Poisoning can cause short-term effects, like a skin rash or brief illness. In serious cases, it can cause brain damage, a coma, or death.

Poison, in biochemistry, a substance, natural or synthetic, that causes damage to living tissues and has an injurious or fatal effect on the body, whether it is ingested, inhaled, or absorbed or injected through the skin.

1. Botulinum (ingested) It’s hard to rank the lethality of toxins, but experts agree that botulinum – several orders of magnitude deadlier than sarin – is the gold standard….The Best: Deadly Poisons, Ingested or Inhaled

1. Botulinum (ingested)
2. Ricin (ingested or inhaled)
3. Anthrax (inhaled)

Contaminated groundwater is the most common cause of arsenic poisoning. Arsenic is already present in the earth and can seep into groundwater. Also, groundwater can contain runoff from industrial plants. Drinking arsenic-laden water over a long period of time can lead to poisoning.

Long-term exposure to arsenic from drinking-water and food can cause cancer and skin lesions. It has also been associated with cardiovascular disease and diabetes. In utero and early childhood exposure has been linked to negative impacts on cognitive development and increased deaths in young adults.

Some scientists believe there are harmful effects from arsenic below the drinking water standard. These include bladder, lung, liver and skin cancer, heart disease, strokes and diabetes. Recent studies have suggested that arsenic may cause IQ deficits in children and may be harmful to fetal development.

Some forms of arsenic are used as medicine. Despite serious safety concerns, arsenic is often used as a part of extremely diluted homeopathic remedies that are used for digestive disorders, food poisoning, sleep problems (insomnia), allergies, anxiety, depression, and obsessive-compulsive disorder (OCD).