By Henrylito D. Tacio
Although there are some indications that it is slowly recovering from depletion, the Department of Environment and Natural Resources (DENR) urged Filipinos to “continue taking preventive steps to help protect the ozone layer.”
“Scientific measures show that the ozone layer is healing itself and is expected to recover by the middle of this century, probably during the period 2050-2075. This could be realized if all of us cooperate to stop patronizing ozone-depleting substances (ODS) and ODS-containing products,” said DENR Secretary Ramon J.P. Paje in a statement.
Last September 16, the Philippines joined the rest of the world in celebrating the International Day for the Preservation of the Ozone Layer. This year’s theme, which coincided with the 30th anniversary of the Vienna Convention for the Protection of the Ozone Layer, was: “30 Years of Healing the Ozone Together.”
The convention, put into force in 1985, is a framework agreement in which the parties agree to cooperate in relevant research and scientific assessments of the ozone problem, exchange information, and adopt appropriate measures to prevent activities that harm the ozone layer. It laid the foundation for the Montreal Protocol on Substances that Deplete the Ozone Layer designed to regulate the production and consumption of ODS.
“It is good news that nations’ adherence to the Vienna Convention for the Protection of the Ozone Layer and the Montreal Protocol on Substances that Deplete the Ozone Layer has helped heal our ozone layer,” said Senator Loren Legarda, UN Champion for Disaster Risk Reduction and Climate Change Adaptation for Asia-Pacific.
“This goes to show that when nations unite and work together, we can fight a challenge as great as ozone layer depletion. This should inspire us as we work towards forging a universal, equitable and ambitious international climate agreement to significantly reduce greenhouse gas emissions in Paris on December,” she added.
Examples of ODS are chlorofluorocarbons (CFCs), halons, carbon tetrachloride, methyl chloroform, methyl bromide, and hydrochlorofluorocarbons (HCFCs). These chemicals are commonly found in aerosol products, foams and fire extinguishers, and are used as refrigerants and in air-conditioning and cooling equipment.
As of January 1, 2010, the following substances have been phased out in the country: chlorofluorocarbons (CFCs), halons, carbon tetrachlorides (CTCs), methyl chloroforms (MCs), non-quarantine and pre-shipment methyl bromides (MBs).
“All (substances) have been phased out according to the commitment period,” Program Manager Ella Deocadiz of the Philippine Ozone Desk at the DENR’s Environmental Management Bureau was quoted as saying. “Currently, the only remaining substance for phase-out in the Philippines is hydrochlorofluorocarbons (HCFCs).”
HCFCs are expected to be phased out in the country by 2040.
Ozone 101
Ozone, a simple molecule composed of three oxygen atoms, is a minor constituent of the atmosphere, comprising only a few millionths of its total volume.
The Earth’s atmosphere is divided into several layers. The lowest region, the troposphere, extends from the planet’s surface up to about 10 kilometers in altitude. Mt. Everest, the tallest mountain on the planet, is only about 9 kilometers high. Virtually all human activities occur in the troposphere. Ozone at the bottom of the troposphere is a harmful pollutant resulting from automobile exhausts and other sources.
The next layer, the stratosphere, continues from 10 kilometers to about 50 kilometers. Most commercial airline traffic occurs in the lower part of the stratosphere. It is in this layer where the ozone shield is found.
If all the ozone contained in the atmosphere from ground level to a height of some 50 kilometers could be assembled at the earth’s surface, it would comprise a layer of gas only about three millimeters thick, weighing some 3,000 million tons.
But terrestrial life depends on the presence of ozone. Ozone has the ability to absorb ultraviolet radiation emitted by the sun. If ultraviolet radiation is allowed to reach the Earth’s surface, life — if it existed at all — would assume very different forms to those we know today. The fact that most of the sun’s damaging ultraviolet radiation in the atmosphere is due mainly to the ozone layer which acts as a kind of umbrella against the ultraviolet, shielding life on this planet from an extremely harmful form of radiation.
Thus, depletion of the ozone would allow more ultraviolet radiation to reach the Earth’s surface. “Protecting the ozone is crucial since it is the only gas in the atmosphere that limits the amount of harmful solar ultraviolet radiation reaching the earth,” points out Cynthia Pollack Shea, a senior researcher at the Washington, D.C.-based Worldwatch Institute. “Without ozone, life on earth would be impossible.”
Ozone depletion
The ozone saga started as early as 1957 when British Antarctic Survey headed by Dr. Joseph Farman monitored ozone levels from Halley Bay, a scientific outpost on the Antarctic coast. Measurements taken with the spectrophotometer remained stable until the team observed in the 1970s a sharp decline in ozone during the months of September and October.
The scientists refused to believe their findings, dismissing them as either human or technical error. The 40 percent drop was too significant to be believed. The “hole,” as media called it, was as big as the United States and as deep as Mount Everest.
In 1974, two American scientists — Mario Molina and F. Sherwood Rowland from the Jet Propulsion Institute of Pasadena and the University of Southern California in Irvine, respectively — hypothesized that man-made chlorofluorocarbons (CFCs) were escaping into the atmosphere and “eating” the ozone layer. Their groundbreaking article, published in the British journal, Nature, touched off a debate in the scientific and corporate communities.
Devastating effects
It was then that scientists became alarmed as the effects could be lethal. UVB (the higher energy ultraviolet radiation absorbed by ozone) is generally accepted to be a contributory factor to skin cancer and to produce Vitamin D. In addition, increased surface ultraviolet leads to increased tropospheric ozone, which is a health risk to humans.
The most common forms of skin cancer in humans — basal and squamous cell carcinomas — have been strongly linked to UVB exposure. The mechanism by which UVB induces these cancers is well understood: absorption of UVB radiation causes the pyrimidine bases in the DNA molecule to form dimers, resulting in transcription errors when the DNA replicates. These cancers are relatively mild and rarely fatal, although the treatment of squamous cell carcinoma sometimes requires extensive reconstructive surgery.
By combining epidemiological data with results of animal studies, scientists have estimated that a one percent decrease in stratospheric ozone would increase the incidence of these cancers by 2% , reports Frank R. de Gruijl in his article, “Impacts of a Projected Depletion of the Ozone Layer,” which appeared in Consequences.
Another form of skin cancer, malignant melanoma, is much less common but far more dangerous, being lethal in about 15–20% of the cases diagnosed. The relationship between malignant melanoma and ultraviolet exposure is not yet well understood, but it appears that both UVB and UVA are involved.
One study showed that a 10% increase in UVB radiation was associated with a 19% increase in melanomas for men and 16% for women. A study of people in Punta Arenas, at the southern tip of Chile, showed a 56% increase in melanoma and a 46% increase in non-melanoma skin cancer over a period of seven years, along with decreased ozone and increased UVB levels.
Studies are suggestive of an association between ocular cortical cataracts and UVB exposure, using crude approximations of exposure and various cataract assessment techniques. A detailed assessment of ocular exposure to UVB was carried out in a study on Chesapeake Bay Watermen, where increases in average annual ocular exposure were associated with increasing risk of cortical opacity.
Ozone depletion can also have devastating effects on the environment. According to the US Environmental Protection Agency (EPA), depletion of the ozone layer could reduce crop yields and seriously disturb the balance of the ecosystems of the oceans.
In a press statement, Senator Legarda reiterated: “I ask that Filipinos be reminded of what they can do for the ozone which might be simple, but when done by the majority will contribute a lot to the ozone and the environment which leads to a better life.”
