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Can using a laptop while charging cause cancer?


A video – watermarked pointing to an Instagram handle called @fenoogreek – made the rounds on WhatsApp. In the video, a young man claims to feel a minor electric shock when he puts his hand on the shoulders of a young woman who is sitting on a sofa and working on a charging laptop. The two individuals exclaim, and the young man claims to know what is happening.

He fetches a portable device and asks the woman to reach out for her hand, and when she does, the device appears to produce a reading which the man says is evidence that there is measurable electrical current on his skin. The video ends with the young man claiming that when such “dirty radiation” circulates and accumulates in our body, it causes cancer.

The clip does not refer to electrical injuries that may result from contact with faulty appliances or power lines.

‘Current Touch’

You may sometimes feel a little tingling sensation when touching a laptop with a metal casing if it is also charging. It is the result of a residual current flowing through the body of the laptop in a body of negative electrical potential – usually referred to as “ground”. But these currents are very weak and not dangerous for humans.

The connection between your laptop’s charger and its power source should be such that current flows from the source into the laptop, through all circuits, and back into the source, forming a closed loop. The current flows in the opposite direction of the electrons. In this case, then, electrons flow from negative potential to positive potential – while current flows in the other direction, from positive potential to negative. The laptop is right in the way.

A small fraction of the current can leak out of the closed loop and linger on the surface of the laptop, especially if the surface is metal (a common example is Apple laptops). This current then flows to the ground through the body of the person touching the metal surface of the laptop. It’s called a touch current.

You can avoid such touch currents by making sure your power source is properly grounded, including using a three-prong outlet instead of a two-prong one.

measure current

In the WhatsApp video, the young man appears to be measuring the strength of the electric field using a handheld device. This device is an electromagnetic field (EMF) meter. Technical experts use EMF meters to detect and measure the quantum of electromagnetic radiation at a given location.

This measurement will vary depending on how close the meter is to the source – in this case, the laptop. So it’s not clear how placing one hand near the EMF meter while touching the laptop with the other, as the woman in the video does, changes the reading.

In fact, the device manual for the TriField TF2 EMF meter – also used in the video – indicates that the reading would be lower near a human body than farther away from it. This is because the human body protects against electric fields.

Finally, touch currents are too small to influence the reading on an EMF meter. In the video, the woman pronounces the counter by reading aloud: “0, 1, 2… very little”, followed by “300”. However, it does not specify the units.

Ionizing vs non-ionizing radiation

When a body emits radiation, it can do so in a range of frequencies depending on the emission conditions. This range of frequencies is what we call the electromagnetic spectrum.

Electromagnetic waves include radio transmissions, visible light, X-rays and gamma rays. High frequency radiation like X-rays and gamma rays are classified as ionizing radiation. The relatively high energy that each of their waves carries can knock electrons out of atoms. When this happens, the atom becomes an ion and can trigger a cascade of changes in the body.

That’s why exposure to large doses of gamma rays can damage DNA and potentially cause cancer (or, in a Marvel movie, turn you in Hulk). This is also why exposure to ionizing radiation is strictly regulated – in India, by the Atomic Energy Regulatory Board.

Radiation whose waves carry insufficient energy to ionize atoms is simply called non-ionizing radiation. All electrical transmission lines, electrical wiring and appliances emit electromagnetic waves. In India they do this at a frequency of 50 Hz – known as service frequency. This is considered an “extremely low frequency” (ELF) on the electromagnetic spectrum.

Such waves are incapable of ionizing the atoms in the body. In fact, their waves have less energy than visible light.

Does ELF radiation cause cancer?

There is no known mechanism by which non-ionizing radiation can pose a cancer risk.

Many studies investigated the possibility of a link between ELF radiation exposure and cancer. They reported no evidence for the claim that exposure to ELF radiation can cause cancer in adult humans.

There is tenuous evidence linking exposure to ELF magnetic field (not electric field) to childhood leukemia – but many scientists refuted these claims too. A WHO working group came to the same conclusion, that there is no connection, 17 years ago.

Electricity and electrical and electronic devices have become ubiquitous in modern life. Electrical appliances such as televisions, refrigerators, air conditioners, etc. only emit ELF radiation, much like the charging (or discharging) of laptops and smartphones. As a result, some level of ELF radiation exposure has become unavoidable. But there is no reason to suspect that it will cause cancer. As stated earlier, visible light carries more energy than ELF radiation per wave.

In sum, there is no evidence in the scientific literature to substantiate the alarming claim in the WhatsApp video – that using a laptop while charging will cause cancer in the body.

Swetha P. is an aspiring science communicator and physicist.