Arsenic, chemical symbol As, is a metalloid solid. Its atomic number is 33, with an atomic weight of 74.92. In its standard state, it is very brittle and crystalline; arsenic sublimates (changes directly from a solid to a gas) when heated.

That's the scientific side of arsenic, but what really makes the element a household name is the fact that it's poisonous. From the movie Arsenic and Old Lace to the latest TV crime drama, arsenic has been the poison of choice for many a fictional criminal.

In real life, though, arsenic poisoning mainly comes from environmental causes. Contaminated air, food and water can all be a source of arsenic ingestion. It is also possible to ingest arsenic when living near improperly controlled toxic waste sites and in regions where rocks contain a high arsenic concentration. Finally, pressure treated wood may include arsenic which can release the poison through sawdust or when burned.

Even at levels low enough to not be toxic, arsenic has unpleasant side effects. Breathing arsenic may cause lung and throat irritation, while ingesting a smaller amount can cause nausea, vomiting and blood problems. Exposure to low levels over a longer period of time can cause darkened skin and wart-like marks.

If you suspect that you have been exposed to arsenic, there are a few tests that doctors can perform. If you can get tested within a few days of the potential exposure, then a urine sample will be the best indicator of arsenic in your system. Over a longer period of 6-12 months, doctors can examine your hair and nails for indicators of high levels of arsenic in your system.

Despite its bad reputation, arsenic does have some innocent uses, such as preserving wood and bronzing. It can also be found as a component in pyrotechnics.