14 seemingly harmless things you eat, drink, and use all the time that could kill you

Water may seem like the least harmful substance, but drinking too much of it can kill.

So can too much of other things that most of us take for granted — from caffeine to the stuff you use to clean your bathroom.

To calculate how much of each of these items would be dangerous enough to kill, we've used a standard measure of toxicity known as LD50, the individual dose it would take to kill half the animals it was tested on.

This amount can vary pretty significantly depending on someone's health, gender, and medical history. The potentially deadly dosages in the slides that follow were calculated for the average 196-pound American male.

120 cups of coffee

Coffee's great for making you feel more alert and boosting your attention span, and, at low doses, it's perfectly safe.

But at high concentrations, caffeine can cause insomnia, dizziness, vomiting, headaches, and heart problems, and too much in one sitting can be deadly.

The risk of overdoing it is highest for pure powdered caffeine. A single tablespoon of this stuff — the equivalent of about 120 cups of coffee — can kill. During the summer of 2014, two young men died in separate incidents after each drank mixtures of pure powdered caffeine and water.

Six liters of water

Water regulates the shape of the cells inside our bodies — too much of it, and they puff up like balloons. Too little, and they shrink.

An excess of water in and around our cells is called water intoxication, or hyponatremia. Drinking too much water, something athletes can do accidentally while training, can cause it. A 2005 study of 2002 Boston Marathon runners, for example, found that about one-sixth of the runners they studied had a mild form of the condition, with symptoms ranging from nausea to vomiting.

But an extreme case of water intoxication takes its worst toll on the brain, where our tightly packed neurons have little room to accommodate the extra water. A variety of neurological problems can result, from headaches to confusion, seizures, and, in rare untreated cases, death.

A well-known case of water intoxication happened in 2007, when 28-year-old Californian Jennifer Strange downed six liters of water in less than three hours as part of a radio-station contest. She died a few hours later.