jobs and invest billions in the research and development. Our bodies take in […] chemicals every day and this exposure has consequences for out health, our safety and our future.

Andy Igrejas “There are 84 thousand chemicals that are legal for commercing in the US and could be used to make all kinds of things, going to the products we bring into our homes, our workplaces and they are basically unregulated”

Theo Colborn “And of course every year new chemicals are coming on the line that have not been fully tested”

Erin Switalski “There are almost 13000 chemicals that are used in cosmetics and just about 10% of them have actually been evaluated for their safety. We found lead in lipsticks, there is mercury out there in skin lightening creams. We have found phormaldeid in products”

Cecil Corbin-Mark “[…] products that people apply to their faces and their skin daily”

pestSean G. Palfrey “Pesticides are clearly poisonous and it should be obvious to us that if they kill insects they are going to have the possibility of hurting us”

Judith Robinson “In our kitchen cabinet. If you open up the doors and you count up all the tin cans in there, all of them are going to be lined with Bisphenol A unless they are labeled that say they are not”

Sean G. Palfrey PCBs (Polychlorinated Biphenyls) might be in plastics, might be in cups, might be in containers we put in our microwaves, might be perfectly safe when they are first put on the shelf but quite dangerous once they start to break down”

Heather White “All we have is chemical companies that have created products that have contaminated literally every living thing on the planet”

Judith Robinson “I think that the corporations who are profiting from this really have run away with our system”

Heather White “Industrial chemical pollution begins in the womb”

Erin Switalski “Everything that we are bringing into our bodies if we choose to have children, we actually pass our rate on through to a developing child”

Mia Davis “Some of the chemicals we know can cross the placenta and enter the womb and have effects at incredibly tiny tiny doses”

Sean G. Palfrey “About ten years ago a seminal study was done on ten newborns cord blood. The cord blood as the baby was born contained several hundred toxic elements which terrified all of us”

endo3Heather White “Chemicals like Bishenol A, many different classes of flame retardants, we found DDT and PCBs, […] chemicals that we interact with every day from consumer products”

We now know that along with the nutrients and oxygen that the mother supplies to the baby comes a […] toxic chemicals.

Sean G. Palfrey “We know that chemicals will affect younger children, fetuses, new born babies and young children in general more than older children and adults and the reason for that is that younger children and fetuses are developing much more rapidly, their organ systems are much more sensitive”

Erin Switalski “What science is starting to show now is that early exposure to toxic chemicals at critical points when a child is in the womb has effects later in life”

Endocrine disruptors are chemicals of growing concern, fetuses and children exposed to even minute amounts may develop a wide range of health conditions from diminished intelligence to cancers. Our endocrine glands produce hormones that regulate the basic processes of our body like metabolism, growth reproduction and development. Endocrine disruptors disturb how these processes work.

baby1Johanna Congleton “Endocrine disrupting chemicals interfere with hormones signaling. Proper hormone signaling is very important for fetal development and for childhood development as well as sexual maturation. Therefore compounds that interfere with these processes could have very profound effects”

Linda S. Birnbaum “Many of these and other chemicals appear to be associated with lower IQs and/or behavioral problems in children”

Theo Colborn “If you look at what these chemicals can do to the brain we know now these chemicals are also interfering with how we process information”

Sean G. Palfrey “They affect our genetic outcome, they increase the possibility that we lose a baby, they change the activity of our hormones, our sex hormones in a variety of different ways”

Linda S. Birnbaum “We’re seeing children starting puberty at younger ages. So there are many little girls that have, for example, breast at the age of seven in the african american community and eight in the white community. This is too young for our children”

980 endocrine disrupting chemicals have now been identified. Among the most ubiquitous are a class of compounds called Phthalates, Bishpenol-A and flame retardants including PBDEs, chemicals so common that almost all of us have them inside our bodies.


ftalaJudith Robinson “So you may have vinyl floors, you may have vinyl shower curtains, you may have vinyl toys that your kids are using, […] leaching Phthalates which are known to be toxic into the environment where you get exposed”

Phthalates are in many common products, including food packaging, building materials and pharmaceuticals; they’re in our cars and even in new cars’ smell. They’re used in cosmetics to hold fragrance and health products to more effectively penetrate and moisturize the skin.

Julia Brody “We’re concerned about their effects on males, on baby boys…”

Johanna Congleton “We see problems with testicular development, problems with sperm development. They can be associated with a decrease in testosterone levels.”

Tracey Woodruff “So if you interfere with the testosterone levels they don’t quite go up all the way. In animal studies it has been shown to be linked to cryptorchidism, so undescended testicles and hypospadias, which is incomplete formation of the male reproductive organ”

babyPhthalates may also be feminizing boys; scientists found that Phthalates may be associated with a shorter anogenital distance, the distance between the genitals and anus, a subtle marker of feminization in boys. The American Chemistry Council which represents chemical manufacturers says Phthalates are among the most thoroughly studied family compounds in the world and have a history of safe use. But Phthalates are banned from children toys in more than 10 countries and the European Union. In the US 3 Phthlates were permanently banned from children toys […] in 2008 because of their potential to leach frel plastic if chewed or sucked.

Johanna Congleton “The worst actors have been taken out of children’s toys but they are still widely used in many other types of consumer products and a monitoring study showed that these chemicals are still showing up in people”



Tracey Woodruff “BPA is of concern because it looks like an estrogen and it has been shown to have a weak estrogenic effect and so if you are exposed to a chemical that might interfere with your hormone levels, in this case estrogen, it can have effects particularly during development.”

Linda S. Birnbaum “And there are preliminary data that say that it may infact […] directly increase the risk of breast cancer in animal”

BPA1Julia Brody “If they are chemicals that affect the development of the breast even before birth, if they are chemicals that cause breast thumors in animals, these are chemicals that we want to be worried about and start thinking about reducing exposure”

In addition to breast cancer BPA may be associated with genetic damage and a wide variety of reproductive, methabolic, behavioral and developmental problems. It’s one of the top industrial chemicals in the world. About 6 billion punds of BPA are produced globally each year, earning manufacturers a profit of some 8 billion dollars.

Johanna Congleton “We’ve made some progress with eliminating BPA from infant productsBPA2 including infant formula packaging, baby bottles and plastic drinking cups.”

But BPA remains widely used in many consumer products from electronic to medial equipmentsand it’s in the resin of cans […] and in plastic bottles where it can leach into the food or liquid contents inside. The Food And Drug Administration, which has jurisdiction over food packagings says BPA is safe at the low doses that occur in food but many research and health organisations remain concerned about BPA’s impact on human health at current levels of exposure.


PBDEOver 1,5 million tons of flame retardants are used worldwide each year. They’re added to consumer products to meet flamability standards, though their effect remains questionable.

Judith Robinson “Any furniture that you have that has polyurethane in it, that is most of our furniture, may contain toxic flame retardants and those flame retardants don’t stay put in the foam, they leach out and they end up in the dust in our house where we are all exposed, in particular kids who are on the ground, low, picking things up with their hands in their mouth. They are exposed to that dust which is gonna have flame retardants chemicals in it”

There are many different kinds of flame retardants. Among the most studied are PolyBrominated Diphenyl Ethers (PBDEs). Scientists have linked PBDEs to a wide range of conditions from delayed development to learning problems and diminished intelligence. […] Two PBDEs, pentaBDE and octaBDE were taken out the US market voluntarily in 2004 because of growing health concerns. Production of PBDEs deca is in the process of of being terminated.

flameLinda S. Birnbaum “The problem with all PBDEs is that they are very persistent in the environment”

Johanna Congleton “The issue with PBDEs is that they’ve been replaced with other types of chemicals that may have very similar concerns and perhaps even the same mechanism action in terms of their ability to disrupt the endocrine system”

The flame retardants Clorinated Tris and Fire Master 550, which may be linked to DNA damage, cancer or neurological defects continue to be widely used in polyurethane foam and in a number of children’s products.

Linda S. Birnbaum “So I think that the whole issue of flame retardants is one for which there is some concern and I think the real question we should ask, and maybe we need to ask this more broadly about other kinds of chemicals as well, is do we really need them?




by Francesco Pochetti

How does a photocopier work?

DADF_(Canon_IR6000)We all know the difference between an insulating and a conductor. Despite that there are also materials which, depending on their conditions, may change their main inner characteristics: photoconductors, for example, are insulating substances which, after absorbing light, turn into conductors. This feature is exploited by a procedure known as xerography, which is at the base of copying machines and laser printers. The working principle of photocopiers consists in creating an electric image of the to-be-copied document over the photoconductor. Some colored pigment particles (toner) are layered on the electric image in order to get stuck to a blank sheet of paper, reproducing the original document.

A thin layer of photoconducting material is applied to a grounded metallic belt.


  1. The free photoconducting surface is electron sprayed by a metallic wire, as if a nebulizer covered it with paint. The electrons polarize the photoconductor and get stuck to it: the effect of the polarization is to form a collection of negative charges on the opposite face of the photoconductor, in contact with the metallic belt. This negative charge attracts a correspondent positive charge which gathers on the upper face of the belt.
  2. At this point, the document is lightened up and its image is projected over the photoconductor. Its exposed areas become conductive and, as this surface has a smaller potential level compared to the ground, the electrons scattered over these regions are immediately grounded. The shadowed areas, instead, keep their charge: over the free photoconductor surface a negative charged copied image is created (whilst a correspondent positively charged picture is kept on the surface facing the metallic belt).
  3. It is now necessary to transfer onto the paper the charged image. By a special brush device, some toner particles (plastic insulating dust containing colored pigments) get positively charged and approached to the photoconductor.  The toner, attracted by charged areas (negative), gets scattered according to the original picture.
  4. In order to let toner particles detach from the photoconductor and attach to the paper, it is necessary to get rid of the electrostatic attraction. The photoconductor gets lightened again and the charged image gets erased. The positive toner particles are kept on the photoconducting layer, in correspondence to the original picture.
  5. After that a previously negatively charged sheet of paper is pressed over the photoconducting layer. The toner particles gets attracted without modifying the original drawing.
  6. The final image gets eventually pressed whilst the toner melted by proper heating. Before a new copy the photoconductor is lightened for a third time to wipe the residual electrons and cleaned, in the very end, from the not transferred toner.

That’s it! Cool, isn’t it?


by Francesco Pochetti

Why does an airbag inflate?

For years, seat belts have represented the unique real safety device in our cars. Despite its not being immediately accepted, eventually the seat belt demonstrated all its efficiency.

The same happened to the airbag, whose concept has been around for many years. Its invention goes back to 1952, by John W. Hetrick who submitted the patent the following year. The first use is remembered at the end of the sixties, together with the big improvements to the other components necessary to its proper functioning. After all the prototypes introduced and tested by practically all the biggest car companies, the first vehicle carrying this kind of innovation was the Oldsmobile Toronado in 1973, followed by other models produced by Buick and Cadillac. In Europe it was Mercedes Benz the first one to offer the accessory on its top cars in 1980. After a first period of indifference and skepticism the airbag briefly took over at industrial level, turning into one of the strongest safety devices on a vehicle. The National Highway Traffic Safety Administration estimates that the combination of an airbag plus a lap/shoulder belt reduces the risk of serious head injury by 85 percent compared with a 60 percentage reduction for belts alone.

But how does an airbag work? Why does it inflate? Well you can believe it or not but chemistry saves our lives!

airTiming is absolutely crucial for the airbag to save a life. An airbag must be able to inflate and work properly in a few milliseconds after the first collision. Meanwhile, it has to be projected in order to be restrained from deploying when the accident is negligible. Therefore, the primary component of the system is a well calibrated sensor able to reveal front strokes and to generate an immediate inflation of the device. One of the simplest mechanism studied for the collision sensor is a steel little sphere which is free to slide inside a smooth pipe. The ball is controlled by a magnet or by a rigid spring, which reduces the movements of the sphere when encountering bumps or potholes. Nevertheless, when the car decelerates rapidly, as for example during a crash, the sphere moves fast to the front triggering an electric circuit.

When the sensor switches on the circuit, a tiny mass of sodium azide (NaN3) starts burning in a very fast reaction, developing nitrogen (N2). This gas fills a nylon or polyamide envelope, which inflates completely after only 40 milliseconds. Ideally the body of the driver should not hit the airbag during the phase of inflation but just after, when it is beginning to lose pression. Otherwise the surface of the envelope would be too hard and may hurt the driver.

imagesInside the airbag there is a gas generator containing a mixture of NaN3, KNO3, and SiO2. When the car undergoes a collision, a series of three chemical reactions occur inside the gas generator. These reactions produce gas (N2) to fill the airbag and convert NaN3, a highly toxic substance, to harmless sodium and potassium silicate, a major ingredient of glass. Sodium azide (NaN3) can decompose at 300oC to produce sodium metal (Na) and nitrogen gas (N2). The signal from the deceleration sensor ignites the gas-generator mixture by an electrical impulse, creating the high-temperature condition necessary for NaN3 to decompose. The nitrogen gas that is generated then fills the airbag. The purpose of the KNO3 and SiO2 is to remove the sodium metal (which is highly reactive and potentially explosive) by converting it to a harmless material.


First, the sodium reacts with potassium nitrate (KNO3) to produce potassium oxide (K2O), sodium oxide (Na2O), and additional N2 gas. The N2 generated in this second reaction also fills the airbag, and the metal oxides react with silicon dioxide (SiO2) in a final reaction to produce silicate, which is harmless and stable. (First-period metal oxides, such as Na2O and K2O, are highly reactive, so it would be unsafe to allow them to be the end product of the airbag detonation.)

Well… as I said chemistry saves lives!

That’s it! Cool, isn’t it?

(Some information summarized from “Gas Laws Saves Lives: The Chemistry Behind Airbags”)


by Francesco Pochetti