It can be produced by the ultraviolet rays of the sun reacting with the Earth's upper atmosphere (which creates a protective ozone layer), by lightning, or it can be created artificially with an ozone generator.
This process is carried out by an electric discharge field as in the CD-type ozone generators (corona discharge simulation of the lightning), or by ultraviolet radiation as in UV-type ozone generators (simulation of the ultra-violet rays from the sun).
A few more products with CFC's are coolants
for refrigerators and air conditioners, foam products, such as cups, and
insulation for houses.
Considering that ozone molecules are so rare, it is extremely
important to keep them intact.
Lately, the effects of our increased activity have begun to manifest themselves in a multitude of subtle, and some not so subtle ways: we have thinned the ozone layer and may now be starting to change the very climate system upon which we and all other life on Earth depend....
Eventually, it became clear to scientists and the government
that certain human activities are changing our ozone, and that the shield
needs to be protected from all of the factors that ... carbon atoms which all form bonds
with the rare ozone molecules.
The suspected cause was the catalytic cycles
involving chlorine and nitrogen.12
Halons, an especially potent source of ozone depleting
molecules, are used in fire extinguishers, refrigerants, chemical
Extensive literature documents the adverse health impacts of exposure to elevated concentrations of air pollutants, particularly ozone, particulate matter with aerodynamic diameters 10) and 2.5), sulfur dioxide, nitrogen dioxide, carbon monoxide, and lead. Worldwide in the year 2000, 0.8 million deaths and 7.9 million disability-adjusted life-years lost from respiratory problems, lung disease, and cancer were attributed to urban air pollution ().
We thank the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) for making this work possible. We also thank the many coauthors and reviewers of the UNEP/WMO Integrated Assessment of Black Carbon and Tropospheric Ozone for their contributions along the way.
Citation: Ebi KL, McGregor G. 2008. Climate Change, Tropospheric Ozone and Particulate Matter, and Health Impacts. Environ Health Perspect 116:1449–1455;
Bromine is estimated to be 50 times more effective than
chlorine in destroying ozone.13
Insect fumigation, burning biomass, and gasoline usage all
release methyl bromide into the air.
Tropospheric ozone and black carbon (BC), a component of fine particulate matter (PM ≤ 2.5 µm in aerodynamic diameter; PM2.5), have been associated with deleterious effects on human health (e.g., ; ; ), agriculture (e.g., ), and climate (e.g., ). Methane, a relatively short-lived greenhouse gas (residence time 8–10 years), is an ozone precursor that affects background ozone concentrations. Controlling methane emissions may be a promising means of simultaneously mitigating climate change and reducing global ozone concentrations, compared with controlling shorter-lived ozone precursors [nitrogen oxides (NOx), carbon monoxide (CO), and non-methane volatile organic compounds (NMVOCs)] (, ). The latter may have larger and more immediate air quality and health benefits near the areas with emission reductions but smaller benefits (CO, NMVOC) or net disbenefits (NOx) for climate. Major anthropogenic sources of methane include fossil fuel production and distribution, landfills, livestock, rice cultivation, and wastewater treatment. BC is a product of incomplete combustion from sources such as biomass burning, transportation (mainly diesel vehicles), residential combustion, and industry, and is coemitted with other pollutants, including NOx, NMVOCs, CO, sulfur dioxide (SO2), and organic carbon. Climate benefits of reducing BC may be partially offset by associated reductions of coemitted pollutants that may have a net cooling effect on climate (and a net warming effect when reduced), either directly (organic carbon) or after chemical transformation in the atmosphere (organic carbon, SO2, and NOx). However, all emission reductions leading to reduced ozone and PM2.5 concentrations would be expected to have health benefits.
They "still contain chlorine atoms that are responsible for the
catalytic destruction of ozone but they contain hydrogen which
makes them vulnerable to the reaction with hydroxyl radicals (OH)
in the lower atmosphere.” The reactions in the troposphere remove
the chlorine before it reaches the stratosphere where ozone
Some of the HFCs and HCFCs being used to replace CFCs are
HFC-134a, HCFC-22, HCFC-141b and HCFC-123.
Additional research is needed to better understand the possible impacts of climate change on air pollution–related health impacts. If improved models continue to project higher ozone concentrations with climate change, then reducing greenhouse gas emissions would enhance the health of current and future generations.