Electricity powers modern life, but it carries inherent risks if not properly managed. Understanding electrical currents and their potential effects on the human body is fundamental for safety. Even small amounts of electricity can pose a significant threat.
Understanding Dangerous Current Levels
The human body reacts to varying levels of electrical current, measured in milliamperes (mA), with distinct physiological effects. A current as low as 1 milliampere can be perceived as a faint tingling sensation. As the current increases to around 5 milliamperes, a slight shock is felt, and most individuals can still let go of the source. However, currents between 9 and 25 milliamperes can cause sustained muscular contraction, making it difficult or impossible for a person to release the electrical source.
Currents in the range of 60 to 100 milliamperes pose a substantial risk of ventricular fibrillation. Currents exceeding 100 milliamperes are likely to cause ventricular fibrillation and nerve damage. At very high currents, such as 500 milliamperes or more, immediate cardiac arrest and severe burns can occur.
Factors Determining Shock Severity
The severity of an electric shock is influenced by several factors. The path the current takes through the body is important; for example, current passing through the chest, especially from hand to hand or hand to foot, is more likely to affect the heart. The duration of contact with the electrical source also plays a role, as longer exposure increases the likelihood and severity of injury.
Voltage affects severity because higher voltages can drive greater currents through the body’s resistance. Body resistance, primarily concentrated in the skin, varies; dry skin offers high resistance, while wet or broken skin can reduce it significantly. The type of current also matters, with alternating current (AC) posing a greater risk of ventricular fibrillation than direct current (DC).
The Mechanism of Cardiac Arrest
Electric current can disrupt the heart’s natural electrical system, leading to cardiac arrest. The heart’s rhythm is controlled by precise electrical signals that cause its chambers to contract and pump blood effectively. When an external electric current passes through the body, especially through the chest, it can interfere with these impulses.
The most common and dangerous cardiac effect is ventricular fibrillation (VF), where the heart’s lower chambers, the ventricles, quiver chaotically instead of performing coordinated contractions. This chaotic electrical activity prevents the heart from pumping blood to the rest of the body, causing a drop in blood pressure. Without immediate intervention, the lack of blood flow to the brain and other organs can cause death. While electric shock can also cause respiratory arrest or burns, ventricular fibrillation is the primary mechanism of sudden cardiac death from electrical injury.
Protecting Yourself from Electric Shock
Preventing electrical accidents involves adhering to practical safety measures. Regularly inspect electrical cords, tools, and appliances for any damage like frayed wires or cracked casings, and promptly replace or repair compromised equipment. Avoid using electrical devices near water sources, and ensure all cords and outlets remain dry, especially outdoors.
Ground Fault Circuit Interrupters (GFCIs) are safety devices designed to prevent electrical shocks by quickly shutting off power when they detect an imbalance in current flow. These are particularly important in areas where water and electricity might interact, such as bathrooms, kitchens, laundry rooms, and outdoor outlets. Always test GFCIs monthly by pressing the “test” button to ensure they are functioning correctly. For complex electrical issues or installations, always consult a qualified electrician.