You may need a backup method of birth control if you have vaginal intercourse during the seven days after a missed pill. Some backup methods are the condom, female condom, diaphragm, or sponge. You can also use emergency contraception (morning after pill) up to five days after unprotected intercourse.
Strontium-90, a radioactive isotope, is a by-product of nuclear reactors and present in nuclear fallout. It has a half-life of 28 years. It is absorbed by bone tissue instead of calcium and can destroy bone marrow and cause cancer. However, it is also useful as it is one of the best high-energy beta-emitters known. It can be used to generate electricity for space vehicles, remote weather stations and navigation buoys.
It is also used as a corrosion inhibitor in aluminum alloys as the compound strontium chromate, and, since it burns with a bright red color, strontium and fireworks go hand in hand. The same compound used in toothpaste, strontium chloride hexahydrate, is used as well in the manufacture of magnetic materials.