As a rule of thumb, this occurs when a person's shadow is longer than his or her height. Current estimates predict that ozone concentration could be reduced by 6 percent or more within several decades if world levels of CFC production continue. Many nations have signed an agreement, called the Montreal Protocol, which would limit and possibly end CFC production by the year 2000. As much as a 2 percent increase in UV-B radiation may be expected for each 1 percent reduction in stratospheric ozone concentration. These concerns are now being studied by a number of federal agencies.
Most individuals have some choice in the amount of sunlight exposure they receive.