Mostly over Antarctica, and to a lesser extent over the North Pole.
Thanks to worldwide agreement and compliance with the 1987 UN Montreal Protocol (which agreed to phase out ozone depleting chemicals) global ozone depletion is no longer increasing. The Montreal Protocol is the most (some would say only) successful international agreement and scientists hope the ozone layer will have completely recovered by 2060.
Ozone gas is present in the ozone layer. It is decreasing due to man made ODS.
Ozone layer is decreasing. It is because of CFC's that are depleting it.
Yes, we should be concerned that the ozone layer is decreasing because it acts as a shield for the earth. It protects us from the harmful ultraviolet radiations of the sun.
The phenomenon of decreasing of ozone layer thickness is called as ozone hole. It is called by various ozone depleting substances.
To protect our self, we have to repair the ozone. For that, curb the CFC's.
See "What can we do to protect the ozone layer?"
Chloroflorocarbons (CFCs) did. From what i've heard the ozone layer is starting to slowly heal up again. According to a report (2011) by the Scientific Assessment Panel of the U.N. Montreal Protocol on Substances that Deplete the Ozone Layer, the ozone layer has, over the last decade, reached a turnaround point. It is no longer decreasing, but it is not yet increasing.
Ozone in the ozone layer appears to be decreasing long term, with significant variations annually, every ~11 years, and even every ~121 years. See link below.
Ozone concentration increases with decreasing altitude to a maximum value, then drops of to near zero at the Earth's surface. The region of high concentration is called a layer, because it covers the entire Earth, and is confined to a few kilometers in height / thickness.
Ozone layer contains ozone in it. Therefore, it is named so.
Some gaseous products of human activity can reduce the about of ozone in the upper atmosphere, thus decreasing the effectiveness of the ozone layer in shielding the surface of the planet from ultraviolet radiation.
The ozone layer in Tagalog is called "tunog ozone."