We’ve all seen the sign “Danger, High Voltage,” but it is actually the current that kills. Voltage and current are two measures of electricity. Voltage is a measure of the pressure that allows electrons to flow, while current is a measure of the volume of electrons. An electrical current at 1,000 volts is no more deadly than a current at 100 volts, but subtle changes in amperage can mean the difference between life and death.
Current is defined as the amount of electricity flowing per time (second). The magnitude of electric current that flows through the body determines the effects of an electric shock.
According to data assembled by the National Fire Protection Association, in addition to the magnitude of the current, the impact of an electric shock incident is influenced by a few other factors.
Body mass is among those factors, and explains why men can generally withstand a slightly larger current before losing muscular control.
A person feels an electric shock when they complete a circuit. People with small frames provide less resistance, and those with large frames provide more. Several studies have confirmed that the magnitude of current is a function of body weight, and the minimum magnitude of current to cause fibrillation is approximately proportional to the weight of the body.
Another factor is the duration of the shock. The length of exposure to an electrical shock will result in variable damage to the human body.
A factor relevant to shocks within water is the type of water. The magnitude of the current depends on the resistivity of the water. Water can be freshwater or saltwater.
The risk of ESD increases as water salinity decreases. Saltwater is more conductive than freshwater. The resistivity of saltwater is 20 ohm-cm compared to 1400 ohm-cm for freshwater. ESD can occur more readily when a person is in freshwater because human body is closer to saltwater than freshwater. According to data on electric shock drownings, the number of incidents in freshwater is far higher than in saltwater.
