Electricity powers our modern world, but this indispensable energy source also carries inherent dangers. Understanding how electricity can harm the human body is crucial for safety.
Understanding Electrical Parameters
To understand electricity’s dangers, it is important to grasp its basic parameters: voltage, current, and resistance. Voltage represents the electrical potential difference, acting as the “pressure” that drives electrical charge. Current is the flow of electrical charge, measured in amperes (A) or milliamperes (mA). Resistance is the opposition to this flow, measured in ohms (Ω), determining how easily current passes through a material.
These three parameters are interconnected; a higher voltage can drive more current through a given resistance. While voltage is often perceived as the primary danger, it is the current flowing through the body that directly causes harm. Voltage pushes current through the body’s resistance, highlighting that even seemingly low voltages can be hazardous if conditions allow a significant current to flow.
How Electricity Harms the Body
Electricity harms the human body primarily through three mechanisms: disrupting natural electrical signals, causing thermal injuries, and inducing muscle contractions. The body relies on electrical impulses for functions like heartbeats and nerve communication. External current can interfere with these vital signals, leading to ventricular fibrillation (ineffective heart fluttering) or asystole (complete heart stoppage).
Electricity can also disrupt the nervous system, leading to respiratory muscle paralysis and stopped breathing. The body’s resistance to current flow generates heat, much like a heating element. This thermal energy causes severe internal and external burns, often appearing as distinct entrance and exit wounds. Internal tissues and organs can suffer extensive damage even if external burns appear minor.
Electric current can trigger involuntary and violent muscle contractions. These uncontrolled spasms, known as tetany, can prevent a person from releasing the electrical source, prolonging exposure. Forceful contractions can also lead to secondary mechanical injuries, including falls, fractures, or dislocations.
Lethal Thresholds of Electrical Current
The amount of electrical current flowing through the body dictates the severity of an electric shock, with relatively small amounts proving lethal. The perception threshold, the minimum current a person can feel, is typically around 1 milliampere (mA) for alternating current (AC) and 5 mA for direct current (DC).
A current between 10 to 20 mA (AC) or 75 mA (DC) can reach the “let-go” threshold, making it impossible to release an electrified object. Currents around 30 mA (AC) can cause respiratory paralysis. Ventricular fibrillation, the most common cause of death from electric shock, can occur with AC currents as low as 60-100 mA traveling through the chest. For DC, 300-500 mA are needed to induce the same effect. Higher currents, exceeding 1000 mA (1 A), can cause immediate cardiac arrest and severe burns.
Factors Affecting Shock Severity
Several variables influence the impact of an electrical shock. The current’s pathway through the body is a critical determinant; for instance, current flowing from one hand through the chest to the other hand or a foot is particularly dangerous as it traverses vital organs. The duration of contact also plays a substantial role, as longer exposure increases the likelihood and severity of harm.
Skin resistance affects how much current enters the body. Dry, intact skin offers high resistance, up to 100,000 ohms. Wet or broken skin, or skin with sweat, significantly reduces this resistance to as little as 1,000 ohms, allowing more current to flow. The type of current, AC versus DC, also matters; AC is generally more dangerous at lower current levels because it is more likely to induce sustained muscle contractions and ventricular fibrillation. Individual health, including pre-existing heart conditions, can increase vulnerability to electrical injury.