Arsenic is one of the "bad boys" of the periodic table. It's been called the "king of poisons" and the "poison of kings," although it's more likely to be used for rat poison than for regicide. While it's true that arsenic is toxic, this element, like all chemical substances, has it's place in the world. Neither a villain nor a hero, arsenic is just an element and the way we put it to use determines whether it helps or harms.
In 2000, the United States Food and Drug Administration (FDA) approved arsenic trioxide as a cancer drug to treat a particular type of leukemia. Previously, forms of arsenic had been used to treat syphilis. Though toxic in large quantities, small doses of the right arsenic compound may save the lives of patients.
Also, while arsenic is a common environmental pollutant, it is also a part of some "green" technologies. Arsenic compounds are used in the manufacture of solar cells that are more efficient than the traditional silicon type when it comes to converting the sun's energy to electricity. This prevents the use of fossil fuels without resorting to nuclear power, thus allowing people to generate electricity without undue environmental damage.
Arsenic is also used in integrated circuits. Interestingly, while it is a component of materials that convert sunlight to electricity (solar cells), it plays the opposite role when it functions in LED's. (An LED is a "light emitting diode".) Electrical components containing arsenic generally function better, but are more expensive than, their silicon-based counterparts.
Historically, arsenic was used to make dyes, including "Paris green," an emerald green colored pigment. Arsenic containing pigments were sometimes used in candies, causing poisoning. Victorian women would sometimes rub arsenic compounds on their skin, or even ingest them, in order to have a paler complexion. Of course such beauty treatments had disastrous effects on human health, causing numerous ailments.
Today, the greatest threat posed by arsenic is accumulation in the watershed, which results from people discarding electronic devices with arsenic-based components. However, even taking into account the pollution from such devices, levels of arsenic are generally too low to be a real threat to human health. Because scientists can now detect arsenic at very low levels, they can identify pollution before it becomes a true threat. This is a mixed blessing, since it can create either awareness or panic, depending on how the information is received.
The element arsenic is a natural substance found on our planet, and in itself, it is neither good nor bad. As chemistry progresses and we are better able to utilize our natural resources, we can continue to use chemicals like arsenic more responsibly. When chemicals like arsenic compounds are used to better human existence without harming people or the environment, out lives are richer for it.