OZONE: 16th September International Day for the Preservation of the Ozone Layer 

The ozone layer shields the earth and all its life from harmful ultraviolet radiation from the sun.  What is commonly known is that there is a hole in the ozone layer, and what is less known is the actual substances that create this hole in the ozone layer.

Health and environmental facts Increased exposure to UV light increases the development of skin cancers and eye cataracts and upsets natural balances in ecosystems.  Upsets to ecosystems can affect food chains including food procurement for human consumption. 

Ozone (O₃, pronounced /ˈoʊzoʊn/), or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope (O₂). Ozone in the lower atmosphere is an air pollutant with harmful effects on the respiratory systems of animals and will burn sensitive plants; however, the ozone layer in the upper atmosphere is beneficial, preventing potentially damaging electromagnetic radiation from reaching the Earth's surface. Ozone is present in low concentrations throughout the Earth's atmosphere. It has many industrial and consumer applications.

The highest levels of ozone in the atmosphere are in the stratosphere, in a region also known as the ozone layer between about 10 km and 50 km above the surface (or between about 6 and 31 miles). Here it filters out photons with shorter wavelengths (less than 320 nm) of ultraviolet light, also called UV rays, (270 to 400 nm) from the Sun that would be harmful to most forms of life in large doses. These same wavelengths are also among those responsible for the production of vitamin D in humans. Ozone in the stratosphere is mostly produced from ultraviolet rays reacting with oxygen:

O₂ + photon (radiation < 240 nm) → 2 O

O + O₂ + M → O₃ + M

It is destroyed by the reaction with atomic oxygen:

O₃ + O → 2 O₂

The latter reaction is catalysed by the presence of certain free radicals, of which the most important are hydroxyl (OH), nitric oxide (NO) and atomic chlorine (Cl) and bromine (Br). In recent decades the amount of ozone in the stratosphere has been declining mostly because of emissions of CFCs and similar chlorinated and brominated organic molecules, which have increased the concentration of ozone-depleting catalysts above the natural background. Ozone only makes up 0.00006% of the atmosphere.

Ground-level ozone is created near the Earth's surface by the action of daylight UV rays on a group of pollutants called ozone precursors. There is a great deal of evidence to show that ground level ozone can harm lung function and irritate the respiratory system. Exposure to ozone and the pollutants that produce it is linked to premature death, asthma, bronchitis, heart attack, and other cardiopulmonary problems.

Long-term exposure to ozone has been shown to increase risk of death from respiratory illness. A study of 450,000 people living in United States cities showed a significant correlation between ozone levels and respiratory illness over the 18-year follow-up period. The study revealed that people living in cities with high ozone levels such as Houston or Los Angeles had an over 30% increased risk of dying from lung disease.

Air quality guidelines such as those from the World Health Organization, the United States Environmental Protection Agency (EPA) and the European Union are based on detailed studies designed to identify the levels that can cause measurable ill health effects.

According to scientists with the EPA, susceptible people can be adversely affected by ozone levels as low as 40 nmol/mol.

In the EU, the current target value for ozone concentrations is 120 µg/m³ which is about 60 nmol/mol. This target applies to all member states in accordance with Directive 2008/50/EC. Ozone concentration is measured as a maximum daily mean of 8 hour averages and the target should not be exceeded on more than 25 calendar days per year, starting from January 2010. Whilst the directive requires in the future a strict compliance with 120 µg/m³ limit (i.e. mean ozone concentration not to be exceeded on any day of the year), there is no date set for this requirement and this is treated as a long-term objective.

The Clean Air Act directs the EPA to set National Ambient Air Quality Standards for several pollutants, including ground-level ozone, and counties out of compliance with these standards are required to take steps to reduce their levels. In May 2008, the EPA lowered its ozone standard from 80 nmol/mol to 75 nmol/mol. This proved controversial, since the Agency's own scientists and advisory board had recommended lowering the standard to 60 nmol/mol, and the World Health Organization recommends 51 nmol/mol. Many public health and environmental groups also supported the 60 nmol/mol standard. On January 7, 2010, the U.S. Environmental Protection Agency (EPA) announced proposed revisions to the National Ambient Air Quality Standard (NAAQS) for the pollutant ozone, the principal component of smog:

... EPA proposes that the level of the 8-hour primary standard, which was set at 0.075 μmol/mol in the 2008 final rule, should instead be set at a lower level within the range of 0.060 to 0.070 μmol/mol, to provide increased protection for children and other ‘‘at risk’’ populations against an array of O3- related adverse health effects that range from decreased lung function and increased respiratory symptoms to serious indicators of respiratory morbidity including emergency department visits and hospital admissions for respiratory causes, and possibly cardiovascular-related morbidity as well as total non- accidental and cardiopulmonary mortality...

The EPA has developed an Air Quality Index (AQI) to help explain air pollution levels to the general public. Under the current standards, eight-hour average ozone mole fractions of 85 to 104 nmol/mol are described as "unhealthy for sensitive groups," 105 nmol/mol to 124 nmol/mol as "unhealthy," and 125 nmol/mol to 404 nmol/mol as "very unhealthy."

Ozone can also be present in indoor air pollution, partly as a result of electronic equipment such as photocopiers. A connection has also been known to exist between the increased pollen, fungal spores, and ozone caused by thunderstorms and hospital admissions of asthma sufferers.

NAAQS –INDIA

The National Ambient Air Quality Standards (NAAQS) are standards established by apply for outdoor air throughout the country. Standards are designed to protect human health, with an adequate margin of safety, including sensitive populations such as children, the elderly, and individuals suffering from respiratory diseases TO protect public welfare from any known or anticipated adverse effects of a pollutant

Clean air is a basic necessity for sustenance of life. In spite of introduction of cleaner technologies in industry, energy production and transport sectors, air pollution remains a major health risk. Recent epidemiological studies have provided evidence that even low pollution levels increase mortality and morbidity. Air quality standards provide a legal framework for air pollution control.  An air quality standard is a description of a level of air quality that is adopted by a regulatory authority as enforceable. The basis of development of standard should be to provide a rational for protecting public health from adverse effects of air pollutants, to eliminate or reduce exposure to hazardous air pollutants, and to guide national and local authorities in their air quality management decisions.

	Parameter, units		Averaging Time
			1-hr	8-hr	24-hr	Annual
11		Ozone (O3), µg/m3	180	90	-

Ozone depleting substances facts

The substances that create this hole are used in everyday life, they are the gases that are contained in refrigerators and air-conditioners and other cooling appliances called chlorofluorocarbons (CFC’s) and hydrochlorofluorocarbons (HCFC’s) and methyl bromide used for fumigation.  In short but not so brief, they are referred to collectively as ozone depleting substances (ODS).  It is important to note that actually using the gas is not harmful, it is when the gas is released into the air is when it is a problem.  Either way, during re-gassing technicians need to release a small amount of the ODS.  

 How ODS affects the ozone layer

The ozone layer is made up of millions of ozone molecules which consist of three oxygen atoms each.  Contained in CFC’s and HCFC’s is a chlorine atom.  This atom gets removed from the CFC/HCFC molecule by UV energy from the sun, travels into the Stratosphere and breaks the bonds in the ozone molecule thereby reducing the number of ozone molecules.  One chlorine atom in a CFC molecule has the ability to break ten thousand ozone molecules before the end of its life which is why countries need to prevent any more of these substances being released into the atmosphere.

Illustration of ozone depleting cycle (Source: Presentation)

Not only is there a hole but this hole is attracted to colder climates therefore the ozone layer hole is situated over Antarctica.  This has further impacts by increasing the amount of heat getting into our atmosphere thereby accentuating global warming.  With New Zealand in close proximity to Antarctica and the ozone layer hole, New Zealand has one of the highest skin cancer rates in the world.

Vienna Convention and the Montreal Protocol

In 2003, the Cook Islands signed the international treaty, the Vienna Convention and the Montreal Protocol (1987) which were put in place to help reduce ozone depletion and its effects.  The National Environment Service, National Ozone Unit is the Cook Islands agency that is responsible for implementing the objectives of the Montreal Protocol such as the already phased out chlorofluorocarbons (CFC’s) and now the impending phase out of hydrochlorofluorocarbons (HCFC’s) stipulated in the Cook Islands HCFC Phase-out Management Plan (HPMP). 

The problem with the environmentally harmful refrigerants is that there is an excess of existing refrigerants so countries such as those in Asia sell illegally at a cheap price, in essence getting rid of their store and in most cases selling the refrigerants to developing countries such as Pacific Islands and other Asian countries.  More so, in some developing countries there is a lack of knowledge about the impacts of ozone depleting substances so there is more likelihood that those handling the gases will release the gas from appliances without the knowledge or the appreciation of the harm to the ozone layer they may do.  Thus, the signing up of countries to the Vienna Convention and the Montreal Protocol to carry out the objectives is imperative to combat the production and use of ozone depleting substances. 

Alternatives
Fortunately there are refrigerant gases available now which are non-ozone depleting, however they have global warming potential (GWP).  Some have a higher global warming potential than others so strict rules on what substances and appliances get imported as well as education and awareness on the subject needs to be disseminated to the refrigerant importers and the public who will be affected by the economics of purchase prices.  If more of the environmentally friendly refrigerants are purchased the cheaper they should become. 

Fumigants
The other ODS not a refrigerant is a substance in fumigants called methyl bromide.  It is very deadly to animals and humans which is why it is used as a fumigant for importing and exporting, protecting importing countries from potentially invasive species.  The difference with the fumigants is that it is not used generally by the public.  Unfortunately methyl bromide has one of the highest ozone depleting potential (ODP) so an alternative to this for bio-security methods is imperative.  There exist alternatives such as heat treatment which can only be used on specific products but with time and the advancement of technology there should be a replacement for methyl bromide. 

Disposal
Fortuitously there is a way to safely dispose of these ozone depleting substances.  There is a facility in Australia and another facility in Japan.  With the impending enforcement of the Environment Act (Ozone Layer Protection) Regulation 2008, importers of HCFC’s are required to have a ‘Controlled Substances Import Permit’. 

It is an aim of the project to create an Ozone Depleting Substances Trust Fund in which the revenue acquired from these permits and future technicians’ licences will be deposited into.  This Fund is a sustainable method to finance the transport to and destruction of contaminated ODS at a destruction facility.   

Dr. Amar Nath Giri