in the 1930s chemists at the dupont corporation one of our big chemical corporations invented freon here's the thing for refrigeration we need a substance that evaporates condenses at the right kind of temperature for keeping food cool for making ice that sort of temperature what kind of substance can we use well let's go back to natural gas for a moment natural gas remember methane c h four one carbon plus four hydrogens it kind of looks like this carbon atom in the middle four hydrogen atoms around it methane won't turn into a liquid until you cool it down to negative 250 degrees not useful in this regard but methane is very light why hydrogen atoms are the lightest atoms in existence hydrogen atoms have a weight of one unit one atomic unit if we could take off the hydrogen and put on something else with a different weight we're going to make the molecule heavier what other atoms can we put on there other atoms that we can put on instead will chemically bond are what are called halogens fluorine chlorine bromine iodide fluorine an atom for fluorine has a weight of 19 19 times heavier than hydrogen chlorine has a weight of 35 okay so take off the hydrogen atoms and put on some blend of fluorine and chlorine it could be one fluorine and three chlorines two and two like i depicted here three and one one and three any proportion will work and you're adding more weight or a much greater amount of weight you can adjust the weight and therefore the evaporation temperature to pretty much exactly what you want substances like this are called chlorofluorocarbons and pleural carbons because there are multiple possibilities this is a mouthful it's usually abbreviated c f cs and the brand name the trademark that dupont corporation patented was the name freon freons are wonderful substances they are colorless odorless non-toxic non-flammable and incredibly stable colorless they won't stain it odorless no bad smells non-toxic if the stuff leaks it's not in any way harmful to your health you can breathe it no problem non-flammable won't catch fire incredibly stable stuff lasts pretty much forever it's not going to break down and stop working some people have refrigerators that have been around for 50 years they're still working so basically a miracle substance with the invention of freon suddenly the domestic refrigerator was not only possible but highly desirable and a whole industry was born refrigerators spread their use around the world air conditioning followed along behind same strategy used to cool a whole room or a whole building instead of just a food storage container air conditioners come in a wide variety of sizes shapes and designs but every air conditioner basically works the same way as a refrigerant has two parts to it the evaporation coils where the liquid evaporates into a gas and takes in heat and cools down its surroundings and the compressor which turns the gas back into liquid condenses it and gives out the heat in like a window air conditioner unit this is on the inside of the window that's on the outside in a whole house installation this is probably in your attic or a dedicated closet this is that big unit standing outside the house with the big fan and you can feel the blast of hot air coming out of it when it's running just like a refrigerator on a larger scale same technology works magnificently and again colorless odorless non-toxic non-flammable and very stable perfect substance so from the 1930s on through the middle of the 20th century major boo freon became one of dupont's best-selling lands we came up with other uses for freya aerosol cans aerosol can produces a spray right you make a liquid turn into a spray by pushing it through a tiny nozzle and i'm sure you've all purchased uh spray bottles where you pump the trigger to squirt the liquid out through a tiny fine nozzle it's kind of episodic if you want to continuous spray you need a compressor to deliver that pressure or much more convenient have the pressure contained in an aerosol can you just press the button every aerosol can contains two substances one is the product hairspray bug spray paint spray whatever the other is what's called the propellant the propellant is a substance which under pressure in the can is a liquid but as soon as you release the pressure and depressing the button on top releases the pressure lower the pressure and the liquid boils into gas the gas expands in volume the volume of the gas pushes the product out the nozzle of course all of that propellant is going straight into the atmosphere but if it's colorless odorless non-toxic and non-flammable who cares the electronics industry loves freya in electronics you are soldering together teeny tiny components lots and lots of them to make perfect electrical circuits any kind of dirt impurity grease especially and just a touch of a finger adds grease the electrical contacts are liable to be defective and then you have to throw out that product make it again so the electronics industry got into the habit of using freon freon is an organic substance gas or liquid organic liquids are awesome solvents so when they were ready to solder parts together like circuit boards they would douse it with liquid freon which would flush off grease and other contaminants and pretty much instantly evaporate into the air seconds later do your soldering again where's the freon going into the atmosphere but it's colorless odorless non-toxic non-flammable not a problem or so we thought it was in the early 1970s 40 years after we'd invented and increased and increased and increased the amount of freon in use 1970s that two chemists not far from here actually you see irvine down the road in orange county as a result of their research they published a paper warning that freon destroys ozone and that can be expected to lead to problems in the future with the protective ozone layer in the atmosphere around the earth here's how this works in this cartoon you see the ozone with the oxygen atoms in blue and the freon with the chlorine atoms in green here comes high energy ultraviolet breaking a chlorine atom off the freon molecule the chlorine atom on its own is highly reactive and looking for something to bond with it pulls an oxygen atom off the first ozone which then grabs another oxygen of the second oxon notice how the chlorine is now free to go do it again ozone threesomes are being turned into oxygen twosomes over and over again one chlorine atom can destroy up to a hundred thousand ozone molecules so that's the problem that the uc irvine chemists identified what do you think the dupont corporation thought about that they didn't like it here were these chemists warning that freon one of dupont's best selling products might be going to in the future endanger the planet first thing the dupont did was to get in touch with the authorities at uc irvine and demand that the chemists be fired uc irvine conducted an investigation and they determined that the chemists were doing their job they were doing science they were doing research analyzing their results and reporting conclusions objectively reporting conclusions like i told you to do in your term papers right nothing wrong there so the university declined to file dupont then embarked on a smear campaign you know how it goes like when we have a political election or something like that coming up people who oppose a candidate try to dig up anything that they can 30 year old tax records what the individual might or might not have inhaled when they were a student 50 years ago what's that got to do with their ability for office today absolutely nothing doesn't matter what we're trying to do is to discredit the person in the public perception dupont went after the uc irvine chemists and for ten years they had a pretty hard time in the scientific community the result of this smear campaign was to make other scientists think hey why has dupont got it in for these guys they must be on to something let's study this some more and so the amount of literature confirming that they had it right and we could expect this to become a problem began to grow and grow and grow and as we move into the 1980s we began to see the effects ever so slightly just a hint what are the effects of ozone depletion too little ozone leads to too much ultraviolet ultraviolet is a form of ionizing radiation in people the immediate consequence is a sunburn the ultraviolet radiation is actually breaking down the molecules of the substances in your skin longer term we have all these unpleasant effects skin cancers eye damage chiefly development of cataracts immune system damage skin aging all of these are consequences we're amazingly selfish usually this is what we think of when we think of ozone depletion but people are not the only things affected by this problem animals on land all animals are affected the same way that we are sunburns and long-term damage affecting their health affecting their ability to reproduce affecting their longevity turns out even in the ocean animals have problems we're seeing more and more sores and lesions on whales for example they spend their life underwater surely they're not affected well they have to come up for air and now we're seeing the effects most worrying in the oceans is the plankton plankton live near the surface of the ocean and um they are getting fried by too much ultraviolet which eventually will lead to total collapse of the nutrition system in the ocean all life in the ocean depends on plankton ultimately as a food source how about plants well why would we care about plants what do we eat where does our food come from crops and are our crops grown carefully shielded and protected from the sun absolutely not fields are laid out like this wide open to sunlight research more and more is showing that ultraviolet causes sunburn damage in plants just the way it does in animals this is some results of a study on ultraviolet in a particular group of plants and here you see the stunting effect of too much ultraviolet on fruit imagine a reduction a 10 reduction say in the amount of crops that we can get effect on humanity do we have enough food around the world that we could accept a 10 reduction in food production basically a 10 reduction in food means a 10 reduction in humanity and to be honest that makes some skin cancers look pretty unimportant ozone depletion is a very big deal indeed it was 10 years before dupont corporation finally gave in and admitted yes our product is harming the ozone layer it's all true so what happened next let's kind of look at a timeline here somewhere around 1930 freon invented that that family of substances does not exist in nature the carbon atom surrounded by hydrogens very much exists in nature taking off the hydrogen and putting on fluorine chlorine easily done but totally man-made there isn't any in nature somewhere in the 1970s it's when we realized there's a problem but the industry opposed it for best part of a decade but scientific understanding there was a problem grew and grew and grew public remained blissfully unaware that there was any kind of problem here finally this is a very important date 1987. the international meeting was called in montreal canada to discuss substances that deplete the ozone and number one substance on that list was freon