In 1987, what is considered to be one of the most successful environmental agreements to date was ratified: the Montreal Protocol. In it, the signatory countries pledged to take measures to control the use of substances that attack the ozone layer, with special attention to CFCs or chlorofluorocarbons. The agreement was signed a few years after the discovery of a huge hole in the ozone layer off Antarctica , and is an example of how the rapid action of the international community was able to put a stop to a problem that threatened health in time. and the global environment. Furthermore, successive amendments to the Montreal Protocol have expanded the list of ozone-depleting substances, always based on the latest scientific evidence.
Today, more than thirty years later, the ozone layer has not yet fully recovered, but we know that, if measures had not been taken, the levels of ultraviolet rays that would reach the Earth would be much more intense and dangerous. For example, a team of American scientists has just published the results of a mathematical model that simulates the effects of the treaty on stratospheric ozone, the associated reductions in ultraviolet radiation, and the health benefits derived from them. The results, published in the journal ACS Earth and Space Chemistry , indicate that, in the United States alone, the agreement has helped prevent more than four hundred million cases of skin cancer and more than sixty million cases of eye cataracts. .
“If the chemicals that destroy it had not been restricted, the depletion of the ozone layer would have progressively worsened throughout the 21st century,” explains Julia Lee-Taylor, a researcher at the National Center for Atmospheric Research (NCAR) and co-author of the work. “According to our estimates, the regulation will prevent at least 1.3 million skin cancer deaths in people born between 1890 and 2100.” In the simulations, the authors found an excess of cases of cataracts and various types of skin cancer that coincide with the beginning of the destruction of the ozone layer. The peak was reached decades later, as the population most exposed to the highest levels of ultraviolet radiation aged. In general, people born between 1900 and 2040 have experienced or will experience a higher probability of suffering from diseases associated with the depletion of stratospheric ozone. In addition, the population born between 1950 and 2000 is at the highest risk.
When will the ozone layer recover? Are we now safe from danger?
Scientists estimate that, in the absence of unexpected factors that slow down the process, the ozone layer could return to pre-1980 conditions in approximately 25 years, around 2046-2047. “You have to remember that ozone depletion is not limited to the hole itself. There is also less intense, but very widespread, ozone depletion in mid-latitude areas where many people live, and we also hope that the situation will improve in these regions ”, Lee-Taylor tells us in an interview with Muy Interesante.
In any case, and since the ozone layer has not yet recovered, any living person still runs the risk of being exposed to levels of ultraviolet rays that are higher than those recommended, which can cause sunburns and skin cancer. “However, the current effects related to ozone depletion are only about 1% of what we would see in the future if we had not complied with the Montreal Protocol”, reflects the researcher. “Thus, children born today have been spared almost all risks related to ozone depletion .”
Although the work has been done with data from the US population, the researchers believe that similar studies could be conducted in other countries as long as data is available on local rates of skin cancer. “The areas most vulnerable to the effects of ozone holes are the southern tip of South America and the northern mid-latitude regions during certain periods of spring . And an important factor for this study is the fact that there is a depletion of the ozone layer in the middle latitudes, in areas where many people live. These are relatively small reductions, but because they are widespread and persist throughout the year, they are significant ”, recalls the expert.
A positive and encouraging message
For Martyn Chipperfield, an atmospheric scientist at the University of Leeds (United Kingdom), and who has not participated in the study, this type of work is very useful to remind us of the importance and success of the Montreal Protocol. “This is not always so obvious once catastrophe has been averted. A model that tells us ‘what would happen if …’ and puts numbers on what would have happened makes us more aware ”, he reflects in an interview with Muy Interesante. In 2015, Chipperfield, together with other authors, unveiled a work that also imagined what the world would be like today if CFCs had not been banned. Their article, published in the journal Nature Communications , concluded that the ozone layer in the mid-latitudes of the northern hemisphere would have been 15% lower than in the middle of the last century. “It is clear that the Montreal Protocol has prevented a very serious depletion of the ozone layer, and I do not think that much more could have been done, or faster. Scientists had to assess the phenomenon, and policy makers responded in a very organized and effective way, ”says the researcher.
However, the evolution of the ozone layer still needs to be closely watched. “We expect continued low and declining emissions of ozone-depleting chemicals, for example from CFC refrigerants leaking from older equipment and being disposed of improperly,” Lee-Taylor explains. Other substances that cause concern are CFC-11, banned in 2010 but whose illegal production raised alarms a few years ago . “Although the Protocol controls the main substances that deplete the ozone layer, it will only be successful if countries follow the rules,” says Chipperfield. For the researcher, once the emission of these and other substances such as dichloromethane, which can delay ozone recovery, has been controlled, the main objective of the Protocol will be protection against climate change.
The reason is that, as a result of the CFC ban, the use of hydrofluorocarbons (HFCs), compounds that do not deplete ozone but contribute to global warming , has become widespread. “The Montreal Protocol started controlling HCFs in 2016, and I think an important step would be to strengthen these measures.”
Climate change: can we learn anything?
The fight against climate change, to which the Montreal Protocol can also contribute with its amendments, is undoubtedly the greatest environmental challenge facing the human population. It is a very complex problem and different from that of the ozone layer, but we also know that, if it is not stopped immediately and effectively, the consequences on human health will be devastating. On the eve of the start of COP26 in Glasgow, and in an atmosphere of widespread pessimism due to the failure of the other climate summits, the experience of the Montreal Protocol is a call for optimism and urgent action. ” I think the message it conveys is to act quickly and cautiously, ” Chipperfield muses. “If we suspect that climate change may have very serious consequences, we must do something now to prevent it. Because once the change occurs, it may be too late. “
